POLYMER STATISTICS .3. POLYMER ADSORPTION ON A SOLID-SURFACE

The statistical mechanics for neutral polymers and polyelectrolytes adsorbed on a flat surface is presented. Polymer segments are placed at simple cubic lattice points. The pair approximation of the cluster variational method modified to take into account chemical bonding within a polymer is used. The theoretical technique is a generalization of the one presented in paper I of the series. We calculate the density profile, thickness of the adsorbed polymer layer, and related properties. For the case of polyelectrolyte adsorption, the surface is either neutral or positively charged while the polyelectrolyte segments are negatively charged. It is noteworthy that the density profile of polyelectrolytes shows a depression close to the surface, reflecting Coulomb repulsion among charged segments. The effect of the strength of the van der Waals type interaction (between the surface and the polymer segments on the plane next to the surface), and of the polymer-solvent interaction are studied.