Recovery of Polymer Glasses from Mechanical Perturbation

A Smessaert and J Rottler, MACROMOLECULES, 45, 2928-2935 (2012).

DOI: 10.1021/ma3000253

Molecular dynamics simulations of a coarse-grained model of a polymer glass were used to study the recovery regime following deformation at constant stress or constant strain rate. We monitor dynamical as well as structural and energetic quantities to characterize the impact of deformation on the relaxation process. The a-relaxation times are reduced relative to an unperturbed sample immediately after deformation, and we observe a gradually increasing "erasure" of memory with increasing amount of deformation. Remarkably, the single deformation parameter that captures this continuous transition is the total strain at the end of deformation. For deformation up to of order the yield strain, the evolution of multiple measures of short-range order and the inherent structure energy closely track changes of the alpha-relaxation time, suggesting that the "rejuvenated" state is close to that of a younger glass. For larger strains accessible by constant strain rate deformation, however, plastic yield generates a distinctly different thermodynamic state.

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