Characteristic sizes, film rigidity and interfacial tensions in microemulsion systems

Abstract

Studies of the structure of microemulsions and of Winsor-type systems have emphasized the importance of the properties of the interfacial film through the parameters of spontaneous curvature and of the film curvature elastic modulus. We discuss here the correlations between measured dispersion sizes, surfactant film curvature elasticity (K), and interfacial tensions in several multiphase microemulsion systems. Sizes L are in agreement with simple random-space filling models, the area per surfactant molecule in the film remaining constant. For small values of K, bicontinuous structures are found when the spontaneous curvature of the film is small: the dispersion size is then close to the persistence length of the film. For larger K, more ordered structures appear. Interfacial tensions correlate only approximately with kT/L ².