• 공업화학
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• 제10권4호
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• pp.576-580
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• 1999

Column에 공기를 분사시켜 수용액으로부터 색을 제거하기 위한 연구를 수행하였다. 착색 용액을 제조하기 위해 Basic Yellow 28 및 Direct Orange 31을 사용하였으며, 모든 색은 8분 이내에 제거되었다. Sodium dodecyl sulfate, oleic acid sodium salt 및 amines와 같은 collector는 색 제거에 효과적이었다. 색 제거는 collector의 첨가량과 수용액 pH의 영향을 받는다고 할 수 있으나, 소량의 collector를 첨가하였을 경우에는 pH에 의존하였으나, 많은 양을 첨가하였을 경우에는 pH에 의존하지 않았음을 알 수 있었다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2008년도 하계학술대회 논문집 Vol.9
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• pp.153-153
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• 2008

Practical application of single-walled carbon nanotubes (SWCNTs) qualified as a promising material has been limited by either poor dispersion or their insolubility in aqueous or organic media due to formation of bundling by relatively high surface energy. Thus, major attention to overcome this issue has been paid at surface modification of CNTs by functionalization, but this introduces defects to the sidewall of CNTs, consequently perturbing the inherent electronic and optical properties. Therefore, using surfactants is a general approach to disperse SWCNTs with lower damages by which bundled nanotubes could be dispersed up to the level of individuals or small bundles. Here, we have investigated various surfactants for their efficiency in dissolving purified SWCNTs produced by arc discharge in deionized water. To compare the surfactants respectively, we have determined the least amount of each surfactant to suspend the nanotubes under optimized experimental conditions(CNT amount, sonication power, and centrifugation speed, etc.) set on the basis of the most common surfactant (sodium dodecyl sulfate, SDS) and discussed the qualitative and quantitative characterization of SWCNT dispersions by UV-Vis absorption spectroscopy. Quantitative aspect about nanotube dispersion was that in particular N-methyl-2-pyrrolidone (NMP) and sodium dodecylbenzene sulfonate (NaDDBS) were found to be effective in dispersing individual tubes.

• Bulletin of the Korean Chemical Society
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• 제26권8호
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• pp.1241-1245
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• 2005

Solvolyses of trifluoromethanesulfonyl chloride (TFMSC) in water and in aqueous binary mixtures of acetone, ethanol and methanol are investigated at 25, 35 and 45 ${^{\circ}C}$. The Grunwald-Winstein plot of first-order rate constants for the solvolytic reaction of TFMSC with YCl (based on 2-adamantyl chloride) shows marked dispersions into three separate curves for three aqueous mixtures. The extended Grunwald-Winstein plots for the solvolysis of TFMSC show better correlation. The large negative ${\Delta}S^{\neq}$ and relatively small positive ${\Delta}H^{\neq}$ reveals that the solvolytic reaction proceeds via a typical bimolecular reaction mechanism. The l and m values determined in various solvents are consistent with the proposed mechanism of the general base catalysis $S_AN/S_N2$reaction mechanism for TFMSC solvolyses based on mass law and stoichiometric solvation effect studies.

• Macromolecular Research
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• 제15권6호
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• pp.575-580
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• 2007

Water-soluble, chiral conducting, poly(diphenylamine) (PDPA) nanocomposites were synthesized by chemical oxidative polymerization of diphenylamine in the presence of poly(acrylic acid) (PAA) as a template and camphor sulphonic acid (CSA) as the chiral inductor, Composites were formed as stable aqueous dispersions under different experimental conditions, such as DPA to PAA molar ratios, PAA molecular weight, etc. Circular dichroism(CD) spectra of the composites indicated the induction of chirality to PDPA. Compared to simple chiral PANI, the PDPA/PAA/CSA nanocomposites showed a different Cotton effect. The appearance of a CD band in the composite was complimentary to the bisignate, exciton-coupled band in the UV-Visible spectrum. FTIR spectra indicated the intimate mixing of PDPA and PAA.

• Journal of Pharmaceutical Investigation
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• 제29권3호
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• pp.185-191
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• 1999

The polymeric films containing drug and various excipients were fabricated using aqueous-based $Eudragit^{\circledR}$ RS 30D dispersions. The diffusional behaviors and mechanism of the fabricated polymeric film were investigated using Keshary-Chien diffusion cell. The melatonin was used as a model drug. The diffusion behaviors of drug through the fabricated polymeric films were highly dependent on drug concentration in donor part, polymer contents and drug concentration, and the types of plasticizers and solubilizers. The fabricated polymeric films containing excipients and solubilizers could be applied for the controlled release of poorly water-soluble drug and for the preparation of drug-containing latex films for topical or oral drug delivery.

• Bulletin of the Korean Chemical Society
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• 제20권12호
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• pp.1451-1456
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• 1999

Solvolyses of α-methoxy-α-(trifluoromethyl)phenylacetyl chloride in H₂O, D₂O, CH₃OD, 50% D₂O-CH₃OD, and in aqueous binary mixtures of acetone, dioxane, ethanol and methanol are investigated at 25.0℃. The Grunwald-Winstein plots of first-order rate constants for α-methoxy- α-(trifluoromethyl)phenylacetyl chloride with $Y_{Cl}$ show a dispersion phenomenon. Solvent nucleophilicity N has been shown to give considerable im-provement when it is added as an 1N term to the original Grunwald-Winstein for the solvolyses of α-methoxy- α-(trifluoromethyl)phenylacetyl chloride. The dispersions in the Grunwald-Winstein correlations in the present studies are caused by solvent nucleophilicity. The magnitude of l and m values associated with a change of solvent composition predicts the associative $S_N2$ transition state. The kinetic solvent isotope effects determined in deuterated water and methanol are consistent with the proposed mechanism of the general base catalyzed associative $S_N2$ or $S_AN$ mechanism for the of α-methoxy- α-(trifluoromethyl)phenylacetyl chloride.

