• Journal of the Korean Chemical Society
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• v.42 no.5
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• pp.519-525
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• 1998

The critical micelle concentration $(CMC^{\ast})$ and the counterion binding constant (B) in a micellar state of the mixed surfactant systems of dodecylpyridinium chloride (DPC) with dodecyltrimethylammonium bromide (DTAB), tetradecyltrimethylammonium bromide (TTAB), and cetyldimethylethylammonium bromide (CDEAB) were determined at $25^{\circ}C$ as a function of ${\alpha}_1$ (the overall molc fraction of DPC) by the use of electric conductivity method. Various thermodynamic parameters $(X_{i},\;{\gamma}_{I},\;C_{i},\;a^{M}_{i}, \beta,\;{\Delta}H_{mix}, \;and\; {\Delta}G^{o}_{m})$ for the micellization of DPC/DTAB, DPC/TTAB, and DPC/CDEAB mixtures were calculated and analyzed for each system by means of the equations derived from the pseudophase separation model. The results show that the DPC/DTAB mixed system has the greatest deviation and the DPC/CDEAB mixed system has the smallest deviation from the ideal mixed micellar model.

• Membrane Journal
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• v.13 no.4
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• pp.211-218
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• 2003

The removal characteristics of cadmium in micellar enhanced ultrafiltration (MEUF) were investigated by using an anionic biosurfactant, deoxycholic acid (DCA). The ultrafiltration experiments were performed in a batch-type stirred cell. The ultrafiltration membranes used were Millipore YM1, YM3, YM10, and YM30 which had a difference in molecular weight cut-off. The presence of cadmium ion in DCA solution tends to reduce the critical micell concentration considerably and increase the micell size. The molecular weight cut-off of ultrafiltration membrane had a minimal effect on cadmium removal whereas DCA/Cd ratio had a substantial influence. When DCA/Cd ratio was 3, the removal efficiency of cadmium was more than 99.6%. A relative flux, which is defined as ratio of the flux for a separation trial to that of deionized water run using the same piece of membrane, decreased in the order of YM3 > YM1 > YM10 > YM30.

• Applied Chemistry for Engineering
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• v.21 no.3
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• pp.337-342
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• 2010

The interaction of monochlorophenol isomers with the micellar system of TTAB (tetradecyltrimethylammonium bromide) was studied by the UV/Vis spectrophotometric method. The solubilization constants ($K_s$) of monochlorophenol isomers into this micellar system have been measured with the change of temperature. Various thermodynamic parameters (${\Delta}G^{\circ}_s$, ${\Delta}H^{\circ}_s$, and ${\Delta}S^{\circ}_s$) have been calculated and analyzed from the dependence of $K_s$ values on the temperature. The results show that the values of ${\Delta}G^{\circ}_s$ and ${\Delta}H^{\circ}_s$ are all negative but the values of ${\Delta}S^{\circ}_s$ are all positive for the solubilizations of all isomers within the measured temperature range. The effects of additives (n-butanol and NaCl) on the solubilization of monochlorophenol isomers by the same surfactant system 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 the solubilization sites of each isomer in the micellar system of TTAB.

• Journal of the Korean Chemical Society
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• v.54 no.4
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• pp.374-379
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• 2010

The interaction of dichlorophenol isomers with the micellar system of TTAB (tetradecyltrimethylammonium bromide) was studied by the UV/Vis spectrophotometric method. The solubilization constants ($K_s$) of dichlorophenol isomers into the micellar system have been measured with the change of temperature and the various thermodynamic parameters have been calculated and analyzed from these changes. The results show that the values of ${\Delta}G^{\circ}_s$ and ${\Delta}H^{\circ}_s$ are all negative within the measured temperature range. The effects of additives (n-butanol and NaCl) on the solubilization of dichlorophenol 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 the solubilization sites of each isomers in the micellar system of TTAB.

• Archives of Pharmacal Research
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• v.26 no.8
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• pp.653-658
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• 2003

It has been reported that at low temperature region, poloxamers existed as a monomer. Upon warming, an equilibrium between unimers and micelles was established, and finally micelle aggregates were formed at higher temperature. In this study, the fluorescence spectroscopy was used to study the micelle formation of the poloxamer 407 in aqueous solution. The excitation and emission spectra of pyrene, a fluorescence probe, were measured as a function of the concentration of poloxamer 407 and temperature. A blue shift in the emission spectrum and a red shift in the excitation spectrum were observed as pyrene transferred from an aqueous to a hydrophobic micellar environment. From the $I_1/I_3 and I_{339}/I_{333}$ results, critical micelle concentration (cmc) and critical micelle temperature (cmt) were determined. Also, from the fluorescence spectra of the probe molecules such as 8-anilino-1-naphthalene sulfonic acid and 1-pyrenecarboxaldehyde, the blue shift of the $\lambda_{max}$ was observed. These results suggest a decrease in the polarity of the microenvironment around probe because of micelle formation. The poloxamer 407 above cmc strongly complexed with hydrophobic fluorescent probes and the binding constant of complex increased with increasing the hydrophobicity of the probe.

