Temperature, Frequency, and Small Static Stress Dependence of the Molecular Mobility in Deformed Amorphous Polymers near Their Glass Transition
Temperature, Frequency, and Small Static Stress Dependence of the Molecular Mobility in Deformed Amorphous Polymers near Their Glass Transition
复制标题
DOI：
10.1021/acs.macromol.5b00550
复制
发表时间：
2015-07
期刊：
影响因子：
5.5
通讯作者：
František Ondreáš;J. Jancar
中科院分区：
文献类型：
--
作者：
František Ondreáš;J. Jancar
本文首次报道了在Tg - 60 K到Tg + 60 K的温度范围内，利用动态力学分析（DMA）直接跟踪PMMA和PC在小的恒定拉伸应力（σ）作用下的分子运动。在Tα′ > Tg时，观察到明显的次级α′弛豫，与主α弛豫相比，其频移更大，σ依赖性更强。在Tg附近达到最大值后，应变速率在α′松弛开始时逐渐降低，在Tα′附近达到最小值。在Tα′以上，应变速率再次逐渐增加，表明迁移率再次增强。我们归因于所观察到的流动性的变化，应变诱导的过渡段从较低的移动的到更多的移动的域，导致构象和取向分布的改变。瞬态模量的宏观变形（e）依赖性，定义为表征α之间的系统刚度…
For the first time, we report on using dynamic mechanical analysis (DMA) to directly follow molecular mobility in PMMA and PC deformed by small constant tensile stress (σ) over the temperature interval from Tg – 60 K to Tg + 60 K. At Tα′ > Tg, a pronounced secondary α′-relaxation was observed exhibiting larger frequency shift and stronger σ-dependence compared to the main α-relaxation. After reaching its maximum at approximately the Tg, the strain rate was progressively reduced at the onset of the α′-relaxation, attaining its minimum value at approximately the Tα′. Above the Tα′, the strain rate increased gradually again, suggesting that mobility has again been enhanced. We ascribe the observed variation in mobility to the strain-induced transition of segments from less mobile into more mobile domains, resulting in the alteration of conformational and orientational distribution. The macroscopic deformation (e) dependence of the transient modulus, defined to characterize the system stiffness between the α ...