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. Naı̈vely, we would expect a wetting transition at a composition φ=φW. We measure the contact angle θ(φ) which decreases from θ(1) up to a plateau value θL for φ⩽φL. In the plateau regime, the solution droplet is in equilibrium with a precursor film of pure solvent. At φL, 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 ec(φ). We observe two regimes of dewetting (i) dry dewetting at composition φ>φL. The final state after dewetting are multitude of droplets on a dry solid, (ii) “wet” dewetting for φ<φL, 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.