PHASE-TRANSITIONS IN CATIONIC AND ANIONIC SURFACTANT MIXTURES

The phase behavior of cationic and anionic surfactant mixtures strongl y depends on the molar ratio and actual concentration of surfactants. The phase diagram contains large areas of coexisting solid crystalline catanionic surfactant and liquid crystalline phases. Intermediate pha ses from pure solid crystalline catanionic surfactant to mixed micelle s were examined by light microscopy under crossed polarizers and poten tiometric and electrophoretic measurements. The mixed liquid crystalli ne phase is composed of both cationic and anionic surfactants. Its app earance as lamellar droplets may be explained by the increase in elect rostatic repulsion at the bilayer surface.