Proceedings of the Polymer Society of Korea Conference (한국고분자학회:학술대회논문집)
- 기타
Domain
- Chemical Engineering > Polymeric Materials and Process
2006.10a
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Polymer architecture plays a great role in determining the properties of functional polymers. This lecture will explore the design and the synthesis of polymers with controlled architecture and functionality. Especially featured will be star and dendritic architectures where the functional group placement and the molecular shape can be controlled. This will be followed by examples of applications illustrated with a few model systems of functional polymers designed for use in areas such as organic electronics, catalysis, surface patterning, separation and molecular recognition, and polymer therapeutics.
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Do, Eui-Doo;Lee, Chang-Hoon;Kwon, Young-Wan;Choi, Dong-Hoon;Jin, Jung-Il;Oh, Dong-Keun;Nishide, Hiroyuki;Kurata, Takashi 3
Natural DNAs in dry state, i.e., A-DNAs, when intercalated with low levels of stable organic free radicals or complexed with low levels of Au(III), are attracted at room temperature to commercial magnets, whereas those containing high levels of intercalators or Au(III) are not. This surprising observation is explained by the EPR spectra and SQUID measurement of magnetization of the modified DNAs. It is conjectured that A-DNAs are morphologically heterogeneous containing ordered and disordered regions. The ordered regions appear to strongly mediate magnetic interactions between spins through their${\pi}_z$ -stacked structures. When the modified DNAs are wet or hydrated, they behave diamagnetically. -
Molecular motion at the surface of monodisperse polystyrene (PS) films with various chain end groups was studied by scanning probe microscopy. Surface glass transition temperature (
$T_{g^s}$ ) of the PS films was much lower than the corresponding bulk value. And, the magnitude of$T_{g^s}$ was strongly dependent on chain end chemistry. This result can be explained in terms of the chain end concentration at the surface. Time-temperature superposition principle was applied to rheological analysis at the surface. The apparent activation energy of the surface${\alpha}_{a}$ -relaxation process was approximately a half of that for the bulk sample. This result clearly indicates that the cooperativity for the surface segmental motion was reduced in comparison with that in the bulk region. -
Interest in "nanotechnology" has triggered the question whether new materials can be obtained blending nanosized particles with polymers. This contribution considers modification of polymer properties by nanoscale particles, stabilization of polymer properties by nanoscale particles, stabilization of nanoscale particles against Ostwald-ripening and agglomeration, synthesis of nanoscale particles assisted by polymers and effects of such particles on polymerization mechanisms.
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Recent work in our laboratory has focused on the molecular and supramolecular engineering of conjugated polymers and oligomers for device applications, including light emitting diodes for displays and lighting, photovoltaic cells, and thin film transistors. A central finding is that the supramolecular structure of conjugated polymers can have a dominant influence on their properties and the performance of devices. Some major results include: highly efficient RGB light-emitting diodes from polymers and oligomers; high mobility n-channel polymer field effect transistors; ambipolar thin film transistors from copolymer semiconductors; and self-assembly and ambipolar charge transport in polymer nanowires.
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Incorporation of chromophores into multi-chromophore-containing dendrimers is shown to lead to a significant enhancement in electro-optic activity. These results are reasonably well simulated by pseudo-atomistic Monte Carlo calculations that permit dendrimers to interpenetrate (entangle). Calculations also lead to the correct prediction of material densities. An even greater enhancement in electro-optic activity is observed when such dendrimer materials are doped with a second chromophore. This latter effect may reflect an Ising-lattice-type phenomenon where one chromophore impacts the ordering of the other and vice versa.
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The use of soft-lithography instead of standard photolithography and dry etching technologies is attractive because inexpensive optical device can be realized. Polymerization using multi-photon absorption of materials is also a good method for optical waveguide fabrication. Laser induced self-writing technology of optical waveguide is also very simple and attractive. Using these processes, we can fabricate and interconnect optical circuits at once. In this presentation, several simple fabrication methods will be introduced. New optical loss evaluation method for polymer optical waveguides will also be presented
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Lee, Kwang-Sup;Kang, Seung-Wan;Kim, Ran-Hee;Kim, Ju-Yeon;Kim, Won-Jin;Park, Sang-Hu;Lim, Tae-Woo;Yang, Dong-Yol;Sun, Hong-Bo;Kawata, Satoshi 15
Since two-photon polymerization (TPP) emerged as a new technology over a decade ago, a large variety of micro-objects including 3-D micro-optical components, micromechanical devices, and 3-D photonic crystals have been fabricated using TPP with a high spatial resolution of approximately submicron scale to 100 nm. Recent efforts have been made to improve the fabrication efficiency and precision of micro-objects obtained with TPP; in particular, many studies have been carried out with the aim of developing efficient two-photon absorbing chromophores. In this presentation, we will discuss our efforts to develop highly efficient two-photon absorbing materials and also describe recent attempts to enhance the resolution and to improve the fabrication efficiency of nanofabrications based on TPP. -
Flat Panel Displays (FPDs) have made a revolution in the display industry. TFT-LCD (Thin Film Transistor Liquid Crystal Display) has been the main player of FPD for last two decades. As the industry continuously develops the technology for better performance with lower cost is constantly demanded where several post LCD technologies are being developed. One of the prime candidates of post LCD technology is AMOLED (Active Matrix Organic Light Emitting Diode) that is considered to be an ideal FPD due to its extraordinary display performance and potentially low cost display structure. This technology has been accepted to small size display applications, such as cellular phone, PDA and PMP, etc. In this paper it is discussed that how this technology can be extended to large size display applications, such as TV. The technical issues and solutions of TFT backplane and color patterning of OLED materials are discussed and proposed
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We report the design of electroluminescent conjugated polymers for high efficiency, turn-on voltage, color Tuning, and easy processing. Three approaches for the design are reported, being: (1) single chain consideration, (2) supramolecular structure consideration, and (3) conformation manipulation. Two polymer systems are to be reported, being fluorene-based and carbazole-based conjugated polymers.
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Holmes Andrew B.;Chan, Khai-Leok;Cho, Sung-Yong;Evans Nicholas R.;Grimsdale Andrew C.;Mak Chris S.K.;Sandee Albertus J.;Watkins Scott E.;Williams Charlotte K. 21
Significant progress has been realized in the design and synthesis of light emitting polymers with emission over the whole range of the visible spectrum. However up to seventy-five percent of charge recombination events can lead to triplet states that decay non-radiatively. Following the pioneering work in the field of small molecule organic light emitting devices it has been found that solution processible iridium polymer complexes can be used to harness the wasted triplet energy. In this paper new results concerning electrophosphorescence of solution processible tethered iridium polymer derivatives will be presented. Furthermore our approaches to the design of new high triplet energy conjugated polymer hosts will be reported. -
Gangopandhyay, Palash;Foerier, Stijn;Vangheluwe, M.;Koeckelberghs, Guy;Verbiest, Thiery;Persoons, Andr 23
Magnetic and magneto-optical properties of regioregular (>99%) poly(3-dodecylthiopenes are investigated. Faraday rotation of spin-coated films show extremely large Verdet constants, falling strongly with decreasing regioregularity. EPR spectroscopy at room temperature shows the presence of about 1 spin/190 monomers, indicative of delocalisation beyond a single polymer chain. SQUID measurements on the polymer give an effective magnetic moment of about 48900 mB, corrsponding to a S-value of 25.000. The Weiss-constant is 1.33 K indicating ferromagnetic coupling. Our experimental results show that organic polymer magnets can be prepared. Large MO effects allow the use of these materials in all-organic MO-sensors and devices. -
Azobenzene functionalized polymers have been extensively investigated due to the potential applications in the areas of optical switching, optical elements, optical information storage, and nonlinear optics. These applications are mainly achievable due to photoinduced properties of azobenzene groups with photoisomerization and photoinduced anisotropy. We report applications to the optoelectronic devices using inscribed one-(1D) and two-dimensional (2D) SRGs on azo polymer films. The inscribed holographic SRGs patterns were useful to control or enhance optoelectronic properties such as transparent electrode patterning, hybrid solar cell and ultraviolet GaN-based LED.
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Chromatographic separation of enantiomers by high-performance liquidchromatography (HPLC) has considerably advanced in the past two, and many optically active polymers have been developed to be usedaschiral stationary phases (CSP). Among many CSPs, cellulose-andamylose-based CSPs are most attractive from the viewpoints of theirwide applicability and easy availability. The polysaccharides are readily modified to ester and carbamates. The derivatives have been used as CSPs after being coated on macroporus silica gel. Here, the CSPs based on phenylcarbamate derivatives of these two polysaccharides will be mainly discussed. The immobilization of the derivatives on silica gel will also be discussed.
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The synthesis of dendritic dipeptides
$(4-3,4-3,5)12G2-CH_{2}-Boc-_{L}-Tyr-X-OMe\;where\;X\;=\;Gly,\;_{L}-Val,\;_{L}-Leu,\;_{L}-Ile,\;_{L}-Phe$ , and L-Pro will be discussed. Their self-assembly in bulk and in solution and the structural and retrostructural analysis of their periodic assemblies will be compared to that of the previously reported and currently reinvestigated dendritic dipeptide with$X=_{L}-Ala$ . All dendritic dipeptides containing as X nonpolar${\alpha}-amino$ acids self-assemble into helical porous columns. The principles via which the aliphatic and aromatic substituents of X program the structure of the helical pores indicate synthetic pathways to helical pores with bioinspired functions based on artificial nonpolar${\alpha}-amino$ acids will be discussed. -
We describe the preparation of nanostructured molecularly-imprinted surfaces using nanomolding on porous alumina. In molecular imprinting functional and cross-linking monomers are copolymerized in the presence of a molecular template, resulting in synthetic receptor materials. The drug propranolol and the dye fluorescein were used as the molecular imprinting templates. Binding studies with imprinted and non-imprinted surfaces revealed specific recognition of the templates and thus the existence of selective binding sites. In addition, the surface properties of the films were studied by water contact angle measurements. It was found that, depending on the monomers used, certain nanostructures induced great changes in the wetting properties of the surface.
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The graft copolymer consisting of poly(N-isopropylacrylamide) (PNIPAAm) and single-stranded DNA was prepared. Interestingly, the copolymer was found to form nanoparticles above physiological temperature. We found that non-crosslinking aggregation of the nanoparticles was induced by the hybridization of the surface-bound DNA with the full-match complementary DNA, but not with one-base mismatch. The core material is not restricted to PNIPAAm; DNA-functionalized gold nanoparticle was found to show a similar aggregation induced only by the fully-complementary DNA, resulting in rapid color change within 3 min at ambient temperature. This methodology is general in principle and applicable for wide variety of clinical gene diagnosis.
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Excited-state intramolecular proton transfer (ESIPT) is a phototautomerization occurring in the excited states of the molecules possessing a cyclic intramolecular or solvent-bridged hydrogen bond. Recently, we have developed novel ESIPT chromophores, molecules, dendrimers and polymers which show very high fluorescence quantum efficiency combined with the characteristic features of optical switching, fluorescence patterining, lasing, and electroluminescence. Broad overview of these topics will be given in this talk.
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Conjugated diacetylene supramolecules are interesting biomimetic materials in view of application to chemical and label-free biological sensors. These supramolecules are unique in changing color from blue to red upon specific binding events. Various binding events including viruses, toxins, glucose, and ionic interactions have been reported detectible. Here, we focus on fabrication of polydiacetylene supramolecule dot array patterns on solid substrates by using a conventional microarrayer. Each dot is found to possess the color-changing property as well as the fluorescence self-emission. This technique allows us, for the first time, to fabricate biochips based on polydiacetylene supramolecules. Label-free detection of small molecules and biological targets will be discussed.
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Lithography and other patterning processes are powerful tools catalyzing many developments in science and engineering. The controlled formation of nanometer scale structures in 2 and 3 dimensions is therefore of increasing importance in many applications ranging from biotechnology to nanotechnology. This presentation will discuss new approaches for the construction of small-scale (a few tens of nm) structures using both 1- and 2-photon processes. Several approaches to fine feature lithography including the use of molecular glasses will be described. Such small scale structures can be used in a variety of biological applications including study of cell function and will be described.
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Willson C. Grant;Hao Jianjun;Stewart Michael;Nishimura Yukio;Palmieri Frank;Jen Wei-Lun;Dickey Michael;Chan, Andrew;Wu Kai;Ekerdt John;Owens Jordan;Wetzel Jeffery T. 41
Step and Flash Imprint Lithography is an interesting low cost alternative to traditional microlithographic processes that offers the ability to efficiently produce nanostructures at unprecedented resolution. New photopolymerizable formulations are required to enable this process. This paper will describe progress in the design and development of acrylate and vinyl ether based platforms for this application together with efforts to prepare photopolymerizable, thermally stable, magterials with low dielectric constants for use in an efficient new method for fabricating the interconnect structures in microprocessors. -
We have prepared random, block and graft copolymers with single or dual sensitivities to various stimuli. We have conjugated these polymers to proteins at random lysine sites or at specific sites designed into the protein by genetic engineering. We are also grafting the smart polymers to the surfaces of nanobeads. We are applying these smart conjugates and smart nanobeads in microfluidic devices for various applications, including diagnostics, affinity separations and enzyme bioprocesses. In this talk I will update our work with these interesting hybrid systems.
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Zhong Zhiyuan;Lin, Chao;Song, Yan;Lok Martin C.;Jiang Xulin;Christensen Lane V.;Engbersen Johan F.J.;Kim, Sung-Wan;Hennink Wim E.;Feijen Jan 44
Gene therapy holds great promise for treating various forms of diseases with a genetic origin including cystic fibrosis, different forms of cancer, and cardiovascular disorders. The clinical use of gene therapy treatments is however restricted, mainly because of the absence of safe and efficient gene delivery technologies. In our group, with an aim of developing efficient and nontoxic polymeric gene delivery systems, several novel types of polymeric gene carriers have been designed, synthesized, and evaluated. Herein, I will mainly present our recent work on low molecular weight linear PEI-PEG-PEI triblock copolymers, degradable hyperbranched poly(ester amine)s, and reduction-sensitive poly(amido amine)s. -
Kirkpatrick C. James;Fuchs Sabine;Motta Antonella;Santos Marina;Hermanns M. Iris;Unger Ronald E.;Reis Rui;Migliaresi Claudio 46
Vascularization is essential for success in regenerative medicine. We have developed in vitro models to study how human microvascular endothelial cells (EC) and endothelial progenitor cells (EPC) colonize polymer scaffolds and express the endothelial phenotype, including angiogenesis. Examples are given of supportive growth and differeniation of EC on microfibre meshes of the silk protein fibroin and blends of starch with poly(epsilon-caprolactone), phenotypic markers being studied at both protein and mRNA level. Experimental models are also shown and concepts discussed to investigate how the stem cell niche, including that responsible for vascularization could be targeted, for example, by using engineered biodegradable polymer nanoparticles. -
The incorporation of heparin to biomaterials has been widely studied to improve the biocompatibility (blood and cell) of biomaterials surfaces. In our laboratory, various kinds of heparinized polymers including heparinized thermosensitive polymers (
$Tetronic^{(R)}$ -PLA(PCL)-heparin copolymers) and star-shaped PLA-heparin copolymers have been developed as a novel blood/cell compatible material. These heparinized polymers have demonstrated their unique properties due to bound heparin, resulting in improved biocompatibility. These heparinized bioactive polymers can be applied as blood and tissue compatible biodegradable materials in variable medical application such as tissue engineering and drug delivery system. -
Meng, Wan;Kim, Se-Yong;Yuan, Jiang;Kim, Jung-Chul;Kwon, Oh-Hyeong;Ito, Yoshihiro;Kang, Inn-Kyu 50
The nanofibrous scaffolds were obtained by co-electrospinning PHBV and collagen Type I in HIFP. The resulting fiber diameters were in the range between 300 and 600 nm. The nanofiber surfaces were characterized by ATR-FTIR, ESCA and AFM. The PHBV and collagen components of the PHBV-Col nanofibrous scaffold were biodegraded by PHB depolymerase and a collagenase Type I aqueous solution, respectively. It was found, from the cell-culture experiment, that the PHBV-Col nanofibrous scaffold accelerated the adhesion of the NIH 3T3 cell compared to the PHBV nanofibrous scaffold, thus showing a good tissue engineering scaffold. -
A new series of PEO-PPO-PEO and PPO-PEO-PPO copolymers having several hydroxyl groups on the PPO chain segment were synthesized, further modified with various poly(lactic acid) PLA oligomeric chains to confer physical stability after thermo-gelation in the body fluid. Gel stability was endowed by either increasing hydrophobic interaction between PLA chains or inducing stereocomplex formation between enatiomeric isomers of PLA chains. Macromolecular drugs were incorporated within the gels and their release patterns were investigated using Pluronic F127 as a control.
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Polymeric micelles, supramolecular assemblies of block copolymers, are useful nanocarriers for the systemic delivery of drugs and genes. Recently, novel polymeric micelles with various functions such as the targetability and stimuli-sensitivity have been emerged as promising carriers that enhance the efficacy of drugs and genes with minimal side effects. This presentation focuses our recent approach to the preparation of functional block copolymers that are useful for constructing smart micellar delivery systems in advanced therapeutics, including chemo-gene therapy. Particular emphasis is placed on the characteristic behaviors of intracellular environment-sensitive micelles that selectively exert drug activity and gene expression in live cells.
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The ultra pH-sensitive polymeric mixed micelles based on poly(L-histidine) chemistry and constructed from block copolymers containing polyHis, present four functionalities as decreasing pH: ligand exposure at pH 7.0, micelle destabilization below pH 6.8, enhanced DOX release and endosomal membrane disruption. The first functionality is expected to endow tumor pH specificity to nonspecific ligands and the rest ones may help to treat solid tumors that are hard-to-treat by conventional chemotherapy (resistant tumors). The concept was proven in vitro studies and in vivo model.
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Less than a decade ago, most alternate membrane materials for fuel cells relied upon a post-sulfonation process to generate ionic groups capable of transporting protons from the anode to the cathode. These random post sulfonations showed some promise, but in general they produced materials that were not sufficiently stable or protonically conductive at ion exchange capacities where aqueous swelling could be restricted. Our group began to synthesize disulfonated monomers that could be used to incorporate into random copolymer proton exchange membranes. The expected limitation was that the aromatic polymers might not be stable enough to withstand fuel cell conditions. However, this was mostly based upon an accelerated test known was the Fenton's Reagent Test, which did not seem to this author as being a reliable predictor of performance. A much better approach has been to evaluate the open circuit voltage (OCV) for alternate membranes, as well as the benchmark perfluorosulfonic acid systems. When this is done, the aromatic ionomers of this study, primarily based upon disulfonated polyarylene ether sulfones, show up quite well. Real time 3000 hours DMFC results have also been generated. Obtaining conductive materials at low humidities is another major issue where alternate membranes have not been particularly successful. In order to address this problem, multiblock copolymers with relatively high water diffusion coefficients have been designed, which show promise for conductivity at lowered humidity.
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New Energy and Industrial Technology Development Organization (NEDO) promotes R&D that individual private sector enterprises can not undertake by themselves. To do this, it utilizes an extensive network that supports cooperation between industries, universities, and public research organizations. NEDO's government-funded R&D budget for FY2005 totals approximately 148.8 billion yen. Fuel cells and hydrogen technology development project is one of NEDO's emphasizing projects. The budget size was
${\yen}$ 20.8 billion, corresponding to about 60% of annual expenditure of Japanese government for fuel cells in FY2005. These projects consist of 8 programs as follows. -
Based on the redox couples of a nitroxide radical, organic radical polymers were utilized as the electrode-active or charge-storage component for a secondary battery. We call a battery composed of the radical polymer electrode as "organic radical battery". Organic radical battery has several advantages: high capacity, high power-rate performance, long cycle ability, and environmentally-benign features. Synthesis and electrochemical studies of nitroxide polymers are described. Battery fabrication and cell performance are also reported.
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The solid state dye-sensitized solar cells (DSSCs) employing polymer electrolytes show high overall energy conversion efficiency as high as 4.5 % at 1 sun conditions. The improved efficiency may be primarily due to the enlarged interfacial contact area between the electrolyte and dyes in addition to the increased ionic conductivity, which were done by utilizing liquid oligomers, followed by in situ self-solidification, to form the solid DSSCs: "Oligomer Approach". The effect of the charge transfer resistance at the counter electrode side on the efficiency has also been investigated.
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[
$TiO_2$ ] single crystalline nanorods are prepared from electrospun fibers which are composed of nanofibrils with an island-in-a-sea morphology. The mechanical pressure produces each fibril into nanorods which are converted to anatase single crystals after calcinations. HRTEM shows that the (001) plane is growing along the longitudinal direction of the rod. In this work, the nanorod electrode provides the efficient photocurrent generation in a quasi-solid state dye-sensitized solar cells (DSSCs) using highly viscous PVDF-HFP based gel electrolytes. The overall converision efficiency of the$TiO_2$ nanorods shows 6.2 % under$100\;mW/cm^2$ (AM 1.5G) illumination. -
Solid polymer electrolyte is very important in the applications to high energy density lithium batteries of high safety. In this work, solid polymer electrolytes based on PE non-woven matrix, hybrid salt, and anion receptor were successfully prepared. They could provide high ion conduction phase with maintaining mechanical strength. They also showed high electrochemical stability and lithium ion transference number. This new type of solid polymer electrolyte is expected to be a good candidate for rechargeable solid state lithium secondary batteries.
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Lee, Sang-Young;Kim, Seok-Koo;Hong, Jang-Hyuck;Shin, Byeong-Jin;Park, Jong-Hyuck;Sohn, Joon-Yong;Jang, Hyun-Min;Ahn, Soon-Ho 69
In lithium-ion batteries, separator membrane's, main role is to physically isolate a cathode and an anode while maintaining rapid transport of ionic charge carriers during the passage of electric current. As far as battery safety is concerned, the electrical isolation of electrodes is most crucial since unexpected short-circuits across the membrane induces hot spots where thermal runaway may break out. Internal short-circuits are generally believed to occur by protrusions on the electrode surface either by unavoidable deposits of metallic impurities or by dendritic lithium growth during battery operation. Another cause is shrinkage of the separator membrane when exposed to heat. If separator membrane can be engineered to prevent the internal short-circuit, it will not be difficult to improve lithium-ion batteries' safety. Commonly the separators employed in lithium-ion batteries are made of polyethylene (PE) and/or polypropylene (PP). These materials have terrible limitations in preventing the fore-mentioned internal short-circuit between electrodes due to their poor dimensional stability and mechanical strength. In this study we have developed a novel separator membrane that possesses very high thermal and mechanical stability. The cells employing this separator provided noticeable safety improvement in the various abuse tests. -
Koizumi, Satoshi;Yamauchi, Kazuhiro;Hasegawa, Hirokazu;Tanaka, Hirokazu;Motokawa, Ryuhei;Hashimoto, Takeji 71
We investigated a simultaneous living anionic polymerization process of isoprene (I) and4styrene-d_8$ (S) in$benzene-d_6$ as a solvent with sec-buthyllithium as an initiator into polyisoprene(PI)-block-poly($styrene-d_8$ )(PS) and the polymerization-induced molecular self-assembling process. This process was observed in-situ by time-resolved small-angle neutron scattering (SANS) experiment. The SANS profiles measured exhibited three time regions, where (i) the selective growth of PI chains occurs; (ii) the living chain ends switch from isoprenyllithium to styryllithium, and (iii) the SANS exhibited the polymerization induced disorder-to-order transition and order-to-order transition. -
We investigate the influence of the confinement on the mesophase formation of diblock copolymer caged in a cylindrical pore in which the surface of the pore preferentially attracts one of the blocks. Using cell dynamics simulation, we construct phase maps as a function of the composition of diblock copolymer (f) and the pore diameter (D) relative to the period at bulk (
$L_{o}$ ). Depending on f and$D/L_{o}$ , we observe a variety of confinement-induced mesophases ranging from a simple dartboard-like structure to more complicated structures involving various forms of helices or doughnuts. -
In organic opto-electronic applications, such as light emitting diodes (LEDs) and photovoltaic devices (PVDs), the morphology of the active layer is of crucial importance. To control the morphology of the active layer the self-assembling properties of block copolymers was used. Several rod-coil semiconducting diblock copolymers consisting of a conjugated block and a second coil block functionalized with electron transporting and/or accepting materials (such as
$C_{60}$ ) were synthesized. The conjugated block acting as light absorbing, electron donating and hole transporting material. The donor/acceptor photovoltaic devices performance with active layer the above mentioned semiconducting block copolymers will be presented. -
Conducting polymers have been attracting considerable attention from both scientific and industrial perspectives by virtue of the beneficial electrical and optical properties originating from their unique
${\pi}-conjugated$ system. Many efforts have been devoted toward fabricating conducting polymer nanomaterials. Of the various synthetic methodologies, soft template method has emerged as a very promising tool in fabricating conducting polymer nanomaterials. For last a few years, our research group has intensively studied the fabrication and application of conducting polymer nanomaterials. In this talk, the recent achievement in the synthetic methodology based on the use of soft templates will be discussed. -
Bio-nanotechnology challenges have been emerging in development of molecular and cellular intelligent bio-materials, engineered cells for enhancing intelligence, biodevices for diagnosis and prevention, and biodevices for therapeutics and prevention. The perspectives of bionanotechnology challenges are overviewed.
