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 the solution over a nide range. Treating the case of good solvents, the profiles of density and pressure are computed and it is shown that thermal equilibrium between the adsorbed layer and the bulk solution is obtained. The case of a wall with purely repulsive potential under otherwise 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 concentrations, 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 directions 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 displacements parallel and perpendicular to the wall are studied, and relaxation times are extracted. For the considered conditions, the polymer films stay in the fluid phase and a glass-like freezing-in into nonequilibrium states does not occur.