Wetting in ternary mixtures - with and without amphiphiles

The interfacial wetting behavior of ternary fluid mixtures is investigated, both for systems where all components have isotropic interaction potentials, as well as for systems where one component is an amphiphile. The BEG model and the corresponding two-order-parameter Ginzburg–Landau model are employed for systems without amphiphiles. We calculate the global wetting phase diagram for nonamphiphilic mixtures. In the investigated range of interaction parameters, the wetting transitions are always continuous at three-phase coexistence. The critical behavior is found to be universal in some, nonuniversal in other parts of the phase diagram. For systems with amphiphiles, two additional interaction terms are taken into account. The first models the aggregation of amphiphilic molecules at the air–water interface, the second the formation of amphiphilic bilayers in water. We find that the first term leads to a reduction of the tension of the air–water interface, and favors wetting by the water-rich phase, while the second—bilayer—term leads to a reduction of the tension of the interface between the water-rich and amphiphile-rich phases.