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As the size scale of features continue to shrink in devices, the use of self-assembly, i.e. a "bottom up" approach, for device fabrication becomes increasingly important. Yet, simple self-assembly alone will not be sufficient to meet the increasing demands place on the registry of structures, particularly nanostructured materials. Several criteria are key in the rapid advancement and technology transfer for self-assembling systems. Specifically, the assembly processes must be compatible with current
$^{\circ}{\infty}top\;down^{\circ}{\pm}$ approaches, where standard photolithographic processes are used for device fabrication. Secondly, simple routes must be available to induce long-range order, in either two or three dimensions, in a rapid, robust and reliable manner. Thirdly, the in-plane orientation and, therefore, ordering of the structures, must be susceptible to a biasing by an external, macroscopic means in at least one, if not two directions, so that individual elements can be accessed in a reliable manner. Block copolymers, specifically block copolymers having a cylindrical microdomain morphology, are one such material that satisfy many, if not all, of the criteria that will be necessary for device fabrication. Here, we discuss several routes by which these versatile materials can be used to produce arrays of nanoscopic elements that have high aspect ratios (ideal for templating and scaffolding), that exhibit long-range order, that give access to multiple length scale structuring, and that are amenable to being biased by macroscopic features placed on a surface. -
In this study, the applications of the block copolymer thin films are introduced. For this purpose, we first obtained cylindrical nanodomains in polystyrene-block-poly(methyl methacrylate) copolymer perpendicularly oriented to a substrate. Then, nanoporous templates were prepared after removing the PMMA nanodomains by UV treatment. By using electropolymerization, high density nanowire arrays of conducting polymer of poly(pyrrole) and poly( 3-hexyl thiopene) were obtained and their electric properties were measured. Also, these nanoporous thin films were found to be very useful for the separation of human Rhinovirus type 14 (HRV 14), major pathogen of a common cold in humans, from the buffer solution.
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In aqueous phase, we directly prepared conducting and photoluminescent nano-structured particles by oxidation polymerization. Thiophene(PT) was initiated by
$FeCl_{3}/H_{2}O_{2}$ (catalyst/oxidant) combination system. And, polydispersed core-shell poly(styrene/thiophene) and polyaniline(PANI)-coated multi core-shell polystyrene latex particles were successfully prepared by oxidative and radical polymerization. The resulting latex particles have fine improved luminescence and conductive efficiency and dispersion state due to the PT and PANI shell. Hyper functionalized nanoparticle would be expected to increase the processibility in various electrical and electro-optical fields. -
The micellization behavior and the metal-nanoparticle formation in PDEAEMA-b-PHEGMA double hydrophilic block copolymers are investigated. The hydrophobic PDEAEMA block is pH-sensitive: at low pH it can be protonated and it becomes hydrophilic, leading to molecular solubility, whereas at higher pH micelles are formed; the behavior is studied by DLS, NMR and AFM. In these micellar nanoreactors, metal nanorystals nucleate and grow upon reduction with sizes in the range of a few nm's as observed by TEM and XRD. Similarly, metal nanocrystals can be formed within pH-sensitive microgels (
${\sim}250nm$ in diameter), synthesized by emulsion copolymerization of DEAEMA, which also exhibit reversible swelling properties in water by adjusting the pH. -
The novel linear- (V-LUM) and cross-type macromonomers (C-VUM) of vinyl-terminated bifunctional polyurethane were synthesized and applied to the dispersion polymerization of styrene and MMA in ethanol. The existence of the vinyl terminal groups and the grafted macromonomer with styrene and PMMA was verified using 1H NMR and 13C NMR. Monodisperse polystyrene (PS) microspheres were successfully obtained above 15 wt % of macromonomer relative to styrene. The macromonomer can efficiently stabilize higher surface area of the particles compared to a conventional stabilizer, PVP. The grafting ratio of the PS calculated from 1H NMR linearly increased up to 0.048 with 20 wt % of the macromonomer and the high molecular weights (501,300 g/mol) of PS with increased glass transition and enhanced thermal stability were obtained. Furthermore, the stable and monodisperse PMMA microspheres having a weight-average diameter of
$5.09{\mu}m$ and a good uniformity of 1.01 were obtained with 20 wt% L-VUM. The molecular weight increased, but the size of the PMMA particles decreased with the macromonomer concentration due to the increased stabilizing effect. The molecular weight of the PMMA was approximately two fold higher than that by a conventional PVP. The L-VUM acts as a reactive stabilizer, which gives polyurethane-grafted PS or PMMA with a high molecular weight. In addition, the XPS result showed that the C-PS (PS using the C-VUM) was anchored with a larger amount of PEG than that of the L-PS (PS using the L-VUM) on the particle surface. Thus, the reaction and stabilizing mechanism of the macromonomers for the formation of PS particles is proposed. -
Polyalkylene phosphates - polymers that are built on the repeating unit of the diester of phosphoric acid: -[OP(O)(OH)Oalkylene]-, are known to form backbones of nucleic and teichoic acids. Various synthetic ways will be reported for the synthesis of the bare chains, where "alkylene" in the formula above means mostly two or three methylene groups. Some other structures have also been prepared. Several applications of these polymers are to be discussed, namely as liquid membranes, as components of two-block copolymers (ionic-nonionic diblock dihydrophilic) used as modifiers of CaCO3 crystallization, and as components of the inorganic-polymer hybrid materials. Some other applications in the biomedical field will also be discussed.
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Mesogen-Jacketed Liquid Crystalline Polymers, MJLCPs, are polymers with mesogenic side groups directly attached to main-chains without using flexible connecting spacers and are able to form liquid crystalline structures. Later work on structure-property of the polymers revealed that the side groups are not necessarily mesogenic for the polymers to form a mesophase so long as that the side groups are directly attached to the backbones and the side groups are large enough. Because of its inherent chain stiffness and that the monomers of MJLCPs are readily polymerizable by "living" free radical polymerizations, MJLCP offered a unique handy tool for making block copolymers. In addition, MJLCP offered also new opportunities for novel functional materials.
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The fine-tuned dendrons provide unique supramolecular self-assemblies in various environments such as in water, organic media, and solid-liquid interfaces. They form nanotubes, vesicles, thin films, columns, lamellar nanoribbons depending on the condition of self-assembly process. Unique characteristics of self-assembly of the amide dendrons are described. In addition, elucidation of the structural correlation between the building blocks and the assemblies, stabilization of assembled structure, and transformation of supramolecular assemblies by using external stimuli. Particular emphasis is placed on the formation of cyclodextrin-covered organic nanotubes derived from self-assembly of amide dendrons and their supramolecular transformation. Finally, unique biosensory characteristics of the self-assembled nanotubes will be discussed.
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This lecture will present an overview of recent advances in our transition metal-mediated living radical polymerization, particularly focused on catalyst design and precision synthesis of functional polymers. Selected topics will include: (A) Design of Transition Metal Complexes: Evolution of Catalysts (B) New Ruthenium and Iron Catalysts: Active and Versatile (C) Functional Methacrylates for Advanced Functional Polymers (D) Functional Star Polymers: Microgel Cores for Metal Catalysts.
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Surface modification of clay minerals has become increasingly important for improving the practical applications of clays such as polymeric nanocomposites. We used the copolymer as modifiers having phenyl components, and successfully developed a route for the preparation of amine functionalized polymer based on oligostyrene and its block copolymers. The oligo(St-co-VBC)s with controlled molecular weight were synthesized via nitroxide mediated polymerization method. We also successfully prepared organophilic layered silicates whose surface is covered with styrenic copolymers. Through the analysis of chemical structure and morphology, we concluded that copolymers were very effective organic modifiers to change the surface characteristics of layered silicates.
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After general introduction for hyperbranched polymers, hyperbranched polysiloxysilanes (HBPS) were introduced as new functional polymers. Vinyl terminated HBPS was synthesized starting from AB2 type monomer by hydrosilylation reaction. Vinyl group can be converted various functional groups such as carboxylic acid and alcohol. HBPS had strong interaction to inorganic surface. As an example of this phenomenon, silica gel bead for HPLC was modified with thermo sensitive polymers. The resulting bead was successfully applied to Green Chronatography.
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Orthogonally protected block copolymers of based on p-hydroxystyrene were prepared with high control via nitroxy mediated radical polymerization using an alkoxyamine as an unimolecular initiator. Thin films of partially protected block copolymer were prepared by spin or dip coating. A well defined nanostructure could be observed as a result of phase separation e.g. cylinders in a matrix oriented perpendicular or parallel to the substrate. The nanostructure of the polymeric films can be defined by the block copolymer composition and it determines surface properties and allows further, selective functionalization, e.g. via click chemistry. The thin films can be designed in a way to allow a patterning based on a thermal or photochemical stimulus.
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We have studied the micellisation of poly(n-butyl acrylate)-block-poly(acrylic acid) and poly(n-butyl acrylate)-graft-poly(acrylic acid) in aqueous solution. The size and structure of the formed micelles was elucidated by scattering and imaging techniques. The micelle structure depends on pH, composition, and topology: graft copolymers form much smaller micelles that block copolymers of similar composition. We have also synthesized block copolymers of acrylic acid and N-isopropylacrylamide (NIPAAm) or N,N-diethylacrylamide (DEAAm). Due to the LCST of polyNIPAAm and polyDEAAm, these block copolymers spontaneously form micelles upon heating and they form inverse micelles upon decreasing pH below 4. If the LCST block is much longer than the PAA one, this presents a very convenient way to prepare crew-cut micelles. The polymers have been successfully used as stabilizers in emulsion polymerization. They also have been conjugated to streptavidin. The conjugates reversibly form mesoscopic particles on heating.
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An important challenge in polymer-based advanced materials aimed at the fabrication of individualized functional molecular objects exhibiting specific and well-defined properties. The strategy developed in our group involves the construction of single giant highly branched macromolecules with controlled architecture and topology. Our presentation will be focused on the design of a series of comb copolymers with (a) PS-PI diblock branches, (b) randomly distributed PS and PI branches and janus type PS-comb-b-PI-comb diblocks. Their synthesis and a study of their behavior in solution and in bulk will be described.
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We succeeded the synthesis of new functional polymers by novel ring-opening addition reactions of bis(oxetane)s with diacyl chlorides, di(active ester)s, and di(carboxylic acid)s using quaternary onium salts as catalysts at appropriate conditions. Hyperbranched polyesters with many pendant hydroxy groups were also synthesized by the polyaddition of bis(oxetane)s with tricarboxylic acid, or by the self-polyadditions of
$AB_2\;or\;A_2B$ type monomers containing oxetane group. The anionic ring-opening polymerization of (3-ethyl-3-hydroxymethyl)oxetane was examined using sodium tert-buthoxide to give hyperbranched poly(ether)s containing one oxetanyl group and many hydroxyl groups in the end of polymer chain. -
A series of vinyl monomers and their saturated model compounds containing different chromophores were synthesized. These monomers display strong intra-molecular fluorescence quenching, their fluorescence quantum yields and lifetimes are generally lower than those of their model compounds. It was found that the C=C bonds in these monomers played a key role in the intra-molecular quenching, which was confirmed by intermolecular fluorescence quenching and time-resolved fluorescence studies. On the basis of the intra-molecular quenching, a new fluorescence approach can be developed to monitor the process of the polymerization and curing of bismaleimides, which can directly reflect the C=C bond consumption during polymerization and curing.
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The role of conformational entropy of polymer chains in polymer crystallization is investigated by molecular modeling and theory. The entropy of folded loops dominates at experimentally relevant temperatures to dictate short equilibrium lamellar thicknesses, which are much smaller than the extended chain thickness. Also the entropic barriers control the kinetics of polymer crystallization. These results based on chain entropy are different from the classical views of how polymer chains crystallize.
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Flexible polymers with densely grafted side chains adopt the shape of cylindrical brushes, because the steric repulsion of the side chains overcomes the entropic restoring force of the main chain. Combined light-and neutron scattering measurements elucidate the extend of main chain and side chain stretching as function of side chain length. The application of cylindrical brushes as molecular actuators in response to external stimuli which is discussed.
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Most applications of polymers involve blends and mixtures of components including solvents, surfactants, copolymers, fillers, organic or inorganic functional additives, and various processing aids. These components provide unique properties of polymeric materials even beyond those tailored into the basic chemical structures. In addition, skillful processing extends the properties for even greater applications. The perennial challenge of polymer science is to understand and exploit the structure-processing-property interplay relationship. We are developing and demonstrating combinatorial methods and high throughput analysis as tools to provide this fundamental understanding.
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Yoon, Do-Y.;Lee, Sang-Hun;Jung, Young-Suk;Jo, Jung-Ho;Jeong, Won-Hee;Chang, Jae-Eon;Luning, Jan 112
Detailed surface characteristics of polymer films have been investigated by atomistic molecular dynamics simulations and NEXAFS spectroscopy experiments. The geometric confinement of the surfaces and the necessity to minimize the surface energy lead to the significant molecular organization and orientation in polymer surfaces, with their properties strongly depending upon the atomistic monomer structures. As compared with polymers, oligomeric electronic materials are much more readily aligned by employing various surface anchoring forces, rendering them highly attractive as polarized-light emitting materials and active semiconducting materials in thin film transistors. -
Polymer separations are used to obtain information on molecular distributions (molecular-weight distribution, chemical-composition distribution, functionality-type distribution, etc.). The existing methods, such as size-exclusion chromatography are reliable, but imperfect. New methods and improvements to existing methods are being studied and some of the results will be discussed. In addition, comprehensive two-dimensional liquid chromatography allows the complete characterization of two mutually dependent distributions. LCxSEC chromatograms provide a very good qualitative impression of the distributions, but calibration is not straightforward. Finally, progress in mass spectrometry allows much better information to be obtained.
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We investigated the effects of annealing on the rearrangement of H-bonding structure and its influence on the thermal and rheological properties of
$2^{nd}\;and\;4^{th}$ pseudo-generation aliphatic hyperbranched (HB) polyesters based on 2,2-bis(methylol)propionic acid. During annealing of amorphous HB polyesters, the structure becomes more ordered as a consequence of multiple H-bonds formation between linear sequences. Structure ordering is more pronounced for the lower pseudo-generation HB polyester with low molar mass, low degree of branching and incompletely reacted core hydroxyl groups which greatly increases the possibility for multiple H-bond interactions. -
Increasing the solvent molecular size leads to shrinkage of the polymer chains and increase of the critical overlap concentrations. In addition, the dependency of
$R_{g}$ on polymer concentration under normal solvent conditions and solvent molecular size is in good agreement with scaling laws. When the solvent molecular size approaches the ideal end-to-end distance of the polymer chain, an extra aggregation of polymer chains occurs, and the solvent becomes the so-called medium-sized solvent. When the size of solvent molecules is smaller than the medium size, the polymer chains are swollen or partially swollen. However, when the size of solvent molecules is larger than the medium size, the polymer coils shrink and segregate, enwrapped by the large solvent molecules. -
The characterization method for associating polymer solutions was briefly reviewed. The method has not yet established in comparison with the characterization method for molecularly dispersed polymers in solution. However, two examples of associating polymer systems, living polybutadiene anions and amphiphilic statistical copolymers, were successfully characterized on the basis of suitable model and theory.
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Ree, Moon-Hor;Lee, Byeong-Du;Yoon, Jin-Hwan;Heo, Kyu-Young;Jin, Kyeong-Sik;Jin, Sang-Woo;Kim, Hyun-Chul;Kim, Gha-Hee;Choi, Seung-Chul;Oh, Weon-Tae;Park, Young-Hee;Hwang, Yong-Taek;Kim, Jong-Seong 120
In our study grazing incidence X-ray scattering (GIXS) measurements with synchrotron radiation sources were conducted statically and in-situ for a series of nanoscale thin films prepared from nanoporous dielectrics, block copolymers, brush polymers, and molecular assemblies. All GIXS measurements were performed at the Pohang Accelerator Laboratory. The measured scattering data were analyzed in detail by using newly developed GIXS scattering theory. All GIXS results will be discussed in details with considering the materials chemistry and nanostructure formation process parameters. -
Paralleled with the development of new materials we need to develop methods and techniques to reveal the environmental interaction and impact of the new materials. Small changes in the chemical structure or product formulation may render the product less environmentally adaptable. Degradation products formed from PLLA were identified after aging in different environments and their assimilation in the biotic environment was shown. Green and degradable hydrogels could be designed from renewable hemicelluloses and lactic acid. Hemicelluloses are a renewable and highly interesting raw material source for new green polymers.
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Ionic liquids (ILs) are collecting keen interests as an advanced substituent of electrolyte solution as well as novel solvents. In the present talk, I will introduce some strategies to fix IL structure on polymer chains to prepare polar polymers with low glass transition temperature. Namely, cationic, anionic, and zwitterionic monomers have been prepared, and they have been homopolymerized or copolymerized to prepare polymer electrolytes with different properties. The polymers themselves showed very poor ionic conductivity, but it was improved by suitable spacer between charged site and main chain. Other unique characteristics of functional ILs and new polymerized ionic liquids will also be mentioned.
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We show that thermal rearrangement of glassy polymers below the thermal degradation temperature can create unexpected and large microvoids in the membranes, leading to unexpected high gas permeability with high gas selectivity. These current polymer membranes display unexpected gas permeation-separation performance. There are above the upper-bound for conventional polymer membranes for several gas pairs. In the present study, molecular simulation, BET sorption, positron annihilation lifetime spectroscopy (PALS), and gas separation experiments were performed to characterize the unusual structure-property relationship of these rigid glassy polymer membranes.
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Nafion/basic polymer composite membranes were prepared to reduce the methanol crossover for the application of direct methanol fuel cell. The thermal and mechanical properties increased with increasing basic polymer contents due to the formation of complex via acid/basic interaction. The water uptake, proton conductivity, methanol permeability decreased with increasing basic polymer concentration by reduction of acidity associated with the formation of acid/base complex. The molecular effect on those properties was not considerable.
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Conventional solvent-based polyurethane (PU) is well established for wide applications, such as textile treatments, surface coating, adhesive and so on. Due to the demands of safety, economic, and environmental protection, the solvent-based PU is restricted and has been phasing out and aqueous-based PU is becoming the world market trend, which is an environmental friendly product. The chemical resistance, physical and mechanical properties of aqueous-based PU are still not competible with solvent-based PU. Because of aqueous-based PU is a linear thermoplastic polymer with lower average molecular weight. Their improvements are normally performed by a post-curing reaction or a polymer hybridization to enhance the polymer cross-linking density. Hybridization of PU with aqueous-based epoxy resin or acrylate emulsion and then cured by a curing agent for improving the performance properties and reducing the cost of aqueous-based PU.Furthermore, a special function is added to aqueous-based PU increasing the application value, for examples, flame retardation, polymeric dyes, hydrophilic and etc.
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Real elastomers show the anomalous behavior in the Ii dependence curves of the derivatives of W with respect to Ii at small strains. The limiting values of the derivatives were evaluated by a simple model based on the assumption that W in the large deformations should coincide with that in the linear elasticity theory. The calculated values were in good agreement with the experimental ones for real elastomers.
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Filler loading (fiber or particulate) usually increases the melt viscosity of polymers. In contrast, the addition of these fillers and fibrillation of thermotropic liquid crystalline polymer (LCP) jointly decreased the viscosity of polymer melts to lower than those of pure component polymers, filler-loaded or LCP-blended ones; and even decreased the viscosity with increasing filler loading. Termed as rheological hybrid effect, this phenomenon correlated well with the LCP fibrillation in these ternary systems. Research taking fillers of various shapes and sizes showed that the filler addition promoted the LCP fibrillation, depending upon thermodynamic and dynamic factors involved.
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In contrast to paints, the surface appearance of adhesive materials is of minor importance, because the adhesive is invisible between the two substrates. Therefore, the rheological properties needed to apply an adhesive dispersion by spray coating can be quite different. The influence of three different kinds of thickeners on the spraying behaviour of polyurethane adhesive dispersions was investigated. The associative thickener showed only minor changes, whereas the higher molecular weight soluble thickeners dramatically changed the spraying angle and the amount of overspray. Determination of the elongational viscosity by means of the CaBER rheometer proved to be of limited use for thickened dispersions.
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The shear flow properties have been reported in many cases by manufactures and fabricators. Only this characteristic is sometimes insufficient for the processings to provide a complete picture of the relationship between the processability and the flow behavior when underwent free-surface processes in which the shape and thickness of the extrudate are determined by the rheological properties of the melt, the die dimensions etc. In this paper the methodology of control of elongational flow is discussed in terms of relaxation time control of the polymer melts.
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TPOs based on polypropylene has been dominating materials in hard automotive parts such as in bumper fascia, instrumental panel and door trim panel owing to their variety of advantages compared to engineering plastics and steels for years. Recently as environmental regulations related to recycle have been strengthened, the use of TPOs in soft automotive parts such as instrument panel skin and door trim skin is being required much more.. Therefore, in this study, we' d like to give an overview of soft TPOs and introduce soft TPO materials requirement and preferable materials composition by vacuum thermoforming and powder slush molding, respectively.
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Qiao, Jinliang;Zhang, Xiaohong;Liu, Yiqun;Dong, Weifu;Wang, Qingguo;Gui, Hua;Gao, Jianming;Song, Zhihai;Lai, Jinmei;Huang, Fan 139
Some of novel halogen-free, elastomeric flame retardants for nylon-6 have been developed. It is found that the S-ENP and clay have a synergistic flame retardant effect on nylon-6 resulted from the formation of two barriers on the nanocomposite residue surface at the end of combustion. A novel flame retardant ternary nanocomposite of nylon-6/ENP/nano-Magnesium hydroxide was also fabricated. The new ternary composite has better flame retardancy and thermal stability than the conventional one because nano-MH can disperse much more homogeneous in the new ternary composite than in the conventional one. -
Petrochemicals contain a wide variety of monomers and their derivatives which are used in the production of plastics, fibers and synthetic rubber. Until now, petrochemicals have had a dramatic impact on our food, clothing, shelter and leisure because they are the least expensive, most readily available, and can be processed most easily into the end use products. Petrochemical industry, which is known as one of the typical cycle profitability businesses, is now moving downward. In order to overcome the anticipated loss of profit, petrochemical companies are making an effort to offer a value-added upgrading to conventional products. This lecture will discuss a few of issues on the current status and prospect of petrochemical industry.
