AI 中文总结
本研究通过光漂白技术测量有无熔融拉伸的PMMA玻璃在应变硬化区的链段动力学，发现熔融拉伸的PMMA应变硬化更显著、链段动力学快约15%，未拉伸PMMA深应变硬化区链段动力学加速最高达40%，结果与模拟一致。
AI 中文摘要
应变硬化是聚合物玻璃在大变形过程中的一种特性，有助于稳定玻璃防止其破裂。实验上，人们对应变硬化过程中的链段动力学知之甚少，而这类数据对于建立该变形区聚合物玻璃的分子水平理论至关重要。本研究采用光漂白技术，测量了有无熔融拉伸的轻度交联聚甲基丙烯酸甲酯（PMMA）玻璃的链段动力学，这些样品在Tg-23K和Tg-33K下被变形至应变硬化区，局部工程应变率范围为10^-4.6 s^-1至10^-4 s^-1。研究发现，与未熔融拉伸的PMMA相比，熔融拉伸的PMMA玻璃表现出更显著的应变硬化特性，链段动力学速度快约15%；在给定真实应变率下，未熔融拉伸的PMMA在深应变硬化区（从刚过屈服点的值开始）的链段动力学被加速，在0.8真实应变时加速幅度达40%，该结果与已发表的模拟结果一致。
英文摘要
Strain-hardening is a feature of polymer glasses during large deformation, which helps to stabilize the glasses against breakage. Experimentally, little is known about the segmental dynamics during strain-hardening, and such data is important for building a molecular-level theory of polymer glasses deformed in this regime. Here, using a photobleaching technique, we measured the segmental dynamics of lightly-crosslinked poly(methyl methacrylate) (PMMA) glasses with and without melt-stretching, which were deformed into the strain-hardening regime with local engineering strain rates from 10^-4.6 s^-1 to 10^-4 s^-1 at Tg-23K and Tg-33K. We find that melt-stretched PMMA glasses show a more prominent strain-hardening feature and faster segmental dynamics by a factor of about 15% compared to PMMA without melt-stretching. At a given true strain rate, the segmental dynamics of PMMA without melt-stretching are accelerated in the deep strain-hardening regime from the value just beyond yield, by up to 40% at 0.8 true strain. Our observations are in agreement with previously published simulation results.
Comments28 pages, 5 figures, 39 references, Supplemental Information with 5 figures
Journal refMacromolecules 2022, 55, 8067-8073
DOI：10.1021/acs.macromol.2c01442
