• Macromolecular Research
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• 제12권4호
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• pp.374-378
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• 2004

The biodegradable and biocompatible poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV), a copolymer of microbial polyester, was fabricated as nanofibrous mats by electrospinning. Image analysis of the electrospun nanofibers fabricated from a 2 wt% 2,2,2-trifluoroethanol solution revealed a unimodal distribution pattern of fiber diameters with an observed average diameter of ca. 185 nm. The fiber diameter of electrospun fabrics could be controlled by adjusting the electro spinning parameters, including the solvent composition, concentration, applied voltage, and tip-to-collector distance. Chondrocytes derived from rabbit ear were cultured on a PHBV cast film and an electrospun PHBV nano-fibrous mat. After incubation for 2 h, the percentages of attached chondrocytes on the surfaces of the flat PHBV film and the PHBV nanofibrous mat were 19.0 and 30.1 %, respectively. On the surface of the electrospun PHBV fabric, more chondrocytes were attached and appeared to have a much greater spreaded morphology than did that of the flat PHBV cast film in the early culture stage. The electro spun PHBV nanofabric provides an attractive structure for the attachment and growth of chondrocytes as cell culture surfaces for tissue engineering.

• Bulletin of the Korean Chemical Society
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• 제19권3호
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• pp.349-353
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• 1998

Solvolysis rates of substituted 2-aryl-1,1-dimethylethyl bromides (1) were determined in a variety of solvents such as aqueous mixtures of ethanol, acetone, 2,2,2-trifluoroethanol, and also mixtures of ethanol and TFE at 25 ℃, 35 ℃, and 45 ℃. The solvent effects were analyzed in terms of Winstein-Grunwald equation. The solvent effects of 1-4-MeO failed to give a single linear correlation against either Y or YCl (YBr), but exhibited a wide split pattern which could not be related to the solvent nucleophilicity. On the other hand 1-4-CH3 and 1-H gave a fairly good linearity. In the case of 1-4-MeO, a fairly good linearity was observed against YΔ defined from the solvolysis of 4-methoxyneophyl tosylate. It is assumed that resonance interaction between reaction site and aryl-π-system operates to give charge delocalization regardless of the different solvolysis mechanisms. The Hammett-Brown treatment of the solvolytic rate constant of compounds 1 was obtained non-linear two separated lines of - 1.06 to - 1.46, suggesting of mechanistic changeover from kc-ks to kΔ on going from electron-withdrawing to electron-donating substituents as a basis of 4-CH3 group.

• Journal of Advanced Marine Engineering and Technology
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• 제36권5호
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• pp.595-602
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• 2012

본 논문에서는 선박에서 배출되는 $CO_2$ 배출을 최소화하기 위한 노력의 일환으로 선박으로부터 배출되는 열에너지를 회수하고 재활용하는 방안으로 유기랭킨사이클 발전장치를 구동함으로써 선박의 에너지 효율을 높이고 온실가스 배출을 최소화할 수 있는 방안을 연구하였다. 선박에서 배출되는 배기가스와 냉각 시스템에서 배출되는 열에너지를 회수하여 터빈 발전기를 구동하는 ORC 발전시스템을 설계하고 시뮬레이션 하였다. 다양한 친환경 유기냉매를 이용하여 냉매를 적용하여 온도와 유량변화에 따른 열 해석을 실시하였고 냉각수 열원 예열기, 배기가스 가열기로 시스템을 구성하여 2,400kW급의 발전 출력을 얻을 수 있었다.

• Korean Membrane Journal
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• 제8권1호
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• pp.31-35
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• 2006

Pervaporation of water/2,2,2-trifluoroethanol (TFEA) mixtures was performed using a NaY zeolite membrane which was prepared by a hydrothermal synthesis. Pervaporation with a zeolite membrane is one of the economic separation technologies for liquid mixtures including organic/water solutions. The effects of a TFEA feed concentration and a temperature were studied on the permeation flux and the separation factor. Not only the water flux increased significantly with the increase of the operating temperature, but also the TFEA flux through the NaY zeolite membrane rapidly increased with the increase of the temperature at the feed concentration below 0.8 mole fraction of TFEA.