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Combinatorial methods are being used increasingly to develop the next generation of polymers, coatings and adhesive formulations. Allied to this approach, a new genre of measurement and characterization methods are emerging. These characterization techniques are required to handle and take measurements from small samples. This has led to a number of uses for this technology which usefully fall between convention test specimen and micro- or nano-scale test methods. A versatile measurement platform will be presented which can offer useful indentation, puncture, compression, adhesion and scratch resistance data for a wide variety of material types and that continues to develop and evolve in capability.
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It is well known that the aromatic polycarbonate of bisphenol A (hereafter BPA polycarbonate) possesses superior transparency, exceptional toughness, high heat resistance and mechanical properties, which allow it to be diversely used for automotive, electrical, electronic, appliance and optical industries. In this paper, polycarbonate is reviewed on not only prospects of technology but market trend from the industrial point of view. It also demonstrates the diverse applications of polycarbonates with respect to its development history.
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Polyamides have been widely used in the various industrial fields on account of their excellent properties. Especially the largest market with more than 40% of the total demand is in automobiles and transportation equipment. In this lecture, we would like to introduce several new functional materials (new polyamide elastomer UBESTA XPA, UBESTA gas pipe system and new polyamide terpolymer TERPALEX) based on polyamides developed by UBE. Here UBESTA is the trademark for UBE's polyamide12.
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TFT-LCD BLU has been remarkably developed for a recent few years as TFT-LCD market is increased. Recently new BLU technologies and components are developed as more aggressively than before since TFT-LCD panel requires higher quality and resolution. Especially Samsung Electronics and LG Philips LCD of Korea are major LCD panel makers and the major optical materials of LCD BLU and panel for Samsung Electronics have been supplied by Samsung Cheil Industries. In this presentation introduction to main components of LCD BLU will be investigated details. Also characteristics and applications of optical polymers such as PMMA, PET etc for LCD display will be included and finally recent trends in optical materials for LCD BLU will be shown briefly.
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Piers Warren E.;Chase Preston A.;Henderson Lee, D.;Sciarone Timo;Collins Scott;Chai, Jianfang;Parvez Masood 150
Perfluoroaryl boranes are widely employed as co-catalysts in olefin polymerization processes. Perfluoroaryl diboranes, possessing borane centers in close proximity, are a subclass of this family of compounds that are in theory capable of chelating neutral and anionic bases. The resulting anions are exceptionally weakly coordinating. We have prepared examples of such compounds and studied their coordination behavior with neutral Lewis bases that have the capability to bridge Lewis acid sites in an effort to delineate the kinetic and thermodynamic factors that influence bonding mode. When protic Lewis bases such as alcohols or water are reacted with diboranes, strong Bronsted acids capable of initiating cationic polymerizations under unusual conditions result. -
Polyolefins show a very healthy growth rate among commodity polymer resins due to their low feedstock prices, recyclable and environmentally friendly characteristics and easily controllable performances. Capacity investment in polyolefin field is now moving from technology region to consumer region and feedstock region. Therefore, key success factors for polyolefin business in the other region such as Korea are cost reduction, development of highly value-added products and new applications and substitution of PVC, PS, PET and other EPs. To add additional value to commodity polyolefin products, high level of platform technology such as catalyst, process and structure-properties relationship is needed. Progress on polyolefin products has been very closely related to catalyst and process technology. According to this trend, SK Corporation has devoted a lot of research effort into development of new value-added polyolefin products based on the proprietary technology platform.
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The development of metal catalysts that can polymerize or copolymerize "polar"
$Ch_2=CHX$ monomers by insertion mechanisms would significantly expand the scope of metal-catalyzed polymerization and enable the synthesis of new materials with enhanced properties. We have studied the reactions of single-site olefin polymerization catalysts with vinyl chloride, acrylonitrile, and vinyl ethers, in order to probe monomer coordination trends, insertion rates and regioselectivity, and the structures and reactivity of metal alkyls that contain functional groups on the alpha and beta positions of the alkyl chain. These studies provide insights to the key issues that underlie the "polar monomer" problem. Copolymerization of olefins and selected vinyl ethers has been achieved. -
Bahuleyan Bijal Kottukkal;Lee Kyoung-Ju;Son Gi-Wan;Choi Jae-Ho;Chandran Deepak;Abraham Sinoj;Ha Chang-Sik;Kim Il 155
The most commercially and academically advanced catalysts of late transition metals are diimine complexes based on Pd(II)/Ni(II) and bis(imino)pyridyl complexes based on Fe(II)/Co(II). It is well known that the former systems yield branched polyethylenes and the latter linear PEs. In this presentation, effect of extremely bulky ligands with electron withdrawing/donating substituents at a remote position from Ni(II) metal center and of using multi-nuclear homo or hetero multi-metal on the ethylene polymerization is to be paged. -
Bazan, Guillermo;Diamanti, Steve;Coffin, Robert;Hotta, Atsushi;Khanna, Vikram;Fredrickson, Glenn;Kramer, Ed 156
Quasi-living polymerization conditions for the copolymerization of ethylene and functionalized norbornenes can be achieved by using an initiator system comprising$[N-(2,6-diisopropylphenyl)-2-(2,6-diisopropylphenylimino)-propanamidato-{\kappa}^2N,O]Ni({\Box}^1-CH_2Ph)(PMe_3)\;and\;Ni(COD)_2$ . It is possible with this polymerization system to obtain block-copolymer and tapered structures. The latter form microdomains similar to those of standard block co-polymers. The mechanism of the reaction will also be discussed. -
The correlation between liquid-liquid phase separation (LLPS) and crystallization at several compositions in statistical copolymer blends of poly (ethylene-co-hexene) (PEH) and poly (ethylene-co-butene) (PEB) has been examined. In this case, the LLPS is coupled with the other ordering process, i.e. crystallization. The overwhelming change in the crystallization kinetics due to the composition fluctuation caused by the spontaneous spinodal LLPS is observed. This coupling mechanism suggests a new mechanism in the nucleation-crystallization process.
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We developed novel catalyst, PHENICS composed of the combination of a cyclopentadienyl group to perform a high catalytic activity and a bulky phenoxy group, which performs the production of high molecular weight polyolefin. The polymerization activity of PHENICS at high temperature is higher than well-known CGC catalyst. PHENICS showed the excellent ability of comonomer incorporation into polymer chain. The obtained copolymer had a high molecular weight. The PHENICS catalyst is also active to the copolymerization of ethylene and several vinyl comonomers such as styrene, norbornen, and conjugated dienes. We will discuss new cocatalysts for PHENICS to improve activity and the ability of molecular weight control.
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Kim, Hyeong-Sun;Kim, Yun-Hi;Jung, Sung-Wook;Yi, Mi-Hye;Pyo, Seung-Moon;No, Yong-Young;Kim, Dong-Yu;Kwon, Soon-Ki 161
New polymeric and oligomeric OTFT materials containing fused aromatics such as anthracene and naphthalene have been designed, synthesized and characterized. The new OTFT materials were prepared by palladium-catalyzed Suzuki cross-coupling reaction. The obtained materials were characterized by various spectroscopic methods such as UV-vis, PL, cyclovoltametry, and XRD. The obtained OTFT materials containing fused aromatics showed high thermal stability above$350^{\circ}C$ In OTFT devices using new materials, high charge carrier mobility and on/off ratio were observed. -
Control over surface induced self-assembly of electronically active pi-conjugated molecules provides great opportunities to fine-tune and optimize their electrical properties in organic electronics. In this study, with the aim of enhancing the electrical performances by promoting surface induced two-dimensional self-assembly in representative pi-conjugated molecules such as poly (3-hexylthiophene) and pentacene, we have controlled the intermolecular interaction at the interface between pi-conjugated molecules and substrate by using self-assembled monolayers functionalized with various groups. We will discuss the dependency of pi-conjugated molecules on the specific properties of the substrate surface and the effect of surface induced self-assembly on electrical performances in organic transistors.
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Polymeric photorefractive materials exhibit two attractive features, the large refractive index modulation (up to the order of
$10^{-2}$ ) and the optical erasabilility of recorded holographic information. These advantages make the organic photorefractive materials to become candidates for optical data processing, e.g., pattern recognition and fingerprint verification. In this work, we demonstrate optically controlled SLMs using photorefractive composite. An incoherent image imposed in Xe-lamp light was converted into a coherent image. -
Kim, Dong-Wook;Ju, Hyun-Kyung;Ahn, Soo-Mi;Yoon, Sung-Cheol;Lim, Jong-Sun;Park, Seung-Ku;Lee, Chang-Jin 165
We prepared nonlinear optical (NLO) polymers possessing thermal and temporal stability, which were based on the polyimides appended with NLO chromophores. NLO chromophores with a terminal hydroxyl group have been synthesized by coupling between aminobenzene or julolidine donor and phenylene bridge, and then subsequent coupling between the resulting product and tricyanofuran acceptor. The chromophores were chemically bonded to the polyimides backbone through Mitsunobu reaction. The NLO polymers showed$160-170^{\circ}C$ of Tgs and were thermally stable up to$200^{\circ}C$ . We obtained optical quality films by spincoating and evaluated their electro-optical properties and temporal stability. -
The photoluminescence (PL) efficiency of
$Ir(ppy)_{3}$ :PVK is lower than$Ir(ppy)_{3}$ :CBP for the whole range of doping concentration and this low PL efficiency can be a reason of the lower efficiency of PhPLED than PhOLED. The lower efficiency is originated from the large bi-excitonic quenching such as the triplet-triplet annihilation. The PhPLEDs showed very short lifetime. The short lifetime was found to be originated from the instability of the doubly reduced$Ir(ppy)_{3^{-2}}$ . The double reduction takes place because of the low electron mobility of PVK and large energy difference of LUMO level between PVK and$Ir(ppy)_{3}$ . -
Photo-/electroactive donor-acceptor (D-A) chromophores were synthesized and investigated for energy- and electron-transfer (ET/eT) properties, for which the chromophores are supramolecularly integrated by encapsulation with helical amylose, rendering the chromophores aggregation-free and rigidified along the helical axis and thus, a remarkably enhanced fluorescence intensity. Fluorescence quenching studies indicated that the helical encapsulation gives the ET/eT a clear D-A distance dependence unlike with the encapsulation-free counterparts, being reflected in their florescence decay profile. Another notable difference is that the helical supramolecule of the chromophores forms a perpendicularly oriented self-assembly. Transport behavior in the solid state will be also discussed.
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Low-operating voltage organic field-effect transistors (OFETs) have been realized with high dielectric constant (
${\kappa}$ ) polymer such as cyanoethylated poly vinyl alcohol (CR-V,${\kappa}=12$ ). Since the$high-{\kappa}$ polymers are likely to contain water and ionic impurities, large hysteresis and considerable leakage current are frequently observed in OFETs. To solve these problems, we cross-linked the CR-V by using a cross-linking agent. Cross-linked CR-V dielectrics showed high dielectric constant of 11.1 and good insulating properties, resulting in a high capacitance ($81nF/cm^{2}$ at 1MHz) at 120 nm of dielectric thickness. Pentacene FETs with cross-linked CR-V dielectrics exhibited high carrier mobility ($0.72\;cm^{2}/Vs$ ), small subthreshold swing (185 mV/dec) and little hysteresis at low-operating voltage (${\Leq}-3V$ ). -
Novel liquid crystalline malonic ester monomers were synthesized from malonyl dichloride and mesogenic alcohols as a photoresponsive group. The monomers were polymerized with aliphatic or aromatic dibromides in the presence of sodium hydride to give 8 kinds of novel poly(malonic esters) with two symmetrical azobenzene groups. We found that the resulting polymer films could be used as rewritable optical data storage (or holographic image) media through a photoisomerization of azobenzene group by Ar laser irradiation. The sensitivity of data recording was dependent not only on the thickness of the polymeric thin film but also on the intensity of laser beam.
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${\pi}-conjugated$ ] organic and polymeric semiconductors are receiving considerable attention because of their suitability as an active layer for electronic devices. An organic inverter with a full swing and a high gain can be obtained through the good qualities of the transfer characteristics of organic thin-film transistors (OTFTs); for example, a low leakage current, a threshold voltage ($V_{th}$ ) close to 0 V, and a low sub-threshold swing. One of the most critical problems with traditional organic inverters is the high operating voltage, which is often greater than 20 V. The high operating voltage may result in not only high power consumption but also device instabilities such as hysteresis and a shift of$V_{th}$ during operation. In this paper, low-voltage and little-hysteresis pentacene OTFTs and inverters in conjunction with PEALD$Al_{2}O_{3}\;and\;ZrO_{2}$ as the gate dielectrics are demonstrated and the relationships between the transfer characteristics of OTFT and the voltage transfer characteristics (VTCs) of inverter are investigated. -
Cho, Gyou-Jin;Song, Jae-Hee;Jung, Min-Hoon;Lee, Bock-Im;Kim, Sun-Hee;Lim, Nam-Soo;Lee, Na-Young 171
In this presentation, we would like to report an inkjet printing method to produce 1 to 2 bit RFID tag working in the range of 6 to 28 MHz with or without transistors. The inkjet printing method especially for the formation of transistors, inductors, capacitors will be presented by the view of polymer chemistry. This presentation also includes the printing schemes for memory cell, ring oscillator, rectifier, antenna, and so forth for constructing RFID tag. I illustrate these strategies by describing recent my works on the formation of all SWNT-TFT and conducting polymer-silver nanocomposite inks that can be applied in the construction of electronic devices. -
Molecular imprinting constitutes a valuable method of preparing polymeric materials with specific binding properties. The most conspicuous merit of molecular imprinting is that structurally three-dimensional recognition sites can be introduced into a polymer matrix with ease and low cost when compared with the complicated process of biological system for antigen and antibody. We used a thermally reversible bond for the preparation of the monomer-template complex, which allowed us to remove the template easily by means of a simple thermal reaction and to simultaneously introduce various functional groups into the cavity. This method is especially propitious for developing artificial receptors for molecules lacking strongly interactive groups.
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We have explored a strategy to control the supramolecular nano-structures self-assembled from rigid segments through attachment of flexible chains through microphase separation and anisotropic arrangement. Supramolecular structures formed by self-assembly of rigid building blocks can be precisely controlled from 1-D layered, 3-D bicontinuous cubic to 2-D cylindrical structures by systematic variation of the type and relative length of the respective blocks. Furthermore, depending on the individual molecular architectures, rigid building blocks self-assemble into a wide range of supramolecular structures such as honeycomb, disk, cylinder, helix, tube, barrel stave, and nano-cage.
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Kwon, Tae-Chang;Kim, Yong-Jung;Kim, Yu-Na;Lee, Hyo-Jin;Rameshbabu Krishnamurthy;Sarwade Bhimrao D.;Kim, Eun-Kyoung 174
By condensing two different functional monomers, highly fluorescent aromatic polymers were prepared to produce a conjugated- conjugated spacer-type copolymer or conjugated-non-conjugated spacer-type copolymer. As synthesized polymers were soluble in an organic solvent and showed significantly enhanced optical properties compared to its monomer. Variation in the monomer composition afforded polymers having multifunctionaility such as photochromic-fluorescent polymers. Transparent thin films of the polymer as a solid medium were prepared using spin coating method and fabricated as a photoswitch, which showed photo-induced conductivity switching properties depending on the core monomeric unit in the polymers. -
Lee, Taek-Seung;Kim, Tae-Hyeon;Kim, Tae-Hoon;Choi, Moon-Soo;Kim, Hyung-Jun;Kwak, Chan-Gyu;Lee, Jung-Hyo;Lee, Chi-Han 175
Considering the number of chemosensors that have been developed for the sensing of metal ions, only a few chemosensors for fluoride anion have been described in the literature that are based on fluorescent or chromogenic responses. We performed colorimetric anion sensing based on the binding of anion analytes with hydrogen donor group in polymer backbone resulting in naked-eye color change and fluorescent quenching. Our challenges using hydrogen donor moiety was designed effectively are continuing in order for high selectivity and sensitivity for ultimate applications such as fluid solution sensing in biomolecules and gas vapor sensing. -
We designed and synthesized new type of nonchemically amplified polymeric and molecular resists and studied their lithographic performance. The polymeric resists [poly(DOBEMA-co-GBLMA)] show very high degree of photobleaching at 248 nm and moderate to good degree of photobleaching at 193 nm. The molecular resist (CDEOPE-POSS) shows high degree of photobleaching at 248 nm and modetate degree of photobleaching at 193 nm. CDEOPE-POSS possesses very high oxygen reactive ion etching resistance, which makes it suitable to be used as a bilayer resist. The lithographic studies of these resist materials suggest the feasibility of these materials to be used as single and bilayer resists.
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Copolymers containing oxime-urethane groups, which led to the formation of pendant amino groups photochemically, were applied to a fluorescent image-recording material through the reaction with fluorescamine, a prefluorescent dye for amino groups. This imaging method permits the fluorescent image to be erased or restored by treatment with base or acid. Copolymers containing phthalimide carbamate groups were applied to a bicolor fluorescent imaging material through the consecutive reaction with fluorescamine and rhodamine. A various colored fluorescent micropattern (green, red or red-yellow) was observed through the changes of excitation wavelength by using a conforcal microscope.
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Chitosan has been investigated as a non-viral vector because it has several advantages such as biocompatibility, biodegradability and low toxicity with high cationic potential. However, low specificity and low transfection efficiency of chitosan as a DNA carrier need to be overcome for clinical trials. In this study, chemical modification for enhancement of cell specificity and transfection efficiency was investigated. Also, the chitosan derivative formulations in vivo were included.
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PLGA/HA composite scaffold fabricated by GF/PL method showed enhanced mechanical property, hydrophilicity and osteoconductivity compared with the SC/PL scaffolds, and this enhancement was most likely due to a higher extent of exposure of HA particles to the scaffold surface. The biodegradable polymer/bioceramic composite scaffolds fabricated by the GF/PL method could enhance bone regeneration efficacy for the treatment of bone defects compared with conventional composite scaffolds.
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A novel preparation method for core/shell nanoparticles with protein drug-loaded lipid core was designed and characterized. The lipid core is composed of lecithin and protein drug and the polymeric shell is composed of Pluronics (poly (ethylene oxide)-poly (propylene oxide)-poly(ethylene oxide) triblock copolymer, F-127 For the application of core/shell nanoparticles as a protein drug carrier, lysozyme and Vascular Endothelial Growth Factor (VEGF) were loaded into the core/shell nanoparticles by electrostatic interaction and the drug release pattern was observed by manipulating the polymeric shell.
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We developed a novel method to fabricate a nerve guide conduit (NGC) with the porosity of submicron pore sizes (to prevent fibrous tissue infiltration) and hydrophilicity (for effective oxygen and nutrient permeation) using poly(lactic-co-glycolic acid) (PLGA) and Pluronic F127 by a modified immersion precipitation method designed by our laboratory. It was recognized that the hydrophilized PLGA/F127 (3 wt%) tube can be a good candidate as a NGC from the analyses of its morphology, mechanical strength, hydrophilicity, model nutrient permeability and in vivo nerve regeneration behavior using a rat model.
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PLLA grafted Hydroxyapatite / polylactide (g-HA/PLA) composites were prepared by three grafting methods. The modified particles (p-HA) were dispersed more uniformly in the PLLA matrix than pure n-HA. The p-HA/PLLA composites exhibited better mechanical properties and thermal stability than the n-HA/PLLA composites. The composites also demonstrated improved cell compatibility due to the good biocompatibility of the HAP nanoparticles and the more uniform distribution of the PLLA-grafted HAP nanoparticles on the film surface. All of these results indicated that the p-HAP/PLLA nano-composites might have a promising medical application in bone repair and in bone tissue-engineering.
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Hyaluronic acid and chitosan-based poly(ethylene oxide) (HA-PEO and Chitosan-PEO) hydrogels have been employed as unique biomedical polymeric materials with properties such as bioactivity from polysaccharide, biocompatibility of HA and chitosan as well as PEO and control release of bioactive molecules from the hydrogel itself. We here examine in situ hydrogels based on hyaluronic acid and chitosan in terms of their synthesis, mechanical properties, morphologies and in vitro cellular interactions on their surface and inside. In vivo bone regeneration of HA-PEO and Chitosan-PEO hydrogels was compared with in mouse model.
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We have succeeded in the preparation of high molecular weight polybenzimidazoles by solution polycondensation of 3,3'-diaminobenzidine tetrahydrochloride with isophthalic acid, terephthalic acid, or with their derivatives using polyphosphoric acid both as solvent and as condensing agent. Also, we modified phosphoric acid into fluoroalkyl-phosphonic acids[F-PA]. The main reasons are as follows, first of all F-PAs are stronger acids than PA and alkylphosphonic acids which should promote proton hopping and transport. In addition, F-PA has weaker adsorption onto Pt which help to prevent electrocatalyst poisoning and promote higher oxygen reduction activity. The ionic conductivity of 85%-H3PO4 doped membranes show
$10^{-2}\;Scm^{-1}\;to\;3{\times}10^{-2}\;Scm^{-1}\;at\;150^{\circ}C$ MEA with 2 %-added electrolyte shows slightly higher cell voltage than the others. -
The performances of proton exchange membrane fuel cell (PEMFC), direct formic acid fuel cell (DFAFC) and direct methanol fuel cell (DMFC) with sulfonated poly(ether sulfone) membrane are reported. Pt/C was coated on the membrane directly to fabricate a MEA for PEMFC operation. A single cell test was carried out using
$H_2/air$ gases as fuel and oxidant. A current density of$730\;mA/cm^2$ at 0.60 V was obtained at$70^{\circ}C$ . Pt-Ru (anode) and Pt (cathode) were coated on the membrane for DMFC operations. It produced$83\;mW/cm^2$ of maximum power density. The sulfonated poly(ether sulfone) membrane was also used for DFAFC operation under several different conditions. It showed good cell performances for several different kinds of polymer electrolyte fuel cell applications. -
We report a new architecture for high efficiency polymer solar cells introducing a new concept of 'optical spacer' with new material. By implementing a novel solution-based titanium oxide (
$TiO_{x}$ ) layer between the active layer and the electron collecting Al electrode, we invented a way to increase${\sim}50\;%$ in power conversion efficiency compared to conventional polymer solar cells. Now the new devices exhibit${\sim}6\;%$ power conversion efficiency, which is the highest value reported to date for a polymer based photovoltaic cell. The$TiO_{x}$ layer increases the efficiency by modifying the spatial distribution of the light intensity inside the device, thereby creating more photogenerated charge carriers in the bulk heterojunction layer. -
A new type solid polymer electrolyte (SPE) composed of poly (vinyl alcohol) (PVA) and lithium trifluoromethanesulfonate (
$LiCF_{3}SO_{3}$ ) was prepared by means of the solution cast technique to observe that Li ion can move by ion hopping decoupled from polymer segmental motion inside of the 'fast cationic transport process'. The highest ion conductivity of the SPEs obtained from ac impedance measurements was$1.42{\times}10^{-3}S/cm$ at room temperature for SPE with 80wt% of salt concentration. Using LSV, we found that the SPEs had good electrochemical stabilities and using FT-IR and AFM, we found the formation of network-like structure. -
We demonstrate two very simple and fast routes to fabricating ordered micro/nanopatterns of polymers over large areas on various substrates using controlled dewetting. The first method is based on utilizing microimprinting to induce the local thickness variation of an initially inverted bilayer which allows the controlled dewetting and partial layer inversion upon subsequent thermal annealing. In the second method, the self assembly of block copolymer was controlled on a chemically micropatterned surface produced by microcontact printing, being combined with its solvent vapor treatment. The kinetically driven, non-lithographical nanopattern structures were easily fabricated over large area by these approaches.
