Prewetting and Layering in Athermal Polymer Solutions

Coexistence conditions for prewetting and layering at a hard surface in additive hard sphere polymer solutions, where the solvent particles are smaller than the monomers, have been calculated by density functional methods. Various chain lengths and pressures have been investigated. An unexpected finding is that prewetting in these systems may proceed below the bulk critical pressure. We rationalize this behavior in terms of local properties of the pressure tensor. For longer chains, a different behavior is observed where the systems display a lower wetting pressure, i.e., a low pressure bound for surface wetting.