• 대한화학회지
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• 제27권2호
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• pp.95-101
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• 1983

여러가지 수용성 혼합용매와 에탄올-TFE 혼합용매에서 시안화 벤조일의 가용매분해반응에 대한 유사-1차반응속도상수를 1, 5, 10, 15, $20^{\circ}C$에서 구하였다. Kivinen polt의 n값, Grunwald-Winstein polt의 m값, Leffler 관계식의 $\beta$값, 확정된 Grunwald-Winstein식의 m 및 l값을 구하였다. More O'Ferrall polt와 양자역학적 해석 방법을 이용하여 용매 변화에 따른 전이상태 변화를 논의하였으며 본 반응은 associative $S_N2$ 반응 메카니즘으로 진행됨을 알 수 있었다.

• 한국자기공명학회논문지
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• 제8권2호
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• pp.127-138
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• 2004

We obtained the chemical shifts of amide protons (NHs) in helical peptides at various temperatures and trifluoroethanol (TFE) concentrations using 2-dimensional NMR spectroscopy. These NH chemical shifts and their temperature dependence exhibited characteristic periodicity of 3-4 residues per cycle along the helix, where downfield shifted NHs showed larger temperature dependence. In an attempt to understand these observations, we focused on hydrogen bonding changes in the peptides and examined the validity of two possible explanations: (1) changes in intermolecular hydrogen bonding caused by differential solvation of backbone carbonyl groups by TFE, and (2) changes in intramolecular hydrogen bonding due to disproportionate variations in the hydrogen bonding within the peptide helix. Interestingly, the slowly exchanging NHs, which were on the hydrophobic side of the helix, showed consistently larger temperature dependences. This could not be explained by the differential solvation assumption, because the slowly exchanging NHs would become more labile if the preceding carbonyl groups were preferentially solvated by TFE. We suggest that the disproportionate changes in intramolecular hydrogen bonding better explain both the temperature dependence and the exchange behavior observed in this study.

• Macromolecular Research
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• 제17권7호
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• pp.522-527
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• 2009

A photocrosslinkable polyphosphazene was used for molecular imprinting. We synthesized polyphosphazene (3) having urea groups for complexation with N-carbobenzyloxyglycin (Z-Gly-OH, template) and chalcone groups for cross-linking reaction. As substituents, 4-hydroxycha1cone (1) and N-(4-hydroxyphenyl)-N'-ethylurea (2) were prepared. Choloro groups of poly(dichlorophosphazene) were replaced by the sequential treatment with sodium salts of compounds 1 and 2, and trifluoroethanol. The template molecule was complexed with the urea groups on the polymer chains via hydrogen bonding. A thin polymer film was prepared by casting a solution of the complex of polymer 3 and the template in dimethylformamide on a quartz cell and irradiated with 365 nm UV light to yield a cross-linked film with a thickness of about $16{\mu}m$. The template molecules in the film were removed by Soxhlet extraction with methanol/acetic acid. The control polymer film was prepared in the same manner for the preparation of the imprinted polymer film, except that the template and triethylamine were omitted. In the rebinding test, the imprinted film exhibited much higher recognition ability for the template than the control polymer. We also investigated the specific recognition ability of the imprinted polymer for the template and its structural analogues. The rebinding tests were conducted using Z-Glu-OH, Z-Asp($O^tBu$)-OH, and Z-Glu-OMe. The imprinted film showed higher specific recognition ability for the template and the lowest response for Z-Asp($O^tBu$)-OH.

