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Article
Atomistic Simulation of Energetic and Entropic Elasticity in Short-chain Polyethylenes
Journal of Rheology (2008)
  • David Keffer, University of Tennessee - Knoxville
  • T. C. Ionescu, University of Tennessee - Knoxville
  • V. G. Mavrantzas
  • B. J. Edwards, University of Tennessee - Knoxville
Abstract

The thermodynamical aspects of polymeric liquids subjected to uniaxial elongational flow are examined using atomistically detailed nonequilibrium Monte Carlo simulations. In particular, attention is paid to the energetic effects, in addition to the entropic ones, which occur under conditions of extreme deformation. Atomistic nonequilibrium Monte Carlo simulations of linear polyethylene systems, ranging in molecular length from C24 to C78 and for temperatures from 300 to 450 K, demonstrate clear contributions of energetic effects to the elasticity of the system. These are manifested in a conformationally dependent heat capacity, which is significant under large deformations. Violations of the hypothesis of purely entropic elasticity are evident in these simulations, in that the free energy of the system is demonstrated to be composed of significant energetic effects under high degrees of orientation. These arise mainly from favorable intermolecular side-to-side interactions developing in the process of elongation due to chain uncoiling and alignment in the direction of extension.

Keywords
  • elasticity,
  • entropy,
  • free energy,
  • Monte Carlo methods,
  • non-Newtonian flow,
  • polymer solutions,
  • specific heat
Publication Date
2008
Publisher Statement
Copyright (2008) American Institute of Physics. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics.
Citation Information
David Keffer, T. C. Ionescu, V. G. Mavrantzas and B. J. Edwards. "Atomistic Simulation of Energetic and Entropic Elasticity in Short-chain Polyethylenes" Journal of Rheology Vol. 52 Iss. 2 (2008)
Available at: http://works.bepress.com/david_keffer/9/