Interactions between Unsaturated-Polymer Adsorbed Surfaces

We use the scaling theory of polymer adsorption from a semidilute solution (in good solvents), introduced by de Gennes, to study the effects of incomplete saturation on the interactions between polymer-coated surfaces. In contrast to interactions between saturated surfaces which are always repulsive, we find that any surface excess lower than the one corresponding to thermodynamic equilibrium yields attractive long-distance interactions; we obtain a new set of exponents characterizing this behavior. Our findings are in qualitative agreement with the available experimental results.