Interaction Between Cationic Gemini and Monomeric Surfactants: Micellar and Surface Properties

Attraction effects in the mixed micelle of gemini (C-16-12-C-16, 2Br(-)) and monomeric surfactants i.e., cetyltrimethylammonium bromide (CTAB), cetyltriphenylphosphonium bromide (CTPB) and cetyltributylphosphonium bromide (CTBuPB) mixtures in aqueous solution were investigated by conductivity and surface tension measurements. The attractive interaction of surfactants in the mixed micelle leading to non-ideality has been theoretically treated by Clint's and Rubingh's model in the light of regular solution theory. The experimental critical micelle concentration (cmc) values were lower than predicted from ideal mixture theory. The negative values of interaction parameters (beta(m) and beta(sigma)) for mixed micelle formation indicate the attractive interaction for all the systems. The Motomura's theory was used to determine the composition of each compound in mixed micelles (X-ideal ). The excess free energy of the mixed systems was also calculated and the obtained negative values for all the mixed systems studied gave an indication that the mixed micelles are thermodynamically more stable relative to the individual component.