• Bulletin of the Korean Chemical Society
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• 제19권8호
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• pp.868-874
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• 1998

An equivalent retention has been experimentally observed in thermal field-flow fractionation (ThFFF) for different polymer-solvent systems. It is shown that iso-retention between two sets of polymer-solvent systems can be obtained by adjusting the temperature difference (ΔT) according to the difference in the ratio of ordinary diffusion coefficient to thermal diffusion coefficient. This method uses a compensation of field strength (ΔT) in ThFFF at a fixed condition of cold wall temperature. It is applied for the calculation of molecular weight of polymers based on a calibration run of different standards obtained at an adjusted AT. The polymer standards used in this study are polystyrene (PS), polymethylmethacrylate (PMMA), and polytetrahydrofuran (PTHF). Three carrier solvents, tetrahydrofuran (THF), methylethylketone (MEK) and ethylacetate (ETAc) were employed. Though the accuracy in the calculation of molecular weight is dependent on the difference in the slope of log λ vs. log M which is related to Mark-Houwink constant a, it shows reasonable agreement within about 6% of relative error in molecular weight calculation for the polymer-solvent systems having similar a value.

• 한국의류학회지
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• 제3권2호
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• pp.37-41
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• 1979

In order to obtain tasic information for solvent dyeing, polyethylene terephthalate (PET) films was pretreated with water, tetrachloroethylene (TCE) and water/TCE emulsion for three hours at $140^{\circ}C$ for stabilizing the substrate. By film roll cyliderical method, Disperse Red 60, Disperse Yellow 42, and Disperse Blue 27 were diffused in the films and examined dyeing properties. The results are summarized as follows; 1) Diffusion coefficient increases in the order, waterTCE>water/TCE 2) A linear relationship between diffusion coefficient and shrinkage was Observed 3) The temperature dependence of the diffusion coefficient can't be expressed by WLF equation.

• 한국막학회:학술대회논문집
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• 한국막학회 1998년도 추계 총회 및 학술발표회
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• pp.59-62
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• 1998

1. 서론 : 막내부에서 물질전달을 설명하는 이론으로 현재 solution-diffusion model과 pore-flow model 두 가지가 있다. 이 중에서 흡착, 확산, 탈착의 3과정을 거치는 solution-diffusion model이 주로 사용되고 있다. 본 연구에서는 solution-diffusion model 에서 상호확산계수를 구하기 위해서 Vrentas-Duda식을 이용하여 자기확산계수를 구하고 Bearman식으로부터 상호확산계수를 구하는 과정을 UNIFAC-FV와 modified UNIFAC-FV을 이용하여 계산하였으며 Flory-Huggins식을 이용한 기존방법과 비교하였다.(생략)

• 폴리머
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• 제24권1호
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• pp.23-28
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• 2000

Solvent 용접에 따른 무정형 고분자 폴리스티렌/폴리스티렌 계면의 접착강도의 변화를 butt joint실험을 통하여 살펴보았다. 폴리스티렌과 용해도 상수가 유사한 용매를 계면에 코팅함으로써 계면 분자쇄의 유동성 증가와 계면의 거침정도의 변화에 따른 접촉표면의 증가로 인하여 접착 강도가 증가함을 확인하였다. 사용용매의 비등점이 접착온도보다 높은 경우, 접착강도의 증가는 용매에 의한 분자쇄의 유동성 증가에 기인되는 반면 용매의 비등점이 접착온도에 비해 낮을 경우 접착강도의 증가는 용매에 의한 접촉표면의 증가에 의존함을 알 수 있었다. 접착온도가 높을수록, 접착시간이 길어질수록 접착강도는 증가되며, 사용용매가 접착강도에 미치는 영향은 감소함을 알 수 있었다.

• Bulletin of the Korean Chemical Society
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• 제17권4호
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• pp.365-373
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• 1996

Time profile of the transient grating signal induced by a nanosecond pulsed laser excitation of methyl red is investigated in alcohols and toluene at several solvent temperatures. The signal decays biexponentially with well-separated time constants; the faster decay is identified as due to thermal diffusion of the solvents and the slower one as mainly due to translational diffusion of the solute. The measured translational diffusion constants of methyl red in toluene are close to a hydrodynamic prediction with a slip boundary condition while those in alcohols are larger by 30% and increase slightly with the size of alcohols. We compare the results with modified hydrodynamic models.

