• Korean Chemical Engineering Research
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• v.51 no.5
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• pp.591-596
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• 2013

Urease activity of Helicobacter pylori was most strongly inhibited by extract of Mume Fructus among ethanol (70%, v/v) extract of 6 herbal materials selected from our previous work, database on traditional herbal materials, and literature data on Korean plant resources. Active compounds in the extract of Mume Fructus were separated by batch extraction, and further purified by chromatography in a silica gel column and an octadecyl silica gel column using solvents of different polarity. By NMR analysis of the last chromatographic fraction we identified ursolic acid as the active compound of urease inhibition. The result suggests that this component in Mume Fructus can possibly be used for the eradication of H. pylori.

• KSBB Journal
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• v.16 no.4
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• pp.327-331
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• 2001

Catechin compounds from the Green tea cultivated in Bosung (Chollanamdo) were extracted using supercritical fluid and various additives, and analyzed by reversed-phase high performance liquid chromatography (RP-HPLC). The chromatographic column was packed with LiChrospher 100RP-18(15 $\mu$m), and water was used as the mobile phase with 0.05% phosphoric acid and acetonitrile. Gradient election was applied to separate EGCG by changing the mobile phase compositions. Comparing the extraction yield of three different types of supercritical fluids, pure CO$_2$, with additives of water and ethanol (5 wt,%), the extraction amount of EGCG was most abundant in the suprcritical CO$_2$with ethanol. However, more was extracted and pure higher purity was achieved by solvent extraction using ethanol.

• Journal of Adhesion and Interface
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• v.4 no.4
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• pp.1-6
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• 2003

After atmospheric pressure plasma treatment of polypropylene(PP) film surface, we measured the contact angle of the surface by using polar solvent (water) and non-polar solvent (diiodomethane). We also calculated the surface free energy of PP film by using the measured values of contact angles. And then we analyzed contact angle and surface free energy with changing the condition of atmospheric pressure plasma treatment. Upon each condition of atmospheric plasma treatment, contact angle and surface free energy showed an optimum value or leveled off.

• Journal of the Korean Chemical Society
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• v.24 no.1
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• pp.44-52
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• 1980

Ionic dissociation rates of $\alpha$-chlorobenzyl ethyl ether in each solvent of toluene-$d_8$ and carbon tetrachloride were measured by the method of dynamic NMR spectroscopy. The spin system of these 1H NMR spectra was $AB_3$. The theoretical spectrum was calculated by computer simulation of dynamic NMR spectra, which agreed very well with observed spectra. From this computer simulation, the ionic dissociation rate constant k was obtained, and by Eyring plot with it, slope and intercept length was gained, from which kinetic parameters were calculated.The easiness of ionic dissociation depended upon solvent polarity. Activation enthalpy was 4.7 kcal/mole in toluene-$d_8$, 10.7 kcal/mole in carbon tetrachloride, and activation entropy was -35. 8 e.u. in toluene-$d_8$, -14.4 e.u. in carbon tetrachloride. It was understood that though the ${\Delta}H^{neq}$ value was small, this ionic dissociation had an easier procession in nonpolar solvents with increasing temperatures. Considering that the ionic dissociation could be thought as the first step of $S_N1$ mechanism, attention might be paid to the results that the value of ${\Delta}S^{neq}$ had a large negative value in comparison with a small ${\Delta}H^{neq}$.

• Applied Chemistry for Engineering
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• v.27 no.1
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• pp.26-34
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• 2016

In this study, core-crosslinked amphiphilic polymer (CCAP) nanoparticles prepared using a reactive amphiphilic polymer precursor (RARP) were used for preparing some valuable compounds encapsulated polymer nanoparticles with high payload through nanoprecipitation process. Various solvents (acetone, ethanol, and THF) having different polarity and CCAP nanoparticles prepared using different amphiphilicity were used for the preparation of ${\alpha}$-tocopherol encapsulated polymer nanoparticles to investigate their effects on the encapsulation efficiency, payload, nanoparticle size, and stability. CCAP dissolved in hydrophobic solvent, THF, could form ${\alpha}$-tocopherol encapsulated polymer nanoparticles dispersed in water with the high payload of ${\alpha}$-tocopherol and encapsulation efficiency. Because of their physically and chemically robust nano-structure originated from crosslinking of the hydrophobic core, CCAP nanoparticles could encapsulate ${\alpha}$-tocopherol with the high payload (33 wt%) and encapsulation efficiency (97%), and form 70 nm-sized stable nanoparticles in water.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2017.05a
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• pp.110-110
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• 2017

