Title | Reversing Strain Deformation Probes Mechanisms for Enhanced Segmental Mobility of Polymer Glasses |
Publication Type | Journal Article |
Year of Publication | 2017 |
Authors | Hebert, K., and M.D. Ediger |
Journal | Macromolecules |
Volume | 50 |
Start Page | 1016 |
Issue | 3 |
Date Published | 02/2017 |
Abstract | Optical probe reorientation measurements were performed to monitor changes in segmental dynamics resulting from the nonlinear deformation of a polymer glass. Segmental dynamics were monitored in a poly(methyl methacrylate) glass near T-g before and after a series of reversing deformations in which the sample was extended at constant strain rate and then allowed to retract back to zero stress at constant strain rate. Evidence of a rejuvenation mechanism, as quantified by a departure of the segmental dynamics from the quiescent aging dynamics after the reversing deformation, is observed for deformations which reach 60% of the yield strain or greater. By this measure, a saturation of the rejuvenation mechanism is not observed until at least 5 times the yield strain. For comparison, purely mechanical measurements of rejuvenation, based upon the reduction of the yield stress in a subsequent deformation, were also performed. These purely mechanical experiments show broad qualitative agreement with the probe reorientation experiments but quantitatively differ in the pre-yield regime. The results are discussed in the context of recent theoretical approaches and simulations which provide a molecular-level description of polymer glass deformation. |
URL | http://pubs.acs.org/doi/abs/10.1021/acs.macromol.6b02490 |
DOI | 10.1021/acsmacromo1.6b02490 |