• Polymer(Korea)
• /
• v.35 no.4
• /
• pp.284-288
• /
• 2011

For the purpose of the pre-industry production of poly(L-lactide) (PLLA) and full understanding of the supercritical polymerization system, large scale polymerization of L-iactide initiated by 1-dodecano/stannous 2-ethyl-hexanoate (DoOH/Sn(Oct)$_2$) was carried out in supercritical chlorodifluoromethane under various reaction conditions (time, temperature and pressure)and reactants (monomer and supercritical solvent) concentrations. A 3 L sized-reactor system was used throughout this study. The monomer conversion increased to 72% on increasing reaction time to 5 h. The molecular weight of PLLA product also increased to 68000 g/moi over the same period. An increase in monomer concentration resulted in a higher molecular weight, up to 144000 g/mol and 97% of monomer conversion. Raising the reaction pressure from 130 to 240 bar also resulted in an increased monomer conversion and molecular weight. To increase heat resistivity of PLLA, methanol treatment and heat-vacuum methods were evaluated. Both of them successfully improved the heat resistivity property of PLLA.

• Korean Journal of Human Ecology
• /
• v.2 no.1
• /
• pp.17-24
• /
• 1993

Insulin polymer was used as an immunogen to elicit homogeneous anti-insulin yolk antibodies in a large scale. Insulin polymer prepared was heterogeneous mixture (MW=6,000-70,000). Insulin polymer showed stronger immunogenecity than insulin monomer. The affinity of yolk antibodies elicited with insulin polymer was slightly lower than that of yolk antibodies elicited with insulin monomer. The specificity of yolk antibodies obtained with insulin monomer and insulin polymer was directed mostly to native insulin.

• Proceedings of the Polymer Society of Korea Conference
• /
• 2006.10a
• /
• pp.15-16
• /
• 2006

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.

• Bulletin of the Korean Chemical Society
• /
• v.35 no.1
• /
• pp.30-34
• /
• 2014

We report a novel approach for fabricating active surface-enhanced Raman scattering (SERS) substrate for sensitive detection. This approach is based on the assembling of gold nanoparticles (AuNPs) onto the electrospun polycaprolactone (PCL) nanofiber film. The hydrophobic surface of PCL nanofiber film was pretreated using UV-inducing graft polymerization with acrylic acid. Afterwards this PCL nanofiber film was incubated with the AuNP solution to promote the assembly of AuNPs onto the PCL nanofibers and the formation of SERS active substrate. 4-aminothiophenol (4-ATP) molecule was used as a test probe for SERS experiments, indicating that the substrate has high sensitivity to SERS response. Our method has great advantage in term of environment-friendly synthesis, large-scale, high stability and good reproducibility. This highly active SERS substrate can be employed to detect the drug molecule, 2-thiouracil.

• Applied Chemistry for Engineering
• /
• v.31 no.3
• /
• pp.267-276
• /
• 2020

Poly(epichlorohydrin) copolyol series (PECH copolyols) were synthesized via cationic ring-opening copolymerization (ROCP) of oxirane-based monomers and effects of reaction temperature, solvent type, and initiator were studied. As a comonomer, two types of alkylene oxides were used, and polymerization conditions were conducted both with diethylene glycol (DEG) as an initiator in methylene chloride (MC) solvent and tripropylene glycol (TPG) in toluene solvent. In order to induce the active monomer (AM) mechanism in the ring-opening copolymerization reaction, the monomer was injected by an incremental monomer addition (IMA) method using a syringe pump, and the polymerization was performed at -5 ℃. PECH copolyol, a synthesized ephichorohydrin (ECH)-based copolyol, was converted to glycidyl azide-based energy-containing copolyol (GAP copolyol) by azadizing the ECH unit through a substitution reaction. It was confirmed that the synthesized azide copolyol had little effects on changes of the solvent and the initiator. Also, the molecular weight increased 500 after the azide reaction, thereby the GAP copolyol was polymerized as designed. As the content of the comonomer increased, both the T_g and viscosity tended to decrease due to the influence of the alkyl chain length. It is possible to fundamentally prevent CH₃N₃ amount produced in the azide reaction process, and it is expected that a large-scale process could be achievable.

• International Journal of Oral Biology
• /
• v.37 no.4
• /
• pp.181-188
• /
• 2012

As the demand for large-scale analysis of gene expression using DNA arrays increases, the importance of the surface characterization of DNA arrays has emerged. We compared the efficiency of molecular biological applications on solid-phases with different surface polarities to identify the most optimal conditions. We employed thiol-gold reactions for DNA immobilization on solid surfaces. The surface polarity was controlled by creating a self-assembled monolayer (SAM) of mercaptohexanol or hepthanethiol, which create hydrophilic or hydrophobic surface properties, respectively. A hydrophilic environment was found to be much more favorable to solid-phase molecular biological manipulations. A SAM of mercaptoethanol had the highest affinity to DNA molecules in our experimetns and it showed greater efficiency in terms of DNA hybridization and polymerization. The optimal DNA concentration for immobilization was found to be 0.5 ${\mu}M$. The optimal reaction time for both thiolated DNA and matrix molecules was 10 min and for the polymerase reaction time was 150 min. Under these optimized conditions, molecular biology techniques including DNA hybridization, ligation, polymerization, PCR and multiplex PCR were shown to be feasible in solid-state conditions. We demonstrated from our present analysis the importance of surface polarity in solid-phase molecular biological applications. A hydrophilic SAM generated a far more favorable environment than hydrophobic SAM for solid-state molecular techniques. Our findings suggest that the conditions and methods identified here could be used for DNA-DNA hybridization applications such as DNA chips and for the further development of solid-phase genetic engineering applications that involve DNA-enzyme interactions.