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The self-assembly of supramolecular dendrimers allows the rapid construction of nanosized structures with regularly ordered features that depend on the shape of the molecules and the relative strength of the intra-and intermolecular interactions. Here we report on a dramatic improvement in the degree of control and selectivity in the orientation of fan-shaped supramolecular molecules over a large area, which has been achieved by confined geometries and applied fields. The order and orientation of supramolecular dendrimers can be controlled by surface anchoring in confined geometries. POM, SEM, TEM, AFM and XRD results show that the molecules form the complicated defect-ordering in the microchannels with different feature sizes. We show that these defect domains are strongly influenced by the boundary and feature size of the surfaces. This technique can be used to create a grain size in the plane of the film that is much larger than that which can be achieved using previously reported soft-material based pattering.
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The approach used in present work allows achieving highly exfoliated state of layered silicate s through confinement of the charged nanobeads within the gallery of swollen pristine clay. The latter is principally promoted by ion exchange that involves polar functional groups on the surface of nanobeads and sodium cation in the interlayer gallery of layered silicates. Surface functionality of the nanobeads plays crucial role in establishment of strong interactions with silicate surface, and eventually, dispersion of individual silicate nanoplatelets.
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The structures of the mesophases and their subunits of PS-b-P4VP in a toluene solution were studied by using SAXS, TEM and GIFT methods. The hierarchical structures of PS-b-P4VP, such as the individual micelle, the face-centered cubic (fcc) and body-centered cubic (bcc) structures and the lamellar structure, were identified for the first time. The diameter of the micelle core was
${\sim}80\;%$ of the most extended chain length of the core chain, suggesting that the core chains were quite stretched. The stretched chain in the core caused the core of the micelle to be not homogenous with a higher density at the center than at the outer part. As the concentration level increases, the fcc and both fcc and bcc appear for the packing of the micelles of PS(3.3k)-b-P4VP(4.7K) and PS(12K)-b-P4VP(11.8K), respectively. The lamellar structure was also identified, with a further increase in the concentration for PS(3.3k)-b-P4VP(4.7K). These hierarchical structures were also identified via TEM images. -
Organic/organic and organic/inorganic multilayer films composed of organic polyelectrolytes (PE) and inorganic nanoparticles/platelets were prepared from the layer-by-layer (LbL) deposition using both spinning and dipping. The difference in both LbL methods is quantitatively compared in terms of internal layer ordering and physical properties of the multilayered films. Additionally, we suggest that the patterned multilayer films can be easily prepared by the combination of the spin SA and the lift-off method. Freestanding films were also prepared with the LbL deposition on low energy substrates, which allows the detailed analysis of composition within the films. Other LbL thin films prepared with block copolymer micelles will be discussed.
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Fluorescent dyes were encapsulated in the nanometer-sized diblock copolymer micelles to control the fluorescence resonance energy transfer. Since acceptor molecules and donor molecules were effectively isolated in the independent micelles, the energy transfer between donors and acceptors was suppressed by the site isolation, leading to the simultaneous emission from both donor and acceptor molecules.
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Polymer light-emitting diodes(PLEDs) have great potential application in large area flat panel displays and general lighting so intense academic and industrial research, and impressive scientific and technological progress has been achieved in this field. However, the efficiency and stability of PLEDs till need to be improved in order to fully realize the advantages of low cost and ease of fabrication provided by organic materials. Here, we report our effort to enhance the PLED' s performance in two approaches : 1) Utilizing nano-structured materials such as nano particles, clay, nano porous silica in active layer 2) Modifying the device structure in nano scale to improve not only the device efficiency but also its stability.
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A superior electrophilic substitution reaction medium that is non-toxic, relatively less corrosive, and non-volatile electrophilic substitution reaction to afford high molecular weight linear and hyperbranched polyetherketones (PEK' s) was developed. The system has very strong driving force to give extra ordinary high molecular weight linear and hyperbranched PEK' s. The reaction medium was further extended to prepare various types of copolymers and covalently grafted polymers onto carbon nanotube (CNT) or carbon nanofiber (CNF). By using characteristic hydrophilic nature of the reaction medium, hyperbranched PEK' s could be synthesized from commercially available
$A_3\;+\;B_2$ monomers without network formation via selective solubility of the monomers. -
Among various polymerization methods to graft polymers on the surface of CNTs, Atom Transfer Radical Polymerization (ATRP) has several advantages, such as a wide range of polymerizable monomers and superb control in molecular structure and weights. Several research groups including us have showed that ATRP is an efficient and versatile method to modify the surface of CNTs. Here, two independent approaches for the covalent attachment of polymers based on ATRP graft-from and graft-onto methods will be discussed.
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We have identified sodium benzanilide (Na-BA), sodium diphenyl amine (Na-DPA) and sodium deoxibenzoin (Na-DB) as very efficient initiators for the living anionic polymerization of HIC. It has a slow propagation rate with the additive function of chain end protection, offering in the process a perfect control over MW and MWD. The well-defined amphiphilic coil-rod, coil-rod-coil, and rod-coil-rod block-copolymers of PHIC and P2VP with controlled architecture have been synthesized for the first time with
${\sim}100\;%$ yields. The resulting block copolymers showed lamellar film, donuts, solid and hollow micelles, by simply varying the solvents and the block compositions. -
Microwave-irradiation has become a common heat source in organic chemistry in the last decade. In recent years, polymer chemists also discovered the advances of microwave heating that include fast and efficient heating as well as the homogeneous heat profile and the easy access to pressurized reaction conditions. In this contribution, we report our investigations on the cationic ring-opening polymerization of 2-oxazolines that lead to a tremendous acceleration from several days to several minutes polymerization time. In addition, the optimized microwave-assisted polymerization procedure was applied for the preparation of libraries of diblock and triblock copolymers that were used for the determination of structure-property relationships in poly(2-oxazoline)s.
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Several polynorbornene or poly(norbornene-7-oxide) based functional block copolymers were synthesized by ring opening metathesis polymerization (ROMP) with good molecular weight and polydispersity control. Some representative functional groups in these polymers are a nitrobenzoyl group or ferrocene. These polymers were subjected to various chemical modification reactions to give other block copolymers that contain novel functionality such as amine, diazonium salt, and diazo groups. The resulting polymers were characterized by various techniques such as GPC, NMR, UV-VIS, AFM, and cyclovotammography (CV).
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In this study the glass transition temperature in thin polymer films has been studied. Ellipsometry has been used to measure
$T_{g}$ of thin film as a function of film thickness. Empirical equation has been proposed to fit the measured$T_{g}$ pattern with thickness. Also, a continuous multilayer model was proposed and derived to describe the effect of surface on the observed$T_{g}$ reduction in thin films, and the depth-dependent$T_{g}$ profile was obtained. These results showed that$T_{g}$ at the top surface was much lower than the bulk$T_{g}$ and gradually approached the bulk$T_{g}$ with increasing distance from the edge of the film. The model and equation were modified to apply for the polymer coated on the strongly favorable substrate and the freely standing film. -
With a modern size exclusion chromatography (SEC) column, molecular weight analysis of a polymer sample takes about 10 min. However, it is desirable to reduce the analysis time further, in particular, for high throughput measurements required in combinatorial analyses or 2D-HPLC analyses. We implemented the high temperature SEC for the purpose. By inserting a narrow bore tubing between the column and the detector, a sufficient backpressure can be maintained to prevent the mobile phase from boiling and the effluent is cooled down enough when it reaches the detector. Therefore, a normal SEC detector can be used without any modification. The SEC resolution is greatly improved at the elevated temperature at high flow rate which allows high speed operation.
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In this study, a novel strategy to prepare a crystallized sample of terpolymer containing high content of
${\gamma}-form$ was experimentally sought. By the foaming process, it was possible for the first time to produce a commercial high molar-mass terpolymer being in a high content of${\Box}-form$ . The large amount of nuclei produced during the foaming process by FIC is ascribed to be the reason. It accounts for the structural disorder in the crystallite formation because of excess amount of chains length for the formation of a stable crystallite. -
The interfacial interaction along with microstructure and some properties of the polyimide(PI)/silica or polyimide/silsesquioxane hybrid nanocomposites will be discussed with reviewing recent publications including our own works. Poly(vinyl silsesquioxane) (PVSSQ), aminosilane (APS), and titania can effectively play vital roles to compatibilize the PI/silica hybrid composites by enhancing interfacial interaction or reducing agglomeration of large domains, which helps the formation of nanocomposites for the PI/silica hybrid system.
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Adsorption behaviors of positively charged matrix (PAH) onto negatively charged probe (sulfate PS particle) were investigated using DLS (dynamic light scattering) and FPR (fluorescence photobleaching recovery) as view points of matrix and salt concentration. The system experienced sharp decrease of diffusion (flocculation) at dilute condition while the system underwent gradual decrease of diffusion above semi-dilute concentration. With FPR and viscometry experiments, we revealed the probe behaviors in polyelectrolyte solution were strongly affected by the coil overlap concentration (0.5 g/L PAH concentration).
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Polymer induced turbulent drag reduction achieved by adding minute amounts of high molecular weight DNAs in aqueous solution was investigated using a rotating disk apparatus. The DNAs in this study include
${\lambda}-DNA$ and calf-thymus (CT) DNA. By putting emphasis on effect of CT-DNA concentration, its DR characteristics were compared with that of${\lambda}-DNA$ possessing monodisperse molecular weight characteristics based on both DR efficiency and a mechanical degradation under turbulence. The DNA chains having much higher molecular size than that of${\lambda}-DNA$ are observed to be more susceptible to mechanical degradation in a turbulent flow. This result was verified via electrophoresis. Furthermore, the coil to globule phase transition of DNA was also investigated under a turbulent flow. -
Here, we discuss various thermodynamic factors that affect the design of nanomaterials based on block copolymers. It is well known that the ordering behavior is determined by composition, chain size N, and the ubiquitous Flory. However, the recent discovery of ordering upon heating, immisibility loops, and baroplasticity addresses a clear need for further microscopic interpretation of such. in order to help to design nanomaterials at aimed purposes. Employing a perturbed hard sphere chain model, the molecular factors such as self and cross-interactions, free space distribution, and directional interactions are incorporated in. It is shown that not only typical ordering phenomena, but also the recent observations just mentioned are all described through this unified way.
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Ultra-fine fibers are spun by expensive fiber spinning technology using special spinnerets. Ultra-fine fibrous materials have attracted considerable attentions because of their potential applications as high performance wiping cloths, water absorbent sound proofing materials and moisture transfer sporting good. However, production expense of ultra-fine fibers is 5 to 7 times higher than general textile materials. The objective of this research is to develop cost-effective recycling process to produce multi-functional ultra-fine fibrous material in terms of the development of garnetting and carding machines for ultra-fine fibrous material waste and scrap. The efficiency of sound absorption for the recycled polyester nonwoven increased with decreasing length and thickness of component fibers, which was attributed to the reduction of air permeability. It is expected that high value and cost-effective textile products are developed using ultra-fine fibrous wastes and that sound proofing material and oil absorbent f
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A series of L-LA polymerizations initiated by
$Sn(Oct)_{2}\;([LA]_{0}/[Sn]_{0}=200)$ were carried out in scR22 at$130^{\circ}C$ and 300 bar, where$[LA]_{0}$ is the initial L-lactide concentration and$[Sn]_{0}$ is the initial$Sn(Oct)_{2}$ concentration. The reaction time dependences of monomer conversion and PLLA MW improved. The monomer conversion and PLLA MW increased with increasing reaction time. The effect of temperature on monomer conversion and PLLA MW was investigated in a series of polymerizations conducted at temperatures ranging from 90 to$150^{\circ}C$ and at a constant pressure of 200 bar. In all of these experiments, the ratio of monomer to R22 concentration was held constant at 12.4 wt.-%. Increasing the reaction temperature from 90 to$130^{\circ}C$ resulted in increased monomer conversion from 11.5 to 72.2 %. -
Polyurethane wastes can be depolymerized with glycols and/or amines. The depolymerization products may be recycled for the preparation of various polyurethanes. Caprolactam was employed to depolymerize Spandex fibers and the depolymerization products were evaluated as raw materials for the preparation of polyurethane elastomers. The depolymerization products were homogeneous and could be used to prepare polyurethane elastomers acceptable for various applications as binders.
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High molecular weight of polycarbonate(PC) and well dispersed PC/MMT nanocomposites were successfully prepared through the novel technology, microwave solid-state polymerization. In our studies, the microwave irradiation is more effective than conventional oil-bath heating on achieving the high molecular weight and uniform nanocomposites. Using the polycarbonate prepolymer made it possible to intercalate the short chains into the galleries of MMT more easily. And it was observed that prepared nanocomposites by microwave solid-state polymerization have more uniform dispersion of silicate of MMT into the polymer matrix than by oil heating.
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The huge amounts of wastes were produced nowadays. Among the solid waste stream, the waste plastic portion is about 20 % in weight, over 50 % in volume. But the most of waste plastics were incinerated or land filled. Only a bit of waste plastics were recycled and reused. On the view point of current energy crisis, this will be an extravagance of beneficial resource. So we should consider the waste plastics as a beneficial raw material. Also need to develop the field of reusing and recycling of post-consumed plastic. In this context, present paper describes the methodology for enhancing or improving the specific properties by way of using inorganic filler waste. Also develop the product from these post-consumed plastic.
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The cyclic butylene terephthalte oligomer was synthesized and the composition of butylenes terephthalate cyclic oligomers was 51.2 % of dimer, 28.1 % of trimer, 7.9 % of tetramer, 8 % of pentamer and 4.8% of hexamer. Polybuthylene terephthalate was polymerized using this cyclic oligomer in the condition of melt process and supercritical process. And PBT/clay nanocomposite were manu- factured from melt process and supercritical process. Chlorodifluoro- methane(HCFC-22) was used as a solvent which has critical point (
$Tc=96.2^{\circ}C$ , Pc=49.7bar). Also polymer nanocomposite were manufactured using rapid expansion of supercritical solution process. -
A special group of polymers, those from renewable resources, has attracted an increasing amount of attention over the last two decades, due to two major reasons: environmental concerns and the limitations of our finite petroleum resources. Generally, polymers from renewable resources (PFRR) can be classified into three groups: (1) natural polymers, such as starch, protein and cellulose; (2) synthetic polymers from natural monomers, such as polylactic acid (PLA); and (3) polymers from microbial fermentation, such as polyhydroxybutyrate (PHB). Like many other petroleum based polymers, various properties of PFRR are also vastly improved through blending and composites formation.
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The surface energy control capability of electrohydrodynamic force provides electrospraying with various potential advantages such as simple particle size control, mono-dispersity, high recovery, and mild processing conditions. Herein, the one step nano-encapsulation of protein drugs using electrospraying was developed. The major processing parameters such as the conductivity of spraying liquids, flow rate, the distance between electric potentials, etc were examined to obtain the maximum efficiency. The recovery of particles was found relatively high as could be conjectured based on the principle of electrospraying. When organic solvents were employed, the processing windows of electrospraying were relatively narrow than water systems. Efficient nano-encapsulation of BSA with polymers was conveniently achieved using electrospraying at above 12 kV.
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A number of new ideas have been implemented to control the droplet morphology and electrooptic properties of holographic polymer dispersed liquid crystal (HPDLC). Doping of conductive fullerene particles to the conventional HPDLC induced dual effects of reducing both droplet coalescence and operating voltage. Chain transfer agent gave higher gel content with lower crosslink density, less dark reactions and less grating shrinkage with much smooth LC-polymer interfaces. Addition of octanoic acid (OA) to the formulation of HPDLC gave a decrease in droplet size and monotonic increase of the off state diffraction throughout the OA content.
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This study focuses on the effects of dispersion method of a nanoparticle in a polymer matrix such as melt mixing, solution blending, and in-situ polymerization on the physical properties of the nanocomposites. Introduction of a nanoparticle to a polymer resulted in some unusual physical properties. In some cases the nanoparticle played a role of a nucleating agent, leading to decreasing induction time to crystallization. In addition, the dispersion state of the nanoparticle in the polymer matrix also had a significant influence on the physical properties of the nanocomposites. Hence the method of introducing the nanoparticle to the polymer made contribution to the rheological properties of the nanocomposite systems.
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Rheological and electrical properties of the polycarbonate (PC) / multi-walled carbon nanotube (MWNT) were studied. The MWNT was funtoinalized by treating with the hydrogen peroxide (
$H_{2}O_{2}$ ). The electrical conductivity showed higher value for the PC/MWNT ($H_{2}O_{2}$ treated, freeze drying) composites compared that of the PC/MWNT ($H_{2}O_{2}$ treated, thermal drying) composites. From the results of the morphological, rheological, and electrical properties of the PC/MWNT composites, it is suggested that the electrical and rheological properties of the PC/MWNT composites are affected by the MWNT-MWNT network structure which is related with the MWNT morphologies such as the degree of aggregation and aspect ratio of the MWNT. -
Kim, Seong-Kyun;Park, Sung-Jin;Kim, Hwa-Kyu;Yoon, Seung-Woong;Lee, Jun-Seong;Park, Myung-Hwan;Do, Young-Kyu 221
The stereochemical control in polypropylenes and styrene-ethylene copolymers based on homogeneous single-site polymerization catalysts has received great attention since the stereocpecificity is one of the key factors in tailoring the polymer properties. Thus, we have developed new tactics for isospecificity in propylene polymerization with the unbridged metallocenebased systems and syndiospecific styrene-styrene sequence in styrene-ethylene copolymerization with the group 4 metallocene system. Brief details of the synthesis, structures and the polymerization behavior of a set of new metallocene catalysts will be presented. -
New types of constrained geometry complexes comprising rigid silacycloalkyl group incorporated into the bridging position between cyclopentadienyl and amido functionalities were prepared. The catalytic activities of olefin polymerization were influenced by the change of exo-cyclic ring size on bridge-head silacycloalkyl unit. It has been noted that the activities of this unique series increase with increasing size of the silacycloalkyl bridge and reach the maximum in six-membered silacyclohexyl-bridged CGC complex. It is noteworthy that conformation of silacycloalkanes gives rise to enhanced catalytic activity of the titanium center although the cyclic ring and titanium center are far remoted from each other.
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A Suzuki-coupling route is developed for preparation of ortho-phenylene-bridged Cp/amido complexes, one of which shows higher activity, higher 1-hexene incorporation, and higher molecular weight than the silylene-bridged standard CGC
$[Me_{2}Si({\eta}^{5}-Me_{4}Cp)(N^{t}Bu)]TiCl_{2}$ . -
The Ethylene polymerization behavior of a series of polymethylene bridged dinuclear CGC
$[Zr({\eta}^{5}:{\eta}^{1}-C_{9}H_{5}SiMe_{2}NCMe_{3})Me_{2}]_{2}[(CH_{2})_{n}]\;[_{n}=6(1),\;9(2),\;12(3)]$ in the cocatalytic activation with$Ph_{3}C^{+}B^{-}(C_{6}F_{5})_{4}\;(B_{1})\;or\;Ph_{3}C^{+}(C_{6}F_{5})_{3}B^{-}C_{6}F_{4}B^{-}(C_{6}F_{5})_{3}Ph_{3}C^{+}\;(B_{2})\;or\;B(C_{6}F_{5})_{3}\;(B_{3})$ were investigated to study the nuclearity effects as well as the counteranion effects. The ethylene polymerization and ethylene/1-hexene copolymerization were conducted at$30^{\circ}C$ It was found that both in ethylene polymerization and ethylene/1-hexene copolymerization, activities increased in the order of 1 < 2 < 3, which indicates the presence of longer bridge between two active sites contributes more efficiently to facilitate the polymerization activity. -
Ethylene was polymerized with a catalyst having sterically hindered pentamethylcyclopentadienyl ligand,
$Cp^{\ast}_{2}ZrCl_{2}/MAO$ , and the polymerization mixture were treated with dry oxygen (oxidative workup) to produce hydroxyl-terminated polyethylenes (PE-OH). Polyethylene-block-Poly (${\Box}-caprolactone$ ) was synthesized from PE-OH and${\cdot}\^{A}-caprolactone$ A by using stannous octoate as a catalyst for ring opening polymerization of${\cdot}\^{A}-caprolactone$ . Polyethylene-block-Poly(methyl methacrylate) was obtained by transforming the hydroxyl-terminated polyethylenes to macroinitiators for atom transfer radical polymerization (ATRP) and by reacting them with MMA. -
It was attempted to synthesize polyimides from PPMDA and 3FPPMDA with mDAPPO/pPDA in order to afford CTE of 17ppm and adhesion property of 80g/mm, besides high Tg (>
$300^{\circ}C$ ), good thermal stability (>$500^{\circ}C$ ), low water absorption and good solubility. The polyimides were prepared via a conventional two-step process; preparation of poly(amic-acid), followed by solution imidization by refluxing in NMP with o-DCB and the molar ratio of mDAPPO/pPDA was varied. The polyimides were characterized by FT-IR, NMR, DSC and TGA. In addition, intrinsic viscosity, solubility and coefficient of thermal expansion (CTE) were also measured. -
Leclere, Ph.;Surin, M.;Sonar, P.;Grimsdale, A.C.;Mllen, K.;Cavallini, M.;Biscarini, F.;Lazzaroni, R. 228
Conjugated oligomers, used as models for fluorene-thiophene copolymers, are compared in terms of the microscopic morphology of thin deposits and the optical properties. The AFM images and the solid-state absorption and emission spectra are interpreted in line with the structural data, in terms of the assembly of the conjugated molecules. The compound with a terthiophene central unit and fluorene end-groups shows well-defined monolayer-by-monolayer assembly into micrometer-long strip-like structures, with a crystalline herringbone-type organization within the monolayers. Polarized confocal microscopy indicates a strong orientation of the crystalline domains within the stripes. In contrast, the compound with a terfluorene central unit and thiophene end groups forms no textured aggregates. The difference in behavior between the two compounds most probably originates from their different capability of forming densely-packed assemblies of${\pi-pi}$ interacting molecules. These assemblies are used as active elements in organic field effect transistors designed by using soft lithography technique. -
Recently there has been significant interest in utilizing functional semiconductor polymers for electronic and opto-electronic devices such as Light-emitting diodes, thin film field effect transistors, solar cells, displays, and chemical and biosensors. However, better materials and further understanding of their electronic properties are critical for devices based on these materials. In this work, we use various scanning probe techniques, spectroscopy, and device fabrication to study the molecular interactions, optical and charge transport properties in conjugated polyelectrolytes. Using chemical synthesis approach, we are able to tune the molecular packing and interactions in these materials, which in turn, influence their electronic properties and device performance.
