• Proceeding of EDISON Challenge
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• 2016.03a
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• pp.120-125
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• 2016

용매화 된 이온들간의 상호작용은 화학을 비롯한 여러 분야에서 중요하게 다뤄지고 있다. 계산화학에 있어 다양한 용매에 용매화 된 이온들간의 상호작용은 분자동력학 시뮬레이션(MD)을 이용한 PMF 계산을 통해 많이 연구되어 왔는데, 본 그룹에서는 물을 표현할 수 있는 다양한 모델과 Salt solution 하에 Na+ 이온과 Cl- 이온 사이 상호작용을 PMF 계산을 통해 알아보았다. 첫 번째로 Polarizable water model인 Tip4p-fq를 사용한 PMF 계산 결과는 아직 진행 중에 있으며 결과적으로는 기본적으로 CHARMM water force field에서 제공해주는 Tip3p 모델 및 양자계산 방법 중 하나인 Ab initio를 이용한 결과와 비교, 분석 할 예정이다. 두 번째로 1M/2M/5M Salt solution의 서로 다른 농도를 사용하여 시뮬레이션 한 결과 1M과 2M에서는 물 속에서 시뮬레이션 한 결과와 큰 차이가 없었으나 농도가 짙은 5M 용매 내에선 $Na^+$이온과 $Cl^-$이온 사이 거리가 멀어질수록 주변 Salt에 영향을 받는 것을 확인 할 수 있었다. 결론적으로 본 연구를 진행함으로써 우리는 서로 다른 전하를 갖는 이온 사이 상호작용에 대한 이해를 더 높일 수 있었다.

• Applied Chemistry for Engineering
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• v.10 no.5
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• pp.718-725
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• 1999

In order to investigate the interaction characteristics of poly(dimethylsiloxane) (PDMS) with various solvents such as water, ethanol, and iso-propanol, Inverse Gas Chromatography(IGC) at finite concentration, which is a very fast, accurate, and thus promising technique in thermodynamic study of polymer systems, is employed. By measuring the specific retention volumes of the probes, the interaction parameters are calculated by means of the Flory-Huggins equation. From the results, the interaction parameters of the probes are, as expected due to the hydrophobicity of the polymer, found to be of large positive values (2$2.0{\times}10^{-3}mol/g$. For the linear PDMS, interpretation of the space distribution of molecules is performed by the Kirkwood-Buff-Zimm(KBZ) integrals, which give intuitive information about physical properties. From the KBZ integrals, water does not show the tendency of preferential solvation with the PDMS but formed self-cluster. The larger solvent molecules show a stronger tendency to distribute more randomly in the mixture.

• Journal of the Korean Wood Science and Technology
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• v.44 no.1
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• pp.124-134
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• 2016

The main goal of this study was to investigate biomodification mechanism of lignin by white rot fungus, Abortiporus biennis, and to depolymerize ethanol organosolv lignin for industrial application. In nitrogen-limited culture, A. biennis polymerized mainly lignin showing a rapid increase of molecular weight and structural changes depending on incubation days. At the initial incubation days, cleavage of ether bonds increased phenolic OH content, while the results were contrary in of the later part of the culture. Based on these results, ascorbic acid as a reducing agent was used to induce depolymerization of lignin during cultivation with white rot fungus. As a result, the degree of increase of average molecular weight of lignin was significantly declined when compared with those of the ascorbic acid free-experiment, although the molecular weight of fungus treated sample slightly increased than that of control. Furthermore, lignin derived oligomers in culture medium were depolymerized with the addition of ascorbic acid, showing that the average molecular weight was 381 Da, and phenolic OH content was 38.63%. These depolymerized lignin oligomers were considered to be applicable for industrial utilization of lignin. In conclusion, A. biennis led to the polymerization of lignin during biomodification period. The addition of ascorbic acid had a positive effect on the depolymerization and increase of phenolic OH content of lignin oligomers in medium.

• Journal of the Korean Chemical Society
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• v.53 no.2
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• pp.133-136
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• 2009

We present calculations for the 4-aminopyrimidine (4AP) – HCl and –HBr complexes. We predict that the charge separated (zwitterionic) form [4AP$H^+-Cl^-$] is not stable, but that [4AP$H^+-Br^-$] is stable enough for experimental detection in gas phase at low temperatures. The latter observation is attributed to smaller dissociation energy of HBr compared with HCl, and to “solvation” of HBr by the amino group in 4AP.

