Continuum theory of an immiscible binary fluid mixture with a surfactant

A Ginzburg-Landau type continuum theory is proposed for an immiscible binary fluid mixture with a surfactant. The field variables that enter are the relative concentration of the binary mixture, and the density and director fields of the surfactant. This model reduces to the sharp interface model in a certain limit. The dynamical extensions of our model are also presented, some of which may be used for the purpose of computer modelling of fluids containing amphiphiles such as microemulsions.