The electrical double layer of micelles in ionic surfactant solutions in the presence of a background electrolyte: 2. Moderately concentrated micellar solutions of sodium dodecyl sulfate

To continue previous studies 1], a model is developed for calculating electrostatic potentials ¹ψ₀ and ¹ψ_d corresponding to the surface of micelle core and the Stern layer, respectively, and the degree ¹β of binding of counterions in moderately concentrated micellar solutions of ionic surfactants. By the example of sodium dodecyl sulfate micellar solutions, dependences of ¹ψ₀ and ¹ψ_d on overall concentration n varying over the range from 0.1 to 0.9 M are determined at different NaCl concentrations in the system. The absolute values of ¹ψ₀ and ¹ψ_d potentials are found to grow with a rise in the degree of micellization and a reduction in the average intermicellar distances. This growth is greatly pronounced at a low content of the background electrolyte, whereas, in concentrated NaCl solutions (of approximately 0.1 M), potentials ¹ψ₀ and ¹ψ_d remain practically constant. Dependence 1 ? ¹β(n) is monotonically decreasing function.