• Journal of the Korean Electrochemical Society
• /
• v.7 no.2
• /
• pp.100-107
• /
• 2004

The nano or micro sized structures of conducting polymer had been prepared by synthesizing the desired polymer within the pores of template of nano or micro porous membrane filter. In this study, we had tried to fabricate conducting polymer microstructures on an electrode by using electrochemical deposition adopting template synthesis. Our attention was focused on two different things, attaching template on the electrode and fabricating microstructures only at limited areas of the electrode. A conducting polymer, PEDiTT (poly 3,4-ethylenedithi-athiophene) solution was blended with PVA(polyvinyl alcohol) solution and used as an conducting adhesive. After attaching template membrane, the electrode were immersed in 0.5M pyrrole in 0.1M KCI solution, and electrochemical polymerization was performed. The growth process of the microstructures studied by SEM. The electrochemical fabrication of conducting polymer was performed by using two-electrode system. A large working electrode and a micro scale disc electrode were used for the confined area synthesis. Polymerization potential was 4V in an electrolytic solution made of KCI in deionized water. The optimum polymerization conditions were, i.e. (4V/100sec) for $250{\mu}m$ electrode and (6V/30 sec) for $10{\mu}m$ electrode.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2013.02a
• /
• pp.221-221
• /
• 2013

Striving to replace the well known silicon nanocrystals embedded in oxides with solution-processable charge-trapping materials has been debated because of large scale and cost effective demands. Herein, a silicon quantum dot-polystyrene nanocomposite (SiQD-PS NC) was synthesized by postfunctionalization of hydrogen-terminated silicon quantum dots (H-SiQDs) with styrene using a thermally induced surface-initiated polymerization approach. The NC contains two miscible components: PS and SiQD@PS, which respectively are polystyrene and polystyrene chains-capped SiQDs. Spin-coated films of the nanocomposite on various substrate were thermally annealed at different temperatures and subsequently used to construct metal-insulator-semiconductor (MIS) devices and thin film field effect transistors (TFTs) having a structure p-$S^{++}$/$SiO_2$/NC/pentacene/Au source-drain. C-V curves obtained from the MIS devices exhibit a well-defined counterclockwise hysteresis with negative fat band shifts, which was stable over a wide range of curing temperature ($50{\sim}250^{\circ}C$. The positive charge trapping capability of the NC originates from the spherical potential well structure of the SiQD@PS component while the strong chemical bonding between SiQDs and polystyrene chains accounts for the thermal stability of the charge trapping property. The transfer curve of the transistor was controllably shifted to the negative direction by chaining applied gate voltage. Thereby, this newly synthesized and solution processable SiQD-PS nanocomposite is applicable as charge trapping materials for TFT based memory devices.

• Journal of Embryo Transfer
• /
• v.10 no.1
• /
• pp.73-82
• /
• 1995

large scale production of cloned embryos requires the technology of multiple generation nuclear transplantation(NT) using NT embryos as the subsequent donor nuclei. The purposes of this study were producing the second generation cloned rabbit embryos, and also to determine the electrofusion rate and in vitro developmental potential comparatively in the cloned embryos of the first and second NT generation. The embryos of 16-cell stage were collected from the mated does by flushing oviducts with Dulbecco's phosphate buffered saline(D-PBS) containing 10% fetal calf serum(FCS) at 47 hours after hCG injection In the first generation NT, the nuclear donor embryos were synchronized in the phase of Gi /S transition of 32-cell stage. The first generation NT embryos which were developed to 8-cell were synchronized in Gi /S transition phase of the following 16-cell stage and used as donor nuclei for second generation Synchronization of the cell cycle of blastomeres was induced, first, using an inhibitor of microtuble polymerization, colcemid for 10 hours to arrest blastomeres in M phase, and secondly, using a DNA synthesis inhibitor, aphidicolin for 1.5 to 2 hours to arrest them in Gi /S transition boundary. The recipient cytoplasms were obtained by removing the nucleus and the first polar body from the oocytes collected at 14 hours after hCG injection. The separated donor blastomeres were injected into the enucleated recipient oocytes by micromanipulation and were electrofused by electrical stimulation of three pulses for 60 $\mu$sec at 1.25 kV /cm in 0.28 M rnannitol solution The fused oocytes were co-cultured with a monolayer of rabbit oviductal epithelial cells in M-199 solution containing 10% FCS for 120 hours at 39$^{\circ}C$ in a 5% $CO_2$ incubator. Following in vitro culture of the first and second generation cloned embryos to blastocyst stage, they were stained with Hoechst 33342 dye for counting the number of blastomeres by fluorescence microscopy. The results obtained were summarized as follows: 1. The electrofusion rate was found to be similar as 79.4 and 91.5% in the first and second generation NT rabbit embryos, respectively. 2. The in vitro developmental potential to blastocyst stage of the second generation NT embryos (23.3%) was found significantly(p<0.05) lower, compared with that of the first generation NT embryos (56.8%). 3. The mean blastomeres counts of embryos developed to blastosyst stage following in vitro culture for 120 hours and also their daily cell cycles during the culture period were decreased significantly (p<0.05) to 104.3 cells and 1.33 cylces in the second NT generation, compoared with 210.4 cells and 1.54 cycles in the first NT generation, respectively.