• Applied Chemistry for Engineering
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• v.9 no.5
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• pp.763-767
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• 1998

Cholesterol-containing surfactant was synthesized, and it was sonicated with monomer [tetradeca(ethylene glycol) diacrylate] in water to from a vesicle solution. This vesicle solution was dried to construct a membrane which had a molecular multilayer structure. The monomer which stay in this membrane was polymerized with photoinitiation, and then surfactant was extracted by organic solvent. The physical properties of the two dimensional polymer network were measured, and these physical properties are tensile strength, elongation, and swelling.

• Polymer(Korea)
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• v.34 no.5
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• pp.415-423
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• 2010

Poly(vinyl alcohol)(PVA) with high degree of hydrolysis of above 98% was dissolved in dimethyl sulfoxide(DMSO), and the shear viscosity was measured up to $C{\simeq}0.14\;g/mL$ in the semi-dilute solution regime. Next, as probe particle, polystyrene(PS) latex was introduced into this matrix system and its delayed diffusion due to polymer concentration was investigated by means of dynamic light scattering. When the solution viscosity of PVA/DMSO was plotted against the reduced concentration $C[{\eta}]$, which is scaled by the intrinsic viscosity, the molecular weight dependence was strongly appeared at C$[{\eta}]$ >2. Some heterogeneties in polymer solution were considered as its source. Contrary, the diffusion of probe particle in the matrix solution was observed as a single mode motion at whole concentration range but its ratio of its diffusion coefficient at solution to that at solvent, D/Do did not show any molecular weight dependence at all. However, the application limit of the stretched exponential function was disclosed at C$[{\eta}]$ >2.5.

• Journal of the Korean Chemical Society
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• v.57 no.5
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• pp.554-559
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• 2013

In this study, we have investigated potential energy of ${\beta}$-D-glucopyranose in vacuum and implicit water condition. By Comparing two conditions we find that how solvation energy influence ${\beta}$-D-glucopyranose structure. We use AMBER package program and GLYCAM_06 force field. Solvation model was used for the generalized Born model with Hawkins, Cramer, Truhlar has been proposed. We conclude that difference of contour map of two conditions is caused by solvation effect by reducing hydrogen bonding interaction.

• Applied Chemistry for Engineering
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• v.21 no.5
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• pp.532-536
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• 2010

A study on the volatile organic compounds (VOCs) and low molecular weight (LMW) amount which is contained within bisphenol A polycarbonate (PC) was performed by the solvent extraction with ketone type solvents (acetone, butanone, pentanone). The LMW amount of untreated PC was 2.6 wt%, but the values of treated samples with acetone and pentanone were 0.96 and 1.53 wt%, respectively. Acetone is a more effective solvent than pentanone on the LMW extraction. Methylene chloride (MC) and toluene were certified and quantified by GC-Mass experiments, and the quantitative results indicated the fact that the pentanone was the effective solvent on VOC extraction. Focused on the change of VOCs and LMW amount, the use of co-solvent might be more useful, and the experimental results of co-solvent extraction showed that the optimum condition was 50 : 50 volume percent.

• Journal of the Korean Chemical Society
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• v.41 no.12
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• pp.645-652
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• 1997

Hydride complexes Cp*Ru(CO)(PR3)H (Cp*=η5-C5Me5, PR3=PMe3, PEt3, PMePh2, PPh3, PCy3)(4a-4f) were synthesized by the reaction of the corresponding chloro complex Cp*Ru(CO)(PR3)Cl (3a-3f) with various hydridic reagent (NaBH4, LiAlH4, LiBEt3H) or NaOMe. Irradiation of Cp*Ru(CO)(PCy3)H (5e) in C6D6 solution with UV light caused H/D exchange reaction between coordinated Cp*, PCy3 and/or Ru-H ligand proton and a deuterium of the deuterated aromatic solvent through a series of inter- and intramolecular C-H activation. The proposed mechanism was described.

• Polymer(Korea)
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• v.36 no.4
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• pp.500-506
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• 2012

In this study, we developed and optimized hydrophilic polymer based solid dispersion formulations (SDs) for enhancing the aqueous solubility of eprosartan, one of poorly soluble drugs, that has been broadly used for the treatment of high blood pressure. Poly(ethylene glycol) (PEG) and poly(vinyl pyrrolidone) (PVP) based SDs were prepared by hot melting and solvent evaporation methods and the drug/polymer composition varied in the range of 1:1~1:5 with or without poloxamer 407 (P407) as a polymeric surfactant. The SDs prepared by solvent evaporation showed more reduced crystallinity than ones by hot melting, and PVP based SDs showed more enhanced solubility and lower crystallinity than PEG based SDs. Furthermore, it was observed from DSC and PXRD analysis that the SDs with P407 (drug:polymer: P407 = 1:5:1) demonstrated no crystallinity and the most enhanced solubility (more than 3~4 times).