• Bulletin of the Korean Chemical Society
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• 제24권4호
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• pp.431-436
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• 2003

Solvolytic rate constants at 25℃ are reported for solvolyses of cinnamyl bromide (1) in binary mixtures of water with acetone, ethanol, methanol, methanol-d, and 2,2,2-trifluoroethanol. Product selectivities are reported for solvolyses of 1 in aqueous ethanol and methanol. Rate ratios in solvents of the same $Y_{Br}$ value and different nucleophilicity provide measures of the minimum extent of nucleophilic solvent assistance (e.g. $[k_{40EW}/k_{97TFE}]$Y = 2.88, EW = ethanol-water). With use of the extended Grunwald-Winstein equation, the l and m values are similar to the values of 0.43 and 0.88 obtained for the solvolyses of 1 using the equation (see below) which includes a parameter (I) for solvation of aromatic rings. The magnitude of l and m values associated with a change of solvent composition predicts the $S_{N1}$ reaction mechanism rather than an $S_{N2}$ channel. Product selectivities (S), defined by S = [ether product]/[alcohol product]×[water]/[alcohol solvent] are related to four rate constants for reactions involving one molecule of solvent as nucleophile and another molecule of solvent as general base catalyst. A linear relationship between 1/S and molar ratio of solvent is derived theoretically and validated experimentally for solvolyses of the above substrates from water up 75% 1/S = $(k_{wa}/k_{aw})$([alcohol solvent]/[water]) + $k_{ww}/k_{aw}$ alcohol-water. The results are best explained by product formation from a “free” carbocation intermediate rather than from a solvent-separated ion pair.

• Bulletin of the Korean Chemical Society
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• 제28권12호
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• pp.2377-2381
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• 2007

Solvolyses of 3,4-dimethoxybenzenesulfonyl chloride (DSC) in water, D2O, CH3OD, and in aqueous binary mixtures of acetone, acetonitrile, 1,4-dioxane, ethanol, methanol, and 2,2,2-trifluoroethanol (TFE) have been investigated at 25.0 oC. Kinetic solvent isotope effects (KSIE) in water and in methanol and product selectivities in alcohol-water mixtures are also reported. The Grunwald-Winstein plot of first-order rate constants for the solvolyic reaction of DSC with YCl shows marked dispersions into separated lines for various aqueous mixtures. With use of the extended Grunwald-Winstein equation, the l and m values obtained are 1.12 and 0.58 respectively for the solvolyses of DSC. The relatively large magnitude of l is consistent with substantial nucleophilic solvent assistance. From Grunwald-Winstein plots the rate data are dissected approximately into contributions from two competing reaction channels. This interpretation is supported for alcohol-water mixtures by the trends of product selectivities, which show a maximum for ethanol-water mixtures. From the KSIE of 1.45 in methanol, it is proposed that the reaction channel favored in methanolwater mixtures and in all less polar media is general-base catalysed and/or is possibly (but less likely) an addition-elimination pathway. Also, the KISE value of 1.35 for DSC in water is expected for SN2-SN1 processes, with minimal general base catalysis, and this mechanism is proposed for solvolyses in the most polar media.

• 한국환경농학회지
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• 제13권2호
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• pp.199-208
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• 1994

토양 침투수중에 잔류하는 제초제 MCPP를 추출, 유도체를 합성하여 GC-MS로 확인하고 capillary GC-ECD로 잔류분석하였다. Diazomethane과 $BF_3$/MeOH 등을 이용하여 합성한 MCPP의 methyl 유도체, 황산을 촉매로 이용하여 합성한 MCPP의 2,2,2-trifluoroethyl(TFE) 및 2,2,2-trichloroethyl(TCE) 유도체, 그리고 MCPP의 pentafluorobenzyl(PFB) 유도체간의 잔류분석법을 비교한 결과 이 연구에서 개발된 MCPP-TFE 유도체화가 간편하고 신속, 안전한 유도체화 기술로서 GC-ECD에서 비교적 감도가 우수한 편이었다. MCPP의 methyl 유도체는 GC-ECD에서 그 감도가 너무 낮아 시료가 소량인 경우 ppb 수준의 잔류분석이 불가능하였고 MCPP-TCE 및 MCPP-PFB 유도체는 그 감도는 우수하였으나 크로마토그람상의 방해물질이 많아 액액분리에 의한 정제만으로는 잔류분석이 곤란하였다. MCPP-TFE 유도체화에 의하면 토양침투수 100ml중 $0.1{\mu}g$ 미만의 농도를 가진 MCPP의 잔류분석이 액액분리에 의한 정제만으로 가능하였다.