Influence of surfactant vesicles and their polymerization on the complex formation between indoleacetate and methylviologen

The association constant K between methylviologen MV and indoleacetate IA was decreased by the addition of cationic vesicles, and the K increased at high vesicle concentrations. The influence of the polymerization of surfactants with different chain lengths on K was different. The concentration dependence of K was analyzed by a theory in terms of the partition coefficients of reactants between the bulk solvent phase and the local vesicle environment. The theoretical partition coefficients were determined graphically. The measured dependence of K on vesicle concentration was satisfactorily reproduced by the theory. When dimyrystyldiallylammonium bromide (DMAB) was added to the complex, the polymerization of the surfactant increased the partition coefficients of IA and the complex but decreased that of MV. However, the polymerization of dicetyldiallylammonium bromide (DCAB) showed the reverse tendency. The influence of polymerization on K or the partition coefficient was discussed in terms of the difference in the polymerization mechanism due to the differences in the distance between the neighboring nonpolymerized surfactant molecules and the polymerization induced change in that distance.