• Bulletin of the Korean Chemical Society
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• v.29 no.8
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• pp.1539-1544
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• 2008

A polymeric micelle, based on the poly(benzyl-L-histidine)-b-poly(ethylene glycol) (polyBz-His-b-PEG) diblock copolymer, was designed as a tumor-specific targeting carrier. The micelles (particle size: 67-80 nm, critical micelle concentration (CMC); 2-3 $\mu$g/mL) were formed from the diafilteration method at pH 7.4, as a result of self-assembly of the polyBz-His block at the core and PEG block on the shell. Removing benzyl (Bz) group from polyBz-His block provided pH-sensitivity of the micellar core; the micelles were physically destabilized in the pH range of pH 7.4-5.5, depending on the content of the His group free from Bz group. The ionization of His group at a slightly acidic pH promoted the deformation of the interior core. These pHdependent physical changes of the micelles provide the mechanism for pH-triggering anticancer drug (e.g., doxorubicin: DOX) release from the micelle in response to the tumor’s extracellular pH range (pH 7.2-6.5).

• Journal of the Korean Chemical Society
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• v.56 no.2
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• pp.188-194
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• 2012

The interaction of 4-alkylbenzoic acid isomers with the micellar system of TTAB (tetradecyltrimethylammonium bromide) was studied by the UV/Vis spectrophotometric method. The solubilization constants ($K_s$) of 4-alkylbenzoic acid isomers into the TTAB micellar system and the critical micelle concentration (CMC) of TTAB have been measured with the change of temperature. Various thermodynamic parameters have been calculated and analyzed from those measurements. The results show that the values of ${\Delta}G^o{_s}$ for the solubilization of all the isomers are negative and the values of ${\Delta}H^o{_s}$ and ${\Delta}S^o{_s}$ are all positive within the measured temperature range. The effects of additives (n-butanol and NaCl) on the solubilization of 4-alkylbenzoic acid isomers have been also measured. There was a great change on the values of $K_s$ and CMC simultaneously with these additives. From these changes we can postulate that the solubilization sites of 4-alkylbenzoic acids are the core or deep palisade region of the TTAB micelle.

• Applied Chemistry for Engineering
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• v.22 no.5
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• pp.473-478
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• 2011

The interaction of para-halogenated benzoic acid isomers with the micellar system of tetradecyltrimethylammonium bromide was studied by the UV/Vis spectrophotometric method. The solubilization constants ($K_s$) of benzoic acid isomers into the micellar system of TTAB and the critical micelle concentration (CMC) of TTAB have been measured with the change of temperature. Various thermodynamic parameters have been calculated and analyzed from those measurement. The results show that the values of ${\Delta}G^{\circ}{_s}$ for the solubilization of all isomers are negative and the values of ${\Delta}H^{\circ}{_s}$ and ${\Delta}S^{\circ}{_s}$ are all positive within the measured temperature range. The effects of additives (n-butanol and NaCl) on the solubilization of benzoic acid isomers have been also measured. There was a great decrease on the values of $K_s$ and CMC simultaneously with these additives. From these changes we can postulate that the solubilization sites of each isomers in the TTAB micellar system are the surface or the palisade region of the micelle.

• Journal of the Korean Chemical Society
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• v.17 no.2
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• pp.73-79
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• 1973

The ultrasonic absorption of Dodecyl pyridinium bromide (D.P.B.) in aqueous solution has been measured at $20^{\circ}C$ over a range of frequencies between 0.1 mc and 90 mc and a range of concentrations from 5 to 100 mM. The excess absorption was observed only in the solutions the concentration of which was higher than the critical micellar concentration (c.m.c.) both in the presence and absence of salt. The excess absorption of sound and the relaxation frequencies obtained from the absorption curves show a discontinuity with the variation of the concentration of D.P.B. in the neighborhood of 60 mM. Other properties such as viscosity, conductivity and velocity of sound also exhibit such a change near the same concentration. It is concluded that a change in the properties of the micelles of D.P.B. occurs in the neighborhood of this concentration. The mechanism of the observed ultrasonic excess absorption in attributed to the reaction $M_2{\rightleftarrow}M_1+2Br^-$where$M_2$ and$M_1$are two types of micelles. The rate constants of forward and backward reactions are found to be $6.9 {\times} 10^5 sec^{-1)$and $6.7{\times}10^{10}sec^{-1}mole{-2}$ respectively. Some kinetic characteristics including free energy, enthalpy, entropy and activation energy were calculated.

• Journal of the Korean Applied Science and Technology
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• v.8 no.1
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• pp.85-89
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• 1991

The thermodynamics of micellization of a new series of ionic surface-active agents, dimethyl alkyl-2-deoxy-2-epi-inosityi-ammonium chlorides, has been examined, A minimum in the critical micelle concentration versus temperature has been observed at $25^{\circ}C$ It has been found that the standard entropy of micellization is always positive showing that miceliization is governed by the gain in entropy associated with the removal of the monomer from an aqueous environment to the micelle over a $15^{\circ}C$ to $45^{\circ}C$ temperature while governed by enthalpy directed process below $25^C{\circ}$.

