2009
DOI: 10.1002/polb.21774
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Molecular mobility of poly(methyl methacrylate) glass during uniaxial tensile creep deformation

Abstract: An optical photobleaching method has been used to measure the segmental dynamics of a poly(methyl methacrylate) (PMMA) glass during uniaxial creep deformation at temperatures between T g À 9 K and T g À 20 K. Up to 1000-fold increases in mobility are observed during deformation, supporting the view that enhanced segmental mobility allows flow in polymer glasses. Although the Eyring model describes this mobility enhancement well at low stress, it fails to capture the dramatic mobility enhancement after flow ons… Show more

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Cited by 69 publications
(146 citation statements)
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“…Second, at both temperatures, after removing the stress, the mobility surprisingly first increases and then decreases toward the mobility of the undeformed PMMA. This observation is consistent with recent experiments 18,19 and with the simulation results described below.…”
Section: Resultssupporting
confidence: 95%
“…Second, at both temperatures, after removing the stress, the mobility surprisingly first increases and then decreases toward the mobility of the undeformed PMMA. This observation is consistent with recent experiments 18,19 and with the simulation results described below.…”
Section: Resultssupporting
confidence: 95%
“…The SCM predicts that the loga pdf has both a significant increase in the average mobility and a significant narrowing as parameterized by the increase in KWW β from 0.35 to 0.46 during tertiary creep (see Fig. 13A), predictions that are in qualitative agreement with the experimental molecular mobility measurements of Ediger and coworkers [5,13,38]. It should be pointed out, however, that the analysis by Ediger yields much bigger decrease in the relaxation time (up to three orders-of-magnitude) as well as much larger increase in KWW β .…”
Section: Accepted Manuscriptsupporting
confidence: 72%
“…the distribution of the mesoscopiclog a ) shifts towards shorter times by one-and-a-half orders of magnitude and becomes narrower, where both of these features are in qualitative agreement with the experimental observations of Ediger and co-workers. [5,38] Although the log a pdf is not exactly fit by the KWW form, for the data in Fig. 13A the KWW β parameter is 0.35 just prior to the application of the stress (i.e.…”
Section: Stochastic Constitutive Model Prediction Of the Various Smentioning
confidence: 99%
“…After the initial period of almost constant strain rate for T < T g , a pronounced nonlinear increase of the strain rate was observed at the onset of the α-relaxation reaching a maximum at T g . This effect was related to the enhanced segmental mobility similarly to that observed at the onset of plastic deformation in isothermal creep below T g by Lee et al 2,3 Qualitatively, the strain-enhanced segmental mobility at T g has been ascribed to the trans−gauche rearrangements increasing the structural disorder S 0 . After reaching its maximum at approximately the T g , the strain rate is progressively reduced at the onset of the α′-relaxation, attaining its minimum value at approximately the T α′ .…”
Section: ■ Results and Discussionmentioning
confidence: 67%
“…Under constant static stress, mobility is greatly enhanced upon onset of plastic yielding. 2,3 In an analogy to the flow region observed in constant strain rate experiment, the portion of the E′(T) dependence observed in our experiments between the α-and α′-relaxation regions and characterized by Γ* encompasses both the "strain sof tening" caused by the enhanced segmental mobility induced by the α-relaxation and the "strain hardening" accompanied by the reduction of the segmental mobility induced by the onset of the α′-relaxation. The latter is gradually prevailing resulting in the minimum strain rate attained near the T α′ .…”
Section: ■ Results and Discussionmentioning
confidence: 91%