Studies of mixed surfactant solutions of cationic dimeric (gemini) surfactant with nonionic surfactant C12E6 in aqueous medium

The interaction between the alkanechyl-alpha,omega-type cationic gemini surfactant, [(C16H33N+(CH3)(2)(CH2)(4)N+(CH3)(2)C16H33)2Br(-)], 16-4-16 and the conventional nonionic surfactant [CH3(CH2)(10)CH2(OCH2CH2)(6)OH], C12E6 in aqueous medium has been investigated. The critical micelle concentrations of different mixtures have been measured by surface tension using a du Nouy tensiometer in aqueous solution at different temperatures (303, 308, and 313 K). Maximum surface excess (Gamma(max)) and minimum area per molecule (A(min)) were evaluated from a surface tension vs log(10)C (C is concentration) plot. The cmc value of the mixture was used to compute beta(m), the interaction parameter. The beta(sigma), the interaction parameter at the monolayer air-water interface, was also calculated. We observed synergism in 16-4-16/C12E6 system at all concentration ratios. The micelle aggregation number (N-agg) has been measured using a steady state fluorescence quenching method at a total surfactant concentration similar to2 mM at 25 degreesC. The micropolarity and the binding constant (K-sv) of mixed systems were determined from the ratio of intensity of peaks (I-1/I-3) of the pyrene fluorescence emission spectrum. The micellar interiors were found to be reasonably polar. We also found, using Maeda's concept, that the chain-chain interactions are very important in this system. (C) 2003 Elsevier Inc. All rights reserved.