title: Possible explanation of the Lambda-shape anomaly in polymer surface diffusion.
abstract: We suggest an explanation for the anomalous behavior of the polymer surface-diffusion coefficient D reported by Zhao and Granick [J. Am. Chem. Soc. 126, 6242 (2004)]: D first increased with increasing polymer surface concentration Gamma, then suddenly dropped at a threshold value Gamma*. Our molecular dynamics simulations show the same behavior. We find that polymers form single-layered pancake structures for Gamma<Gamma*, while double layers form for Gamma>Gamma*. The double-layer structures allow the polymers to better adapt to the substrate corrugation. This increases barriers for lateral diffusion and is thus consistent with small values of D at larger Gamma.
authors.affiliation: Department of Physics & Astronomy, University of Western Ontario, London, Ontario N6A 3K7, Canada.
authors.forename: Debashish
authors.initials: D
authors.lastname: Mukherji
authors.forename: Martin H
authors.initials: MH
authors.lastname: Müser