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Density functional theory (DFT) calculations using the B3LYP hybrid functional and the 6-311++G(d,p) basis set have been performed to predict the wavelength dispersion of optical absorbance and refractive indices for organic compounds and polymers in the range between the vacuum UV (
${\sim}157\;nm$ ) and near-IR (${\sim}850\;nm$ ). The DFT calculations can reproduce the experimental dispersions of absorbance and refractive indices with high accuracy and low costs. The calculated dispersions demonstrate that the judicious introductions of$-F\;and\;-CF_{3}$ into alicyclic and heterocyclic compounds are effective in reducing the absorption at shorter wavelengths. In addition, the calculated Abbe numbers that represent the refractive index dispersion in the visble region are linearly proportional to the calculated refractive indices at 589 nm. -
We fabricated a polymer sub-microstructure for optical device application by two-photon-induced laser lithography technique. Polymer pattern could be minimized as small as
${\sim}100\;nm$ . The photopolymerization resin contains laser-dye, thus promising a high level of the optical gain. We utilized the lithography technique to the photonic crystal application, where the template of the two-dimensional photonic crystal was modified by polymer gain medium as defect-shape and line-shape orientations. Photonic band gap effect from polymer-doped photonic crystals is expected to exploit the application such as organic solid-state laser device. -
Intramolecular energy transfer in heteroleptic red phosphorescent dopant materials with mixed ligand units in one molecule was studied. 1-phenylisoquinoline(piq) and phenylpyridine(ppy) moieties were introduced as ligands for Ir based phosphorescent dopants and light emission mechanism was investigated. Intramolecular energy transfer from ppy ligand to piq ligand resulted in pure red emission without any green emission from ppy. Current efficiency of red devices was improved from 4 cd/A to 4.8 cd/A by using mixed ligand structures and deposition temperature of red dopant could be lowered by introducing ppy ligand.
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[
$Y_{2}O_{2}S:Eu$ ], a red phosphor, coated with silica nanoparticles or nanocomposites composed of silica nanoparticles and polymeric materials such as PMMA and PVP was prepared via sol-gel process. Samples were prepared from four different methods coded P1, P2, P3, and P4. P1 includes a conventional sol-gel process and a dip-coating method while P2 has the same procedure with P1 except that nanocomposites containing both silica nanoparticles and polymer prepared by sol-gel process were used as coating materials. In P3 method, phosphors were dispersed in a solution containing silica precursor, i.e., TEOS and then polymerization was performed to coat onto the phosphors surface while P4 followed the same procedure with P3 except that a solution containing both TEOS and organic monomer were used in preparing coating materials. Among various coating methods examined in this study, uniform coating of phosphor could be achieved by using method P4, i.e., phosphor surface coating in a solution containing hydrophobic monomer and TEOS. Furthermore,$Y_{2}O_{2}S:Eu$ red phosphor coated with nanocomposite composed of PMMA matrix and silica nanoparticles exhibited enhanced PL intensity and long-term stability. -
Novel molecular glassy POSS-based material having carbazole moiety as a photo- and electroactive group was synthesized, and its thermal, morphological, electrochemical, and optical properties were investigated. POSS having carbazole (POSS-Cz) was found to form easily amorphous glassy film by cooling the melt sample or by spin coasting onto glass substrate. POSS-Cz showed monomeric emission even in solid film, which suggests that carbazole moiety can be isolated even in solid state.
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Triphenylamine derivatives play important roles as hole transporting materials in organic light emitting devices. However, low molecular weight triphenylamine derivatives show low glass transition temperature and aggregation behavior, and the vapor deposition step of low molecular weight materials is incompatible with large area display fabrication. Conventional polymer PEDOT-PSS HTL has serious drawbacks such as the ITO anode corrosion, poor surface energy match with aromatic EMLs. To solve these problems, we introduced crosslinkable units to triphenylamine-based polymers to make insoluble HTL by thermal curing following spin-coating. Electrochemical and optical properties of the new hole transporting materials were investigated. In addition, the device characteristics obtained with new hole transporting polymers were investigated in details.
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Kang, Ji-Hoon;Shin, Na-Yool;Jo Jung-Ho;Keivanidis Panagiotis E.;Laquai Frederic;Wegner Gerhard;Yoon, Do-Y. 236
Time-resolved photoluminescence spectroscopy measurements of oligofluorenes with various side chains were studied. With extremely pure oligofluorenes, two kinds of red-shifted green emission were observed which have different origins; aggregate formation and on-chain chemical defect. The green emission around 490 nm was largely dependent upon the intermolecular interaction of oliglfuorene molecules. Moreover, by using oligofluorene with high-order liquid crystalline phase, we observed that the green emission was strongly dependent upon the molecular packing in solid films. -
P(VDF/TrFE(72/28) ultrathin films were used in the fabrication of Metal-Ferroelectric polymer-Metal (MFM) single bit device with special emphasis on uniform film surface, faster dipole switching time under applied external field and longer memory retention time. AFM and FTIR-GIRAS were complementary in analyzing surface crystalline morphology and the resultant change in chain orientation with varying thermal history. DC-EFM technique was used to 'write-read-erase' the data on the memory bit in a much faster time than P-E studies. The results obtained from this study will enable us to have a good understanding of the ferroelectric and piezoelectric behavior of P(VDF/TrFE)(72/28) thin films suitable for high density data storage applications.
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Hong, Ki-Pyo;Lee, Jong-Won;Yang, Sang-Yoon;Shin, Kwon-Woo;Jeon, Ha-Young;Kim, Se-Hyun;Park, Chan-Eon 238
Through ultra-violet photoemission spectroscopy in-situ experiment, 0.67 eV energy barrier between 1-hexadecanethiol (HDT)-modified gold and pentacene was observed, which was 0.03 eV smaller than the energy barrier between bare gold and pentacene despite HDT modified gold had 0.8 eV lower work function than that of bare gold. This result is opposed to the idea that increasing the work function a metal decreases the energy barrier. This can be explained by two factors. One is the absence of interface dipole, which is observed in pentacene deposited on gold. The other is reduced ionization energy which can be explained through polarization energy or electronic splitting of molecular orbital with more crystalline structure observed through X-ray diffraction patterns. -
In the present study, we synthesized CBDA-FDA and its analogue, poly(4,4' -(9,9-fluorenyl)diphenylene pyromellitimide) (PMDA-FDA), and then investigated quantitatively the orientational distributions of the polymer chain segments in the surfaces of their films by using linearly polarized Fourier transform infrared (FTIR) spectroscopy and optical retardation analysis. We also examined the films' surface topographies using high spatial resolution atomic force microscopy (AFM). Further, rubbed films were used to assemble antiparallel and
$90^{\circ}-twisted$ nematic (TN) LC cells, and the alignment behaviors, pretilt angles and anchoring energies of the LC molecules in the cells were determined. The films were found to have very interesting surface morphologies and LC alignment behaviors, which have not previously been reported. The observed LC alignments, pretilt angles and anchoring energies are discussed by taking into account the interactions of the LC molecules with the oriented polymer chain segments and the surface morphologies. -
Thin films of poly(vinyl cinnamate) (PVCi) were prepared on indium tin oxide (ITO) glass and silicon substrates by conventional spin coating and subsequent drying process. The thicknesses of the films ranged 50-120 nm. The films' surface was treated by rubbing, ultraviolet exposure or their combinations in various ways with changing rubbing strength and exposure dose. These films were examined in detail in the aspects of surface morphology and chain orientation. Further, the anchoring and orientation behaviors of liquid crystals on the film surfaces were investigated. All the results will be discussed in detail.
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Absolute configuration of carboxylic acids, including amino acids can be determined by circular dichroism (CD) exciton chirality method. This method employs cyclic oligopyrroles able to form stable complexes with carboxylic acids. Addition of carboxylic acids to the oligopyrroles induce CD spectrum at the macrocycle absorption region and in which the sign of the
$1^{st}$ Cotton effect is determined solely by the absolute configuration of the carboxylic acid. The basicity of the pyrrole nitrogen can be controlled by macrocycle substitution thus yielding more sensitive chirality sensors. -
Chiral Mesophase Derived from Achiral Polymers with Banana-Shaped Mesogens and Their Model CompoundsIn this work, we report the synthesis and characterization of azomethineester polymers that consist of banana-shaped mesogen in their backbone. Two parts of the key structure of five-ring bent-core mesogen were modified by connecting different angle of central unit (Ar), and introducing lateral substituent into the outer ring (X). The synthetic details includes (1) placing the dioxydodecamethylene unit as a flexible spacer, (2) possessing 2,3- or 2,7-naphthylene, or 1,2-phenylene connection on the central unit, and (3) introducing fluorine or chlorine substituent (X = F or Cl) into the outer phenylene unit.
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Sumaru, Kimio;Takagi, Toshiyuki;Szilagyi, Andras;Sugiura, Shinji;Kanamori, Toshiyuki;Shinbo, Toshio 244
We developed novel polymer materials composed of thermoresponsive pNIPAAm main chain and photo-resnposive side chains of spirobenzopyran, and analyzed the photoresponsive characteristrics of the aqueous solutions of these copolymers. Further, we prepared various photoresponsive hydrogels composed of the copolymer, and investigated the effect of light irradiation on their properties. As a result, the copolymer exhibited quite unique response to light irradiation and the change in temperature and pH. Especially the drastic photo-induced dehydration was observed in low pH conditions, and photo-induced micro-relief formation was demonstrated using the hydrogel layer composed of the polymer. -
Recent studies of single wall carbon nanotube (SWNT)/polyimide nanocomposites indicate that these materials have a potential to provide the combination of structural integrity and sensing/actuation capability. This study shows the effect of the SWNT type and concentration on the dipole orientation and piezoelectric properties of the electroactive polymide nanocomposites using a thermally stimulated current (TSC) spectroscopy. These nanocomposites exhibit very thermally stable piezoelectric properties up to
$150^{\circ}C$ . This presentation will highlight the dipole orientation and electroactive characteristics of the SWNT/polyimide nanocomposites and discuss their potential multifunctional aerospace applications. -
Ionic Polymer-Metal Composite Actuator with Increased Air-Operating stability by Using Ionic LiquidsIonic polymer-metal composite (IPMC) soaked with various ionic liquids was prepared by using polystyrene sulfonic acid-grafted poly(vinylidene fluoride-co-hexafluoropropylene) as ion-exchange membrane (IEM). The prepared IPMCs were effectively deformed three times larger and actuated for 300 times longer than those of Nafion with water at the same applied conditions. The experimental results indicated than the increase in the bending capability can be caused by the increase in the improved properties of the IEMs and ionic liquids such as uptake content and ionic conductivity. And air-operating stability of the IPMCs is appreciably governed by various physical and electrochemical properties of soaked solvents in IEMs.
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Chemical and physical synthesis routes were combined to prepare macroporous thin films of semiconducting metal-oxides such as
$CaCu_{3}Ti_{4}O_{12}\;and\;TiO_{2}$ by sputtering onto (PMMA) microsphere templated substrates. Subsequently, the colloidal templates were removed by thermal decomposition. The remaining inorganic films comprised a monolayer of hollow hemispheres with diameter commensurate with that of the microspheres. This unique morphology increases the surface area and reduces the interfacial area between film and substrate. Consequently, the surface activity is markedly enhanced while deleterious interfacial effects between film and substrate are significantly reduced. Both effects are highly advantageous for gas sensing applications. -
The notable feature of the Cu(II) coordination polymer investigated here is its ability to self-assemble into a double-stranded helical structure with regular grooves along the helical axis, through the combination of metal-chloride dimeric interactions and repulsive interactions, as an organizing force. It is also remarkable that the double-stranded helices self-organize into a 2-D columnar structure in both the bulk state and aqueous solution. These results represent a unique example that weak metal-ligand bridging interactions can provide a useful strategy to construct stable double-stranded helical nanotubes.
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We have prepared an amphiphilic wedge-coil molecule consisting of a hydrophobic wedge-like segment and a hydrophilic poly(ethylene oxide) (PEO) segment. The wedge-coil block molecule self-assembles into cylindrical nanofibers in both polar as well as nonpolar solvents. Remarkably, the resulting nanofibers, as solvent polarity change from water to n-hexane, change from highly flexible coil-like to stiff rod-like characteristics. This dynamic switching in the stiffness of the nanofibers in response to solvent polarity is attributed to the structural inversion of cylindrical core from bulky dendritic segments with amorphous nature to crystallizable linear PEO segments.
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A real time bio-imaging of HA degradation was successfully carried out using HA-quantum dot conjugates. HA-ADH with ADH content of ca. 70 mol% was synthesized and conjugated with quantum dots containing carboxyl terminal ligands which were activated by the addition of HOBt and EDC in DMSO. When the concentration of HA-ADH solution was higher than 4 wt%, HA-ADH hydrogels incorporating quantum dots could be synthesized in 30 minutes. These novel HA-quantum dot conjugates and the precursor solution of HA hydrogels incorporating quantum dots were injected to the nude mouse and investigated to elucidate the biological roles of HA in the body for various future tissue engineering applications.
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Utilizing the existence of the induction period in photo-polymerization, we propose a new injection method of photo-polymerizable, thermocrosslinking hydrogels made of di-acrylated Pluronic F127 (DA-PF127). This method can solve the problem of fast dissolution of thermal gelation as a scaffold and the disadvantages of the existing injection method that photo-polymerize di-acrylated Pluronic polymer after injection using optical fiber. Injectable gelation of DA-PF127 by the proposed method was demonstrated both in vitro and in vivo. The enhanced stability by this novel photo-polymerization strategy was confirmed by the more sustained release of loaded protein as well as the prolonged degradation time of the hydrogels.
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DNA has not been played the role as a biocatalyst in evolutionary history, although RNA and protein function as a biocatalyst. DNA double helix structure is believed to be impossible to form intricate active enzymatic sites. In addition, the chemical stability of DNA prevents the ability from self-modifying reactions. However, recent development of DNA engineering enables to create artificial enzymatic ability of DNA (deoxyribozyme) such as RNA cleavage and DNA modification. We investigated optimal conditions for enzymatic activity of DNA-Pt complex, and compared it with that of horse radish peroxidase. We report here that base sequence of DNA, pH and temperature affect the enzymatic activity of DNA-Pt complex.
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The sensitivity of plasmid DNA (pDNA) to S1 nuclease, an enzyme to cleave a single-strand DNA, was dramatically modulated through a supramolecular assembly (polyion complex micelle) with a synthetic block copolymer, poly(ethylene glycol)-b-poly(L-lysine) (PEG-PLL). The pDNA condensed in stoichiometric charge ratio was cleaved into 7 fragments each being 10/12, 9/12, 8/12, 6/12, 4/12, 3/12, and 2/12 of the original DNA length, on the other hand, the pDNA condensed in higher charge ratios (>4), were digested into non-specific manner. Condensation of the pDNA was investigated from two viewpoints that how does the rigid DNA molecules fold and condense and how does the condensation influence their biological activity.
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Remant Bahadur K.C.;Bhattarai Shanta Raj;Aryal Santosh;Khil, Myung-Seob;Kim, Hak-Yong;Lee, Douk-Rae 255
Polymeric nanoparticles are recognized as promising drug carriers [1]. Here, novel tri-block copolymers based on poly PPDO, PCL and PEG were synthesized and employed for the formulation of reproducible polymeric nanoparticles [2]. To estimate the feasibility of the polymer to form polymeric nanoparticles, nanoparticles were prepared by co-solvent evaporation technique. Polymerization and structural features of the polymer were analyzed by different physico-chemical techniques. Existence of hydrophobic domains as a core of nanoparticles was characterized by$^{1}H-NMR$ spectroscopy, and further confirmed by fluorescence technique using pyrene as probe. -
Production and properties of cross-linked recombinant pro-resilin: an insect rubber-like biomaterialThe design and synthesis of novel biomolecular materials, based on mimicking the properties of molecules found in nature, is providing materials with unusual properties. Resilin serves as an energy storage material in insects and facilitates flight, jumping (in fleas, froghoppers etc) and sound production (cicadas, etc). Resilin is initially produced as a soluble protein and in its mature form is crosslinked through formation of dityrosine units into a very large insoluble polymer. In the present study, we have synthesized a recombinant form of resilin that can be photochemically cross-linked into a resilient, rubber-like biomaterial that may be suitable for spinal disc implants. This material is almost perfectly elastic and its fatigue lifetime in insects must be >500 million cycles.
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We chose three synthetic polymers, poly(propylene carbonate) (PPC), poly(vinylidene fluoride-co-hexafluoropropylene) (PVFHFP), and
$Nafion^{(R)}$ that reveal different chemical and physical characteristics, and investigate their biocompatibilities to five different bacteria (that are most notorious for opportunistic and iatrogenic infections) and a human cell (HEp-2). The bacteria chosen in this study found to adhere onto the PPC and Nafion films but not to adhere on the PVFHFP film. On the other hand, both PVFHFP and Nafion films revealed good compatibility to HEp-2 and allowed the growth of the HEp-2 on the film surface but PPC showed poor compatibility to HEp-2. All results will be discussed with taking into account the surface characteristics of the polymers. -
Electrospun fibers of poly(vinyl alcohol) (PVA) were successfully prepared and applied as drug carriers for transdermal drug delivery system. Sodium Salicylate (SS) was the model drug and it was incorporated in the PVA fibers by adding 20 % of SS in a PVA solution prior to electrospinning. Electrospinning of SS-containing PVA solution resulted in the formation of beaded fibers. In order to control the rate of SS release and decrease water solubility of PVA, the SS-loaded electrospun PVA mat was cross-linked by either glutaraldehyde or glyoxal vapor. The morphology, thermal behavior, swelling behavior, release characteristic, kinetics of drug release and also toxicity of the cross-linked sample were investigated.
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PAU is the block copolymer consists of a small amount of a small amount of poly(
${\gamma}-methyl-L-glutamate$ ) (PMLG) and the polyurethane. The urethane segments are hydrophobic and then strongly interact with the other hydrophobic materials such as PTFE, and the PMLG segments with the${\alpha}-helix$ structure possess the cytocompatibility. Therefore, PAU can be easily coated onto the PTFE fiber and acts as an artificial extracellular matrix with the high cytocompatibility Results shows, the immobilization, cultured and functions of porcine hepatocytes is greatly improved. -
Sericin was modified by solution blending (10-30 wt%) with 70-90 wt% polyacrylamide (PAM) in water. The reactive sites of sericin such as serine and tyrosine were attached to PAM. Proton Nuclear Magnetic Resonance (
$^{1}H-NMR$ ) and thermogravimetric analysis were used to characterize the modified sericin. The electrospinning conditions i.e. the blend composition and the power supply voltage, at a tip to target distance of 15 cm were studied. The morphology of nanoparticles and nanofibers was observed by scanning electron microscopy. The average particles size of the nanoparticle obtained was 191 nm and nanofibers was 150-300 nm. -
Membranes are a central feature of all biological systems and their ability to control many cellular processes is critically important. As a result, a better understanding of how molecules bind to biological membranes is an active area of research. In this report, the interaction between our biomimetic structures and different biological membranes is reported using both model vesicle and in vitro bacterial cell experiments. These results show that lipid composition is more important for selectivity than overall net charge. An effort is made to connect model vesicle studies with in vitro data and naturally occurring lipid compositions.
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Biodegradable and amphiphilic di-block and tri-block copolymers, prepared with monomethoxy poly ethylene glycol (MPEG) and
${\varepsilon}-caprolactone\;({\varepsilon}-CL)$ , were used for the application of W1/O/W2 multi- emulsion capsules. The effects of topology and the ratio of hydrophilic moiety of PCL-based polymers on the encapsulation efficiency of the$W_{1}/O/W_{2}$ multi-emulsion capsules containing Ascorbic Acid-2-Glucoside (AA-2-G) were investigated. The ratio of PEG and PCL was 1:0.5, 1:0.75, 1:1, and 1:1.25. PEG-PCL block copolymers were added to the first step of the preparation of$W_{1}/O$ emulsions. The dispersion stability, the particle size, the morphology of the$W_{1}/O/W_{2}$ multi-emulsion capsules were observed using an on-line turbidity meter, dynamic light scattering (DLS), a confocal microscopy (with FITC) and an optical microscopy. Biodegradable behavior of the PEG-PCL block copolymers and release behavior of AA-2-G were also observed by Gel Permeation Chromatography (GPC) and High Performance Liquid Chromatography (HPLC). -
Poly (ethylene glycol)(PEG) - Poly (
${\varepsilon}-caprolactone(CL)$ ) - Poly (D,L lactide(LA) (PCLA-PEG-PCLA) was synthesized by ring-opening polymerization to form temperature sensitive hydrogel triblock copolymer. The triblock copolymer was acrylated by acryloyl chloride.${\beta}-amino$ ester was used as a pH sensitive moiety, in this study${\beta}$ - amino ester obtained from 1,4-butandiol diacrylate, and 4, 4' trimethylene dipiperidine, it have pKb around 6.6. pH/temperature sensitive penta-block copolymer (PAE-PCL-PEG-PCL-PAE) was synthesized by addition polymerization from acrylated triblock copolymer, 1,4-butandiol diacrylate, and 4, 4' trimethylene dipiperidine. Their physicochemical properties of triblock and penta-block copolymers were characterized by$^1H-NMR$ spectroscopy and gel permeation spectroscopy. Sol-gel phase transition behavior of PAE-PCL-PEG-PCL-PAE block copolymers were investigated by remains stable method. Aqueous media of the penta-block copolymer (at 20 wt%) changed from a sol phase at pH 6.4 and$10^{\circ}C$ to a gel phase at pH 7.4 and$37^{\circ}C$ . The sol-gel transition properties of these block copolymers are influenced by the hydrophobic/hydrophilic balance of the copolymers, block length, hydrophobicity, stereo-regularity of the hydrophobic of the block copolymer, and the ionization of the pH function groups in the copolymer depended on the changing of environmental pH, respectively. The degradation and the stabilization at pH 7.4 and$37^{\circ}C$ , and the stabilization at pH 6.4 and$10^{\circ}C,\;5^{\circ}C,\;0^{\circ}C$ , of the gel were determined. The results of toxicity experiment show that the penta block copolymer can be used for injection drug delivery system. The sol?gel transition of this block copolymer also study by in vitro test ($200{\mu}l$ aqueous solution at 20wt% polymer was injected to mouse). Insulin loading and releasing by in vitro test was investigated, the results showed that insulin can loading easily into polymer matrix and release time is around 14-16days. The PAE-PCL-PEG-PCL-PAE can be used as biomaterial for drug, protein, gene loading and delivery. -
The nanoparticle-hydrogel complex as a new bone defect replacement matrix, which is composed of the nanoparticles for the sustained release of BMP and the hydrogel for filling the bone defect site and playing a role as a matrix where new bone can grow, is presented. In vivo evaluation of bone formation was characterized by soft X-ray, MT staining, and calcium assay, based on the rat calvarial critical size defect model. The effective bone regeneration was achieved by the BMP-2 loaded nanoparticles in fibrin gel, compare to bare fibrin gel, the nanoparticle-fibrin gel complex without BMP-2, or the BMP-2 in fibrin gel, in terms of the new bone area and the gray level in X-ray, the bone marrow are, and the calcium content in the initial defect site. These findings suggest that the BMP-2 loaded nanoparticle-fibrin gel complex can a promising candidate for a new bone defect replacement matrix.
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Supramolecular assembly of peptide molecules for applications in biological multivalent interactionsLim, Yong-Beom;Park, So-Mi;Lee, Eun-Ji;Jeong, Hae-Mi;Ryu, Ja-Hyoung;Yang, Won-Young;Lee, Myong-Soo 265
Multivalent interactions, which are characterized by the simultaneous binding of multiple ligands on multiple receptors, are prevalent in biological system. We have shown that it is able to make a supramolecular aggregate coated with multiple functional molecules fairly easily by simply mixing one building block. In this particular example, a mannose-coated object was able to agglutinate bacterial cells with cognate binding partners through multivalent interactions. This kind of strategy can be applied in developing materials that can selectively remove pathogens. Supramolecular assembly of this type should be very useful in exploring multivalent biological interactions. -
The cell spheroid (multicellular mass) is enhanced cell functions because of the cell-cell interaction compared with the individual cell. The objective of this study is synthesis, characterization and evaluation of novel crosslinkers to form spheroid in a short time. Our approach to bridge cells is based on the crosslinking of the cell membrane via the hydrophobic interaction. The crosslinker was prepared by the reaction between ethylenediamine and poly(ethylene glycol) (PEG) derivative with oleyl group as hydrophobic group at the terminal group. The product was characterized with gel permeation chromatography (GPC) and FT-IR. Furthermore, cell culture experiment was also performed to confirm spheroid formation. The function of prepared spheroids was evaluated.
