Formula omitted] microemulsion studies with mono- and dialkyl amic acid surfactants

Abstract

A series of new surfactants was prepared by reacting aromatic anhydrides and dianhydrides with long-chain amines to give mono- and bis-( N-alkylamic acids), which was then converted to water-soluble potassium salts. As an example, the reaction product of dodecyl amine and benzophenone tetracarboxylic dianhydride was neutralized with potassium hydroxide to form a surfactant. Two types of surfactants were synthesized and their structures are: ▪ The ability of the new surfactants to stabilize water-in-oil ( W O ) microemulsions was examined by determining the pseudoternary component phase behavior of each material in combination with water, pentanol (cosurfactant), and benzene (oil). In general, the monofunctional surfactants could support higher water content microemulsions than those of the corresponding difunctional (bis) surfactants. Microemulsions prepared from the latter materials, however, were more stable to the addition of hydrocarbon. The structure of the parent three-component systems and the four-component microemulsions was probed by measuring the self-diffusion coefficients of water, cosurfactant, and oil at various levels of water and hydrocarbon. The diffusion coefficient measurements were consistent with an inverted to normal micelle transition occurring at high water levels. From inverted micellar solutions, the addition of benzene (up to 50%) formed closed W O structures.