Analytic models for the equilibrium behavior of binary mixtures in the presence of a solid surface

Analytical relationships are presented to predict concentration profiles for the components of a binary mixture in the presence of a solid surface. These relationships are based on a modified lattice model which accounts for interactions between the components and the surface, and interactions between components in adjacent lattice layers. Approximations are introduced to isolate the important role of two dimensionless groups in establishing the nature and extent of interphase zones. The first group is a measure of the intensity of the concentration perturbation at the surface. The second group serves as a measure of the system's ability to propagate the perturbation away from the surface. These groups contain interaction energies, the bulk concentration of the components, the degree of polymerization of each of the binary components, and temperature. Consequently, these groups provide guidelines for selecting components and processing temperatures to control the nature and extent of interphase zones next to a solid surface. (C) 1998 Published by Elsevier Science Ltd. ALI rights reserved.