On the role of the activity coefficient in the processes of diffusion of ionic surfactants in micellar solutions

Theoretical relations are formulated to describe the effect of an activity coefficient reflecting interparticle interaction on the diffusion coefficient of a surfactant in a micellar system. The activity coefficient of hexadecyltrimethylammonium bromide in an aqueous micellar solution is measured with a bromide-selective electrode. Analysis of the data obtained shows that, above the critical micelle concentration, surfactant mobility and solution viscosity stronger affect an increase in the diffusion coefficient followed by its reduction than the interparticle interaction in a micellar system dose.