Study of the interactions in dicationic gemini-anionic conventional mixed surfactant systems in the viewpoint of regular solution theory

In the present study, the influence of the hydrocarbon chain length of gemini surfactants on the process of micellization in mixed surfactant systems was investigated. Experiments were carried out with alkyldiyl-alpha, omega-bis(tetradecyldimethylammonium bromide) (m-4-m) dicationic gemini (m = 14, 16)/anionic sodium dodecylbenzene sulfonate (SDBS) mixed surfactant systems in different ratios. The critical micelle concentration (cmc) values of binary mixtures of surfactants were evaluated using surface tension measurements. Results showed that mixtures of the SDBS with gemini surfactants possessed significant deviations from ideal behavior (attractive interactions). The application of the regular solution theory (RST) to experimental data yielded the interaction parameter at mixed micelles (beta) and air-water interface (beta(sigma)), indicating an attractive interaction and reflecting the synergistic behavior in both the systems. The experimental mole fraction (X-1) was found to be lower than the ideal mole fraction (X-1(ideal)), the mole fractions of SDBS for both systems, provided that mixed micelles were more occupied by SDBS. In addition, the micelle aggregation number (N-agg) increased with an increase in the length of the hydrophobic tail. The micropolarity and binding constant (K-SV) values of various combinations were determined from the ratio of intensity (I-1/I-3) of peaks of pyrene fluorescence emission spectrum and its quenching. (C) 2014 Elsevier B.V. All rights reserved.