Statistical-Mechanical Analysis of the First-Order Wetting Transition in Polymer Solutions

Abstract

The present paper analyzes theoretically a first-order transition from partial to perfect wetting of a wall by demixed polymer solutions. On the basis of Cahn’s construction for the free energy, we evaluate the interfacial tension, adsorption amounts and the contact angle as a function of χ−χ_c, chain length and the adsorption energy parameter ε, where χ_c is the value of the Flory-Huggins parameter χ at the critical point. It is shown that a value χ_w exists, where a transition from partial to perfect wetting occurs. The capital region χ_c<χ<χ_w(χ_w<χ) corresponds to perfect (partial) wetting state. The perfect-wetting region becoms larger as the molecular weight of the polymer increases. The wetting transition in polymer blends, i.e., mixed chains of different length, is also studied.