• Journal of the Korean Applied Science and Technology
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• v.15 no.3
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• pp.39-45
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• 1998

In recent years, there has been considerable interest in the development of new functional surfactant including new type of anionic surfactants. Anionic surfactants, ${\alpha}-sulfo$ fatty acids that straight long chain alkyl group having from 12 to 18 carbon atoms, were synthesized with sulfur trioxide-dioxane complex to good yield. Xylitol ${\alpha}-sulfo$ fatty acid esters were obtained by reaction that the acetification and esterification of xylitol, by addition reaction with sodium chloride and hydrolysis respectively. These compounds were a new group of destructible surfactants which readily hydrolyzed and oxidized in natural water reservoirs. Physical properties of these new compounds involved surface tension, critical micelle concentration(cmc), foaming power, emulsion power, and hydrolysis properties, were measured. The cmc values of the compounds by ring method were assumed to $7.0{\times}10^{-3}{\sim}3.0{\times}10^{-2}mol/{\ell}$ range and surface tensions at cmc were $25{\sim}31dyne/cm$ respectively.

• Proceedings of the Korean Fiber Society Conference
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• 2003.10b
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• pp.243-244
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• 2003

계면활성제는 모터오일, 제약, 비누, 세제 등의 용도가 다양한 화학 제품 중 하나이다. 계면활성제는 비극성의 긴 탄화수소 체인으로 이루어진 꼬리(tail)부분과 보통은 이온으로 이루어진 극성을 띄는 머리(head)부분으로 구성되어있다. 보통 계면활성제를 나타낼 때는 fig. 1의 성냥개비와 같은 모형으로 표시하는 경우가 많다. 머리부분이 친수기를 나타내고, 꼬리부분이 친유기를 나타낸다. (1-2) 물과 같은 극성용매에서, 친수성과 친유성의 두 가지의 특징을 동시에 가지고 있는 계면활성제는 미셀(micelle)이라고 알려진 정리된 분자 화합이 일어난다.[3] (중략)

• Bulletin of the Korean Chemical Society
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• v.13 no.6
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• pp.647-649
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• 1992

The critical micelle concentration (CMC) values of cetylpyridinium chloride (CPC) in some alcohol-aqueous solutions were determined by UV-Vis spectroscopy at 25$25^{\circ}C$. The CMC of CPC was increased with the addition of methanol and ethanol, while with the addition of propanol it was decreased because of the solubilization of propanol into the micelle of CPC. The ratio (${\beta}$) of the number of counterions to that of surfactant ions associated into micelles in alcohol (methanol, ethanol and propanol) aqueous solutions was measured by using the Shinoda $equation^{17}$. The ratio of counterion binding to the CPC micelles in methanol-and ethanol-water mixtures was larger than in pure water, while the ratio in propanol-water mixture might be much decreased.

• Macromolecular Research
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• v.13 no.4
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• pp.344-351
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• 2005

pH-sensitive block copolymers were synthesized by coupling reaction of sulfamethazine and amphiphilic diblock copolymer, and their micellization-demicellization behavior was investigated. Sulfamethazine (SM), a derivative of sulfonamide, was introduced as a pH responsive moiety while methoxy poly(ethylene glycol)poly(D,L-lactide) (MPEG-PDLLA) and methoxy poly(ethylene glycol)-poly($D,L-lactide-co-{\varepsilon}-caprolactone$) (MPEG-PCLA) were used as biodegradable amphiphilic diblock copolymers. After the sulfamethazine was carboxylated by the reaction with succinic anhydride, the diblock copolymer was conjugated with sulfamethazine by coupling reaction in the presence of DCC. The critical micelle concentration (CMC) and mean diameter of the micelles were examined at various pH conditions through fluorescence spectroscopy, dynamic light scattering and transmission electron microscopy. For MPEG-PDLLA-SM and MPEG-PCLA-SM solutions, the pH-dependent micellization-demicellization was achieved within a narrow pH band, which was not observed in the MPEG-PDLLA and MPEG-PCLA solutions. The micelle showed a spherical morphology and had a very narrow size distribution. This pH-sensitive block copolymer shows potential as a site-targeted drug carrier.

• Proceedings of the SAREK Conference
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• 2008.11a
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• pp.275-280
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• 2008

The effects of the surfactant type, i.e., CTAB(cationic), SDS(anionic), and GA(polymeric), on the stability of 0.1 vol.% $Al_2O_3$ nanofluids were investigated. The changes in size and zeta potential of nanoparticles in nanofluids with pH, surfactant concentration, and time were experimentally observed. The nanofluids adding CTAB, which ionizes of the same charge with the bare particle surface, was found to have the best stability regardless of the surfactant concentration, whereas those with SDS became unstable under low surfactant concentration conditions, i.e. lower than the critical micellel concentration(CMC), before the charge reversal occurred. With higher SDS concentration over CMC, they became stable. Gum Arabic, which had been used often to stabilize the nanofluids, was also tested. In result, it was found that the type and concentration of surfactants to add should be selected considering pH and the sign of the bare particle surface charge.