SPONTANEOUS FORMATION OF MONODISPERSE VESICLES NEAR THE CLOUD POINT OF AN AQUEOUS AMPHIPHILIC SYSTEM

Monodisperse vesicular structures have been produced spontaneously fro m an almost structure-less aqueous amphiphilic system: water/di(ethyle ne glycol) mono-hexyl ether (C6E2)/sodium cholate. Individually, neith er C6E2 nor the bile acid produces noticeable aggregate structures in an aqueous solution. However, the presence of small amounts of bile ac id in the C6E2/water binary system is found to produce large microstru ctures, besides pushing the miscibility gap to higher temperatures. Dy namic light scattering studies indicate the presence of very monodispe rse structures of sizes ranging from 15 to 50 nm in radii. The radii o f these structures show strong dependence on the concentrations of the components and on the distance in temperature from the cloud point. F or a given set of conditions the sizes are very stable and reproducibl e. Electron microscopy and conductivity measurements confirm these str uctures as vesicles. These may be formed due to the association of bil e acid with C6E2 producing the geometrical parameters necessary for th e formation of vesicles.