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

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. (C) 2019 Elsevier B.V. All rights reserved.