We discuss the force between two surfaces coated with adsorbed polymer
layers in thermodynamic equilibrium with a polymer solution. We use a
mean-field theory that explicitly takes into account the loops and ta
ils structure of the adsorbed polymer layers. The force has a non-mono
tonic variation with distance: it is attractive at short distances whe
re the loops dominate and where bridging is important and it is repuls
ive at large distances where the tails dominate.