Critical point wetting for binary two-phase polymer-solvent mixtures on solid interfaces

Abstract

\u3cp\u3eCahn argued that the wetting temperature, T\u3csub\u3ew\u3c/sub\u3e, is always below the critical temperature, T\u3csub\u3ec\u3c/sub\u3e, of a binary solvent mixture. A self-consistent field theory is used to show that this phenomenon is expected to be best observable for low molecular weight compounds. In polymer-solvent mixtures in contact with a rigid surface made of the same material as the polymer units, the difference T\u3csub\u3ew\u3c/sub\u3e -T\u3csub\u3ec\u3c/sub\u3e becomes minimal for an intermediate degree of polymerization N = N** (∼65). The polymer wets the surface for N < N**, whereas for larger N the solvent is at the wall. Critical wetting is the rule; first-order wetting is only found for relatively short chains, 2 ≤ N ≤ 16.\u3c/p\u3