• Membrane Journal
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• v.20 no.4
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• pp.297-303
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• 2010

Composite membranes were prepared for membrane/cold condensation process for recovery of unreacted olefin monomer from the polyolefin polymerization process by solution coating and plasma polymerization processes. Poly(dimethylsiloxane) (PDMS) solution was coated on polysulfone (PSF) support and increase of prepolymer content in solution made more dense membrane structure to result in the increase of separation factor while absolute flux decreased. Permeation of organic materials through the composite membranes follows the sorption and diffusion mechanism, which brought about the results that separation factor increased with critical temperature of the organic materials, and that flux increased with the increase of the molar volume. Crosslinking period affected the permeation characteristics. Other types of composite membranes were fabricated by plasma polymerization of siloxane materials on polypropylene (PP) and PSF supports. PP was tested as a support for composite membranes, which had not been used so far in solution coating process, and plasma polymerization made the composite membranes equivalent performances to those of membranes prepared by solution coating process.

• 한국신재생에너지학회:학술대회논문집
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• 2010.06a
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• pp.129.2-129.2
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• 2010

AEM which were used for solid alkaline fuel cell(SAFC) were prepared by photo polymerization in method pore-filling with various quaternary ammonium cationic monomers and crosslinkers without an amination process. Their specific thermal and chemical properties were characterized through various analyses and the physico-chemical properties of the prepared electrolyte membranes such as swelling behavior, ion exchange capacity and ionic conductivity were also investigated in correlation with the electrolyte composition. The polymer electrolyte membranes prepared in this study have a very wide hydroxyl ion conductivity range of 0.01 - 0.45S/cm depending on the composition ratio of the electrolyte monomer and crosslinking agent used for polymerization. However, the hydroxyl ion conductivity of the membranes was relatively higher at the whole cases than those of commercial products such as A201 membrane of Tokuyama. These pore-filling membranes have also excellent properties such as smaller dimensional affects when swollen in solvents, higher mechanical strength, lowest electrolyte crossover through the membranes, and easier preparation process compared of traditional cast membranes. The prepared membranes were then applied to solid alkaline fuel cell and it was found comparable fuel cell performance to A201 membrane of Tokuyama.

• Applied Chemistry for Engineering
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• v.7 no.2
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• pp.350-355
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• 1996

Poly(AA-co-EGDMA) microgels were prepared by precipitation polymerization in highly swollen polystyrene gel solution. The polymerization was carried out in selective solvent such as cyclohexane/acetone at $60^{\circ}C$. Poly(AA-co-EGDMA) microgels with various site of $0.18{\sim}0.55{\mu}m$ were obtained from different concentration of polystyrene(PS), concentration of crosslinking agent(EGDMA), ratio of Ps/monomer and volume ratio of solvents. The particle size of poly(AA-co-EGDMA) microgels decreased with increasing the concentration of PS and increased with that of EGDMA.

• Applied Chemistry for Engineering
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• v.5 no.5
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• pp.857-861
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• 1994

UV curable hybrid systems have been investigated in the urethane acrylate based formulations where potentially irritant acrylate monomers have been substituted by vinyl ethers. Generally, among the systems studied, coating properties of hybrid system are superior to those of free radical hut inferior to those of cationic systems. When the content of acrylic oligomer is above 70%, however, hybrid system could render an excellent combination of coating and curing properties which outperforms both cationic and free radical systems. Photo-DSC has been used to follow the progress of crosslinking of various coating systems. Results imply that the critical factors in determining the curing rates of coating formulations are different depending upon the formulation characteristics. In the same type of hybrid formulations, the monomer/oligomer ratio rather than photoinitiator efficiency is the critical factor determining the curing rate of the systems.

• Macromolecular Research
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• v.17 no.4
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• pp.265-270
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• 2009

Noble thermosensitive nanoparticles, based on a PNIPAAm-co-AA core and a chitosan shell structure, were designed and synthesized for the controlled release of the loaded drug. PNIPAAm nanoparticles containing a carboxylic group on their surface were synthesized using emulsion polymerization. The carboxylic groups were conjugated with the amino group of a low molecular weight, water soluble chitosan. The particle size of the synthesized nanoparticles was decreased from 380 to 25 nm as the temperature of the dispersed medium was increased. Chitosan-conjugated nanoparticles with $2{\sim}5$ wt% MBA, a crosslinking monomer, induced a stable aqueous dispersion at a concentration of 1mg/1mL. The chitosan-conjugated nanoparticles showed thermo sensitive behaviors such as LCST and size shrinkage that were affected by the PNIPAAm core and induced some particle aggregation around LCST, which was not shown in the NIPAAm-co-AA nanoparticles. These chitosan-conjugated nanoparticles are also expected to be more biocompatible than the PNIPAAm core itself through the chitosan shell structures.