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Human umbilical cord blood was stored at
$4^{\circ}C$ in the Pluronic-immobilized flask as well as commercially available bio-inert flasks, and flow cytometric analysis of surface markers was performed on hematopoietic stem cells after cultivation. The number of cells expressing$CD34^{+}$ in umbilical cord blood on the Pluronic-immobilized flask was extremely higher than those obtained using other flasks. It is concluded that the flexible and hydrophilic segments of Pluronic conjugated on the flask surface are the reason for the effective preservation of hematopoietic stem cells in the Pluronic-immobilized flask. -
Due to their multipotency, stem cells can differentiate into a variety of specialized cell types, such as chondrocytes, osteoblasts, myoblasts, and nerve cells. As an alternative to mature tissue cells, stem cells are of importance in tissue engineering and regenerative medicine. Since interactions between scaffold and cells play an important role in the tissue development in vitro, synthetic oligopeptides have been immobilized onto polymeric scaffolds to improve specific cell attachment and even to stimulate cell differentiation. In this study, chondrogenic differentiation of stem cells was evaluated using surface-modified PLLA scaffolds, i.e., either hydrophilic acrylic acid (AA)-grafted PLLA or RGD-immobilized one. Porous PLLA scaffolds were prepared using a gas foaming method, followed by plasma treatment and subsequent grafting of AA to introduce a hydrophilicity (PLLA-PAA). This was further processed to fix RGD peptide to make an RGD-immobilized scaffold (PLLA-PAA-RGD). Stem cells were seeded at
$1{\times}10^{6}$ cells per scaffold and the cell-PLLA constructs were cultured for up to 4 weeks in the chondrogenic medium. Using these surface-modified scaffolds, adhesion, proliferation, and chondrogenic differentiation of stem cells were evaluated. The surface of PLLA scaffolds turned hydrophilic (water contact angle, 45 degrees) with both plasma treatment and AA grafting. The hydrophilicity of RGD-immobilized surface was not significantly altered. Cell proliferation rate on the either PLLA-PAA or PLLA-PAA-RGD surface was obviously improved, especially with the RGD-immobilized one as compared to the control PLLA one. Chondrogenic differentiation was clearly identified with Safranin O staining of GAG in the AA- or RGD-grafted PLLA substrates. This study demonstrated that modified polymer surfaces may provide better environment for chondrogenesis of stem cells. -
The molecular structure of poly(2,6-dimethyl-4,4' -phenylene oxide)-g-poly (styrenesulfonic acid) (PPO-g-PSSA) graft copolymer was designed, and synthesized via living radical polymerization. Obtained graft copolymers were transformed into proton exchange membranes for direct methanol fuel cell (DMFC) application. The performance of the membranes was measured in terms of water uptake, proton conductivity, methanol permeability, and thermal stability. Very low methanol permeability and good proton conductivity were observed by adjusting grafting frequency and PSSA block content.
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We have prepared polymer electrolyte membranes (PEMs) for DMFC from polymer mixture of poly(vinyl alcohol) and poly(vinyl alcohol-co-2-acrylamido-2-methylpropane sulfonic acid) (AP-2) changing the AP-2 content. The proton conductivity(
${\Box}$ ) and methanol permeability(P) of the PEMs increase with increasing AP-2 content because the water content of the PEMs increases with increasing AP-2 content. The proton permselectivity of the PEMs, which is defined as${\Box}={\Box}/P$ , indicates higher values than that of$Nafion{(R)}$ 117. -
The present article describes a novel method of preparing the sulfonated polysulfone-based PEMs for DMFC, which are excellent in film quality, proton conductivity, methanol impermeability and mechanical properties. No depression in film quality or difficulty in film preparation is observed, even though sulfonated group of the PEMs are kept as high as 70 mol %. Allyl-terminated cooligo-PESs containing the organic sulfonate groups were solvent-cast into films and then thermally treated for cross-linking. Cross-linked sulfonated polysulfone-based PEMs gave unprecedented reduction of methanol cross-over and high ionic conductivity through in-situ thermal polymerization and cross-linking of telechelic sulfonated sulfone oligomers during a membrane preparation.
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In recent years, water-free polymer electrolyte membranes are attracting serious attention due to the possibility of the fuel cell operation at intermediate temperatures (
$100{\sim}200^{\circ}C$ ). It was reported that phosphonic acids have proton conductivity under anhydrous conditions and in particular, relatively high proton conductivity could be obtained from the composite materials with heterocycles such as imidazole, pyrazole, etc. In this work, styrene based polymers, poly((4-vinylbenzyloxy)alkylphosphonic acid), which have phophonic acid group at the end of alkyl chain was synthesized. These polymers were analyzed in terms of thermal stability and proton conductivity. Additionally, cyclic oligosiloxanes tethered with triazole were prepared and analyzed. -
The encapsulation of volatile organic electrolytes is a major challenge in practical applications of the DSSC. Ionic liquid (IL) within polymer electrolytes is an attractive candidate for replacement. Here we used a low viscosity ionic liquid 1-ethyl 3-methylimidazolium thiocyanate in order to modify ionic conductivity (
${\sigma}$ ) of polymer electrolyte ($PEO:Kl/l_{2}$ ) and hence DSSC efficiency. The doping of IL enhanced${\sigma}$ and attained maximum (${\sigma}=7.62{\times}10^{-4}S/cm$ ) at 80 wt% of IL concentration. Beyond this it was harder to get stable films. XRD confirmed that the intensity of the sharp PEO crystalline peaks decreased when IL was added. The DSC studies confirmed the reduction in crystallinity by adding ionic liquid.The efficiency of solar cell using aforesaid material was 0.6 % at 1 sun irradiation. -
Recently, conjugated polymer solar cells have attracted a great deal of attention. In this work, we applied the various scanning probe techniques to characterize composite materials typically used to fabricate polymer solar cells: poly-3(hexylthiophene) (P3HT) and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) and P3HT/PCBM/Au nanoparticle (NP) samples. The latter is studied due to the idea of using the gold NP surface plasmon to enhance the optical absorption of the composite films. AFM is used to characterize the film morphology whereas conducting AFM is used to study the charge transport properties at the nanoscale. We found that there is a direct correlation between the nanoscale charge transport measurements and the device efficiencies.
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A series of organoboron polymer electrolytes were prepared and their ion conductive characteristics was investigated in detail. Alkylborane type polymer electrolytes prepared by hydroboration polymerization exhibited improve lithium transference number due to efficient anion trapping of alkylborane unit. A lithium borate type polymer/salt hybrid was also successfully prepared by dehydrocoupling polymerization of lithium mesitylhydrorate. Ionic conductivity of single ion conductive polymer/salt hybrid was further improved in the case of comb like polymer/boron stabilized imido anion hybrid prepared via polymer reaction of poly(organoboron halide) with hexylamine and PEO monomethylether and subsequent neutralization with lithium hydride.
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The incorporation of room temperature ionic liquids (IL) in poly (ethyleneoxide)-lithium salt (PEO-LiX) based solid polymer electrolytes is presently being studied as an effective means of enhancing the room temperature ionic conductivity of these electrolytes to acceptable levels for use in lithium batteries. In the present study,
$PEO_{20}-LiTFSI$ solid polymer electrolyte was blended with three different ionic liquids, namely 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide (BMIMTFSI), 1-butyl-3-methylimidazolium tetraflouroborate (BMIMBF4) and 1-butyl-3-methylimidazolium trifluromethanesulfonate ($BMIMCF_{3}SO_{3}$ ). The incorporation of all these ILs resulted in the enhancement of ionic conductivity, the effect being more pronounced at lower temperatures. Electrochemical properties of the blended electrolytes were studied by cyclic voltammetry, linear sweep voltammetry and interfacial resistance measurements. The optimum results were obtained with the blending of BMIMTFSI in the solid polymer electrolyte. -
Conducting polymers (e.g. poly[2-methoxy-5-(2'-ethyl-hexyloxy)-1,4-phenylen vinylene] (MEH-PPV)) confined in one-dimensional nanoscale channels of mesoporous materials, are expected to lead the novel applications for electroconductive and optoelectronic devices. We investigated the adsorption behavior of MEH-PPV on organically surface-modified mesoporous silica (FSM-16) and mesoporous organosilica. The amount of the confined MEH-PPV was found to strongly depend on the surface modifications of the mesoporous materials. The optical absorption edge of the confined MHE-PPV was clearly blue-shifted when compared to that of a free MHE-PPV.
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Polymer architectures containing metal-ligands in their side chain represent a diverse approach to generating multi-functional materials. The ability to define a versatile synthetic platform will enable many chemistries and architectures to be studied. This report describes our latest efforts to prepare these unique polymers; random and block copolymers have been successfully prepared. Subsequent functionalization with metal ions leads to a variety of properties including metal induced gelation, solvochromic and metal ion sensors, and unique hierarchical self-assembled structures.
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Matsui, Jun;Yamamoto, Kohei;Inokuma, Nobuhiro;Orikasa, Hironori;Kyotani, Takashi;Miyashita, Tokuji 279
We report a fabrication of carbon nanotube (CNT) monolayer thin film using liquid-liquid interface. The multiwalled carbon nanotube (MWCNT), which were synthesized by the alumina template method formed a monolayer at the liquid-liquid interface after sonicating the MWCNT water-oil dispersion. Moreover, with the addition of ethanol, the MWCNT monlayer was also formed at the liquid-liquid interface. The monolayer is transferable onto solid substrates and the transferred film was observed using atomic force microscopy (AFM) -
Na-bentonite (local clay mineral) and Na-montmorillonite were treated with quaternary alkylammonium cations. The effect of the molecular structure and functional groups of the surfactants on the organoclays was investigated by X-ray diffraction (XRD). For the preparation of nanocomposites, organoclays were melt-blended with polypropylene in a twin screw extruder and
$Surlyn^{(R)$ . ionomer was used as a reactive compatibilizer. The clay dispersions in the composites were investigated by X-ray diffraction (XRD). XRD spectra showed no peak at low angle indicated that the silicate clay layer has a nearly exfoliated dispersion in the polymer matrix. Thermal and mechanical properties of nanocomposites were higher than those of PP. -
In this study, the polyurethane which has versatile applications has been reinforced with the natural clay, hectorite. The hectorite has better properties than montmorillonite. There are studies on polyurethane and montmorillonite but polyurethane and hectorite composite is published first time. Polyurethane is industrial polyurethane which makes the study to be applicable to the industry. Exfoliated structure has been obtained without using organic modifiers due to the hydrophilic nature of the polymer matrix and the mineral clay. Mechanical properties have been improved as well.
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Nanoporous organosilicate thin films were realized by the microphase separation of pore generating components mixed with an organosilicate matrix. The refractive index of such nanoporous organosilicate films can be tuned in the range of
$1.40{\sim}1.22$ . With a nanoporous single layer with n${\sim}1.225,\;99.85\;%$ transmittance in the visible range was achieved. In order to overcome the limitation on the narrow wavelength for high transmittance imposed by single nanoporous thin films, bilayer thin films with different reflectance for each layer were prepared by inserting high refractive index layer with a refractive index of 1.447. It is demonstrated that the novel broadband antireflection coating with improved transmittance can be easily achieved by the nanoporous bilayer thin films described in present study. -
Multigram-scale product exclusively containing magnetic carbon nanoparticles (MNCPs) with uniform size was successfully fabricated without a specific separation process. The iron-doped PPy nanoparticles were synthesized by micelle templating and used as the carbon precursor in order to generate MCNPs. The magnetic carbon nanoparticles possessed a microporous structure and exhibited ferromagnetic properties at room temperature. This approach may be an effective alternative to generate magnetic carbon nanoparticles against the conventional arc-discharge technique.
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Electrospray deposited films of poly(vinylidene fluoride) were prepared with various conditions. A model has been developed, which provides the state of the electrosprayed droplet at impact. With a combination of the experimental films and the model calculations, it can be shown that growth rate, the increase of the sprayed solution on the substrate per second, defines the film morphology in electrospray deposition. Growth rate indicates which factors play the main role in the film formation process. The most important factors are liquid flow, surface tension and shear rate. The model can calculate the shear rate and it is shown that PVDF, and most likely polymers in general, has a large range of growth rates, where the morphology only depends on the shear rate of the depositing droplet. This method can also be used to describe electrospray deposition of other compounds.
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The ionic layer-by-layer (LBL) assembled films can be formed by sequentially dipping of substrates to oppositely charged polyions solution in the multilayer, called polyelectrolytes multilayer (PEM) films. Easy way of these assemblies of charged polymers offer the ability to adjust important parameters such as controllability of thickness in the nanometer-scale level and functionality of most top layer of PEM films. Nevertheless, we do not know of any trials to fabricate PEM organic films into nanometer size. Herein, we show the integration of the LBL technique with DPN in fabricating nanometer size patterns of multilayered polyelectrolyte structures. Through the use of single and multiple cantilever AFM probes, we demonstrate the parallel writing capabilities of DPN.
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We report on a fascinating morphology; giant spherical conducting polythiophene by the in-situ gamma radiation-induced chemical polymerization method. The resultant micron-size buckyball-shaped polymer structures were identified by high resolution transmission electron microscopy and scanning electron microscopy. Different characterizations e.g. Fourier transform infrared, x-ray diffraction, and x-ray photoelectron microscopy were utilized to prove that the new morphological conducting polythiophene was synthesized successfully by this novel method.
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Amphiphilic random copolymers can form various types of micelles in aqueous media depending on the balance between two opposite interactions- electrostatic repulsion and hydrophobic attraction. This balance can change by addition of some organic solvent to the aqueous solution, and as a result, we can control the micellar structure and micellization equilibrium by changing the solvent content. In the present study, we have investigated the micellization equilibrium of an amphiphilic statistical copolymer consisting of sodium 2-(acrylamido)-2- methylpropanesulfonate and hexyl methacrylate in mixtures of water and methanol by sedimentation equilibrium and fluorescence.
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Natural rubbers (NR) reinforced by multi-wall carbon nanotubes (MWCNT) was found to show extraordinary improvement of mechanical property. We speculated that this was owing to the interfacial phase that surrounded CNT and investigated about the phase by atomic force microscopy (AFM). Using force modulation mode and force-distance curve analyses, we succeeded in obtaining the information of its nanometer-scale rheological property. We found that was actually surrounded by the interfacial phase, that had softer modulus than NR matrix.
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The carboxylated MWNTs were successfully prepared by conventional acid treatment, and their structures were confirmed by FT-IR, Raman and TEM analysis. The water-dispersibility of the surface modified WNTs were good. The COOH-MWNT will show better stability during the emulsion polymerization as compared with Pristine MWNT. In-situ emulsion polymerizations of methyl methacrylate N(MMA) and n-butyl acrylate (BA) were carried out. Aggregate size and dispersion stability of the CNTs in water phase were measured using dynamic light scattering, turbidity, UV-visible spectrophotometer, and electron microscope. In addition, thermo-mechanical properties of MWNT/polymer nanocomposites were investigated.
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Effect of Calcium Carbonate Nanoparticle on the Toughening Mechanisms of Polypropylene NanocompositeThe toughening mechanisms of polypropylene (PP) containing 9.2 vol % of calcium carbonate (
$CaCO_{3}$ ) nanoparticles were investigated using optical microscopy and transmission electron microscopy. Double-notch four-point bending (DN-4PB) Charpy impact specimens were utilized to study the fracture mechanism(s) responsible for the observed toughening effect. A detailed investigation reveals that the$CaCO_{3}$ nanoparticles act as stress concentrators to initiate massive crazes, followed by shear banding in PP matrix. These toughening mechanisms are responsible for the observed improved impact strength. -
Two different sources of clay, Na-Bentonite (Thai local clay) and Na-Montmorillonite were modified with Hexadodeccyltrimethyl ammonium bromide. The nanocomposites of polypropylene were successfully prepared via melt blending in a co-rotating twin screw extruder by using PP-g-MA as a compatibilizer at various contents of organoclays. The morphology of nanocomposites was investigated by using XRD and SEM. The results showed that the intercalated and exfoliated structures were obtained. The thermal behavior was also studied by using DSC and TGA. The degradation temperature of filled PP was greater than that of unfilled PP by 20%. And, the tensile strength and modulus were improved when a small amount of organoclays were added.
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A two-step process of the solution blending and the subsequent melt mixing in a Brabender mixer was used to prepare clay nanocomposites of SAN/PVC and of ABS, respectively. It was found that the new method was effective in obtaining well-dispersed nanocomposites for both cases. The glass transition behavior of the organoclay nanocomposites were analyzed by using theoretical equations. The interaction characteristics were evaluated by using the solubility parameters estimated from the group molar attraction constants.
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Self-assembled nanostructures of block copolymer thin films have gathered significant attention due to their potential applications as templates for nanofabrication. However the lack of a robust strategy to control the structure formation in thin film geometries has been considered a major obstacle for the practical application. In this presentation 'epitaxial self-assembly' will be introduced as a successful strategy to control the self-assembled nanostructure of block copolymer. Chemically patterned surfaces prepared by advanced lithographic techniques successfully registered nanodomains in block copolymer thin film without any single defect over an arbitrarily large area.
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Diblock copolymers whose morphology in the bulk is dictated by the volume fraction of the components and segmental interactions were confined within nanoscopic cylindrical pores. Since the confining geometry is nonplanar and nanoscopic, the extreme imposed curvature, comparable to molecular dimensions, places significant packing frustration on the chains. When incommensurability between the repeating period of diblock copolymers and the diameter of nanopore is coupled with the curvature, it causes the marked departures from bulk or even thin film behavior. The entropy penalty from the constraints and the curvature of the physical confinement determines unique nanostructures available only with this curved confinement.
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In present study, poly(acrylic acid) (PAA) and hydrophobically modified poly(ethylene oxide) (HM-PEO) multilayers based on the hydrogen bonding between the component polymer pair have been prepared by the LbL deposition method. Dip assembled HM-PEO/PAA multilayers yield unique film morphologies in comparison with PEO/PAA multilayers due to the micellar formation of HM-PEO owing to the hydrophobic attraction between alkyl chains end-capped with the PEO chains. Individual HM-PEO micelles were connected through the bridging PEO chains to form temporary networks on multilayer surface and induced peculiar surface morphology on HM-PEO/PAA multilayers above the critical number of bilayers.
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Highly temperature stable mesoporous materials have excellent properties and potential applications. Here we show a novel poly(vinyl)silazane-block-polystyrene diblock copolymer, which was synthesized by controlled/living free radical polymerization with reversible addition fragmentation chain transfer (RAFT) route. The obtained diblock copolymer occurs the phaseseparation on the nanoscale to form ordered nanostructure, which is converted to mesoprorous ceramic after heating at 800oC. This route demonstrates the preparation of highly temperature stable mesoporous silicon carbon nitrides (SiCN) ceramic film directed from highly cross-linking poly(vinyl)silazane blocks with high ceramic yield, which is different from previous pathway.
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Recently columnar liquid crystals have been studied due to their possible application to organic conducting materials. Supramolecular columnar liquid crystals consist of mesogenic unit which can aggregate into discs that will make up the columns which associate to form a two-dimensional network. In this study, we prepared supramolecular columnar liquid crystals containing hydrogen bonding between carboxylic acid and, pyridine moieties. Thermal and structural properties of prepared complexe were investigated, and it exhibited hexagonal columnar structure (
$Col_{h}$ ) at room temperature. -
Heo, Kyu-Young;Yoon, Jin-Hwan;Jin, Kyeong-Sik;Jin, Sang-Woo;Oh, Kyoung-Suk;Choi, Chi-Kyu;Ree, Moon-Hor 298
There has been much interest in incorporating nanoscale voids into dielectric materials in order to reduce their k value, and thus in producing low-k porous interdielectric materials. One approach to the development of low-k dielectric materials is the templated polycondensation of organosilicate precursors in the presence of a thermally labile, organic polymeric porogen. The other is SiOCH films have low dielectric constant as well as good mechanical strength and high thermal stability through PECVD. In this article we explore the nanopore generation mechanism of organosilicate film using star-shape porogen and SiOCH film using bis-trimethylsilylmethane (BTMSM) precursor. -
Polydioxanone nanofibers for TEM observation can be produced. To collect parallelly aligned nanofibers can crystallize them partially. The SAED pattern of nanofibers drawn and/or heat-treated shows a well-developed fiber pattern, and in the patterns we can observe crystalline reflections up to third layer line.
