• Bulletin of the Korean Chemical Society
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• v.32 no.4
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• pp.1303-1309
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• 2011

Melt copolymerization reactions of bis(diethylamino)tetramethyldisiloxane with several aryldiols were carried out to afford poly(carbotetramethyldisiloxane)s containing fluorescent aromatic chromophore groups in the polymer main chain: poly{oxy(4,4'-biphenylene)oxytetramethyldisiloxane}, poly{oxy(1,4-phenylene)oxytetramethyldisiloxane}, poly[oxy{(4,4'-isopropylidene)diphenylene}oxytetramethyldisiloxane], poly[oxy{(4,4'-hexafluoroisopropylidene)diphenylene}oxytetramethyldisiloxane], poly{oxy(2,6-naphthalene)oxytetramethyldisiloxane}, poly[oxy{4,4'-(9-fluorenylidene)diphenylene}oxytetramethyldisiloxane], poly{oxy(fluorene-9,9-dimethylene)oxytetramethyldisiloxane}, and poly[oxy{4,4'-(9-fluorenylidene)bis(2-phenoxyethylene)}oxytetramethyldisiloxane]. These materials are soluble in common organic solvents such as $CHCl_3$ and THF. The FTIR spectra of all the polymers exhibit the characteristic Si-O-C stretching frequencies at 1021-1082 $cm^{-1}$. In the THF solution, the polymeric materials show strong maximum absorption peaks at 215-311 nm, with strong maximum excitation peaks at 250-310 nm, and strong maximum fluorescence emission bands at 310-360 nm. TGA thermograms indicate that most of the polymers are stable up to $200^{\circ}C$ with a weight loss of less than 10% in nitrogen.

• Macromolecular Research
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• v.17 no.12
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• pp.1021-1024
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• 2009

We successfully prepared high-flow polycarbonate (PC) by blending commercial PC with a low molecular weight PC oligomer. The oligomer was synthesized by the addition of a large quantity of mono functional phenol groups, and the chain end group was reacted with p-tertiary butyl phenol (PTBP) to block the reactivity. The viscosity average molecular weight ($M_v$) for the oligomer was about 4,000-5,000 g/mol, compared to ~19,000 g/mol for the PC blend obtained by blending 10 wt% of the prepared oligomer with the commercial grade PC ($M_v$ of 21,000 g/mol). The blended PC had a melt flow index of 45, which is 2.5 times higher, and a processing temperature that was $20^{\circ}C$ lower, than that of commercial grade PC having a similar $M_v$.

• Korea-Australia Rheology Journal
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• v.11 no.4
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• pp.305-311
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• 1999

The shear behavior of polymers obtained by means of devices such as capillary and cone-and-plate rheo-meters is commonly used to assess their processing performance and as a characterization tool. However, the number of instances when two polymers have the same shear properties but perform differently during certain types of processing operations (e.g. film blowing and sheet extrusion) indicate that shear properties alone may not be sufficient to characterize polymeric fluids. We begin by defining the kinematics of shear-free or extensional flow and the associated material functions. The extensional and shear behavior of three different types of polyethylene (PE) are then compared to illustrate the points that one cannot ascertain the extensional properties of polymer melts from their shear properties and, furthermore, there may not be a simple relation between properties obtained from one type of extensional flow and those of another type. The kinematics of most processing flows are extensional rather than shear in nature, and , hence, the performance of polymers during processes such as fiber spinning, film casting, film blowing, thermoforming, blow molding, and even extrusion is more readily accounted for through extensional viscosity measurements. Methods for carrying out extensional flow measurements are then reviewed including approximate methods. To illustrate the sensitivity of extensional viscosity measurements to subtle changes in the molecular architecture of PEs, results are presented for samples with a narrow molecular weight distribution but with varying numbers of long chain branches. Finally, constitutive equations which allow one to separate shear and extensional flow behavior are discussed as any attempts to simulate the subtle processing differences between two polymers will require constitutive equations of this nature.

• Macromolecular Research
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• v.12 no.4
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• pp.379-383
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• 2004

Poly(ethylene glycol)s (PEGs) are unique in their material properties, such as biocompatibility, non-toxicity, and water-solublizing ability, which are extremely useful for a variety of biomedical applications. In addition, a variety of functional PEGs with specific functionality at one or both chain ends have been synthesized for many specialized applications. Surface modifications using PEG have been demonstrated to decrease protein adsorption and platelet or cell adhesion on biomaterials. Furthermore, PEGs having anionic sulfonate terminal units have been proven to enhance the blood compatibility of materials, which has been demonstrated by the negative cilia concept. The preparation of telechelic PEGs having a sulfonic acid group at one end and a polymerizable methacryloyl group at the other is an interesting undertaking for providing macromers that can be used in various vinyl copolymerization and gel systems. In this paper, preliminary results on the synthesis and polymerization behavior of a novel PEG macromer is described with the aim of identifying a biocompatible material for applications in various blood-contacting devices.

