Vesicle stability in aqueous mixtures of zwitterionic/anionic surfactants

It was studied that the influences of the aging, temperature, addition of the polymer and cosolvent on the stability of the vesicles spontaneously formed in the mixtures of zwitterionic surfact ant (dodecyl carboxyl betaine, C12BE) and double-tailed anionic surfactant (sodium bis(2-ethylhexyl) sulfosuccinate, AOT) under the inducement of salt by means of freeze-fracture and negative-stai ni ng transmission electron microscopy (TEM), dynamic light scattering (DLS) and turbidity measurements. It is found that the vesicles can exist over a long period of aging (about 300 days) at room temperature, show good stability after a heating-cooling cycle of 90-25 degrees C and a freeze-thaw cycle of - 10 to 25 degrees C, respectively, and may be transformed from spherical vesicles to tubelike structures induced by high temperature 90 degrees C. Under the effect of (PEO)(13)(PPO)(30)(PEO)(13) (L64), the transition from unilameller vesicles to large multivesicular vesicles. The presence of ethanol-may decrease the stability of vesicles, resulting in the fusion among vesicles to form large vesicles. The excessive amount of ethanol may destroy the vesicles, and the order of ability of destroying vesicles was obtained to be C5H11OH>C4H9OH>C3H7OH>C2H5OH>CH3OH. (c) 2007 Elsevier B.V. All rights reserved.