title: Synergistic interactions in the mixed micelles of cationic gemini with zwitterionic surfactants: the pH and spacer effect.
abstract: Mixed micelle formation of binary cationic gemini (12-s-12, s=4, 6) and zwitterionic (N-dodecyl-N,N-dimethylglycine, EBB) surfactants has been investigated by measuring the surface tension of aqueous solution as a function of total concentration at various pH values from acidic to basic, under conditions of 298.15 K and atmospheric pressure. The results were analyzed by applying regular solution theory (RST), and Motomura's theory, which allows for the calculation of the excess Gibbs energy of micellization purely on the basis of thermodynamic equations. The synergistic interactions of all the investigated cationic gemini + zwitterionic surfactants mixtures were found to be dependent upon the pH of the solution and the length of hydrophobic spacer of gemini surfactant. The evaluated excess Gibbs free energy is negative for all the systems.
authors.affiliation: Department of Chemistry, St Francis Xavier University, PO Box 5000, Antigonish, NS, B2G 2W5 Canada.
authors.forename: Kulbir
authors.initials: K
authors.lastname: Singh
authors.forename: D Gerrard
authors.initials: DG
authors.lastname: Marangoni