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Defect Generation and Motion in Polyethylene-Like Crystals, Analyzed by Simulation With Supercomputers*

Published online by Cambridge University Press:  26 February 2011

Bernhard Wunderlich
Affiliation:
Department of Chemistry, The University of Tennessee, Knoxville, TN 37996–1600 and the Division of Chemistry, Oak Ridge National Laboratory, Oak Ridge, TN 37831–6197
A. Xenopoulos
Affiliation:
Department of Chemistry, The University of Tennessee, Knoxville, TN 37996–1600 and the Division of Chemistry, Oak Ridge National Laboratory, Oak Ridge, TN 37831–6197
D. W. Noid
Affiliation:
Department of Chemistry, The University of Tennessee, Knoxville, TN 37996–1600 and the Division of Chemistry, Oak Ridge National Laboratory, Oak Ridge, TN 37831–6197
B. G. Sumpter
Affiliation:
Department of Chemistry, The University of Tennessee, Knoxville, TN 37996–1600 and the Division of Chemistry, Oak Ridge National Laboratory, Oak Ridge, TN 37831–6197
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Abstract

Defects in polymers were observed by high resolution electron microscopy and inferred from their mechanical and dielectrical behavior. The details of their generation was not known, however, in the past. During the last few years we have been able to extend the molecular dynamics simulation of polyethylene to crystals containing up to 6100 atoms and to times as long as 100 ps. The major observation was that single bond rotations of more than 90° become possible already more than 100 K below the melting temperature. These defects have lifetimes of only a few ps. By coupling to kinks (2g1) they can extend their lifetime considerably. Addition of a thermal, mechanical or dielectric free energy gradient to the thermally created defects seems to be able to account for the microscopic motion needed to explain the macroscopically observed annealing, deformations and relaxation effects. Key to the mechanical and dielectric properties is thus the existence of conformational disorder (condis crystal).

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Type
Research Article
Copyright
Copyright © Materials Research Society 1991

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