• Elastomers and Composites
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• 제56권4호
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• pp.223-233
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• 2021

In this study, epoxidized liquid isoprene rubber (E-LqIR) was used as a processing aid in a silica-filled natural rubber compound to improve the fuel efficiency, abrasion resistance, and oil migration problems of truck and bus radial tire tread. The wear resistance, fuel efficiency, and extraction resistance of the compound were evaluated according to the molecular weight of E-LqIR. Results of the evaluation showed that the E-LqIR compound had a lower chemical crosslink density than that of a treated distillate aromatic extract (TDAE) oil compound because of the sulfur consumption of E-LqIR. However, the filler-rubber interaction improved because of the reaction of E-LqIR with silica and crosslink with the base rubber by sulfur. As the molecular weight of E-LqIR increased, crosslink with sulfur was facilitated, and the filler-rubber interaction improved, resulting in improved abrasion resistance. The fuel efficiency performance of the E-LqIR compound was poorer than that of the TDAE oil compound because of the low chemical crosslink density and hysteresis loss at the free chain end of E-LqIR. However, the fuel efficiency performance improved as the molecular weight of E-LqIR increased.

• 대한화학회지
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• 제55권6호
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• pp.988-993
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• 2011

Cyclodehydration of 6-amino-5-cyano pyrimidine derivative (2) afforded pyrimidoisoindole derivatives (3). Compound (3) reacted with carbethoxymethylene derivative to give pyridopyrimidine derivatives (5a,b). Compound (3) was also reacted with formamide to give the corresponding pyrimidopyrimdine derivatives (6) that condensed with benzaldehyde to give Schiff's base (7). Refluxing of compound (3) with triethyl orthoformate afforded compound (8) that cyclized with ammonium hydroxide giving the same compound (6). Compound (8) cyclized with hydrazine hydrate giving compound (9) which also cyclized with triethyl orthoformate affording compound (10). Diazotization of compound (3) led to the formation of triazinopyrimidine derivative (11). Cyclization of compound (11) upon treatment with hydrazine hydrate afforded compound (12). Compound (15) was prepared from reaction of compound (3) and ethylenediamine in presence of carbon disulfide. The behaviour of compound (15) toward benzoyl chloride, triethyl orthoformate, nitrous acid and/or carbon disulfide was also described. All proposed structures were supported by elemental analyses, spectroscopic data and some of the new products showed antimicrobial activity.

• Elastomers and Composites
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• 제54권1호
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• pp.54-60
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• 2019

The rapid development of the automobile industry is an important factor that led to the dramatic development of synthetic rubber. The tread part of tire that comes in direct contact with the road surface is related to the service life of the tire. Rubber compounds used in tire treads are often blended with SBR (styrene-butadiene rubber) and BR (butadiene rubber) to satisfy physical property requirements. However, when two or more kinds of rubber are blended, phase separation and silica dispersion problems may occur due to non-uniform mixing of the rubber. Therefore, in this study, we synthesized an SBR copolymer with the same composition as that of a typical SBR/BR blend compound by controlling butadiene content during ESBR (emulsion styrene-butadiene rubber) synthesis. Subsequently, silica filled compounds were manufactured using the synthesized ESBR, and their mechanical properties, dynamic viscoelasticity, and crosslinking density were compared with those of the SBR/BR blended compound. When the content of butadiene was increased in the silica filled compound, the cure rate accelerated due to an increased number of allylic positions, which typically exhibit higher reactivity. However, the T-2 compound with increased butadiene content by synthesis less likely to show an increase in crosslink density due to poor silica dispersion. In addition, the T-3 compound containing high cis BR content showed high crosslink density due to its monosulfide crosslinking structure. Because of the phase separation, SBR/BR blend compounds were easily broken and showed similar $M_{100%}$ and $M_{300%}$ values as those of other compounds despite their high crosslink density. However, the developed blend showed excellent abrasion resistance due to the high cis-1,4 butadiene content and low rolling resistance due to the high crosslink density.