• Bulletin of the Korean Chemical Society
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• 제20권5호
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• pp.577-580
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• 1999

Solvolyses of phenyl chlorothionoformate in water, D2O, CH3OD, 50% D2O-CH3OD, and in aqueous binary mixtures of acetone, ethanol and methanol are investigated at 25.0℃. The Grunwald-Winstein plots of firstorder rate constants for phenyl chlorothionoformate with Ycl (based on 2-adamantyl chloride) show a dispersion phenomenon, and also the extended Grunwald-Winstein plots show a poor correlation for the solvolyses of phenyl chlorothionoformate. The ring parameter (I) has been shown to give considerable improvement when it is added as an hI term to the original and extended Grunwald-Winstein correlations. The dispersions in the Grunwald-Winstein correlations in the present studies are caused by the conjugation between the reaction center and the aromatic ring in the vicinity of the reaction center. This study has shown that the magnitude of l and m values associated with a change of solvent composition leads to predict the SN2 transition state. The kinetic solvent isotope effects determined in deuterated water and methanol are consistent with the proposed mechanism of the general base catalyzed SN2 mechanism.

• Bulletin of the Korean Chemical Society
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• 제23권1호
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• pp.123-131
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• 2002

Solvolyses rate constant of 1- and 2- naphthoyl chlorides (1 and 2) are reported for aqueous binary mixtures with methanol, ethanol, fluorinated alcohol, acetonitrile and dioxane. Kinetic solvent isotope effects (KISE) in methanol and product selectivities (S) of 2-naphthoyl chloride (2) in alcohol-water are also reported. Dispersions in Grunwald-Winstein correlations $(r{\leq}0.901)$ are discussed by multiple regression analysis incorporating ionizing power $(Y_{Cl})$ scale and rate-rate profiles. Major causes for these phenomena are investigated as an aromatic ring solvation effects, in conjunction with weakly nucleophilic solvation effects ($S_N2$ character), for solvolyses of 1 and for solvolyses of 2, as dual reaction channels, described as $S_N1$-$S_N2$ and $S_AN$-$S_N2$ processes. Distinct border lines between the two pathways are derived from solvolyses rates of 2 in 18 solvent using the results of $log(k/k_o)=mY_{Cl}+lN_T+hI$ plot with values of 1.13 for m, 0.37 for l and 0.15 for h value in 5 aqueous fluorinated alcohol mixtures. Using rate-product correlation, the validity of a third order model based on a general base catalyzed by solvent and contribution from these rate constants, $k_{aa},\;k_{aw}$ and $k_{aw}$, are investigated for $S_AN$-$S_N2$ solvolyses of 2 favored in more rich alcohol media and gradual addition of water to alcohol solvent shows a great shift away from stoichiometric solvation to predominantly medium effects. Rate-rate correlation between solvolyses of 2 and trimethyl acetylchloride (5) with alkyl group in the 29 aqueous solvent mixtures shows appreciable linearity (slope = 0.84, r = 0.987), caused by the same pathway ($S_N1$-$S_N2$ process), even if this correlation coincides with appreciable dispersion (different solvation effect).

• 대한화학회지
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• 제43권5호
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• pp.527-534
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• 1999

아세톤, 에탄올, 메탄올 이성분 혼합수용액에서 파라치환된 cinnamoyl chloride의 가용매분해반응을 25$^{\circ}C$에서 수행하였다. 이들 속도자료로부터 Grunwald-Winstein관계식, Hammett 식, PES 모형과 QM모형을 이용하여 해석 하였다. 파라 치환된 cinnamoyl chloride의 일차반응속도상수를 이용하여 Grunwald-Winstein 도시를 한 결과 세 개의 분리된 곡선으로 분산 현상을 보였으며 알코올 수용액에서 큰 m 값을 나타내었다. PES 모형과 QM 모형에 의한 전이상태 변화에 대한 예측으로부터 본 연구에서의 반응은 결합 이탈이 많이 진전된 $S_N1$형 $S_N2$ 반응으로 진행되고 있음을 알 수 있었다.

• 폴리머
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• 제37권4호
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• pp.442-448
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• 2013

본 연구에서는 분무건조방법을 이용하여 고혈압 치료제로 사용되고 있는 난용성 약물인 에프로살탄의 고체분산체 제형을 다양한 조성 하에서 제조 및 평가하고, 효과적인 약물의 용해도 향상을 위한 제조 조건을 최적화하였다. 친수성 고분자 기제로 hydroxylpropylcellulose(HPC)와 poly(vinyl pyrrolidone)(PVP)를 사용하였고, 고분자 계면활성제로 poloxamer 407을 첨가하여 약물과 고분자의 다양한 조성비를 갖는 고체분산체를 제조한 후, 물리화학적 특성을 비교 평가하였다. 친수성 고분자의 조성비 증가와 함께 약물 결정성이 감소되었으며, HPC보다는 PVP가 약물과의 우수한 상용성을 바탕으로 결정화도 감소와 용출거동 개선 효과가 상대적으로 우수하였다. 친수성 고분자로 PVP를 사용한 경우 약물의 결정성이 대부분 사라져 고체분산체 내 대부분의 약물 분자들이 무정형으로 분산되어 있으며 약물의 용출률이 에프로살탄 대비 3~7배 이상 향상되었다.