The statistical thermodynamics of microemulsions. II. The interfacial region

Abstract

We show that the Voronoi model of microemulsionphase equilibria developed in an earlier paper can be extended to provide a description of the interfacial region. For two‐phase equilibria at near‐critical surfactant concentrations, we have calculated the influence parameters which control the interface thickness, and carried through a van der Waals (mean field) analysis to obtain interfacial composition profiles showing an excess surfactant concentration. Interfacial tensions calculated using oil/water domain sizes available from light scatteringmeasurements give values similar to the minima reported under optimal conditions of salinity and co‐surfactant concentration.