Study on the size of reversed micelles of anionic and cationic surfactants

The size of reversed micelles and its distribution formed by some aionic surfactants having different polar groups and by chiral and achiral cationic surfactants in apolar solvents were investigated by means of the vapor pressure osmometry. The study was also carried out for Aerosol OT purified carefully. The micellar size depended on the kind of polar groups of surfactants and the magnitude of the size was order of sulfonate > carboxylate > sulfate. However, solvent dependence of the micellar size was hardly found for any anionic surfactants. In case of cationic surfactants, the micellar size was independent of the chirality of surfactants and was larger for chiral surfactants than for achiral one. The distribution of micellar size was estimated from the analysis of the dependence of apparent aggregation number upon surfactant concentration by the curvefitting method.