SELF-CONSISTENT-FIELD THEORY FOR WETTING OF BINARY POLYMER-SOLVENT MIXTURES ON RIGID AND SOFT INTERFACES

An inhomogeneous lattice self-consistent field (SCF) theory is applied to wetting problems. In this method molecular details, such as chain length, chain architecture, and short-range molecular interaction para meters are the input parameters. In a 1D (one-dimensional) SCF calcula tion adsorption isotherms, interfacial tensions and segment density pr ofiles are calculated, from which wetting characteristics, such as the contact angle, follow. In a 2D SCF calculation, droplet shapes are pr oduced and direct contact-angle measurements are possible. The two app roaches complement each other. Examples of critical wetting and first- order wetting (including pre-wetting transitions) are shown for molecu les spreading on a flat surface. Short-chain molecules (C-10) wet a br ush made of end-grafted C-10 molecules only for intermediate grafting densities. The wetting transitions for these soft interface systems te nd to be second order. This is in contrast to wetting transitions on r igid interfaces, which appear to be first order when the chain length of the wetting fluid exceeds that of the solvent.