A fluid confined between two parallel walls that exert different (competitive) surface fields may exhibit phase equilibria strikingly different from those found for equal fields. Macroscopic arguments and an explicit mean-field analysis predict that if the fields are such that the fluid wets one wall and dries the other (above a certain critical wetting transition temperature $T_w$) coexistence of two phases can only occur, for finite wall separation L, when T<$T_c$,L, where the critical temperature $T_c$,L lies below $T_w$. A scaling Ansatz suggests & where ${\beta }_s$ is the exponent that describes the growth of the wetting layer.

• Received 10 October 1989

DOI:https://doi.org/10.1103/PhysRevLett.64.439