Monte Carlo simulation of free-standing polymer films near the glass transition temperature

Monte Carlo simulations have been applied to investigate the behavior of thin polymeric films near the glass transition. Free-standing films of both linear and cyclic polymeric chains have been considered in this work. In agreement with experiments, we find that the apparent glass transition temperature of free-standing films decreases with decreasing film thickness. We find that in free-standing films linear chains are no longer Gaussian but are considerably more compact. Near the glass transition temperature, the ring polymers show a slower bond relaxation than the linear chains; for a given film thickness, ring polymers exhibit a higher glass transition temperature than linear polymers of the same molecular weight. It is found that both linear and ring polymer thin films exhibit a fluidlike interfacial region where mobility is considerably higher than in the bulk of the film.