A Comparative Study of Phase Behaviour in Aqueous Systems of Catanionic Surfactants and Ionic Surfactants with Organic Counterions

Abstract

Abstract Phase diagrams were determined at different temperatures for aqueous systems of alkylamines and alkanoic acids in an equimolecular ratio. The number of carbon atoms in the amines was varied from 4 to 12 and in the acids from 2 to 12. The obtained aqueous catanionic surfactant systems exhibit only two one-phase regions, i. e., isotropic liquid and lamellar liquid crystalline phases, while the obtained aqueous systems of ionic surfactant with organic counterion exhibit in addition also isotropic cubic and hexagonal liquid crystalline phases, and dispersions of vesicles. For one of the surfactants the parent acid was fluorinated. Optical microscopy and low-angle X-ray diffraction measurements were performed on selected systems.