Mixed micelles of some anionic‐anionic, cationic‐cationic, and ionic‐nonionic surfactants in aqueous media

Abstract

AbstractCritical micelle concentrations (CMC) were obtained from tensiometric studies on several binary surfactant mixtures (anionic‐anionic, cationic‐cationic, anionic‐nonionic, and cationic‐nonionic) in water at different mole fractions (0–1). The composition of mixed micelles and the interaction parameter β, evaluated from the CMC data for different systems using Rubingh's theory, are discussed. Marked interaction is observed for ionic‐nonionic systems, whereas it is weak in the case of similarly charged surfactants. The influence of counterion valence in the formation of mixed micelles was investigated, and results suggest that in similarly charged surfactant mixtures, the degree of counterion binding does have a major role in deciding the extent of interactions. Salt addition reveals a weakening of interactions in ionic‐nonionic systems, and this is attributed to head group charge neutralization and dehydration of the ethylene oxide units of the nonionic surfactants. Cloud point and viscosity data on these systems support the observation.