• Macromolecular Research
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• v.17 no.9
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• pp.682-687
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• 2009

Nanofibrous membranes of poly(D,L-lactic acid)/chitin blend were prepared by electro spinning for a barrier of guided tissue regeneration. A miscible solution was obtained by the blending chitin-salt complex into 1-methyl-2-pyrrolidone solution of poly(D,L-lactic acid). The properties of the blend were examined for nanofibrous fabrication. The viscosity of the blend solution was increased significantly due to chain entanglement despite the low ratio of chitin to poly(D,L-lactic acid). An interaction between two polymeric compositions was confirmed by Fourier transform infrared spectroscopy. X-ray diffraction detected an appreciably ordered microstructure in the nanofiber of the blend. A membrane of thinner nanofibers was fabricated by electro spinning the chitin blend. The permeability of the membranes was examined using bioactive model compounds.

• Bulletin of the Korean Chemical Society
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• v.33 no.6
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• pp.2031-2036
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• 2012

Melt copolymerization reactions of several bis(diethylamino)silane derivatives, bis(diethylamino)methylphenylsilane, bis(diethylamino)methyloctylsilane, 1,2-bis(diethylamino)tetramethyldisilane, and 1,3-bis(diethylamino) tetramethyldisiloxane, with 2,7-dihydroxyfluoren-9-one were carried out to yield poly[oxy(2,7-fluoren- 9-onenylene)oxy(diorganosilylene)]s bearing the fluoren-9-one fluorescent aromatic group in the polymer main chain: poly[oxy(2,7-fluoren-9-onenylene)oxy(methylphenylsilylene)], poly[oxy(2,7-fluoren-9-onenylene) oxy(methyloctylsilylene)], poly[oxy(2,7-fluoren-9-onenylene)oxy(tetramethyldisilylene)], and poly[oxy- (2,7-fluoren-9-onenylene)oxy(tetramethyldisiloxanylene)]. These polymeric materials are soluble in common organic solvents such as $CHCl_3$ and THF. FTIR spectra of all the materials reveal characteristic Si-O-C stretching frequencies at 1012-1018 $cm^{-1}$. In the THF solution, the prepared materials show strong maximum absorption peaks at 258-270 nm, strong maximum excitation peaks at 260-280 nm, and strong maximum fluorescence emission bands at 310-420 nm. TGA thermograms suggest that most of the polymers are essentially stable to $200^{\circ}C$ without any weight loss and up to $300^{\circ}C$ with only a weight loss of less than 5% in nitrogen.

• Bulletin of the Korean Chemical Society
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• v.33 no.5
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• pp.1581-1585
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• 2012

Two pyridinecarboxamide dicyanidecobalt(III) building blocks and two mononuclear seven-coordinated macrocycle manganese(II) compounds have been rationally selected to assemble cyanide-bridged heterobimetallic complexes, resulting in three cyanide-bridged $Co^{III}-Mn^{II}$ complexes. Single X-ray diffraction analysis show that these complexes $\{[Mn(L^1)][Co(bpb)]\}ClO_4{\cdot}CH_3OH{\cdot}0.5H_2O$ ($\mathbf{1}$), $\{[Mn(L^2)][Co(bpb)]\}ClO_4{\cdot}0.5CH_3OH$ ($\mathbf{2}$) and ${[Mn(L^1)][Co(bpb)]\}ClO_4{\cdot}H_2O$ ($\mathbf{3}$) ($L^1$ = 3,6-diazaoctane-1,8-diamine, $L^2$ = 3,6-dioxaoctano-1,8-diamine; $bpb2^{2-}$ = 1,2-bis(pyridine-2-carboxamido)benzenate, $bpmb2^{2-}$ = 1,2-bis(pyridine-2-carboxamido)-4-methyl-benzenate) all present predictable one-dimensional single chain structures. The molecular structures of these one-dimensional complexes consists of alternating units of $[Mn(L)]^{2+}$ ($L=L^1$ or $L^2$) and $[Co(L^{\prime})(CN)2]^-$ ($L^{\prime}=bpb2^{2-}$, or $bpmb2^{2-}$), forming a cyanide-bridged cationic polymeric chain with free $ClO_4{^-}$ as the balance anion. The coordination geometry of manganese(II) ion in the three one-dimensional complexes is a slightly distorted pentagonal-bipyrimidal with two cyanide nitrogen atoms at the trans positions and $N_5$ or $N_3O_2$ coordinating mode at the equatorial plane from ligand $L^1$ or $L^2$. Investigation over magnetic properties of these complexes reveals that the very weak magnetic coupling between neighboring Mn(II) ions connected by the diamagnetic dicyanidecobalt(III) building block. A best-fit to the magnetic susceptibility of complex ${\mathbf}{1}$ leads to the magnetic coupling constants $J=-0.084(3)cm^{-1}$.