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Yoon, Jin-Hwan;Yang, Seung-Yun;Lee, Byeong-Du;Joo, Won-Chul;Heo, Kyu-Young;Kim, Jin-Kon;Ree, Moon-Hor 300
Nondestructive nanostructural analysis is indispensable in the development of nano-materials and nano-fabrication processes for use in nanotechnology applications. In this paper, we demonstrate for the first time a quantitative, nondestructive analysis of nanostructured thin films supported on substrates and their templated nanopores by using grazing incidence X-ray scattering and data analysis with a derived scattering theory. Our analysis disclosed that vertically oriented nanodomain cylinders had formed in 20-100 nm thick films supported on substrates consisting of a mixture of poly(styrene-b-methyl methacrylate) (PS-b-PMMA) and PMMA homopolymer, and that the PMMA nanodomains were selectively etched out by ultraviolet light exposure and a subsequent rinse with acetic acid, resulting in a structure consisting of hexagonally packed cylindrical nanopores. -
Jin, Sang-Woo;Higashihara, Tomoya;Jin, Kyeong-Sik;Yoon, Jin-Hwan;Heo, Kyu-Young;Kim, Je-Han;Kim, Kwang-Woo;Hirao, Akira;Ree, Moon-Hor 301
The physical properties of well-defined star-shape polystyrenes with high number of arms (6 to 57 arms) in good and theta solvents were studied using synchrotron X-ray scattering. The scattering profiles for multi-armed polystyrenes shown the molecular shape is changed according to increasing of number of arm. From various parameters which were obtained from scattering profiles, the molecular shape was determined more detail. As results, the molecular shape was changed from a fuzzy-ellipsoid for 6-armed PS to a fuzzy-sphere sphere for 57-armed PS according to increasing of number of arm. -
Fabrication of nanoaggregates of triple hydrophilic block copolymers by binding of ionic surfactantsNanoaggregates of triple hydrophilic block copolymers comprised of poly(ethylene oxide), poly(sodium 2-acrylamido)-2-methylpropanesulfonate), and poly(methacrylic acid) (PEO-PAMPS-PMAA) and the cationic surfactant, dodecyltrimethylammonium chloride (DTAC) have been fabricated. The formation of
$^{\circ}^{\circ}$ the nanoaggregates is based on electrostatic interaction of sulfonate and carboxylate groups of PAMPS and PMAA blocks with the cationic surfactant, which results in insolubilization of these blocks. The formation of micelle is observed by dynamic light scattering measurements. Binding of DTAC to the anionic blocks of PEO-PAMPS-PMAA is confirmed by electrophoresis measurements. -
In-situ ring opening polymerization of
${\varepsilon}-caprolactum$ was carried out in the presence of aminoethylaminopropylisobutyl POSS and stoichiometric amount of adipic acid. The covalent bond formation of POSS on the polyamide was confirmed by the appearance of FT-IR peak at$1123\;cm^{-1}$ that corresponds to the Si-O stretching of POSS structures. Gradual decrease in melting endotherm peak was observed on loading POSS in PA6/POSS nanocomposites. Sharp increase in intrinsic viscosity was observed upto 2.5 wt % loading POSS in the polyamide 6 nanocomposites. These nanocomposites were further characterized using nuclear magnetic resonance, melt viscosity and X-ray diffraction. -
The possibility to develop optoelectronic devices with improved properties by controlling the degree of organization at the molecular level of organic materials has been driving the design of new
${\pi}-conjugated$ systems. In particular, the organization by self-assembling processes (${\tilde{\Box}}{\d{\Box}}}$ interactions, hydrogen bonding) of well-defined oligomeric systems such as disubstituted oligothiophene derivatives has been demonstrated as a promising approach to conjugated materials with a high degree of structural order of the constituent building blocks. The self-organization of conjugated building blocks in solution or on surfaces, leading to the construction of nanoscopic and mesoscopic architectures, represents a starting point for the construction of molecular electronics or even circuits, through surface patterning with nanometer-sized objects. -
The molecular structure and dynamics of inclusion compounds (ICs) consisting of n-perfluoroalkane (PFA) guests and
${\Box}-cyclodextrin$ (${\Box}-CD$ ) host were investigated using$^{19}F$ magic angle spinning (MAS) and$^{1}H{\to}^{19}F$ cross polarization (CP) / MAS NMR spectroscopy with the aid of thermal analyses, FT-IR spectroscopy, X-ray diffraction, and$^{1}H{\to}^{19}F$ CP/MAS technique revealed that$C_{9}F_{20}$ molecules included in${\Box}-CD$ undergo vigorous molecular motion and partly come out of the${\Box}-CD$ channel above$80^{\circ}C$ . In case of$C_{20}F_{42}/{\Box}-CD$ , an exothermic peak is observed by differential scanning calorimetry (DSC) at ca.$40^{\circ}C$ which suggests that${\Box}-CD$ molecules become mobile and commence rearrangements that form more ordered structures at higher temperatures. -
We immobilized and patterned PDA vesicles on solid substrate using micro arrayer, which have moieties to react with chemical and biological materials. Immobilized vesicle system was developed since it possesses many advantages in multiple screening, durable stability, and higher sensitivity. We applied polydiacetylene supramolecules to chemical and biological sensors for detection of
${\alpha}-cyclodextrin$ and E.coli cell selectively. This detection method could be applied as DNA chip, protein chip, and cell chip for multiple screening as well as chemical sensor by modifying the functional groups of diacetylene monomer. -
The reduction behavior of silver ions to silver nanoparticles is an important research topic in polymer/silver salt complex membranes for facilitated olefin transport, because it has a significant effect on the long-term stability of membrane performance. In this study, the effects of solvent on the formation of silver nanoparticles and long-term membrane performance in polymer/silver salt complex membrane were investigated. This effect was assessed for the complexes of poly(N-vinyl pyrrolidone)
$(PVP)/AgBF_{4}$ with the use of ionic liquid (IL), acetonitrile (ACN) and water as a solvent. Membrane performance test shows that long-term stability is strongly dependent on the kind of solvent and arranged: IL > ACN >> water. -
We have demonstrated that the cylindrical micelles self-assembled from coil-rod-coil molecules can be interconnected by addition of a small amount of rod-coil-rod molecule as a bridging agent. Subsequently, these dynamic interconnections lead to stiff bundles composed of cylindrical micelles that are responsible for the formation of a reversible nematic gel. The results described here represent a significant example that dynamic bridging of supramolecular cylinders in aqueous solution can provide a useful strategy to construct one-dimensional nematic structure with three dimensional elastic properties.
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Latest developments on hybrid nanostructured materials fabricated by applying self-assembly strategies on organic/inorganic nanotemplates are discussed. Within this frame, numerous functional nanomaterials including arrays of composite metal/semiconductor nanoparticles, planar waveguides and functional multilayer thin films are generated using self-assembled polymers as templates or building blocks. In particular, surface plasmon resonance based optical sensing is employed to investigate nanofabrication processes occurring in nanoscale dimention. We also suggest unprecedented pathways to hybrid supramolecular multilayer nanoarchitectures in 1D or 2D geometry via layer-by-layer self-assembly.
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We have demonstrated the formation of highly nanoporous films composed of two different BCMs through layer-by-layer (LbL) assembly on substrates. The films thus prepared showed tunable optical properties, with strong antireflective properties with light transmission above 99%. Considering the wide application areas of both LbL multilayers and block copolymer thin films, the approaches introduced in present study are likely to open up new possibilities for devices with multifunctional properties.
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The morphology of Poly(styrene-b-methylmethacrylate) (P(S-b-MMA)) block copolymer thin films deposited on silicon wafers was controlled by treating the substrates with Self-Assembled Monolayers (SAM) of phenylsilanes with different alkyl chain lengths. It was found that the treatment with SAM strongly modified the substrates properties, especillay the surface energy, as compared with bare silicon oxide. By futher adjusting the molecular weight of P(S-b-MMA), a variety of morphologies could be generated, including a perpendicular orientation of lamellea of PS and PMMA, which is required for industrial applications.
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Block copolymers with well-defined nanoscopic structures have recently gained much attention for their potential uses as functional nanostructures. Here, we show that nanoporous templates made from polystyrene-block-poly (methyl methacrylate) (PS-b-PMMA) satisfy a novel design concept. At first, arrays of nanoscopic cylindrical microdomains oriented normal to the surface can easily be prepared. Then, we fabricated ultra high density arrays of conducting polymer as poly(pyrrole) (Ppy) and poly(3,4-ethylenedioxythiophene) (PEDOT) nanowires with diameters of
$25{\sim}40\;nm$ on the ITO glass by electropolymerization of the monomers inside nanoholes. These high density arrays of conducting polymer nanowires could be used as P-type materials for photovoltaic devices. -
In this study, we describe a new double layered nanoporous membrane suitable for virus filtration. One layer is an 80 nm thick film having cylindrical pores with diameters of 15 nm and a narrow pore size distribution. This layer is prepared by using a thin film of the mixture of a block copolymer and a homopolymer, and mainly acts to separate viruses. The support layer (
${\sim}150\;microns\;thick$ ) is a conventional micro-filtration membrane with a broad pore size distribution. This asymmetric membrane showed very high selectivity and flux for the separation of human rhinovirus type 14 (HRV 14) which has a diameter of${\sim}30\;nm$ and is a major pathogen of the common cold in humans. -
The FRET property has been extensively studied from the theoretical view points to the practical applications. In case that the donor and acceptor are confined in nanodimension, the FRET effectively occurs, because of their distant dependent characteristic. However, there are no reports concerning FRET with one dimensional (1D) nanomaterial. We have successfully prepared the PMMA nanotubes using vapor deposition polymerization as the platform of FRET. The dye-PMMA composite nanofiber has also been produced without phase separation and any deterioration of properties of the dyes. The PMMA 1D nanocomposite doped two dyes with great spectral overlap between donor and acceptor displayed FRET property.
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A variable surface coating with the potential to fulfill the requirements of industry will be presented. Via controlled radical polymerization methods from a functionalized Polymethylsilsesquioxane delivers an inorganic-organic block copolymer, which can be easily modified and tuned for different applications. Spin coated or dip coated on various substrates show promising results. By using different block copolymers the contact angle on a silicon wafer can be varied in a range of
$90^{\circ}\;up\;to\;145^{\circ}$ After curing and complete condensation a perfect adhesion on glasses, plastics and metals is achieved. -
The preparation of an organic/inorganic polymer hybrid from a novolac derivatives is described. The hybrid was prepared by the acid-catalyzed solgel reaction of phenyl-trimethoxysilane (PhTMOS) in the presence of anisole novolac. The resulting film was transparent and showed a high heat stability. The dispersion of two components might be due to the utilization of the p-p interaction between the phenyl ring of the silica matrix and that of novolac. This makes it possible to prepare a hybrid glass having a highly content of novolac derivatives.
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Dendronized linear polymers have recently come forward as new materials for nanoscale applications. These "molecular cylinders" may be modified with specific chemical makeup, rigidity, surface decoration, and backbone properties much like their spherical analogs, dendrimers. There exist three main synthetic pathways to yield dendronized polymers: (i) graft-to; (ii) graft-from; and (iii) macromonomer. We present an efficient "graft-to" approach towards dendronized microstructures utilizing click chemistry. With the capacity to manipulate their chemical composition, these dendronized structures have already found broad use in site-isolation for catalysis, nanolithography and organic light emitting diodes. These and other potential applications of these materials will be also presented.
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4-Vinylbenzyl maltohexaoside peracetate, 1, was copolymerized with divinylbenzene using the initiator for nitroxide-mediated living radical polymerization, 2, to afford the polystyrene microgel with acetyl maltohexaose, 3. The deacetylation of 3 was achieved by treatment with sodium methoxide in dry 1,4-dioxane to produce the polystyrene microgel with maltohexaose, 4. A good coating property of the polystyrene microgel was combined with an excellent hydrophilic property derived from maltohexaose. In addition, 4 showed the ability to solubilize fullerene in aqueous solution. Therefore, 4 has a potential application as a special coating using functional but incompatible compounds such as fullerene on the surface of various hydrophilic materials.
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RAFT polymerization can produce under controlled conditions polymer chains incorporating well-defined chain ends. By designing a simple way of producing functional RAFT agents, a variety of
${\Box}-end$ groups was successfully introduced onto hydrophilic polymer chains. The${\Box}-end$ group being a thiocarbonyl thio function was used as efficient chain transfer agent in dispersion or emulsion polymerization to produce original functional latex particles. -
The authors report the synthesis and radical ring-crossover polymerization of macrocycles with radically exchangeable dynamic covalent bonds. The macrocyclic compounds with alkoxyamine units were designed and synthesized by condensation from alkoxyamine-based diol and the corresponding acid chlorides in the presence of pyridine under high-dilution condition. The macrocycles can thermally polymerize by intermolecular radical crossover reaction. Furthermore, the poly(alkoxyamine)s depolymerized to the monomers principally by the intramolecular radical exchange process under high-dilution conditions.
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Aromatic diacetylenes form stable oligomeric diradicals when irradiated with UV light or heated at temperatures above their melting points. In this paper, the formation of stable diradicals is discussed, and the mechanism of polymerization in the presence of peroxide in solution, is discussed. The diphenyldiacetylene undergoes polymerization through coupling of diradicals, and not by the successive addition of radical species.
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Well-defined poly(N-vinylcarbazole), poly(NVC), was synthesized by macromolecular design via interchange of the xanthate (MADIX)/reversible addition-fragmentation chain transfer (RAFT) polymerization in the presence of a suitable xanthate-type chain transfer agent (CTA). Good control of the polymerization was confirmed by the linear first-order kinetic plot, the molecular weight controlled by the monomer/CTA molar ratio, linear increase in the molecular weight with the conversion, and the ability to extend the chains by the second addition of the monomer. Star polymers having various architectures were also synthesized using this technique.
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Multi-vinyl monomer, which contains many vinyl groups in a molecule, was prepared by esterification of hydroxyl groups of poly(2-hydroxyethyl methacrylate) with methacryloyl chloride. Then, copper-mediated atom transfer radical polymerization was carried out as a template polymerization. The propagation of polymerization was investigated by kinetic analysis.
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In copolymerization of methyl acrylate (MA) and methyl methacrylate (MMA) with various ratios of MA to MMA and
$[CuCl]/[PMDETA]/[PVAc-CCl_{3}]$ catalyst system in bulk at$80^{\circ}C$ via ATRP, several terpolymer with different copolymer composition, were synthesized. The atom transfer radical copolymerization of MA and MMA with macroinitiator, is very sensitive to molecular weight and its distribution. In this work it was possible to calculate the molecular weight of the terpolymers and show that it is close to the experimentally determined number average molecular weight from GPC. -
Cationic polymerization of isobutyl vinyl ether using various metal halides was examined in toluene in the presence of an added base at
$0^{\circ}C$ . In conjunction with an appropriate weak base such as ethyl acetate or 1,4-dioxane, all metal halides but$FeBr_{3}\;and\;GaCl_{3}$ led to living cationic polymerization. The polymerization rates varied as follows:$FeBr_{3},\;GaCl_{3}\;>\;FeCl_{3}\;>\;SnCl_{4}\;>\;InCl_{3}\;>\;ZnCl_{2}\;>>\;AlCl_{3},\;HfCl_{4},\;ZrCl_{4}\;>\;EtAlCl_{2},\;BiCl_{3},\;TiCl4\;>>\;SiCl_{4}\;>\;GeCl_{4}$ . This order partially corresponds to that of the equilibrium constant in the formation of a carbocation from a chloroalkane in the presence of a carbonyl compound. With extremely active Lewis acids, such as$FeBr_{3}\;and\;GaCl_{3}$ , the use of a stronger base, THF, was required to achieve living polymerization. -
The combination of living anionic and coordination polymerization techniques enabled to synthesize the polystyrene-b-polyisoprene-b-poly (butyl isocyanate) triblock polymers. Their microphase-separated structures were zig-zag structures for high
${\phi}_{PIC}$ samples, and hockey-puck structures were also observed. The phase diagram for PSt-b-PIp-b-PIC rod-coil polymers was different from that for PS-PBd-PMMA triblock polymers, and it was found that${\phi}_{PIC}$ was the important factor to determine the microphase-separated structures. -
Methyl glycidyl ether has been polymerized in a controlled fashion at low temperature in toluene using the combination of tetraoctyl ammonium bromide and triisobutyl aluminum. Poly(glycidyl methyl ether)s with molar masses ranging from 3 000 to about 90 000 g/mol and narrow polydispersities (<1.2) were prepared and the dependence of their solubility and LCST in water as a function on their molar masses investigated.
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On mixing of 1,3-dehydroadamantane, 1, with electron-deficient vinyl monomers such as acrylonitrile and methyl acrylate in THF at r.t. in the absence of any initiator, the copolymerization spontaneously proceeded to give alternating copolymers in 28-88 % yield. By contrast, no reaction of 1 occurred, when isobutyl vinyl ether or styrene was mixed under the similar conditions. These contrastive results indicate the high electron density of a central s-bond in a strained [3.3.1]propellane derivative, 1. Alternating sequences of the resulting copolymers were characterized by NMR and MALDI-TOF-MS measurements. DSC and TGA measurements revealed the high thermal stability of the alternating copolymers containing bulky and stiff adamantane skeletons.
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Various new active ester monomers based on (meth)acrylates and 4-vinylbenzoic acid have been prepared. Investigation of the controlled radical polymerization behavior of the respective monomers resulted in excellent polymerization control, thus, opening synthetic routes to reactive block copolymers. Polymer analogous reactions with amines yielded functional polymers. In the case of the copolymer poly(N-isopropylacrylamide-co-acetone oxime acrylate) a lower critical solution temperature could be measured at
$52^{\circ}C$ . Thus, the reactive copolymer features two characters: reactive AND stimuliresponsive behavior. -
Joumaa, Nancy;Lansalot, M.;Theretz, A.;Elaissari, A.;Sukhanova, A.;Artemyev, M.;Nabiev, I.;Cohen, J.H.M. 330
The elaboration of fluorescent submicronic polymer particles exhibiting narrow particle size distribution as well as good photostability is of particular interest in various biomedical applications. In the frame of this work, labeled polystyrene latexes have been synthesized by miniemulsion polymerization using luminescent semiconductor nanoparticles (quantum dots, QD). The influence of incorporation of QDs on the polymerization kinetics as well as on the optical properties of the obtained latexes will be discussed. -
Polylactic acid (PLA) is a promising polymer because it can be derived from renewable resources and provides a biodegradable alternative to petrochemical based polymers. This research aims to synthesize PLA, through direct polycondensation and also tries to avoid the occurrence of separation by-product and the use of catalysts in the process. The polymerization of lactic acid was done at three different temperatures
$150^{\circ}C,\;180^{\circ}C\;and\;200^{\circ}C$ for 90 h without catalysts and organic solvent. The proposed process provides results that are comparable to those that incorporate catalysts; during polymerization temperature was$180^{\circ}C$ the molecular weight of PLA obtained reached 42448 Da. The thermal properties of PLA analysis by Differential Scanning Calorimetry (DSC). -
Well difined sulfonated styrene and n-butyl acrylate (nBA) block copolymers were synthesized by CuBr catalyzed living radical polymerization followed by acification by thermolysis. Neopentyl styrene sulfonate (NSS) was polymerized with PnBA macroinitator precursor (
$M_{n}=19,500,\;PDI\;<\;1.09$ ) and CuBr catalyst with N,N,N',N' -pentamethylethyleneamine (PMDETA) to give nBA-NSS block copolymer with narrow polydispersity ($M_{n}=29,900,\;PDI\;<\;1.15$ ). PNSS segments in the block copolymer were then acidified by thermolysis at$150^{\circ}C$ resulting in polystyrene segments with 100 % sulfonic acid groups. -
We synthesized two novel polynorbornene derivatives, chiral poly(norbornene acid methyl ester) (C-PNME) and racemic poly(norbornene acid n-butyl ester) (R-PNME), which are potential low dielectric constant materials for applications in advanced microelectronic and display devices. Thin films of these polymers deposited on substrates were investigated by structural analyses using synchrotron grazing incidence X-ray scattering, specular reflectivity and ellipsometry. These analyses provided important information on the structure, electron density gradient across film thickness, chain orientation, refractive index and thermal expansion of the polymers in substrate-supported thin films. The structural characteristics and properties of the thin films were first dependent on the polymer chain' tacticity and further influenced by film thickness and thermal annealing.
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Helical polymers like polyisocyanates with single screw sense are essential to exhibit sophisticated functions like molecular recognition, self-replication, chirality memory and catalytic activity. One approach that has not been explored is the effect on handedness of the polyisocyanates through end-capping with a chiral residue. Induction of chirality in poly(n-hexyl isocyanate) was studied by end-capping with chiral (R and S) 2-bromo-3-methylbutyryl chloride(R-BMBC and S-BMBC). We have shown that a control over living anionic polymerization of HIC by using a suitable initiator affords an opportunity to introduce chiral end-groups with 100% yield and in high purity. This has resulted in helicity induction through extended lengths several orders of magnitude.
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Polyacrylonitrile (PAN) was deposited as an adherent film on Cu-substrate by the cathodic electropolymerization. This work is an attempt to compare the molecular weight and the fractured surface of PAN prepared by CV and chronoamperometry. The molecular weight and increase weight of PAN measured the according to AN-concentration, scan rate, and cycle number (or time) using CV and chronoamperometry. The morphology of PAN was characterized by SEM image. Mechanism and optimal conditions for electropolymerization of acrylonitrile on Cu-substrate were investigated and discussed.
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The present work is focused on the synthesis of a series of fully aliphatic polyimides and the incorporation of adamantane moieties and siloxane groups to them and studies the deviation in the basic traits of the fully aliphatic polyimides. In this work, we wish to discuss how adamantyl group and siloxane moieties influence the basic properties of aliphatic polyimides (APIs), by synthesizing various fully aliphatic polyimides and polyimidesiloxanes (APISiO).
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The synthesis of an octafunctional resorcinarene based initiator for nitroxide mediated polymerization and its ability to yield random star copolymers of styrene and methyl methacrylate is studied. The effect of the initiator conformations towards its activity and the conditions that permit the formation of well-defined star block copolymers is also investigated in detail. The characterization of the initiator and the polymers were carried out by various spectro-analytical techniques. Well-defined random copolymers were obtained with controlled molecular weight and low PDI depending on the monomer feed.
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Equilibrium behavior of ABA triblock copolymer with different lengths of endblock A chains was examined using self-consistent field theory by Matsenl. It was found that at small asymmetries, the A block bidispersity reduces the stretching energy of the A domains. This effect causes a slight increase in the domain spacing and shifts the order-order transitions toward higher A volume fractions. At large asymmetries, the short A blocks pull free of their domains allowing their B blocks to relax. A feature of microphase-separated structure of asymmetric poly(methyl acyrylate) (PMA)-b-polystyrene-b-PMA using SAXS, DSC and ESR was experimentally examined. These measurements gave an evidence of the solubilization of short A chains to the B domains.
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In this study, the microvoids in glassy polymers were investigated by Xe sorption and
$^{129}Xe$ NMR measurements. Xe sorption isotherms of glassy polymers have been successfully interpreted by the dual-mode sorption model.$^{129}Xe$ NMR chemical shift of the$^{129}Xe$ in the samples show nonlinear low-field shift with increasing sorption amount of Xe because of a fast exchange of Xe atoms between Henry and Langmuir sites, whereas it has showed linear shift against sorption amount of Xe into the Langmuir site. From this Xe-density dependence of the$^{129}Xe$ NMR chemical shift, it has been able to estimate mean size of the microvoids in glassy polymer. It is confirmed that there is correlation between${C_H}'$ and volume or number of microvoids. From these findings, it is demonstrated that$^{129}Xe$ NMR spectroscopy is a powerful technique to determine the mean size and number of microvoids in glassy polymers. -
Applying force-distance curve measurement by atomic force microscopy to a theoretical mechanical model gives us elastic properties of polymer surfaces. Our group focuses on force-mapping method, in which force-distance curve is performed at each lattice point on a sample surface and subsequently a variety of properties derived from analytical results are combined to construct a 2-dimensional image. With this method we succeeded in deriving Young' s modulus distribution map method of rubbery/rubbery polymer blend surfaces with
${\sim}100\;nm$ lateral resolution. We also applied force-mapping method to another theory to divide distribution of hardness from that of adhesion. We will demonstrate recent progress. -
Nanofishing enabled us to stretch a single polymer chain with picking it at its two modified termini using atomic force microscope (AFM). Stress-strain curves obtained to date had been the result on slow pulling events and therefore observed phenomena had been interpreted as quasi-static responses. In this study, we extended the capability of nanofishing to the phenomena far from equilibrium state by giving much faster pulling speeds. We could observe a momental increase entanglement and a successive stress relaxation.
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Atomic force microscope (AFM) enables us to stretch a single polymer chain by picking it at its two modified termini. Using this method called "nanofishing," we have studied statistical properties of single polymer chains. A force-extention curve obtained for a polystyrene with thiol termini in a cyclohexane showed a good agreement with a worm-like chain (WLC) model, and thus gave microscopic information about entropic elasticity. In this report, the experiments were performed at wide-range temperatures, resulting in wide-range solvent qualities from poor to good solvent condition. The temperature dependence of statistical properties of polystyrene was examined. The coil-strand transformation realized in a poor solvent was also discussed.