• Journal of Physiology & Pathology in Korean Medicine
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• v.16 no.4
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• pp.680-683
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• 2002

Bovine aortic endothelial cells(BAEC) produce two variant forms of laminin with a subunit composition of AB1B2 and A'B1B2. Analyses of the intracellular assembly of these subunits revealed that the B1B2 dimer formed first, and that A or A' joined to form the AB1B2 or A'B1B2 trimer. Angiostatic steroids shifted the relative size of the A and A' monomer pool in BAEC, and competition between the A and A' subunits in joining the B1B2 dimer produced AB1B2 and A'B1B2 in different ratios. This result suggests that subunit replacement is the general mechanism for producing laminin variants by various cells for tissue morphogenesis. When laminin subunits in BAEC were cross-linked with dithio-bis-succinimidylpropionate(DSP) and immunoprecipitated with anti-Iaminin antiserum, monomeric A,A',B1 and B2 monomers and the B1B2 dimer migrated as extremely large molecules in sodium dodecyl sulfate gel electrophoresis under nonreducing conditions. When the crosslinking disulfide bonds were cleaved under reducing conditions, they migrated as the usual subunits. This result suggests that molecular chaperones were involved in the process of the assembly and replacement of laminin subunits.

• Journal of the Korean Applied Science and Technology
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• v.23 no.1
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• pp.85-91
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• 2006

Acrylic resins (HSCs : EA/EMA/2-HEMA/CLA) which contain 80% solid content were synthesized by the copolymerization of monomers (ethyl acrylate, ethyl methacrylate, 2-hydroxyethyl methacrylate) and functional monomer (caprolactone acrylate : CLA) which improves the crosslinking density and physical properties of films. The physical properties of the prepared acrylic resins (HSCs) containing CLA, are as follows: viscosity 1440$^{\sim}$2630 cps ; $M_n$ 1590$^{\sim}$1660 ; and conversions, 81$^{\sim}$86%, respectively. From the correlation of $T_g$ values, viscosities, and $M_n$ of the HSCs, it was found thst viscosity and $M_n$ increased with $T_g$ value.

• Journal of the Korean Applied Science and Technology
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• v.21 no.3
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• pp.197-203
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• 2004

Acrylic resins ($HSC_s$ : EA/EMA/2-HEMA/CLA) which contain 70% solid content were synthesized by the copolymerization of monomers (2-hydroxyethyl methacrylate, ethyl acrylate, and ethyl methacrylate) and functional monomer (caprolactone acrylate : CLA) which improves the crosslinking density and physical properties of films. The physical properties of the prepared acrylic resins (HSCs) containing CLA, are as follows : viscosity 245${\sim}$515 cps ; $M_n$ 2670${\sim}$2840 ; and conversions, 83${\sim}$91%, respectively. From the correlation of $T_g$ values, viscosities, and $M_n$ of the HSCs, it was found that viscosity and $M_n$ increased with $T_g$ value.

• Polymer(Korea)
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• v.37 no.4
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• pp.513-517
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• 2013

A novel conductive composite thin film was prepared for the first time by hybridization between polybenzoxazine (PBZ) having high heat resistance property and conductive graphene. Mechanically robust conductive graphene/PBZ composite thin films could effectively be prepared by a simple thermal treatment, which simultaneously induces reduction of graphene oxide (GO) and crosslinking reaction of benzoxazine monomer. Graphene sheets seem to be uniformly dispersed up to 3 wt% graphene content in the composite thin film as shown in the results of chemical/crystal structural and morphological analyses. This efficient route for making graphene/PBZ composite thin film would provide simultaneous improvement of mechanical property as well as electrical conductivity.

• Korean Chemical Engineering Research
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• v.59 no.1
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• pp.112-117
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• 2021

In this study, a method of self-assembly of peptides based on irreversible covalent bonds was studied by mimicking a biological covalent bond, dityrosine bond. A tyrosine-rich short peptide monomer having the sequence of Tyr-Tyr-Leu-Tyr-Tyr (YYLYY) was selected to achieve a high-density of dityrosine bond. The peptide nanoparticles covalently self-assembled with dityrosine bonds were synthesized by one-step photo-crosslinking of a peptide using a ruthenium catalyst under visible light. The effect of the concentration of each component for the size of the peptide nanoparticle was studied using dynamic light scattering, UV-Vis spectroscopy, and transmission electron microscopy. As a result, the synthesis conditions for size of the peptide nanoparticles ranging from 130 nm to 350 nm were optimized.