Micellization behavior of mixed surfactants in pure water and methanol-water mixed solvent media by density methods (original) (raw)
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The effect of temperature onthe micellization of an anionic surfactant in mixed solvent systems
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The micellization and thermodynamic properties of Sodium dodecyl sulphate (SDS) in ethylene glycol-water mixture has been studied at various mole fractions (X) of the solvent mixture and at different temperatures through conductivity measurements. The critical micelle concentration of SDS decreasedas the mole fraction of ethylene glycol (EG) increasedatconstant temperatureand increased with increasing temperature at constant mixture composition. Similarly, the degree of micelle ionization was inverselyproportional to mixture composition but directly proportional to temperature. Thesetrends are indicative of the interactions of SDS ionic head groups and the association of SDS molecules with the binary mixed solvents. The properties of the mixtures also indicate spontaneous formation of thermodynamically stable micelles.
Micellization and Interaction of Anionic and Nonionic Mixed Surfactant Systems In Water
Colloids and Surfaces A: Physicochemical …, 2005
Interaction between binary surfactant mixtures containing anionic surfactants viz. sodium dodecyl sulphates (NaDS) and magnesium dodecyl sulphates (Mg(DS)2) and a nonionic surfactants viz. dodecyl dodecapolyethylene glycol ether (C12E12) and dodecyl pentadecapolyethylene glycol ether (C12E15) in water at different mole fractions (0–1) were studied by surface tension, viscometry and dynamic light scattering (DLS) methods. The composition of mixed micelles and the interaction parameter, β evaluated from the CMC data obtained by surface tension for different systems using Rubingh’s theory were discussed. Activity coefficient (f1 and f2) of metal dodecyl sulphates (MDS)/C12Em (m= 12, 15) mixed surfactant systems were evaluated, which shows extent of ideality of individual surfactant in mixed system. The estimated interaction parameter indicates an overall attractive interaction in the mixed micelles, which is predominant for NaDS as compared to Mg(DS)2. Counter ion valency has specific effect on the mixed micelles, as Mg(DS)2 has less interaction with nonionic surfactants in comparison to NaDS due to strong condensation of counter ion. The stability factors for mixed micelles were also discussed by Maeda’s approach, which was justified on the basis of steric factor due to difference in head group of nonionic surfactant. DLS measurements and viscosity data reveals the synergism in mixed micelles, showing typical viscosity trends and linearity in sizes were observed.
Micellization of cationic surfactants in alcohol — water mixed solvent media
The effect of addition of methanol and ethanol on the micellization of cationic surfactants dodecyltrimethylammonium bromide (DTAB) and cetyltrimethylammonium bromide (CTAB) in aqueous medium have been studied by conductance and surface tension measurements at 298.15 K. Different physicochemical properties such as Gibb's free energy of micellization (ΔG° m), free energy of surfactant tail transfer (ΔG° trans), maximum surface excess concentration (Г max), area occupied by surfactant molecule (A min), surface pressure at the cmc (π cmc), packing parameters (P) and standard free energy interfacial adsorption (ΔG° ads) are calculated in water, 0.10, 0.20, 0.30 and 0.40 volume fractions of methanol–water and in water, 0.10, 0.20, 0.30, 0.40, 0.50 and 0.60 volume fractions of ethanol–water respectively at 298.15 K. Addition of alcohol significantly affects the physicochemical properties of both DTAB and CTAB. With increasing concentration of alcohol, cohesive force and dielectric constant decrease that affects the micellization and other physicochemical properties. However , at the higher volume fraction of ethanol–water a slight variation of properties are seen. The micellization of DTAB and CTAB have been assessed in terms of different solvent parameters. The ratio of the solvent surface tension to the limiting surface tension at the cmc has been used as the solvophobic effect. The sol-vophobic parameter characterized by Gibbs energy of transfer of hydrocarbon from gas into a given solvent can be used to account for the effect of alcohol on the formation and growth of the cationic surfactants aggregate in water.
Journal of Dispersion Science …, 2008
The micellization process of binary surfactant mixtures containing cationic surfactants viz.dodecyl pyridinium halide (C12PyX; X 5 Cl, Br, I), tetradecyl pyridium bromide (C14PyBr),and hexadecyl pyridium halide (C16PyX; X 5 Cl, Br) and a nonionic surfactants viz.dodecyl nonapolyethylene glycol ether (C12E9), dodecyl decapolyethylene glycol ether (C12E10), dodecyl dodecapolyethylene glycol ether (C12E12), and dodecyl pentadecapolyethylene glycol ether (C12E15) in water at different mole fractions (0–1) were studied by surface tension and viscosity methods. The composition of mixed micelles and the interaction parameter 'b' evaluated from the CMC data obtained by surface tension for different systems using Rubingh’s theory were discussed. Activity coefficient (f1 and f2) of cationic surfactant (CnPyBr)/C12Em (n 5 12, 14, 16 and m 5 10, 12, 15) mixed surfactant systems were evaluated, which shows extent of ideality of individual surfactant in mixed system. The stability factors for mixed micelles were also discussed by Maeda’s approach, which was justified on the basis of steric factor due to difference in head group of nonionic surfactant.