Application of statistical mechanics to the wetting of complex liquids

We study the wetting laws for binary mixtures with antagonist components: the solvent wets but the solute does not. Naively, we would expect a wetting transition at a composition phi=phi(w) We measure the contact angle theta(phi) which decreases from theta(1) up to a plateau value theta(L) for phi less than or equal to phi(L) In the plateau regime, the solution droplet is in equilibrium with a precursor film of pure solvent. At phi(L), We have a "leak out transition", which results from the frustration of the solvent attracted by both the polymer and the solid. Because the contact angle is finite at all composition, films of solution dewet below a critical thickness e(c)(phi). We observe two regimes of dewetting (i) dry dewetting at composition phi > phi(L). The final state after dewetting are multitude of droplets on a dry solid, (ii) "wet" dewetting for phi < phi(L), where the final droplets coexist with a film of pure solvent. All these results can be extended to other complex systems, where wetting processes and phase separation are coupled. (C) 1999 Elsevier Science B.V. All rights reserved.