EFFECTS OF SURFACE-ROUGHNESS ON ADSORBED POLYMERS

Polymer chains adsorbed on rough impenetrable surfaces have been investigated analytically and by simulations. The cases of physical and chemical roughness of surfaces are identified and their distinctive effects on the adsorption characteristics are studied. For the chemically rough surface the adsorption temperature is depressed by an amount proportional to the concentration of the impurities. A polymer adsorbed on a physically rough surface can be interpreted using the analogy to a one-dimensional electron in a periodic potential. It is shown that at low temperatures the chain is "localized" in one of the wells. Between the localized regime and the unbinding transition point, there exists a "diffusive" regime, where the chain is diffusing by being shared by several potential wells. This regime is equivalent to the conduction band in the electron analogy. In contrast to the case of a flat surface, the unbinding transition of a chain from a periodically rough surface is markedly sharp due to an effective anchoring of the chain in the wells.