Benetzung in ternaeren Fluessigkeitsmischungen

Abstract

The wetting behaviour of ternary fluid mixtures is investigated in this work. The first part deals with the wetting properties of the BEG model, a model for fluids with short-range interactions. We find two types of wetting in the BEG model: Wetting close to critical points of the fluid mixture (Cahn wetting), and wetting further away from the critical points, which occurs, if one of the interfacial tensions exceeds the other two very much. The transitions to Cahn wetting are critical. We have calculated the effective interfacial potential in the vicinity of critical wetting transitions and the critical exponents of the transitions. The transitions to the other type of wetting are first order. In the second part the BEG model is extended by two interactions which add amphiphilic properties to one of the fluid components. We investigate the wetting behaviour of the microemulsion phase. One of the interactions models the amphiphiles' property to assemble at interfaces. It reduces interfacial tensions and therefore supports wetting. Especially we find in agreement with experimental results, that it produces wetting of the microemulsion-air interface by the water phase. The other interaction induces structure into the microemulsion phase and therefore counteracts wetting. In the third part the twist grain boundary between lamellarly structured grains of ternary amphiphilic mixtures is investigated in a Ginzburg-Landau model, the #PHI#"6 model. We find that the interfacial tension depends on the interaction between the lamellae, i.-e. the compressibility of the system. The surfaces which the amphiphiles assemble on are not minimal surfaces, but the solution is rather a compromise between bending and compression energy. (orig.)SIGLEAvailable from TIB Hannover: RA 831(3879) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman