• Polymer(Korea)
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• v.38 no.6
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• pp.720-725
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• 2014

Aminopropyl terminated polydimethylsiloxane was synthesized by hydrosilylation reaction with hydride terminated polydimethlysiloxane and allyl amine. Polydimethylsiloxane modified urea with isocyanate group was prepared from cyclic trimer of hexamethyldiisocyanate with aminopropyl terminated polydimethylsiloxane. Polydimethylsiloxane modified urea/acrylate resin (PUA) was prepared from the urethane reaction of PU with isocyanate group and 2-hydroxyethylmethacrylate. PUA structure was analyzed by FTIR and NMR. Coating materials were prepared by mixing PUA, acrylic monomer, photo-initiator, and solvent and coated on PET film to obtain flexible hard coating film by UV irradiation.

• Journal of Applied Biological Chemistry
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• v.63 no.4
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• pp.319-325
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• 2020

The liquids of Lycopersicon esculentum were extracted with 70% aqueous MeOH and the concentrates were partitioned into EtOAc, n-BuOH, and H2O fractions. The repeated silica gel and octadecyl silica gel column chromatographies for the EtOAc fraction, whose activity was confirmed, led to isolation of one flavonol compound. The chemical structures of the compound were determined as quercetin (1) based on spectroscopic analyses including nuclear magnetic resornance, infrarad spectroscopy, and mass spectroscopy. Through this study, the antioxidant efficacy was confirmed by demonstrating that the L. esculentum fraction showing an increase in glutathione mean (GM) and a decrease in glutathione heterogeneity (GH) uniformly raises the intracellular glutathione (GSH) level.

• Polymer(Korea)
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• v.28 no.1
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• pp.24-34
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• 2004

Transient sorption experiments were conducted among several combinations of fluoropolymers and various organic solvents. Fully fluorinated polymer tended to exhibit ideal sorption behavior, while partially fluorinated polymers showed anomalous sorption behaviors with a drastic acceleration at the final stage of uptake. Minimization of least-squares of the measured and predicted fractional uptake, which indicated the increasing degree of deviation from Fickian diffusion, gave values of 3.0${\times}$10$\^$-4/, 1.75${\times}$10$\^$-3/, 8.68${\times}$10/sup-3/, 1.75${\times}$10$\^$-2/, respectively, for perfluoroalkoxy copolymer, poly(ethylene-co-tetrafluoroethylene), poly(vinylidene fluoride), poly(ethylene-co-chlorotrifluoroethylene). From stress-strain tests, it was confirmed that non-Fickian diffusion is closely related to the significant variation of mechanical properties (such as modulus and tensile strength) of swollen polymer. Anomalous sorption behavior stemmed from non-Fickian diffusion caused by nonlinear disruption of polar inter-segmental bonds due to solvent-induced plasticization. Thus, it is imperative to investigate the diffusion behavior of swelling solvents in partially fluorinated polymers, especially for the application to barrier materials or perm-selective membranes.

• Korean Chemical Engineering Research
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• v.57 no.4
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• pp.512-518
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• 2019

To develop a membrane electrode assembly (MEA) with lower Pt loading and higher performance in proton exchange membrane fuel cells (PEMFCs), it is an important research issue to understand interfacial structure of Pt/C catalyst and ionomer and design the catalyst layer structure. In this study, we prepared short-side-chain Nafion-based ionomer dispersion using propylene glycol (PG) as a solvent instead of water which is commonly used as a solvent for commercially available ionomers. Cathode catalyst layers with different ionomer content from 20 to 35 wt% were prepared using the ionomer dispersion for the fabrication of four different MEAs, and their fuel cell performance was evaluated. As the ionomer content increased to 35 wt%, the performance of the prepared MEAs increased proportionally, unlike the commercially available water-based ionomer, which exhibited an optimum at about 25 wt%. Small size micelles and slow evaporation of PG in the ionomer dispersion were effective in proton transfer by inducing the formation of a uniformly structured catalyst layer, but the low oxygen permeability problem of the PG-based ionomer film should be resolved to improve the MEA performance.

• Journal of Applied Biological Chemistry
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• v.65 no.4
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• pp.247-252
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• 2022

The arial parts of Artemisia argyi were extracted with methanol : water (70:30), and the concentrates was partitioned into EtOAc (ethyl acetate), n-BuOH (normal butanol), and H₂O (water) fractions. The repeated silica gel and ODS (octadecyl silica gel) column chromatographies for EtOAc and n-BuOH fractions led to isolation of four flavonoids without any ambiguity based on intensive interpretation of several spectroscopic data including nuclear magnetic resonance, and mass spectrometry. The chemical structure of the isolated compounds revealed to (2S)-naringenin (1), 3-methylkaempferol (2), 3,3'-dimethylquercetin (3), and 3,3',4'-trimethylquercetin (4). These four compounds were first isolated from A. argyi through this study. In this study, four compounds isolated from A. argyi showed an increase in glutathione mean and a decrease in glutathione heterogeneity so that the compounds uniformly raised the intracellular glutathione (GSH) level. Based on these results, it is considered that it can be used as a functional pharmacological material.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.8
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• pp.378-384
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• 2018

