A RANDOM INTERFACE MODEL OF MICROEMULSIONS

Sponge-like phases of amphiphilic mixtures are characterized by mesosc opic domains of water and/or oil, separated by surfactant films. These systems are analysed using a mean-spherical model to approximate the free energy of an interfacial system with a bending Hamiltonian for th e case of zero spontaneous curvature. Both the scattering structure fa ctor and die phase diagram are determined as functions of concentratio ns and bending moduli. The scaling properties of the structure factor distinguish a typical microemulsion regime with a well defined structu ral length scale from a regime unstable with respect to phase separati on. The phase diagram shows the multi-phase sequence observed in exper iment.