Mixed micelles of anionic and cationic surfactants in aqueous solutions

Critical micelle concentrations (c.m.c.s) were obtained from tensiometric studies on several binary cationic-an ionic surfactant mixtures in water at different mole fractions (0-1). The interaction parameter, P, and composition of the mixed micelles were estimated using Rubingh's theory. Strong interaction was observed for each mixed system, a common feature of cationic-anionic mixtures. Remarkably strong interaction was observed for mixed systems in which the hydrophobic tails of the mixed surfactants had similar carbon chain lengths, while the interaction weakened with increase in the difference between the carbon chain lengths of the hydrophobic tails of the constituent surfactants. Viscosity and conductance data are also reported for the same mixed surfactant systems.