Mobility Gradients in Supported Glass-Forming Polymer Films Do Not Imply Gradients in Cooperative Motion

ORAL

Abstract

We investigate the extent of collective motion in the interfacial regions of a thin supported polymer film and within the film interior by molecular dynamics simulations to understand the role of collective motion in the often large changes in interfacial molecular mobility observed in polymer films. Contrary to commonly stated expectations, we find that the extent of collective motion determining the temperature dependence of the structural relaxation time does not vary significantly within the film, a finding consistent with Adam-Gibbs proposal that the extent of collective motion in glass-forming liquids is related to the configurational entropy, a thermodynamic property that cannot vary with position within the film.

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Presenters

  • Jack Douglas

    National Institute of Standards and Technology, Materials Science and Engineering Division, National Institute of Standards and Technology, Materials Science and Engineering Division, NIST, Materials Science and Engineering Division, National Institute of Standards and Technology, Gaithersburg, MD 20899

Authors

  • Jack Douglas

    National Institute of Standards and Technology, Materials Science and Engineering Division, National Institute of Standards and Technology, Materials Science and Engineering Division, NIST, Materials Science and Engineering Division, National Institute of Standards and Technology, Gaithersburg, MD 20899

  • Wengang Zhang

    National Institute of Standards and Technology, Materials Science and Engineering Division, NIST

  • Francis Starr

    Wesleyan University, Department of Physics, Wesleyan University, Department of of Physics, Wesleyan University, Physics Department, Wesleyan University, Middletown, CT