• Analytical Science and Technology
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• v.18 no.3
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• pp.194-200
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• 2005

The N hyperfine coupling constants ($a_N$) of di-t-butyl nitroxide (DTBN) radicals in water-solvent system were measured with EPR spectroscopy. Various kinds of the solvents with different polarity such as acetone, dimethylsulfoxide (DMSO), methanol, ethanol and 1-propanol were applied and studied. Equilibrium constants for the solvation equilibrium and the solvent parameters ($E_T$, molar transition energy) of various water-solvent system were obtained from the experimental results and are presented. The $a_N$ values were plotted as a function of mole fraction of the solvent. In case of water-DMSO, water-ethanol and water-1-propanol system, slight negative deviations from the straight line were observed. In water-acetone system, the absorption wavelength (${\lambda}$) due to ${\eta}{\rightarrow}{\pi}^{\ast}$ transition increased linearly with the increase of mole fraction of acetone. The relationship between $a_N$ of DTBN and ${\lambda}$ due to ${\eta}{\rightarrow}{\pi}^{\ast}$ transition in water-acetone and water-DMSO system was examined. It was found that the electronic structure of the nitroxide radicals is stablized from the fact that the N hyperfine coupling constants of DTBN radicals are greatly unaffected in the environment of water-solvent system.

• Applied Chemistry for Engineering
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• v.3 no.3
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• pp.516-521
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• 1992

Hydroxypropyl chitin (HPCH) was prepared by reacting chitin with propylene oxide. HPCH showed the improved solubility in several organic solvents compared with chitin. It showed the remarkable solubility in formic acid. Form the results of polarized microscopic observatoin of HPCH solution in formic acid, finger-print pattern was observed in concentrations over 30 wt% solution. Since no typical thermogram was observed in DSC scan, the HPCH showed a lyotropic cholestric liquid crystallinity.

• Applied Chemistry for Engineering
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• v.16 no.2
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• pp.169-179
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• 2005

Porous materials are useful in a wide range of applications including bio/electronic products. The preparation and processing of these materials are mainly progressed by using an organic solvent, which gives rise to air pollution by its emissions. Alternatively, supercritical fluids are well suited to the production of functional porous materials due to a number of specific physical, chemical, and toxicological advantages. In this review, we will introduce the preparation and processing techniques for the formation of the nano/macro pore structure and their morphology, which can be controled by using supercritical fluids.

• Polymer(Korea)
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• v.34 no.3
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• pp.210-214
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• 2010

The structural development of triacetyl cellulose (TAC) was studied as a function of solution casting processing parameters such as dope concentration, evaporation temperature, annealing temperature and the addition of plasticizer. The crystalline structure was developed by the solution casting and the level of crystallinity was increased with increasing dope concentration and evaporation temperature. The crystalline structure could be enhanced by the annealing process after formation of TAC film. Introducing plasticizer resulted in decreasing melting temperature and crytallinity of TAC film due to the increase of chain mobility. It was also found that thermal stability of TAC was improved due to the rigid structure of applied plasticizer.

• Applied Chemistry for Engineering
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• v.16 no.1
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• pp.153-157
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• 2005

4-(Dimethylamino)pyridinium dichromate was synthesized by the reaction of 4-(dimethylamino)pyridine with chromium(VI)trioxide in $H_2O$, and characterized by IR, EA and ICP. The oxidation of benzyl alcohol using 4-(dimethylamino)pyridinium dichromate in various solvents showed that the reactivity increased with the increase of the dielectric constant, in the order: cyclohexen < chloroform < acetone < N,N-dimethylformamide. In the presence of hydrochloric acid(HCl), 4-(dimethylamino)pyridinium dichromate oxidized benzyl alcohol and its derivatives ($p-CH_3$, H, m-Br, $m-NO_2$) smoothly in N,N-dimethylformamide. Electron-donating substituents accelerated the reaction, whereas electron-withdrawing groups retarded the reaction. The Hammett reaction constant($\rho$) was -0.70 at 303K. The observed experimental data have been rationalized as follows: the proton transfer occurs after the prior formation of a chromate ester in the rate-determining step.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.12 no.12
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• pp.5990-5996
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• 2011

