Molecular segregation in lyotropic complex fluids: A phenomenological approach

A phenomenological approach describing the formation of segregated lyotropi c mesophases from the isotropic solution is proposed. It provides the order -parameter symmetries of the transitions to the main periodically ordered m esophases. The order-parameter amplitudes are shown to be periodic function s of the probabilities for the surfactant molecules to be in the segregated regions. It allows us to work out the phase diagrams associated with the i sotropic to segregated states. These phase diagrams exhibit regions of stab ility for partially and fully segregated states, and for direct and inverte d mesophases. [S1063-651X(99)06801-4].