SEMIDILUTE AND CONCENTRATED POLYMER-SOLUTIONS NEAR ATTRACTIVE WALLS -DYNAMIC MONTE-CARLO SIMULATION OF DENSITY AND PRESSURE PROFILES OF A COARSE-GRAINED MODEL

Using a bead-spring model of flexible polymer chains, we study polymer adsorption from solutions onto attractive planar walls, varying both the strength of the adsorption potential a and the concentration of th e solution over a nide range. Treating the case of good solvents, the profiles of density and pressure are computed and it is shown that the rmal equilibrium between the adsorbed layer and the bulk solution is o btained. The case of a wall with purely repulsive potential under othe rwise identical conditions is treated for comparison. It is shown that for the strongly adsorbing wall there is a pronounced layering, while a layered structure at the repulsive wall occurs only for high concen trations, and this layering is also much weaker. These features carry over to the profile of the total pressure as well. From the difference in the pressure components in the parallel and perpendicular directio ns we compute also the interfacial energy between the polymer film and the repulsive wall as a function of the bulk density in the film. We use a dynamic Monte Carlo method which yields a Rouse behavior for the chain length N that is used, N = 32. The time-dependent mean-square d isplacements parallel and perpendicular to the wall are studied, and r elaxation times are extracted. For the considered conditions, the poly mer films stay in the fluid phase and a glass-like freezing-in into no nequilibrium states does not occur.