• Bulletin of the Korean Chemical Society
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• v.34 no.11
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• pp.3340-3344
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• 2013

The fabrication of polymer field-effect transistors with good electrical properties requires the minimization of molecular defects caused by low molecular weight (MW) fractions of a conjugated polymer. Here we report that the electrical properties of a narrow bandgap conjugated polymer could be dramatically improved as a result of dipping a thin film into a poor solvent. The dipping time in hexanes was controlled to efficiently eliminate the low molecular weight fractions and concomitantly improve the molecular ordering of the conjugated polymer. The correlation between the structural order and the electrical properties was used to optimize the dipping time and investigate the effects of the low MW fraction on the electrical properties of the resulting thin film.

• Polymer(Korea)
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• v.31 no.6
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• pp.555-561
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• 2007

To obtain low molecular weight water soluble chitosan (LMWSC) with various molecular weights, chitosan oligosaccharides (COS) with lactic acid was separated by using ultrafilteration technique and LMWSC with a free amine group was prepared by the novel salts-removal method. The characterization of LMWSC removed the lactic acid and degree of deacetylation (DDA) were identified by FT-IR and $^1H-NMR$ spectra. Polydispersity index (PDI) was $1.278{\sim}1.499$, which indicates a relatively molecular weight distribution. To identify the potential as a gene carrier, we confirmed the transfection efficiency of COS fractioned according to molecular weight successfully and the salt-removed LMWSC using 293T cell. Also, LMWSC derivatives prepared for improvement transfection efficiency were evaluated using Balb/C mice.

• Economic and Environmental Geology
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• v.32 no.3
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• pp.307-315
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• 1999

Four organic polymers were mixed with mothmorillonite. Two cationic polymers a hi로 molecular weight polyacrylamide (494C) and a low molecular weight polymer (587C).Two anionic polymers include a high molecular weight polymer (aerotil). Each clay supension series were allowed to stand for 24 hours and were centrifuged, and the clay plugs were washed and dried. The dried samples investigated by XRD, IR and CEC measurement. The suspended clay containing anionic polymers was not flocculated at any concentratuons of polymer. But the suspendions containing two cationic polymers were rapidly flocculated at almost all concentrations. the d(001) spacings of Na-montmorillonite after being with cationic polymer 587C show about 15$\AA$ suggesting the polymers may have entered the interlayer spaces. The polymer 494C-treated sample produced double peaks of about 12 and 15$\AA$ in XRD. It indicates that the high molecular weight polymer. And cationic polymer 494C may be adsorbed mainy on the outside surface of clay, and some polymers may peretrate into olny interlayers in the margin of montmorillonite particles because of its high molecular weught. CEC of polumer 587-treated sample was reduecd mmarkedly suggesting polymer blocks CEC sites. The d(001) spacings of Ca-montmorillonite after being treated with cationic polymers show about 15$\AA$ suggesting that the interlayer spaces have not been expanded. In the experiment using a dilute Ca-bearing solution, the suspended caly containinf anionic polymers was flocculated. The results indicate that the flocculation behavior of montmorillonite-polymer supension depends on not only polymer properties such as concentration, electric charge and molecular weight but also compositions of solvent.

• Polymer(Korea)
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• v.39 no.3
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• pp.388-393
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• 2015

Low molecular weight species were extracted from PC and SAN by a solvent extraction method in order to investigate the effect of low molecular weight species on interfacial tension and affinity between PC and SAN. From the analysis of molecular weight distribution by the GPC, it was confirmed that the low molecular weight species were effectively eliminated by the solvent extraction. Interfacial tension measurements and morphological observation were carried out with the PC and SAN of which the low molecular weight species were extracted. Interfacial tension was increased and the infinity was decreased for the extracted PC and SAN pair. This result implied that the low molecular weight species play a role as a compatibilizer between two polymers. Among two polymers, low molecular weight SAN contributes more in the compatibilization. Thus, it is favorable to use SAN containing a larger amount of low molecular weight species in fabrication of PC/ABS blend.

• Macromolecular Research
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• v.12 no.4
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• pp.325-335
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• 2004

Molecular weight distributions of poly(vinyl neo-decanoate) produced by the bulk polymerization of the monomer to low conversions were investigated to obtain values of the rate constants for the chain transfer to monomer ( $C_{M}$). The value of $C_{M}$ of 7.5($\pm$0.6)${\times}$10$^{-4}$ was obtained from a logarithmic plot of the number distribution at 5,25, and 5$0^{\circ}C$, which suggests that the activation energy for chain transfer is on the order of 20-25 kJ ㏖$^{-1}$ . These plots were linear between the number and weight-average degrees of polymerization, but not over the whole molecular weight range for which a significant signal was observed in the gel permeation chromatography (GPC) trace. Modeling suggests that the deviations observed at high molecular weights can be explained by branching of the chains through chain transfer to the polymer, with a branching density as low as 10$^{-5}$ , without affecting the slope at low values of the number of monomer unit, N. This deviation from the expected distribution of linear chains was used to estimate the branching densities at low conversion.ion.

