Adsorption and orientation of amphiphilic molecules at a liquid-liquid interface

A generalized van der Walls theory for non-uniform molecular fluids was applied to the (A-rich, B-rich) liquid-liquid interface of a ternary mixture (A, B, C) with one amphiphilic component (C). We have calculated the surface tension, adsorption and density-orientation profiles at the interface at fixed temperature T and pressure p, over the whole range of concentration of C in the two liquid phase region. At fixed pressure this region terminates at a triple point at low T and at a plait point at higher T. The surface tension decreases with the concentration of C and tends to zero as the plait point is approached. At the triple point the surface tension is finite but can be very low. As p and T are varied this interface can exhibit a wetting transition. The dependence of the interfacial properties on the parameters characterizing the potentials (especially those involving C) has been investigated.