Title | Comparison of mechanical and molecular measures of mobility during constant strain rate deformation of a PMMA glass |
Publication Type | Journal Article |
Year of Publication | 2016 |
Authors | Bending, Benjamin, and M. D. Ediger |
Journal | Journal of Polymer Science, Part B: Polymer Physics |
Volume | 54 |
Start Page | 1957 |
Date Published | 06/2016 |
Abstract | We performed constant strain rate deformation and stress relaxation on a poly(methyl methacrylate) glass at Tg – 19 K, utilizing three strain rates and initiating the stress relaxation over a large range of strain values. Following previous workers, we interpret the initial rate of decay of the stress during the relaxation experiment as a purely mechanical measure of mobility for the system. In our experiments, the mechanical mobility obtained in this manner changes by less than a factor of 3 prior to yield. During these mechanical experiments, we also performed an optical measurement of segmental mobility based on the reorientation of a molecular probe; we observe that the probe mobility increases up to a factor of 100 prior to yield. In the post-yield regime, in contrast, the mobilities determined mechanically and by probe reorientation are quite similar and show a similar dependence on the strain rate. Dynamic heterogeneity is found to initially decrease during constant strain rate deformation and then remain constant in the post-yield regime. These combined observations of mechanical mobility, probe mobility, and dynamic heterogeneity present a challenge for theoretical modeling of polymer glass deformation. |
URL | http://onlinelibrary.wiley.com/doi/10.1002/polb.24110/full |
DOI | 10.1002/polb.24110 |