On the existence of prewetting in supracritical fluid mixtures

We demonstrate the existence of a first-order prewetting transition of a supracritical model polymer solution adjacent to an attractive surface. The model fluid we use mimics (qualitatively) an aqueous polyethylene oxide solution and, like the actual solution, displays a closed loop 2-phase region with an upper and lower critical solution temperature. The model fluid is shown to undergo a prewetting transition at an adjacent attractive surface. For sufficiently strong surface affinities, the prewetting transition may occur even at temperatures below the lower critical solution temperature (supracriticality). This phenomenon follows from non-local thermodynamics when the length-scale of the relevant fluid structures of surface films are commensurate or smaller than the range of intermolecular interactions.