FORMATION AND COEXISTENCE OF THE MICELLES AND VESICLES IN MIXED-SOLUTION OF CATIONIC AND ANIONIC SURFACTANT

In the aqueous mixtures of sodium alkylcarboxylate and alkyltrimethylammonium bromide, large unilamelar vesciles can be formed spontaneously or by sonication as the total carbon number in the HC chains is 19 (or larger). Vesicle formation can be influenced by changes of pH, molar ratio of the two surfactant components, and the polar head group of cationic surfactant. Micelles may coexist with the vesiciles in these mixed systems. The larger hydrodynamic radius (approximately 200 nm) and aggregation number (approximately 800) illustrate that the shape of the micelle in 1:1 C9H19COONa-C10H21N(CH3)Br is rod-like. In some mixed systems, the micelles can be transformed into stable vesciles by sonication - a phenomenon revealed for the first time. The surface-chemical properties of these catanionic surfactant solutions and the stabilities of vesicle have been studied systematically.