Multilamellar to unilamellar vesicle transformation in aqueous solutions of a catanionic surface active ionic liquid

Abstract A catanionic surface active ionic liquid 4-butylazobenzene-4′-hexyloxy-trimethylammonium bis (2-ethylhexyl) sulfosuccinate (AZOAOT) was synthesized. The aggregate structure of AZOAOT/NaAOT mixed surfactants in aqueous solution was investigated and characterized by the measurements of surface tension, zeta potential, transmission electron microscopy (TEM), static/dynamic light scattering (SLS/DLS), and atomic force microscope (AFM). The results showed that mutilamellar vesicle was formed when the total concentration of the mixed surfactants ( c tot ) in the aqueous solution was larger than the critical aggregation concentration (CAC) and a structural transformation to uilamellar vesicles occurred when c tot was greater than about 2 mM. The coexistence of multilamellar and unilamellar vesicles was presented until c tot exceeded about 3 mM and only unilamellar vesicles were left in the aqueous solution thereafter.