Thermodynamics of Micellization. Part-I. Micelle Formation of CTAB, NaLS and Triton-X-100 in DMF-H2O, DMSO-H2O, Dioxane-H2O and MeOH-H2O Systems by Dye Incorporation Method

Post Graduate Department of Chemistry, Sambalpur University, Burla-768 017 Manuscript received 16 April 1984, accepted 8 November 1984 The critical micelle concentration (one) of the surfactants cetyl trimethylam­monium bromide (CTAB), sodium lauryl sulphate (NaLS), and polyoxyethylene(9.5) p-1,1,3,3-tetramethyl butyl phenol (Triton-X-100) have been determined spectropho­tometrically by dye incorporation method at 25° in DMF-water, DMSO-water, dioxane-water and methanol-water systems. The cmc values obtained in this method compare well with the values obtained by other methods. It has been found that the cmc of all the surfactants increase with increasing mole fraction of the organic solvent and beyond a particular solvent composition no micelle formation is found to take place. The change of cmc with solvent composition has, however, been rationa­lised on the basis of co-solvent effect on water structure and change in free energy of micellization. The thermodynamic parameters of the process of micellization have been evaluated for all the systems