• Macromolecular Research
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• v.14 no.4
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• pp.430-437
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• 2006

The ultra-drawing process of an ultra high molecular weight polyethylene (UHMWPE) gel film was examined by incorporating linear low-density polyethylene (LLDPE) and $BaTiO_3$ nanoparticles. The effects of LLDPE and the draw ratios on the morphological development and mechanical properties of the nanocomposite membrane systems were investigated. By incorporating $BaTiO_3$ nanoparticles in the UHMWPE/LLDPE blend systems, the ultra-drawing process provided a highly extended, fibril structure of UHMWPE chains to form highly porous, composite membranes with well-dispersed nanoparticles. The ultra-drawing process of UHMWPE/LLDPE dry-gel films desirably dispersed the highly loaded $BaTiO_3$ nanoparticles in the porous membrane, which could be used to form multi-layered structures for electronic applications in various embedded, printed circuit board (PCB) systems.

• Macromolecular Research
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• v.9 no.6
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• pp.332-338
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• 2001

Waterborne polyurethane as a new polymer electrolyte was synthesized by using relatively hydrophilic polyols. The morphology of polyurethane was changed as it was dispersed in water. In contrast to polyurethane ionomer, waterborne polyurethane did not form an ionic cluster but produced a binary system composed of hydrophilic and hydrophobic groups. In the colloidal system, the former and the latter existed at outward and inward, respectively. Waterborne polyurethane was prepared from poly(ethylene glycol) (PEG) /poly(propylene glycol) (PPG) copolymer, 4,4'-diphenylmethane diisocyanate(MDI), ethylene diamine as a chain extender, and three ionization agents, 1,3-propane sultone, sodium hydride and lithium hydroxide. PEG/PPG copolymer was used for suppressing the crystallinity of PEG and N-H bond was ionized for increasing the electrochemical stability of polyurethane. Low molecular weight poly(ethylene glycol) and poly(ethylene glycol dimethyl ether) (PEGDME) were used as plasticizers. DSC, FT-IR and $^1$H-NMR of the waterborne polyurethane were measured. Also, the ionic conductivity of solid polymer electrolytes based on waterborne polyurethane and various concentrations of low molecular weight poly(ethylene glycol) or PEGDME were measured by AC impedance.

• Bulletin of the Korean Chemical Society
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• v.17 no.3
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• pp.245-253
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• 1996

A topological theory has been introduced to explain and evaluate the fractional volumes of system materials, the change of the weight and concentration of monomer molecules, molecular weight distribution, and interaction functions of polymer-polymer and polymer-oligomer, etc. for dispersion polymerization. The previous theory of Lu et al. has offered only an incomplete simulation model for dispersion polymer systems, whereas our present one gives a general theoretical model applicable to all the polymerization systems. The theory of Lu et al. considered only the physical property term caused by interaction between matters of low molecular weight (i.e., diluent, monomer, and oligomer) and polymer particles without dealing with physical properties caused by the structure of polymer networks in polymer particles, while our theory deals with all physical effect possible, caused by the displacement of not only entangled points but also junction points in polymer particles. The theoretically predictive values show good agreement with the experimental data for dispersion polymerization systems.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.43 no.2
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• pp.77-82
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• 2011

The changes in the wet pressing response of old corrugated container(OCC) stock depending on the beating treatment and the addition of polymer aids were investigated with laboratory roll press instrument. Two types of polymer aids, such as high molecular weight polymer with low charge density and low molecular weight polymer with high charge density, were applied in this study. The more beaten OCC stock showed the lower dryness after wet pressing. The addition of polymer aids had great influences on the wet pressing efficiency and paper properties. The dryness after wet pressing was increased by the addition of polymer aids, but the pattern of changes in dryness were different depending on the type of polymer and the properties of stock. The higher molecular weight polymer aids showed the greater increase in the dryness. The properties of paper such as air permeability, bulk, formation, tensile strength were also greatly affected by the addition of polymer aids.

• Proceedings of the Polymer Society of Korea Conference
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• 2006.10a
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• pp.235-235
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• 2006

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.