Diffusion and Exchange of Adsorbed Polymers Studied by Monte Carlo Simulations

Monte Carlo simulations are performed of adsorbed polymers with various polymer lengths N and adsorption energies χ s . Exchange times and the rates of lateral diffusion (along the surface) are investigated as a function of N and χ s . Lateral diffusion is found to be a combination of reptation (diffusion of stored length along the chain) which is hardly affected by χ s and dominates for longer polymers, and Rouse-like behavior (sideways movement), which is strongly affected by χ s and dominates for shorter polymers. We relate the characteristic time for exchange of adsorbed polymers, as a function of polymer length N and adsorption energy χ s, to the bulk diffusion coefficient at the surface density, to the polymer length and to the ratio of the surface and bulk densities. The differences of 2 and 3 orders in magnitude of the exchange times at fixed χ s and N, respectively, can thus be reduced to factors of 4 and 2.