Using the single chain mean field (SCMF) theory we investigate the effect o
f soluble polymer chains on the surface tension between a solid surface and
liquid films. We find that end-grafted chains (brush) strongly reduce the
surface tension between a liquid and an incompatible solid. This reduction
is insensitive to the type and strength of monomer-solid interactions. Free
chains reduce the surface tension between the liquid and the solid only if
the monomer-solid interaction is attractive. Combining free and densely en
d-grafted chains is found to inhibit wetting, due to an inherent incompatib
ility between the grafted polymer brush and the free chain solution. Combin
ing free and moderately end-grafted chains is found to enhance wetting if t
he monomer-surface interactions are attractive. These predictions are in go
od agreement with the experiments of Yerushalmi-Rozen et al.