Physicochemical investigations of mixed micelles of cationic gemini surfactants with different triblock polymers

The surface tensions of cationic geminis, alkanediyl-alpha,omega-bis(dimethylalkylammonium bromide) (mGs-m = 14,16 and s = 5,6) + triblock polymers (TBPs-F68, F127, L64) mixtures, over the entire mole fraction range were determined. Cationic conventional surfactants, alkyltrimethylammonium bromides (TTAB, CTAB) + TBP systems, were also studied for comparison. Analysis of the data by means of regular solution theory revealed that the adsorbed monolayer at the air/water interface was much richer in surfactants than the micelles and the intermicellar solution. The interaction between surfactants and TBP molecules at the air/water interface was strong in most of the cases. The participation of monomeric surfactants was lower than of gemini surfactants. The critical micelle concentration (cmc) was studied by the regular solution theory and the interaction parameter; the activity coefficient and the activity of components in mixed micelles were determined. The micelle composition at the cmc was also computed, and it was found that the mixed micelles were systematically richer in TBPs. Participation of surfactants in mixed micelles is lower than their contribution at interface.