Homologous mixed micellar systems with non-ideal and asymmetric thermodynamic behavior

Abstract

Mixtures of different kinds of homologous surfactants (potassium soaps, alkyltrimethylammonium bromides, alkylammonium chlorides, alkylsulfinyl ethanols and tritons) have been studied contemplating the peculiarities of each case. Two aggregation behaviors at low total molar fractions of the more hydrophilic surfactant at the mixture CMC have been identified: one-step micellization with mixed micelles with a relative large proportion of the more hydrophilic surfactant in the mixed micelles, and two-steps micellization with micelles with a very low proportion of the more hydrophilic surfactant, i.e. pure or almost pure micelles of the more hydrophobic component. A recently developed procedure for the thermodynamic analysis, the Equation Oriented Mixed Micellization Model (EOMMM) has been employed evidencing that these systems are not only non-ideal but also asymmetric.