AI 中文总结
该研究通过光学探针重取向测量与纯力学测量，探究反向应变变形对聚合物玻璃链段流动性的影响，发现屈服应变60%及以上变形可引发老化机制，且与理论模拟结果相符。
AI 中文摘要
本研究采用光学探针重取向测量，监测聚合物玻璃非线性变形引发的链段动力学变化。在聚甲基丙烯酸甲酯（PMMA）玻璃的玻璃化转变温度（Tg）附近，对样品进行一系列反向变形：以恒定应变速率拉伸后，再以恒定应变速率回缩至零应力，分别监测变形前后的链段动力学。结果显示，当变形达到屈服应变的60%及以上时，观测到老化机制的证据——反向变形后链段动力学偏离静止老化动力学；按此衡量，老化机制的饱和至少出现在屈服应变的5倍时。作为对比，还开展了基于后续变形屈服应力降低的纯力学老化测量，此类实验与探针重取向实验在定性上具有广泛一致性，但在屈服前区域存在定量差异。研究结合近期提供聚合物玻璃变形分子层面描述的理论方法与模拟，对上述结果进行了讨论。
英文摘要
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 Tg 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 five 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.
Comments41 pages, 6 figures, 57 references
Journal refMacromolecules 2017, 50, 1016-1026
DOI：10.1021/acs.macromol.6b02490
