A self-consistent field study of the wetting transition in binary polymer blends

A self-consistent field approach is used to investigate the partial to complete wetting transition for an A:B polymer blend at coexistence where polymers A and B have equal numbers of segments, N. The surface free energy, Fs , is modeled using the quadratic form suggested by Schmidt and Binder J. Phys. II France 46, 1631 1985 , namely, Fs 1 0.5g 1 , where and g are the surface equivalents of the bulk chemical potential and interaction energy, respectively, and 1 is the surface volume fraction of the surface preferred component A . For selected values of g and the bulk volume fraction of A, , the volume fraction profile and A surface excess, z*, are calculated as a function of increasing . The first and second order wetting transitions are indicated by a discontinuity and divergence, respectively, of z* and 1 . In our simulations, at high values of only first order transitions are detected for both N 100 and N 1000. However, both first and second order wetting transitions are observed for low values of depending on the value of g. The latter results contrast with those of Carmesin and Noolandi Macromolecules 22, 1689 1989 , who found that only first order wetting transitions are possible polymer mixtures. However, our results are in agreement with recent Monte Carlo simulations carried out by Wang and Binder J. Chem. Phys. 94, 8537 1991 and Pereira and Wang J. Chem. Phys. 104, 5294 1996 . © 1997 American Institute of Physics. S0021-9606 97 50803-8