title: Nanoparticle diffusion in polymer nanocomposites.
abstract: Large-scale molecular dynamics simulations show that nanoparticle (NP) diffusivity in weakly interacting mixtures of NPs and polymer melts has two very different classes of behavior depending on their size. NP relaxation times and their diffusivities are completely described by the local, Rouse dynamics of the polymer chains for NPs smaller than the polymer entanglement mesh size. The motion of larger NPs, which are comparable to the entanglement mesh size, is significantly slowed by chain entanglements, and is not describable by the Stokes-Einstein relationship. Our results are in essentially quantitative agreement with a force-level generalized Langevin equation theory for all the NP sizes and chain lengths explored, and imply that for these lightly entangled systems, activated NP hopping is not important.
authors.affiliation: Department of Chemical Engineering, Columbia University, New York, New York 10027, USA.
authors.forename: Jagannathan T
authors.initials: JT
authors.lastname: Kalathi
authors.affiliation: Department of Physics, University of Illinois, Urbana, Illinois 61801, USA.
authors.forename: Umi
authors.initials: U
authors.lastname: Yamamoto
authors.affiliation: Departments of Materials Science and Chemistry, University of Illinois, Urbana, Illinois 61801, USA.
authors.forename: Kenneth S
authors.initials: KS
authors.lastname: Schweizer
authors.affiliation: Sandia National Laboratories, Albuquerque, New Mexico 87185, USA.
authors.forename: Gary S
authors.initials: GS
authors.lastname: Grest
authors.affiliation: Department of Chemical Engineering, Columbia University, New York, New York 10027, USA.
authors.forename: Sanat K
authors.initials: SK
authors.lastname: Kumar