Mixed Micellar Aggregates of Anionic and Nonionic Surfactants with Short Hydrophobic Tails. A PGSE-NMR Study

Intradiffusion coeffs. for the ternary system heavy water-sodium hexanesulfonate (C6SNa)-pentaethylene glycol monohexyl ether (C6E5), in both the premicellar and micellar compn. ranges, were measured by the PGSE-NMR technique at 25°C. Exptl. data show the formation of mixed micelles and allow the detn. of the cmc. In the premicellar compn. range the monomer-monomer interactions are analyzed. The compns. of the aq. and micellar pseudophase have been computed in the whole micellar compn. range; they indicate that C6E5 has a larger tendency to form aggregates than C6SNa. The aggregation no. and the free energy of micellization are calcd. and interpreted in terms of interactions among the tensides in the micellar aggregates. The exptl. results have been interpreted in terms of a regular soln. model, and the interaction parameter β is computed. β Increases by increasing the no. of micellar aggregates in the system; this effect can be interpreted in terms of intermicellar interactions