6-Methylquinolinium dichromate[$(C_{10}H_9NH)_2Cr_2O_7$] was synthesized by the reaction of 6-methylquinoline with chromium trioxide in $H_2O$, and characterized by IR, ICP. The oxidation of benzyl alcohol using 6-methylquinolinium dichromate in various solvents showed that the reactivity increased with the increase of the dielectric constant(${\varepsilon}$), in the order: cyclohexene < chloroform < acetone < N,N- dimethylformamide. In the presence of hydrochloric acid($H_2SO_4$ solution), 6-methylquinolinium dichromate oxidized benzyl alcohol and its derivatives(p-$OCH_3$, m-$CH_3$, H, m-$OCH_3$, m-Cl, m-$NO_2$) smoothly in DMF. Electron-donating substituents accelerated the reaction, whereas electron acceptor groups retarded the reaction. The Hammett reaction constant(${\rho}$) was -0.67(303K). The observed experimental data was used to rationalize the hydride ion transfer in the rate-determining step.

• Proceedings of the Korean Vacuum Society Conference
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• 2015.08a
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• pp.141.1-141.1
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• 2015

탄소나노튜브는 우수한 전기적 특성과 더불어 열전도도, 강도, 높은 화학적 안정성, 바이오 물질과의 친화성 때문에 많은 응용이 가능하며 최근까지도 활발히 연구되는 대표적인 탄소질의 물질이다. 이러한 다중 벽 탄소나노튜브를 제품화시키기 위해서는 특정 용매에서 용이한 분산성을 지닐 수 있도록 기능화 공정이 필수적이고 많은 양의 파우더를 기능화 시킬 수 있는 장비의 구조 및 공정개선이 요구된다. 플라즈마 기술을 이용한 건식의 순환형 나노분산 파우더 플라즈마 반복처리장치를 통하여 기능화 처리된 탄소나노튜브를 습식공정에 비해 간편한 공정으로 재현성 있고 균일한 결과로 많은 양의 확보가 가능하다. 이에 탄소나노튜브의 기능화 결과를 제시함으로써 본 장비를 소개하고자 한다.

• 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.

• Journal of the Korean Chemical Society
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• v.41 no.1
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• pp.22-46
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• 1997

Kinetic studies on nucleophilic substitution reaction of phenacyl bromide and phenacyl chloride with pyridines were conducted at 25℃ and 35℃ in methanol-acetonitrile solvents mixtures. It was shown that the reaction proceeds via an SN2 reaction mechanism based on the transition state parameters, ΔH≠ and ΔS≠ and Bro nsted β values. Quantum mechanical model predicted a product-like transition state, where bond-formation is much more progressed than bond breaking, upon changing the leaving group to that with a better leaving ability.

• Prospectives of Industrial Chemistry
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• v.22 no.3
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• pp.6-10
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• 2019

용액공정을 이용하여 우수한 특성을 가지는 OLED를 제작하기 위해서는 다층 박막을 형성하여야 하며, 일반적인 용액공정으로는 다층 구조를 형성하는 데에 어려움이 있어 다양한 공정 및 재료에 대한 연구와 개발이 이루어지고 있다. 박막을 전사하는 방법은 상부막에 사용되는 용매의 침투에 의한 하부막 손상을 최소화할 수 있다는 장점을 가지고 있지만, 사용할 수 있는 전사 공정은 극히 제한적이다. 본 기고에서는 전사 공정으로서 산업에 이용되고 있는 hydrographic printing (수전사) 공정을 OLED 제조에 적용하고 그 가능성에 대하여 알아보고자 한다.