Eur. Phys. J. E (2015) 38: 37
https://doi.org/10.1140/epje/i2015-15037-0

Regular Article

Dielectric α-relaxation of 1,4-polybutadiene confined between graphite walls

Molecular dynamics investigations through numerical simulations of polymer molecules relaxation

¹ Institut Charles Sadron (UPR22-CNRS), University of Strasbourg, 23 rue du Loess, BP 84047, F-67034, Strasbourg, France
² Theoretical Polymer Science in Department of Physics, Martin-Luther-University Halle-Wittenberg, Naturwissenschaftliche Fakultät II, 06099, Halle (Saale), Germany

^* e-mail: mathieu.solar@ics-cnrs.unistra.fr

Received: 8 March 2015
Revised: 11 March 2015
Accepted: 11 March 2015
Published online: 15 May 2015

Abstract

We present results of Molecular Dynamics (MD) simulations of a chemically realistic model of 1,4-polybutadiene confined by crystalline graphite walls. The simulations cover a large range of temperatures from T ≈ 2T _g to T ≈ 1.15T _g, where relevant time scales are accessible using such computational methods. We investigate the dielectric relaxation close to the walls in comparison to the one in the center of the film, and study the latter as a function of the film thickness from the walls. The segmental dynamics in the film is slowed down close to the walls, in comparison to the bulk. In addition to the α-process, the relaxation exhibits an additional long time decay, the so-called wall desorption process. We focus here on the α-process and find no significant shift of the dielectric T _g as a function of layer thickness, in agreement with recent dielectric experiments. These findings can be correlated with the importance of the dihedral dynamics for all relaxation processes in polymers, which is unaltered except for the first nanometer next to the walls.