The Effect of Surfactant Micelles on the Reaction between Hydrated Electrons and Dimethyl Viologen

The rates of reaction between hydrated electrons and dimethyl viologen cations in aqueous solutions containing varying amounts of sodium dodecyl sulfate have been investigated by pulse radiolysis. The results are interpreted on a model in which, above the critical micelle concentration, viologen is irreversibly associated with surfactant micelles. The details of the effects of increased micelle concentration resulting in increased bimolecular rate constant lead to consideration of the primary salt effect on the electron decay. Evidence is obtained for the existence of agglomerates of surfactant even below the critical micelle concentration. The similarity of micelles to biological supramolecular assemblies and the necessity for taking such considerations into effect is pointed out.