• 대한화학회지
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• 제22권6호
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• pp.403-411
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• 1978

Collagen의 model compound인 poly(Gly-Pro-Pro)의 수화에 관해서 empirical ppotential energy 함수를 사용하여 이론적으로 연구하였다. 물 분자와 model compound 간의 상호작용 energy를 최소화시켜서 물 분자들의 위치와 결합 energies를 계산하였다. 다음에는 일차수화층에 물이 붙음으로써 생기는 안정화 energy를 계산하고, 전체 안정화에 기여하는 여러 energy components의 기여도에 대해 논의하였다.

• Bulletin of the Korean Chemical Society
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• 제27권4호
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• pp.503-507
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• 2006

The rhodium(II)-catalyzed reactions of diazo compound derived from Meldrum's acid with a variety of styrenes have been examined. These reactions provide a rapid route to the preparation of cyclopropanes with a variety of substituents on the benzene ring. The mechanistic pathway for the formation of these products has been also described in terms of a stepwise mechanism.

• Bulletin of the Korean Chemical Society
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• 제23권11호
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• pp.1664-1666
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• 2002

• 한국식품과학회지
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• 제35권5호
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• pp.959-967
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• 2003

한국산 배를 60% acetone으로 추출하여 Sephadex LH-20 gel column chromatography, MCI-CHP 20 gel column chromatography, Bondapack $C_{18}$ gel column chromatography을 이용하여 TLC와 HPLC로 순도를 검증한 후 4종의 polyphenol 화합물을 분리, 정제하였다. Compound A와 B는 Sepadex LH-20 gel column chromatography에서 증류수상에서 용출되었고 compound C는 40% methanol상에서 용출됨을 보아 compound B와 compound C는 흡착성이 강한 polyphenol 화합물이라 추정되었다. 분리, 정제한 4종의 compound를 NMR, FAM-mass 및 FT-IR를 이용하여 화학구조를 결정한 결과 compound A는 (+)-catechin, compound B는 (+)-gallocatechin, compound C는 (-)-epigallocatechin이고 compound D는 procyanidin B-3-3-o-gallate로 밝혀졌다.

• Bulletin of the Korean Chemical Society
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• 제21권12호
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• pp.1199-1201
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• 2000

31-Hydroxycarbowyacetylquercinic acid, a lanostenoid hydroxyl acid has been isolated from D. dickinsii by solbent extraction, silica gel column chromatography and recrystallization. The structure of this compound has been determined to be 31-hydroxycarboxyacetylquercinic acid by a combinationof spectral data and by HM-BC. This compound showed antimicrobial activities against human pathogenic fungi and bacteria.

• Journal of Microbiology and Biotechnology
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• 제27권6호
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• pp.1065-1070
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• 2017

This study aimed to examine the anti-candidal efficacy of a novel ketone derivative isolated from Diaporthe sp. ED2, an endophytic fungus residing in medicinal herb Orthosiphon stamieus Benth. The ethyl acetate extract of the fungal culture was separated by open column and reverse phase high-performance liquid chromatography (HPLC). The eluent at retention time 5.64 min in the HPLC system was the only compound that exhibited anti-candidal activity on Kirby-Bauer assay. The structure of the compound was also elucidated by nuclear magnetic resonance and spectroscopy techniques. The purified anti-candidal compound was obtained as a colorless solid and characterized as 3-hydroxy-5-methoxyhex-5-ene-2,4-dione. On broth microdilution assay, the compound also exhibited fungicidal activity on a clinical strain of Candida albicans at a minimal inhibitory concentration of $3.1{\mu}g/ml$. The killing kinetic analysis also revealed that the compound was fungicidal against C. albicans in a concentration- and time-dependent manner. The compound was heat-stable up to $70^{\circ}C$, but its anti-candidal activity was affected at pH 2.

• 분석과학
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• 제13권4호
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• pp.534-538
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• 2000

The title compound, $[Co(H_2O)_6](CH_3C_6H_4SO_3)_2$, has been prepared and characterized by X-ray crystallography. The crystal structure of the compound demonstrates a layered material constituted by hexaaquacobalt (II) cations and p-toluenesulfonate anions. Geometrical environment of the cobalt atom is octahedrally coordinated by water molecules. The p-toluenesulfonate anions are arranged with the sulfonate groups turned toward opposite side of the layer, alternately. The layered structure is stabilized by the hydrogen bondings between the ligated water molecules and the anionic sulfonate oxygen atoms.