• Journal of the Korean Chemical Society
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• v.51 no.2
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• pp.129-135
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• 2007

The critical micelle concentrations (CMC) and the counter ion binding constants (B) in a micellar state of the mixed surfactant systems of Tetradecyltrimethylammonium bromide (TTAB) with Polyoxyethylene(23) lauryl ether (Brij 35) in water were determined as a function of α1 (the overall mole fraction of TTAB) by the use of electric conductivity method and surface tensiometer method from 15 oC to 35 oC. Values of thermodynamic parameters (ΔGom, ΔHom, and ΔSom) for the micellization of TTAB/Brij 35 mixtures were calculated and analyzed from the temperature dependence of CMC values. The results say that the measured values of ΔGom are all negative at the whole measured condition but the values of ΔSom and ΔHom are positive or negative, depending on the measured temperature and α1.

• Journal of the Korean Chemical Society
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• v.50 no.3
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• pp.190-195
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• 2006

The critical micelle concentrations (CMC) and the counter ion binding constants (B) in a micellar state of the mixed surfactant systems of sodium dodecylbenzenesulfonate (DBS) with polyoxyethylene(4) lauryl ether (Brij 30) in water were determined as a function of 1 (the overall mole fraction of DBS) by the use of electric conductivity method and surface tensiometer method from 288 K to 308 K. Various thermodynamic parameters (Smo, Hmo, and Gmo) for the micellization of DBS/Brij 30 mixtures were calculated and analyzed from the temperature dependence of CMC values. The measured values of Gomare all negative but the values of Smo are positive in the whole measured temperature region. On the other hand, the values of Hmo are positive or negative, depending on the measured temperature and 1.

• Korea-Australia Rheology Journal
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• v.14 no.4
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• pp.189-201
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• 2002

The interaction between hydrophobically modified hydroxyethyl cellulose (hmHEC), containing approximately 1 wt% side-alkyl chains of $C_{16}$, and an anionic sodium dodecyl sulphate (SDS) surfactant was investigated. For a semi-dilute solution of 0.5 wt% hmHEC, the previously observed behaviour of a maximum in solution viscosity at intermediate SDS concentrations, followed by a drop at higher SDS concentrations, until above the cmc of surfactant when the solution resembles that of the unsubstituted polymer, was confirmed. Additionally, a two-phase region containing a hydrogel phase and a water-like supernatant was found at low SDS concentrations up to 0.2 wt%, a concentration which is akin to the critical association concentration, cac, of SDS in the presence of hmHEC. Above this concentration, SDS molecules bind strongly to form mixed micellar aggregates with the polymer alkyl side-chains, thus strengthening the network junctions, resulting in the observed increase in viscosity and elastic modulus of the solution. The shear behaviour of this polymer-surfactant complex during steady and step stress experiments was examined In great detail. Between SDS concentrations of 0.2 and 0.25 wt%, the shear viscosity of the hmHEC-polymer complex network undergoes shear-induced thickening, followed by a two-stage shear-induced fracture or break-up of the network. The thickening is thought to be due to structural rearrangement, causing the network of flexible polymers to expand, enabling some polymer hydrophobic groups to be converted from intra- to inter-chain associations. At higher applied stress, a partial local break-up of the network occurs, while at even higher stress, above the critical or network yield stress, a complete fracture of the network into small microgel-like units, Is believed to occur. This second network rupture is progressive with time of shear and no steady state in viscosity was observed even after 300 s. The structure which was reformed after the cessation of shear is found to be significantly different from the original state.

• Korean Chemical Engineering Research
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• v.46 no.4
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• pp.824-832
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• 2008

micellar solution which is comprised of surfactant monomers, monodisperse micelles, and solvent(water) is studied from a statistical-mechanical point of view. The model examined in this article is for the ideal mixture of monomers, micelles, and solvent with the dielectric constant identical to that of solvent, which is an assumption common to continuum models. The model also reflects interactions between monomer and solvent molecule, and also between micelle and solvent molecule. The statistical-mechanical model under consideration yields ln $X_{CMC}=A+BT+C/T+D{\ln}T$ with $X_{CMC}$ being critical mcielle concentration (in mole fraction), being temperature, and A, B, C, D being constants which depend on the properties of the surfactant molecules. The statistical-mechanical model discussed in this article provides a theoretical basis on the thermal dependence of critical micelle concentration

• Journal of the Korean Chemical Society
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• v.55 no.2
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• pp.163-168
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• 2011

The variations of molar conductivity of various surfactants such as sodium caprylate, sodium laurate, sodium palmitate, sodium stearate, sodium oleate, sodium dodecyl sulphate, and lithium dodecyl sulphate with concentrations of the surfactants for each of the solutions consisting of mixtures of varying concentrations of N-methyl acetamide in water at constant temperature of $30{\pm}0.2^{\circ}C$ were studied. The critical micelle concentration (CMC) for each surfactant is measured. It is found that the CMC values in mixtures of N-methyl acetamide and water solutions of various surfactants are lower than the CMC values in water, and the driving force for micelle formation correlates with solvophobicity. The surfactant-solvent interactions that drive amphiphilic self-organization in N-methyl acetamide in water are discussed. Thermodynamic parameters were evaluated for micellar system to explain the results.