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Kobayashi, Motoyasu;Ishihara, Kazuhiko;Takahara, Atsushi;Suzuki, Atsushi;Kaido, Masataka;Zhe, Wang 343
Surface-initiated atom transfer radical polymerization of 2-methacryloyloxyethyl phosphorylcholine (MPC) was carried out to produce high-density poly(MPC) brush on silicon wafer. Frictional properties of poly(MPC) was investigated by by sliding a glass ball (${\phi}\;10\;nm$ ) on the substrates over a distance of 20 mm at a sliding velocity of 90 mm/min under loading of 0.49 N at 298 K. Higher friction coefficients were observed in dry N2 atmosphere and in toluene condition, whereas the friction coefficients decreased to 0.02 in humid air and in water. It is supposed that water-swollen poly(MPC) brush works as a lubricant to moderate the interaction between brush and probe. -
Terao, Ken;Kikuchi, Noriaki;Sato, Takahiro;Teramoto, Akio;Fujiki, Michiya;Dobashi2, Toshiaki 344
Poly(n-hexyl-(S)-3-methylpentylsilane) aggregates confined in microcapsules to keep the aggregation number and ranging in average polymer mass in a microcapsule from$2{\Box}10^{-16}\;to\;2{\Box}10^{-14}g$ . were studied by circular dichroism measurements in ethanol (a non solvent) and tetrahydrofuran (an associative solvent at low temperature) at varioustemperatures. The size of each aggregate did not affect the optical activity because the circular dichroism was proportional to the aggregation number at the same condition. Moreover, the circular dichroism appreciably reflected the prepared method, i.e. temperature and solvent. -
It is well known that poly(glutamate)s with long n-alkyl side chains form thermotropic liquid crystalline state by melting of the side-chain crystallites and also poly(glutamate)s such as poly(
${\gamma}-benzyl\;L-glutamate$ )(PBLG), poly(${\gamma}-n-alkyl\;L-glutamate$ ), etc. in solvent form the isotropic, biphasic and liquid crystalline phases which contains cholesteric and columnar liquid crystalline forms depending on the polypeptide concentration. Although there is no diffusion study for PBLG in liquid crystalline state, because it is difficult to observed$^{1}H$ spectrum of PBLG in liquid crystalline state for its very short$^{1}H\;T_{2}$ . In this study, the diffusional behavior of rodlike PBLG in concentrated solution is successfully elucidated as studied by the field-gradient$^{1}H$ NMR methods. -
Several types of dynamic atomic force microscopy such as tapping-mode, force modulation-mode are commonly cooperated by phase-contrast imaging techniques, which were interpreted as elastic contrast by mistake in the past and are nowadays regarded as the representation of energy dissipative processes. However, as theoretically reported, the situation is not so simple when the strong adhesive interaction is involved. Furthermore, elastic and viscous contributions are not easily divided in the case of polymeric systems. Thus, the interpretation of image contrast for them must be very carefully treated. In this study, we will demonstrate how such contrast mechanisms are complicated, using several miscible and immiscible polymer blend systems as model samples.
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Lee, Young-Joo;Bingol Bahar;Murakhtina Tatiana;Sebastiani Daniel;Ok, Jong-Hwa;Meyer Wolfgang H.;Wegner Gerhard;Spiess Hans Wolfgang 347
Polymers containing poly(vinyl phosphonic) acid segments are promising candidates to be used as proton conducting membranes. Solid state NMR spectroscopy represents an ideal probe of proton motion on the molecular level, because it allows us to selectively detect the nuclei of interest. In this paper, we apply solid state NMR methods to poly(vinyl phosphonic) acid in order to demonstrate that the proton conduction of poly(vinyl phosphonic acid) results from P-OH proton through hydrogen bonding and that the condensation of phosphonic acid leads to decrease in proton conductivity.$^{1}H\;and\;^{31}P$ solid state NMR experiments are supported by quantum chemical computation of NMR parameters. -
Jin, Kyeong-Sik;Jin, Sang-Woo;Yoon, Jin-Hwan;Heo, Kyu-Young;Kim, Jae-Han;Kim, Hee-Soo;Ree, Moon-Hor 348
In the present study, porcine pepsin in various pH conditions was investigated by small-angle X-ray scattering (SAXS) in order to detailed information on the structure and its variations with pH conditions. These analyses identified the structure of pepsin, and compared with that obtained by single crystallography. Moreover, this study found the structure' variations with changing pH conditions. All the results will be discussed with considering the conformational characteristics of pepsin in solution and further correlate to the biological and spectroscopic characteristics reported previously. -
Vinyl-polynorbornene has good thermal stability, high transparency and low dielectric constant. However, it has low solubility, poor mechanical and adhesive properties. In this work, polynorbornene derivatives were prepared by Pd(II) late transition metal catalyst. The polymers have good solubility, and are thermally stable up to
$300^{\circ}C$ The glass transition temperature is decreased as the side-chain becomes bulkier. Structure-property relationship of polynorbornene derivatives measured by X-ray scattering, mechanical and electrical properties will be discussed. -
We investigated, via atomic force microscopy and transmission electron microscopy, the effect of shear force on the interfacial morphology of a reactive bilayer polymer system composed of PS-mCOOH and PMMAGMA. It has been observed that in the absence of oscillatory shearing the roughness of the interface increased with reaction period, while at large values of
${\gamma}_{0}\;and\;{\omega}$ it became less than that observed in the absence of oscillatory shearing. This observation may be attributable to the possibility that oscillatory shearing might have hindered the diffusion of polymer chains, which are located away from the interface, to the interface of the layers. However, the effect of${\gamma}_{0}\;and\;{\omega}$ on the roughness of the interface of (PS-mCOOH)/(PMMA-GMA) bilayer is found to be quite different. -
The possible interactions between cyclodextrins and biodegradable polyesters were investigated. The hydrophobicity of cyclodextrin could be varied with the methyl substitution of host CD, and the possibility of IC formation and the types of interaction between respective CDs and polyesters were subsequently changed. Further, the effect of cyclodextrins on the morphological change of biodegradable polymer was shown to depend on the degree of IC formation between cyclodextrin and biodegradable polymer as well as on the type of interaction between respective CDs and polyesters. That is, the enhancement and/or the restriction of the crystallization of P(3HB) were observed by the incorporation of various kind of cyclodextrins with different cavity size and hydrophobicity.
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Corynebacterium glutamicum, which is well known as an amino acid fermentation bacterium, has been used as a producer of poly(3-hydroxybutyrate) [P(3HB)]. P(3HB) was synthesized in recombinant C. glutamicum harboring the expression plasmid vector with a strong promoter for cell surface protein gene derived from C. glutamicum and P(3HB) biosynthetic gene operon derived from Ralstonia eutropha. The expression of P(3HB) synthase gene was detected by enzyme activity assay. Intracellular P(3HB) was microscopically observed as inclusion granules and its content was calculated to be 22.5 % (w/w) with molecular weight of
$2.1{\times}10^{5}$ and polydispersity of 1.63. -
Deoxyribonucelic acid (DNA) molecules have a huge molecular weight so that DNA was reported to be a promising natural polymer to give durable films. Among many applications of DNA, the authors focused their attention on separation membranes derived from DNA because membranes will play an important role in environmental and energy related processes. DNA-polyion complex membranes were prepared from DNA and corresponding polycations. The DNA-polyion complex membranes showed chiral separation ability toward racemic amino acid mixtures.
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Alginic acid-silica hydrogel films was prepared for testing as protective coating materials for PTFE OD membranes. Unprotected hydrophobic membranes are subject to wet-out when contacted by surface-active agents. Films were characterised using SEM, XRD, DSC, mechanical strength measurements, and water-swelling measurements. In OD trials using coated membranes, no wet-out occurred over the 15 h duration of three consecutive 5 h OD trials using orange oil-water mixtures. In the case of detergent solutions, the coating afforded protection to the membrane for 4-5 h. In a separate trial, no wet-out occurred when the coated side of the membrane was placed in contact with 1.2 wt % orange oil for 72 hours.
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In this study, we have applied principal component analysis-based 2D (PCA2D) correlation spectroscopy to the temperature-dependent IR spectra of biodegradable poly(hydroxyalkanoate). PCA2D analysis reveals clearly that there are two components in crystalline band of C=O stretching mode without being hampered by noise. To better understand the thermal behavior of biodegradable poly(hydroxyalkanoate), eigenvalue manipulating transformation (EMT) technique was also employed. By uniformly lowering the power of a set of eigenvalues associated with the original data, the subtle contributions from minor eigenvectors are highlighted. Details of thermal behavior of biodegradable poly(hydroxyalkanoate) studied by PCA2D correlation spectroscopy with EMT will be discussed.
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The use of renewable feedstock is an important issue to reduce the fossil fuel consumption. In this contribution, we report the cationic ring-opening polymerization of a 2-oxazoline monomer with soybean fatty acid side chains (SoyOx) under microwave irradiation. Kinetic experiments were performed to investigate the livingness of the polymerization in both acetonitrile and in the absence of solvent. In addition, both block and statistical copolymers were prepared using the SoyOx monomer. The synthesized (co)polymers were crosslinked under UV-irradiation resulting in insoluble polymeric materials and core-crosslinked micelles.
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Many industrial sources of proteins can be used as raw materials to produce films, molded materials, and various hollow items either by "casting" techniques or by "thermoplastic processing". Combining proteins with natural fibbers, paper or biodegradable polyesters is very promising to form biodegradable composites witch take advantage of the barrier and mechanical properties of each component. Using nano-fillers to form nanocomposites has also been shown to be interesting to improve properties. Production, with low transformation cost, of protein based materials to form biodegradable materials with controlled functional properties for food uses, medical uses, packaging, agriculture, controlled release systems, etc. is discussed.
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Wan Yunus Wan Md Zin;Ibrahim NorAzowa;Rahman Mohd Zaki Ab.;Ahmad Mansor B.;M. Dahlan Khairul Zaman 358
The graft copolymerization of methyl methacrylate (MMA), butyl acrylate (BA) and acrylamide (AAm) onto oil palm empty fruit bunch (OPEFB) fiber were successfully carried out in aqueous solution using$H_{2}O_{2}/Fe^{2+}$ as initiator. For all monomers the percentage of grafting increases with the amount of monomer and can be controlled by setting the appropriate reaction conditions. The optimum reaction period were found to be 120 minutes for all monomers whereas the optimum temperature and the amount of initiator needed for grafting depend on the type of the monomer used. The mechanisms of grafting vinyl monomer onto OPEFB were proposed. The grafted products were characterized by gravimetric analysis, FTIR and SEM. -
This study deals with development of new bio-based polymeric materials from epoxidized soybean oil (ESO). The curing of ESO in the presence of organophilic montmorillonite produced an oil polymer-clay nanocomposite ("green nanocomposite") showing flexible property. A green nanocomposite (oil polymer-silica nanocomposite) coatings were synthesized by an acidcatalyzed curing of ESO with 3-glycidoxypropyltrimethoxysilane. The curing of ESO in the presence of a biodegradable plastic, poly(caprolactone), produced a composite with semi-IPN structure. The mechanical properties of the composite was much superior to those of polyESO. These new oil-based materials have large potential for applications in various fields.
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Zein protein is one of the best biopolymer for edible film making and polyols are convenient plasticizers for biopolymers. Sorbitol, glycerol and manitol at three levels (0.5, 0.7, 1g/g of zein) were used as plasticizers. Rheological and thermal properties of zein resins were studied for determining their plasticization effectiveness. Sorbitol and glycerol had good plasticizing effects and could decrease viscoelastic modulus of zein resins considerably, but manitol was not as effective as them. Effects of plasticizers on thermal properties of resins were investigated by DSC at -100 to
$150^{\circ}C$ . No crystallization and melting peaks related to zein resin and plasticizers were observed. Thermograms showed that polyolic plasticizers and zein resin remained a homogeneous material throughout the cooling and heating cycles. -
To clarify the structure development of cyclic olefin copolymers in stretching and relaxation processes, on-line measurements of optical retardation and tensile force were performed. Birefringence increased continuously whereas stress showed yielding at stretching temperatures of
$160^{\circ}C$ . At$170^{\circ}C$ , stress yielding was not observed and stress and birefringence increased monotonously with an increase in the strain. In the relaxation process, stress and birefringence decreased monotonously at all the temperatures examined. The slope for the stress vs. birefringence relation at initial stage of stretching increased with an increase in temperature, whereas that for the relaxation stage was significantly larger that for the stretching process, and therefore showed a significant hysteresis. -
Chromic acid anodizing of aluminium is an effective process for producing a substrate which provides excellent surface properties to assembly. However, new chromium-free finishing metal treatments are being developed to reach new environmental goals. Present study deals with chromium free experimental conditions for both deoxidizing and anodizing treatments. Results clearly demonstrate the potentiality for environmentally friendly treatments to get suitable metal-adhesive performance. In particular, the role of both metal surface porosity and chemical composition has been highlighted thus allowing to propose alternative to classical treatments for aeronautic applications.
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Bonding of composite materials with an adhesive layer is one of the most promising alternatives to classical bonding techniques. The use of several surface treatments may greatly increase this adhesion behavior at the initial state. Then in order to see the influence of the thickness of polymer matrix on the adhesion of composite assembly, different surface treatment, which can reduce or increase this thickness, are used (peel ply, tear ply, excimer laser). The influence of this specific parameter is not only discussed at the initial state but also after thermal ageing of the whole bonded assembly. Results show that the best performances at the initial state are not obviously the best performances after ageing.
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The rheological properties of Parmax 1200, a new semi-flexible substituted polyphenylene, were investigated. The reported high stiffness of the material was confirmed. The rheological measurements proved that, despite the very high stiffness of the molecules, Parmax showed shear thinning and that, although the viscosity is very high and the melt is highly elastic, the polymer can be extruded in the melt. A worm-like morphology was detected in AFM and TEM. This morphology could explain the reported mechanical and rheological behaviour. The compatibility with flexible chain polymers (e.g. polycarbonate) could also be explained by the worm-like morphology.
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The wavelength dispersion of birefringence (or retardation) is very important property for optical use of polymer films. Birefringence free film and retardation film have been widely used for applications such as liquid crystal display (LCD). In this study, miscible polymer blends which consist of polymers of positive and negative birefringence were found. By operating composition and orientation of molecules in the transparent blend films, the behavior of wavelength dispersion of birefringence (retardation) was controlled. The applicability to wideband birefringence free film and quarter wave (retardation) film was discussed.
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Five sandwiched multilayers consisting of PBT(Polybutyleneterephthalate), PS(Polystyrene) and clay were prepared to investigate the migration mechanism of clay in the polymer blend system. Rheometry (RMS800) was used to apply well-defined shear on the above multilayer samples in order to well understand dominant factors controlling the migration. Applied shear force was enough to move clay tactoids to the interface, if either long time or high shear was available, but it was not sufficient to separate into individual platelets of clay. The morphology evolution was subsequently studied in term of scanning electron microscopy (SEM) and high resolution transmission electron microscopy (HR-TEM), respectively.
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Liu, Hongzhi;Lim, Hyoung-Taek;Kim, Yong-Kyoung;Han, Nam-Kun;Ahn, Kyung-Hyun;Lee, Seoung-Jong 367
With poly (ethylene-co-methacrylic acid) ionomer (i.e. Surlyn) as a compatibilizer, PP/organoclay (Cloisite(R)20A) nanocomposites were prepared via melt compounding in a co-rotating twin-screw extruder. For comparison, the widely used PP-g-MA was also used as a reference. The content of organoclay was fixed at 5phr based on the total weight of polymer resins. The structures of nanocomposites were characterized by XRD, rheometry in small amplitude oscillatory shear, SEM, and TEM, respectively. It was found that PP/Surlyn/OMMT nanocomposites displayed higher intercalation degree and better dispersion effect than the corresponding PP/PP-g-MA/OMMT counterpart. Additionally, their mechanical properties and wettability were measured. -
Micro-molded parts can be defined as parts with microgram weight, parts with micro-structured surface, and parts with micro-precision. In this study, various micro-scale molded parts for various polymers were produced by using a precision micro-molding machine. Molded parts with nano-structure surface were also produced to analyze the effect of molding conditions on replication of surface pattern and higher-order structure development of molded parts. Replication of molded parts was influenced by material properties, molding conditions and size of surface pattern. Higher-order structure of molded parts was investigated by using polarized microscope. Skin-shear-core regions inside the molded parts were observed and shear region affected to surface replication.
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Compatibilizers contribute to many processes in polymer industry, such as manufacturing polymer blends and composites. They are usually designed to be block or graft form which is combined in polar and non-polar parts in the first synthesis process level, for example, the general form of maleic anhydride (MA) as a compatiblizer is a grafted counterpart. However, the process of making the compatibilizer is related to the first synthesis level and it has some problems, such as high cost, poor processability, limitation on use and properties, and so on. So, in order to improve its poor processability and overcome the limitation on use, we developed compatibilizers which have various chemical forms by high intensity ultrasound and super critical fluid nitrogen in polymer melt reactive extrusion.
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Thermoplastic elastomer gels, which has molecular networks composed of a microphase-separated multiblock copolymer swollen to a large extent by a low volatility mid-block selective solvent such as white oil have various applications. In this particular study, the effect of several network-forming nanoscale fillers such as two different graphite particles and carbon nanotube on the properties of TPE gels prepared from a microphaseordered poly[styrene-b-(ethylene-co-butylene)-b-styrene] (SEBS) triblock copolymer with an EB compatible white oil was studied. The linear viscoelastic behavior, sol-gel transition, x-ray diffraction and mechanical properties were discussed. The properties of thermoplastic elastomer gels hybrid with graphite prepared by mixing Poly(styrene-b-ethylene-co-butylene)-b-styrene) with paraffin oil and different amount of expandable graphite were found to increase the mechanical properties at only lower graphite concentration but tends to decrease when paraffin oil/SEBS ratio is lower. The gelation temperature is the same for all TPE gels with different amounts of graphite. Both storage (G') modulus loss (G") modulus of TPE gels slightly increase with addition of graphite.
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Poly(
${\varepsilon}-caprolactone$ ) (PCL) is a highly crystalline polymer that is miscible with several amorphous polymers including chlorinated polyether, poly(vinylchloride), poly(hydroxyether) and Bisphenol A polycarbonate. The crystallization behavior of miscible blend of amorphous/crystalline polymers has widely been studied. Generally a depression of the crystallization ability has been found with addition of amorphous component because of the reduction of chain mobility, the change of free energy of nucleation as a result of a specific interaction, and so on [1]. In this work, for the first time, the blend of PCL and copolymer of polyurethane containing polycaprolactone as a soft segment is considered. The structural similarity of TPU soft segment with PCL affects on formation of the miscible component and crystallization behavior of PCL in the blend. This has been studied using differential scanning calorimetry (DSC) and Wide-angle X-ray Scattering (WAXS). -
Rigid polyurethane foams(PUFs) are widely used in most areas of insulations such as storage tank and pipe line for transporting liquefied gas. Glass fiber and nanoclay are used for improvement in mechanical property and thermal insulation of rigid PUF at very low temperature(<
$-150^{\circ}C$ ). These rigid PUFs have been characterized in terms of thermal, mechanical, dynamic mechanical properties and cell morphology. It was found that mechanical properties, thermal conductivity and dimensional stability of rigid PU foams were improved by glass fiber and nanoclay. -
Poly (N-isopropylacrylamide) (PNIPAAm) shows a lower critical solution temperature (LCST) at
$32^{\circ}C$ . Consequently, its thermosensitivity has extensively been investigated in coating materials as well as biomedical and agricultural industry. However, mechanical properties of the swollen gels are generally poor and reinforcement is often desired. A series of interpenetrating polymer networks (IPNs) and emulsion blends hydrogels of polyurethane (PU) and PNIPAAm were prepared in order to overcome the shortcomings of a normal PNIPAAm hydrogels. Regarding the mechanical reinforcement of swollen gel, a significant increase in compression and tensile properties has been obtained by incorporating PU. -
The preparation methods are to be used as "melting method" and "absorption method", respectively. The reaction mixture in the reaction container was heating up the reaction mixture to
$200^{\circ}C$ for 2 hour. The mixing time of lab scale preparation should be provided quit long, instead of the short working time in a compounder vessel. And The PP-PCM mixture in the reaction container was heating up the mixture around$60-80^{\circ}C$ for 2 hour. A melting method of frozen gel with 50/50 weight ratio of polypropylene-normal octadecane was prepared by adding PP chip and normal octadecane. An absorption method of frozen gel with 70/30 weight ratio of PP 4.8-normal n-octadecane was prepared by adding PP powder and normal octadecnae. -
The process of weaving fabrics with high levels of tension and abrasion can cause damage to the yarn threads. To protect threadlines during the process, a protective polymer is coated on the surface of the yarns prior to weaving. This application process is known as slashing. The current slashing system is incompatible with today's demand activated manufacturing strategies. Methods of improving the uniformity of polymer coating application were studied, and several applicators were designed and evaluated. Prewetting of the threadlines before coating application was shown to greatly improve coating uniformity. The objective of the research is to design a single-end slashing process that is environmentally friendly and will improve productivity and flexibility.
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Alkoxyamine and thiocarbonyl thio end capped polyethylene (PE) chains were synthesized using a direct and simple approach consisting in reacting di(polyethylenyl)magnesium (PE-Mg-PE) chains with a range of nitroxides and disulfides of thiocarbonyl thio compounds. PE-Mg-PE compounds were prepared by a catalyzed chain growth reaction of ethylene on nbutyloctylmagnesium (BOMg) with a neodymocene complex
$(C_{5}Me_{5})_{2}NdCl_{2}Li(OEt_{2})_{2}$ . Complete characterizations confirm the introduction of the desired end groups. The controlled radical polymerization (NMP and RAFT) of butyl acrylate mediated by these functional polyethylenes was successful. -
Choi, Seok-Bong;Jepperson, John;Thomas, Johnson;Jarabek, Laura;Chisholm, Bret;Boudjouk, Philip 378
The preparation, characterization, and bio-testing of biocide incorporated silicone coatings for marine applications have been conducted. Derivatives of the biocide, Triclosan (5-chloro-2-(2, 4-dichlorophenoxy) phenol), were used to covalently attach the biocide moiety to a silicone backbone. The synthetic process allowed for control of the resulting coating's mechanical properties as well as antifouling/fouling release performance in laboratory and ocean site testing. The test results showed significantly reduce macro fouling with sustained fouling release characteristics for the coatings produced. -
AcAP was prepared by reacting p-hydroxyacetophenone (HAP) with acryloyl chloride (Ac) in presence of triethylamine (TEA) in MEK at
$0^{\circ}C$ . The reaction was monitored by TLC and the prepared monomer was characterized by UV, IR,$^{1}H-NMR\;and\;GC-MS$ . The homo- [poly (AcAP)] and copolymers [poly (AcAP-co-MMA)] were prepared by solution polymerization at$70^{\circ}C$ , in which BPO as initiator. The molecular weight of the polymers was determined by GPC. In order to find out the AF activity of prepared polymers, representatives of marine microfoulers, shipfouling bacteria (B. macroides & P. aeruginosa) and microalgae (A. coffeaeformis & N. incerta) were screened. The results of antibacterial activity and diatom attachment assays revealed potential AF efficiency of these polymers. -
Styrene-Butadiene diblock or styrene-butadiene-styrene triblock copolymers are industrially important materials for asphalt modification and adhesives. A kinetic modeling study on non-isothermal anionic styrene-butadiene diblock copolymerization system is presented. The model deals with the association/dissociation reaction of initiator and propagating ion pairs in its kinetic scheme. By comparing model calculation results with real plant data, it is possible to obtain useful ideas for more efficient plant operation. For example, the model clearly provides important relation between the reaction temperature profile and the conversion of monomers.
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AcDP and AcAP were prepared by the reaction of acryloyl chloride (Ac) with 2,4,4' -trichloro-2' -hydroxydiphenyl ether (DP) and p-hydroxyacetophenone respectively in presence of triethylamine (TEA) in MEK at
$0^{\circ}C$ . The reaction was monitored by TLC and the prepared monomer was characterized by UV, IR,$1^H-NMR$ and GC-MS. Further, copolymers poly (AcDP-MMA-AcAP) were prepared in different feed ratio of monomers by free radical polymerization at$70^{\circ}C$ , in which BPO as initiator and their molecular weight was determined by GPC. The AF activity of prepared polymers was investigated against representatives of marine microfoulers, shipfouling bacteria (B. macroides & P. aeruginosa) and microalgae (A.coffeaeformis & N. incerta). The antibacterial activity and diatom attachment assays showed significant AF potential of these polymers.