Charge and Potential of the Diffuse Part of the Double Layer for Sodium Dodecyl Sulfate Micelles in NaCl Solutions

A method is proposed for calculating the ψd potential of the diffuse part of the electrical double layer in micelles on the basis of data concerning the binding of counterions by these micelles, the composition of the intermicellar medium, and the association of surface-active ions. The charges of sodium dodecyl sulfate micelles in aqueous solutions at various concentrations of the surfactant and background electrolyte are determined by the potentiometric method. The calculated ψd values turned out to be much lower than the values of the electrokinetic potentials, thus allowing the conclusion that the slipping plane corresponding to the electrophoretic motion of micelles with respect to the intermicellar medium is localized in the dense part of the double layer.