Properties and Vesicle Formation in Mixed Systems of a Branched Anionic Carboxylate Surfactant and a Cationic Surfactant

Mixtures of the anionic surfactant AEC(7)-Na (branched alcohol ether carboxylate) and the cationic surfactant didecylmethylhy-droxyethylammonium chloride (DEQ) were systematically investigated. The results showed that the mixtures possess synergisms. The DEQ-AEC(7)-Na mixture with a mass ratio of 1:1 showed the best result in terms of surface activity, wettability and emulsifying performance. However, when the mass ratio m(DEQ):m(AEC(7)-Na) = 8:2, the foaming ability and foam stability of the individual surfactants are better. Vesicles smaller than 100 nm coexist with worm-like micelles as soon as a small amount of AEC(7)-Na is added to DEQ (m(DEQ):m(AEC(7)-Na)= 8:2). At m(DEQ):m(AEC(7)-Na) = 4:6 and 2:8, vesicles of approximately 80 nm were observed.