Ordered micelle structuring in thin films formed from anionic surfactant solutions: II. Model development

Abstract

We observed the phenomenon of the stratification of thinning liquid films with both micellar solutions of anionic surfactants and solutions containing latex particles. To explain this phenomenon, we suggest that the stratification is a layer-by-layer decrease of the thickness of an ordered micellar (or latex) structure inside the film. To interpret the available experimental data for stratifying films from micellar solutions of sodium dodecyl sulfate (NaDS), a simple cell model is suggested. It permits calculation of the disjoining pressure contribution which is due to the presence of micellar structure inside the film. The micelles interact via screened electrostatic repulsion forming an ordered structure due to the restricted volume of the film. The calculated excess energy per unit area of the film exhibits a number of minima corresponding to the metastable states with micellar layers inside the film. The values of the film thickness at the metastable states were predicted by the model and agreed with the experiment.