• Korean Chemical Engineering Research
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• v.45 no.5
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• pp.466-472
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• 2007

A technology platform for wafer-level three-dimensional integration circuits (3D-ICs) is presented, and that uses wafer bonding with low-k polymeric adhesives and Cu damascene inter-wafer interconnects. In this work, one of such technical platforms is explained and characterized using a test vehicle of inter-wafer 3D via-chain structures. Electrical and mechanical characterizations of the structure are performed using continuously connected 3D via-chains. Evaluation results of the wafer bonding, which is a necessary process for stacking the wafers and uses low-k dielectrics as polymeric adhesive, are also presented through the wafer bonding between a glass wafer and a silicon wafer. After wafer bonding, three evaluations are conducted; (1) the fraction of bonded area is measured through the optical inspection, (2) the qualitative bond strength test to inspect the separation of the bonded wafers is taken by a razor blade, and (3) the quantitative bond strength is measured by a four point bending. To date, benzocyclobutene (BCB), $Flare^{TM}$, methylsilsesquioxane (MSSQ) and parylene-N were considered as bonding adhesives. Of the candidates, BCB and $Flare^{TM}$ were determined as adhesives after screening tests. By comparing BCB and $Flare^{TM}$, it was deduced that BCB is better as a baseline adhesive. It was because although wafer pairs bonded using $Flare^{TM}$ has a higher bond strength than those using BCB, wafer pairs bonded using BCB is still higher than that at the interface between Cu and porous low-k interlevel dielectrics (ILD), indicating almost 100% of bonded area routinely.

• Membrane Journal
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• v.29 no.4
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• pp.223-230
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• 2019

In this paper, we develop a polymeric blend membrane based on $CO_2$-philic poly(2-[3-(2H-benzotriazol-2-yl)-4-hydroxyphenyl] ethyl methacrylate)-poly(oxyethylene methacrylate) (PBEM-POEM) comb copolymer, which was synthesized by facile free radical polymerization. The PBEM-POEM (PBE) comb copolymer was blended with a commercial oligomer, low-molecular-weight poly(ethylene glycol) (PEG, $M_w=200gmol^{-1}$) with various ratios to prepare $CO_2/N_2$ separation membranes. From the result of $CO_2/N_2$ separation test of the PBE/PEG blend membranes with the various PEG contents, we could conclude that with increasing PEG content, the $CO_2/N_2$ selectivity significantly increased while the CO2 permeability decreased showing trade-off relationship. However, when comparing the performance of the PBE/PEG (9 : 1) with the PBE/PEG (7 : 3) membrane, the $CO_2$ permeance decreased by only 8.3%, while the $N_2$ permeance decreased by 69.1%. Therefore, the $CO_2/N_2$ selectivity dramatically increased from 33.8 to 100.3. This could be because the POEM chains, which account for 80% of the PBE copolymer, favorably interact with PEG and lead to a more compact chain structure, which was confirmed by FT-IR, XRD and SEM analysis. The PBE/PEG (7 : 3) blend membrane had the most optimal gas separation performance, showing a $CO_2$ permeance of 170.5 GPU and $CO_2/N_2$ selectivity of 100.3.

• Elastomers and Composites
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• v.35 no.1
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• pp.29-37
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• 2000

In this study as a basic research of the elastomer, we show the results of the behavior of the two different chain length polymers in the melt confined between two impenetrable planes. The cubic lattice simulations are conducted in the canonical ensemble with a method that is a combination of reptation and crackshaft bond flip motions. A total of 680 chains which are 544 short chains comprising 10 beads and 136 long chains comprising 160 beads were placed in 20 lattice layers. It was assumed that there is no energetic interactions between covalently connected beads. while all other neighbors will interact with a truncated 6-12 Lennard-Jones potential. From the analysis of the simulation results, it was shown that purely entropic effects caused the shorter chains to partition preferentially to the surface. We also showed that the center of mass density of the shorter chains shows maximum near the surface. This is the opposite phenomena when compared to that of the longer chains. However, the segments of the shorter and the longer chains did not display any significant changes in bond order.