Diffusion of interacting micelles: A general treatment at low salt concentrations

Abstract

The micellar diffusivity, measured by quasielastic light scattering, is described by a simple phenomenological expression for a variety of surfactants over a range of surfactant concentrations and temperatures at low salt concentration where electrostatic interactions dominate. This universal expression contains the low order perturbations to the micellar diffusivity in the absence of interactions. The dominant correction scales with the ratio of surfactant to salt concentrations and results from repulsive electrostatic interactions, screened by the added salt ions. By fitting experimental data to this expression, we obtain the Stokes–Einstein micellar radius and a relative measure of the micellar ionization fraction.