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Effects of three organic solvents, viz. methyl cellosolve, acetonitrile, and formamide, on the micellization process of Gemini surfactant pentamethylene-1,5-bis(tetradecyldimethylammonium bromide) aqueous solutions, with the volume percentages of the organic solvents up to 50%, have been investigated conductometrically. The studies were made at different temperatures and the data were used to find out different micellization parameters. From the study, it was observed that, although an increment in the amount of the organic solvents delays the micellization, the increase in the critical micelle concentration (cmc) is comparatively less below 20%(v/v) showing the predominance of water character in the bulk phase at lower compositions of the organic solvents. Applying equilibrium model for micelle formation, various thermodynamic parameters were also calculated from the temperature dependence of the cmc values and the results show that the micellization process becomes less spontaneous as the volume % of the organic solvent increases in the system due to the action of water-organic solvent mixed media as better solvent than pure water (solvophobic effect) for the studied Gemini molecules. [ABSTRACT FROM AUTHOR]

Abstract: In this work, densities of binary mixtures of {water+formamide (FM), or + N,N-dimethylformamide (DMF), or +dimethylsulfoxide (DMSO), or + N,N-dimethylacetamide (DMA), or +1,4-dioxane}, have been determined under atmospheric pressure as a function of composition and temperature using a vibrating-tube densimeter. The temperatures studied were T =(288.15, 293.15, 298.15, and 303.15) K. The excess molar volumes , calculated from density data, are negative over the whole mole fraction range for the temperature range studied. The values have been fitted to Redlich–Kister polynomial equation and others volumetric properties were calculated. The partial molar volumes at infinite dilution of each component have been determined using three different methods. [Copyright &y& Elsevier]