Intermolecular Interactions in the Binary Systems of Cationic and Nonionic Surfactants

The micellization of the mixtures of cationic (cetyltrimethylammonium bromide, cetylpyridinium bromide) and nonionic (Triton X-100) surfactants at various content of components in aqueous solutions, as well as the adsorption of surfactants at the air/solution interface were studied. The effect of negative deviation from the ideality was discovered during the formation of mixed micelles and adsorption layers. Various theoretical approaches to the quantitative description of mixed systems were compared within the framework of the model of pseudophase separation. The parameters of intermolecular interaction in mixed micelles and adsorption layers, excess free energies of micellization and adsorption, compositions of micelles and adsorption layers were calculated. It was shown that the use of various theoretical approaches for the analysis of interactions in surfactant mixtures leads to close numerical results. It was shown that the composition of mixed micelles and adsorption layers, as well as the parameters of intermolecular interaction and the excess free energy depend on the relative content and molecular structure of surfactants (mixture components).