Asymmetric water-oil-amphiphile mixtures: Lamellar phases and droplet microemulsions

Abstract

A continuum microscopic model for symmetric amphiphilic mixtures, is generalized by considering explicitly water-oil asymmetry, through the interactions between amphiphiles and water and oil. The phase diagram, including lamellar phases, and the properties of water-oil interfaces are studied, using an approximate free energy density-functional, for a wide range of amphiphilic interactions. We also consider the structure and stability of spherical micelles and study the dilute micellar regime. By combining the microscopic density-functional description with the phenomenologic Helfrich elastic free energy, we calculate the elastic properties of the amphiphilic film. Our results for the elastic constant, ks=2k+k̄, are compared with experimental data.