Wetting transitions of asymmetric binary polymer mixtures

We examine the effect on surface-wetting phase transitions in polymer mixtures when the degrees of polymerization of the two components are different. It has been demonstrated by Schmidt and Binder (J. Phys. (Paris)46, 1631 (1985)) that in a symmetric polymer mixture a second-order wetting transition occurs if the wall-polymer interaction f(ϕ0) has a negative curvature f″(ϕ0), where ϕ0 is the surface volume fraction of the polymer component preferred by the wall. We found that in an asymmetric mixture this is not necessarily the case.