The behavior of salt-free polyelectrolyte solutions at charged surfaces

The properties of polyelectrolytes at oppositely charged surfaces are studied using Monte Carlo (MC) simulations and integral equation theory. The polymer molecules are modeled as chains of charged spheres, the counterions and co-ions are charged spheres, and the surface is smooth and uniformly charged. The polymer concentration in the simulations is strongly peaked at the surface, and this is accompanied by a depletion of polymers at larger distances from the surface. The thickness of the adsorbed layer decreases with increasing polymer concentration or surface charge density, but the total adsorbed amount displays a non-monotonic dependence on polymer concentration. The integral equation theory predictions are in qualitative agreement with the MC results.