$C_9H_7NHCrO_3Cl$ was synthesized by reacting $C_9H_7NH$ with chromium (VI) trioxide. The structure of the product was characterized by FT-IR (Fourier transform infrared) spectroscopy and elemental analysis. The oxidation of benzyl alcohol by $C_9H_7NHCrO_3Cl$ in various solvents showed that the reactivity increased with increasing dielectric constant(${\varepsilon}$) in the following order: DMF (N,N'-dimethylformamide) > acetone > chloroform > cyclohexane. The oxidation of alcohols was examined by $C_9H_7NHCrO_3Cl$ in DMF. As a result, $C_9H_7NHCrO_3Cl$ was found to be an efficient oxidizing agent that converts benzyl alcohol, allyl alcohol, primary alcohols, and secondary alcohols to the corresponding aldehydes or ketones (75%-95%). The selective oxidation of alcohols was also examined by $C_9H_7NHCrO_3Cl$ in DMF. $C_9H_7NHCrO_3Cl$ was the selective oxidizing agent of benzyl, allyl and primary alcohol in the presence of secondary ones. In the presence of DMF with an acidic catalyst, such as $H_2SO_4$, $C_9H_7NHCrO_3Cl$ oxidized benzyl alcohol (H) and its derivatives ($p-OCH_3$, $m-CH_3$, $m-OCH_3$, m-Cl, and $m-NO_2$). Electron donating substituents accelerated the reaction rate, whereas electron acceptor groups retarded the reaction rate. The Hammett reaction constant (${\rho}$) was -0.69 (308K). The observed experimental data were used to rationalize hydride ion transfer in the rate-determining step.

• Journal of the Korean Ceramic Society
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• v.38 no.3
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• pp.287-292
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• 2001

본 실험은 목적은 CRT(Cathode Ray Tube)용 청색 형광체인 ZnS:Ag 분말 표면에 액상법으로 SnO$_2$를 균일하게 코팅하는 공정조건을 연구하는 것이다. 용매로서 물을 사용하고, Sn의 공급물질로서 SnCl$_4$.4$H_2O$, 침전 촉매로서 CO(NH$_2$)$_2$를 각각 사용하여, 균일 침전 방법으로 ZnS:Ag 분말표면에 SnO$_2$를 코팅할 수 있었다. 초기에 첨가되는 SnCl$_4$.4$H_2O$의 량이 Sn/Zn의 몰비기준으로 0.017인 경우에 ZnS:Ag 분말표면에 Sn(OH)$_4$가 균일하게 코팅되지만, 그 이상 첨가되면 과량의 Sn(OH)$_4$가 입자들 사이에 응집되었다. 코팅된 Sn(OH)$_4$는 비정질 구조로 규명되었으며, 이를 SnO$_2$결정상으로 전이시키기 위하여 300~$700^{\circ}C$ 범위 내에서 열처리를 행하였다. 비정질 Sn(OH)$_4$는 20$0^{\circ}C$이하에서 탈수되었고 45$0^{\circ}C$부터 SnO$_2$로 결정화되기 시작하였다. 순수한 ZnS의 경우, 50$0^{\circ}C$이하에서는 상변화가 없으나, $600^{\circ}C$에서 일부 산화되었으며 $700^{\circ}C$에서는 완전히 ZnO로 산화되므로, ZnS의 산화방지 및 SnO$_2$의 결정화를 동시에 만족하는 최고 열처리온도는 50$0^{\circ}C$로 규명되었다. 그러나 ZnS에 SnO$_2$가 코팅된 시편의 경우에는 $600^{\circ}C$가 되어도 ZnS 상이 거의 산화되지 않았고, $700^{\circ}C$에서도 ZnS와 ZnO 상이 공존한 것으로 보아 SnO$_2$코팅이 ZnS의 산화를 억제하는 것으로 나타났다.

• Applied Chemistry for Engineering
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• v.8 no.3
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• pp.365-373
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• 1997

Chitosan oligomer having aldehyde group at reducing end was prepared by oxidative-deamination reaction of chitosan by using sodium nitrite, and the resulting aldehyde group was redeced to 2,5-anhydro-D-mannitol group. The obtained chitosan oligomer showed an average degree of polymerization(DP) 2 by GPC analysis. It was highly soluble in lipophilic solvents. N,N-diacyl, O-acyl chitosan oligomer was obtained trom the reaction between chitosan oligomer and acyl chloride under 4-dimethoxyaminopyridine catalyst. From DSC measurement, N,N-dilauroyl, O-lauroyl chitosan oligomer showed mesophase region, which was confirmed by polarizing microscope as thermotropic liquid crystalline state. X-ray diffraction pattern revealed that N,N-dilauroyl, O-lauroyl chitosan oligomer was highly crystalline, whereas chitosan oligomer was not.

• Applied Biological Chemistry
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• v.40 no.6
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• pp.583-587
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• 1997

The MeOH extracts obtained from the tuber of Ipomoea batatas Lam. were solvent-fractionated with EtOAc, n-BuOH, and $H_2O$, respectively. From EtOAc fraction four different compounds were isolated through the repeated silica gel column chromatographies. From not only the results of NMR and MS data but also the adaptation of hydrolysis, methylation, and acetylation, the chemical structures of compounds were elucidated as resin glycoside, simonin I, ${\beta}-sitosterol$, and two kinds of unsaturated fatty acids.

• Polymer(Korea)
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• v.35 no.2
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• pp.176-182
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• 2011

Liquid crystalline aromatic polyesters (LCPs) are representative examples of thermotropic liquid crystalline polymers, whose structure-property relationships have been the subject of many researches. In this study, we synthesized organo-soluble liquid crystalline aromatic polyesters, and their composites with acetylene-terminated thermoset resins were prepared and characterized. Soluble LCPs were synthesized by employing 6-hydroxy-2-naphthoic acid, terephthalic acid, isophthalic acid, and 4-aminophenol as monomers via condensation polymerization based on transesterfication and transamidation. Acetylene-terminated thermoset resins were synthesized by the reaction of 4-ethynylaniline with terephthaloyl dichloride, isophthaloyl dichloride or 4,4'-biphenyldicarbonyl dichloride. We prepared the soluble LCP/thermoset composites by solution blending followed by thermal treatment. The thermal stability, thermal expansion coefficient, and dielectric properties of the composite were studied.