Regensburg 2010 – wissenschaftliches Programm

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SYMR: Symposium Nuclear Magnetic Resonance: from Applications in Condensed-Matter Physics to New Frontiers

SYMR 6: Polymer Dynamics

SYMR 6.6: Vortrag

Mittwoch, 24. März 2010, 11:30–11:45, H48

Atomistic molecular dynamics simulations of polybutadiene at graphite: slowing down of orientation relaxations in confinement vs. bulk system — •Leonid Yelash1, Peter Virnau1, Wolfgang Paul2, and Kurt Binder11Institut für Physik, Johannes-Gutenberg Universität Mainz — 2Institut für Physik, Martin-Luther-Universität Halle-Wittenberg

A nanoscopic thin polybutadiene film confined between two graphite surfaces is studied using molecular dynamics simulations. Polymer is described with an united atom model incl. Lennard-Jones, bending and torsion interactions[1]. The crystalline surface is modeled by several layers of graphite atoms placed at their crystallographic positions[2]. Our previous study has shown that the confinement affects the statics as well as the dynamics. E.g., gyration radius calculated perpendicular to the surface decreases strongly near the surface showing that the whole molecules prefer to orient parallel to the surface. The mean square displacement shows a preferred lateral diffusion of polymer; the diffusion perpendicular to the surface is significantly slowed down.

Here we report results of our recent analysis of the MD data for the orientation relaxations of specific chemical bonds (α-, β-, and double-bonds) present in polybutadiene as well as dielectric relaxation in bulk and confined systems. Such relaxation functions can be obtained experimentally, e.g., from NMR measurements[3].

[1] Smith, G.D., and Paul, W., J. Phys. Chem. A, 102, 1200 (1998); Krushev, S., Diss. Mainz 2002. [2] Steele, W.A., Surf. Sci., 36, 317 (1973). [3] Saalwächter, K., Prog. NMR Spec., 51, 1 (2007)

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