• Advances in nano research
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• 제13권2호
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• pp.187-197
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• 2022

The synthesis of organic and hybrid organic-inorganic perovskites directly from solution improves the cost- and energy-efficiency of processing. To date, numerous research efforts have been devoted to investigating the influence of the various solvent parameters for the synthesis of lead halide perovskites, focused on the effects of different single solvents on the efficiency of the resulting perovskites. In this work, we investigated the effect of solvent blends for the first time on the structure and phase of perovskites produced via the Lewis base vapor diffusion method to develop a new synthetic approach for water-stable CsPbBr₃ particles with nanometer-sized dimensions. Solvent blends prepared with DMF and water-miscible solvents with different Gutmann's donor numbers (D_N) affect the Pb ions differently, resulting in a variety of lead bromide species with various colors. The use of a DMF/isopropanol solvent mixture was found to induce the formation of the Ruddlesden-Popper perovskite based on lead bromide. This perovskite undergoes a blue color shift in the solvated state owing to the separation of nanoplatelets. In contrast, the replacement of isopropanol with DMSO, which has a high DN, induces the formation of spherical CsPbBr₃ perovskite nanoparticles that exhibit green emission. Finally, the integration of acetone in the solvent system leads to the formation of lead bromide complexes with a yellow-orange color and the perovskite CsPbBr₃.

• Membrane and Water Treatment
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• 제11권4호
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• pp.237-245
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• 2020

The effects of the mixed two solvents, Dimethylacetamide (DMAc) and Dimethylformamide (DMF), and Polyethylene glycol (PEG) and Polyvinylpyrrolidone (PVP) as additives on performance of Polyvinylidene fluoride (PVDF) membranes were studied. Initially, PEG200 was used as a primary additive at fixed percentage of 5% wt. PVP was then blended with PEG200 in different concentrations. PVDF and DMAc were used as polymer and solvent in the casting solutions, respectively. To control the diffusion rate of PVP in the presence of PEG200 and PVP blend, mixtures of DMAc and DMF were used as the mixed solvent in the casting solutions. Asymmetric PVDF membranes were prepared via phase inversion process in a water bath and the effects of two additives and two solvents on the membrane morphology, pure water flux (PWF), hydrophilicity and rejection (R) were investigated. Attenuated Total Reflection Fourier Transform Infrared Spectra (ATR-FTIR) analysis was used to show the residual PVP on the surface of the membranes. Atomic Force Microscopy (AFM) was utilized to determine roughness of membrane surface. The use of mixed solvents in the casting solution resulted in reduction of PVP diffusion rate and increment of PEG diffusion rate. Eventually, PWF and R values reduced, while porosity and hydrophilicity increased.

• 한국토양환경학회지
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• 제2권2호
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• pp.95-103
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• 1997

유기화합물로 오염된 지반을 정화하는 방법 가운데 화학약액을 주입하는 흙세척 방법은 매우 효과적인 것으로 알려져 있다. 이를 실험실에서 재현하는 경우에는 일반적으로 연성벽체의 주상실험을 실시하게 된다. 이때 유기화합물로 오염된 시편을 화학약액으로 세척하는 과정 중에서 일부의 유기화합물은 연성벽체를 통하여 확산되고, 확산된 양은 화학약액에 의한 세척효율 산정시 반드시 고려하여야 할 것으로 나타났다. 연성벽막을 통한 확산량을 조사하고자 다섯가지의 유기화합물(페놀, 아닐린, 나이트로벤젠, 퀴놀린, 및 2나프톨)을 이용하여 breakthrough 시험을 실시하였다. 나이트로벤젠은 75% 이상이 벽막을 통하여 확산되었다. 나머지의 유기화합물은 25%이하의 확산량을 보였다. 실험중 생분해 효과는 관찰되지 않았다.

• Bulletin of the Korean Chemical Society
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• 제7권6호
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• pp.416-421
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• 1986

The solvent coordination effect on the excited state processes of Mg(II)- and Zn(II)-phthalocyanines has been described. The triplet state of these compounds decays with mixed first and second order kinetics or mainly second order kinetics depending on the solvents used. The first order component of the rate constants decrease along with the series, dimethylsulfoxide (5-coordinated), 1-chloronaphthalene (4-coordinated) and piperidine (6-coordinated), while the second order rate constant is dependent on the diffusion rate constant of the solvents. The excited state quenching by methylviologen or p-benzoquinone is discussed. And ion recombination rate constant is given.

• Bulletin of the Korean Chemical Society
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• 제21권1호
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• pp.93-96
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• 2000

A diffusion-influenced pseudo-first order reversible reaction A + B ⇔C + B is investigated by the molecular dynamics (MD) simulation method. Theoretical finding that the temporal evolution of reactants [conditional probabilities] in the reversible system can be expressed by the irreversible survival probability with an effective rate parameter is confirmed even in the presence of solvent particles. We carry out molecular dynamics simulations for both the irreversible and the reversible cases to evaluate the survival and the conditional probabilities for each cases. When the resultant irreversible survival probability is inserted into the proposed relation, the conditional probabilities given by the simulation are exactly reproduced.