Effect of acetonitrile–water mixtures on aggregation and counterion binding behavior of sodium dioctylsulphosuccinate micelles

Abstract The aggregation and counterion binding behavior of sodium dioctylsulphosuccinate(AOT) has been studied in the mixtures of acetonitrile (AN) and water by using surface tension and small angle neutron scattering (SANS) techniques. The study in the weakly hydrogen bonded AN reveals some interesting features. The solvent mixtures affect the critical micelle concentration (cmc), primarily due to the change in the solvophobicity of the medium. The solvophobicity of the medium is expressed in terms of cohesive energy density and it has been correlated to the counterion binding behavior. The special counterion binding behavior of AOT shows a strong dependence on the solvent quality. SANS studies reveal no micellar transition as normally observed for AOT on the addition of salts.