마이크로 플루이딕 디바이스는 화학, 생물학 실험 및 생체 의학 진단을 위한 플랫폼으로 지난 20년간 그 사용 및 연구가 증가되어 왔다. 마이크로 플루이딕 디바이스를 제작하는 데 있어 가장 일반적으로 사용되는 재료는 실리콘이지만 비용이 많이 들고 불투명하므로 광학 검출이 필요한 곳에 적용이 제한된다. 이러한 측면에서 열가소성 플라스틱은 상업화의 중요한 요소인 대량 생산에 있어 큰 잠재력을 가지고 있으며 저렴하고, 가공이 쉽고, 유연하고, 광학적으로 투명하고, 화학적으로 불활성이며, 생체적합성을 가진다. 본 연구에서는 열가소성 플라스틱의 일종인 PMMA Poly(methylmethacrylate)를 효율적으로 접합하기 위해 비교적 낮은 온도와 낮은 압력에서 에탄올을 활용한 접착방식을 개발하였다. 먼저, PMMA 기판의 전체 표면을 $80^{\circ}C$에서 20 분 동안 에탄올로 처리한 후, $60^{\circ}C$에서 20 분간 열 압착하는 방식으로 영구적인 결합이 이루어졌다. 결합 강도 및 채널의 sealing 정도를 확인하기 위해, 인장 강도, 누수 및 파열 테스트를 수행하였다. 결합강도는 약 12.4 MPa로 타 연구와 비교할 때 매우 높았으며 마이크로 채널의 전체 내부 체적보다 거의 450 배 높은 강한 액체 흐름을 견딜 정도로 견고한 결합이 유지되었다. 열가소성 플라스틱의 본딩에 사용되는 유기 용매는 광학 특성을 희생시키지 않으면서 결합 속도를 높일 수 있지만, 결합 공정 중에 용매로 인해 마이크로 채널이 막히는 현상이 발생될 수 있다. 따라서, 견고한 본딩을 유지하면서 채널 막힘을 방지하기 위해 마이크로 채널을 소수성으로 선택적으로 처리하여 내벽의 표면 특성을 튜닝해 주는 기법을 추가로 적용하였다. 본 연구에서 사용한 방법은 아민-PDMS (polydimethylsiloxane) 링커를 적용하여 기판 표면의 극성을 변경시켜 주었다. 아민-PDMS 링커는 PC (polycarbonate), PET (polyethylene terephthalate), PVC (polyvinyl chloride) 및 PI (polyimide)와 같은 다양한 열가소성 플라스틱의 표면 소수성을 현저히 증가시키며 화학적, 열적 안정성이 뛰어나다. 아민-PDMS 링커는 PMMA의 카보닐 그룹과 반응할 수 있는 아민 사이드 그룹을 포함하는 PDMS 백본으로 구성되며 처리된 대상표면을 소수성으로 만든다. 아민-PDMS 링커 처리 이후 채널은 소수성으로 변화되었으며 이는 접촉각(contact angle)의 증가로 확인되었다. 코팅된 채널을 에탄올로 30분간 80도에서 처리하여도 소수성은 그대로 유지되어 마이크로 채널의 선택적인 소수성 코팅이 성공적으로 수행되었다.

• Journal of the Korean Chemical Society
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• v.35 no.5
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• pp.580-585
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• 1991

Quinolone derivatives have been used as antibacterial agents. In this work, the competitive C-and O-acylation reaction of 3,4-dichloroacetophenone, as a model study for the synthesis of quinolone intermediate, is studied. The effects of various bases, solvents and the leaving groups of acylating agents on the ratio of C-versus O-acylation of 3,4-dichloroacetophenone are elucidated by means of employing ethylchloroformate, ethylphenylcarbonate and diethylcarbonate as acylating agents. In aprotic solvents, C-acylation reactions occur more predominantly as the size of metal ions composing bases becomes smaller. Regarding the effects of leaving groups, it is shown that C-acylation product is increased as the ability of leaving groups of acylating agents decreases. The ratio of C/O-acylation is also observed to be increased as the polarity of solvents decreases.

• Korean Journal of Weed Science
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• v.14 no.1
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• pp.42-48
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• 1994

The toxic compounds of sorghum stem extracts were isolated by different organic solvents and pH, and characterized and quantified in terms of their inhibition of seed germination and seedling growth in Echinochloa colona(L.) Link and radish(Raphanus sativus L.). Sequential partitioning of stem extract with various organic solvents with increasing polarity showed that all fractions of hexane, ethyl ether, methylene chloride, ethyl acetate, and the aqueous remainder inhibited germination and seedling growth in E. colona. Of the five fractions, the ethyl ether fraction had the greatest inhibitory effect on E. colona. Further separation of the ethyl ether fraction at different pH(pH 2-11) showed that phytotoxic compounds were acidic. The result indicates that the phytotoxin present in the stem extract may be nonpolar and acidic.

• Applied Chemistry for Engineering
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• v.19 no.4
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• pp.370-375
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• 2008

Optimum synthesis conditions were investigated for the non-aqueous dispersion (NAD) polymerization of environmentally-friendly acrylic resin. The optimum amount of stabilizer was observed to be 20 wt% to prevent flocculation of the synthesized polymer particles. The optimum ratio of aliphatic solvents to aromatic solvents turned out to be 80 to 20 in order to obtain a stabilized NAD resins. The viscosity of NAD resins was affected not only by the reaction time but also by the amount of initiator and the impeller rpm. Also, the particle size and the size distribution were influenced by the amount of stabilizers and initiators. Since the stability of NAD resin was devastated by the increase in particle size when all the monomers were fed at the beginning of polymerization, the monomers need to be put into the reactor step by step throughout the entire polymerization process.

• Journal of the Korean Chemical Society
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• v.36 no.2
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• pp.174-179
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• 1992

Reaction of aniline and iodine in$CHCl_3,\;CH_2Cl_2 : CHCl_3$(1 : 1), and $CH_2Cl_2$ has been studied kinetically by using conductivity method, Pseudo first-order rate constants ($k_{obs}$) and second-order rate constants ($k_{obs}$/[aniline]) are dependent on the aniline concentration. Second-order rate constants obtained were increased with increasing aniline concentration. We analysed these results on the basis of formation of charge transfer complex as reaction intermediate. From the construction of react ion scheme and derivation of rate equation, we calculated equilibrium constants and activation parameters for the formation and transformation of charge transfer complex. The equilibrium constants were decreased by an increase in the dielectric constant of the solvent and the value is 1.7-3.7$M^{-1}$. The rate of transformation are markedly affected by the solvent polarity. ${\Delta}H^{\neq}$ is about 14.2kJ/mol, and ${\Delta}S^{\neq}$ is large negative value of -243J/mol K.