Roles of repeating-unit interactions in the stress relaxation process of bulk amorphous polymers: 2. nonlinear viscoelasticity
Roles of repeating-unit interactions in the stress relaxation process of bulk amorphous polymers: 2. nonlinear viscoelasticity
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重复单元相互作用在块状非晶聚合物应力松弛过程中的作用：2.非线性粘弹性
DOI：
10.1016/j.polymer.2022.125367
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发表时间：
2022
期刊：
影响因子：
4.6
通讯作者：
Wenbing Hu
中科院分区：
文献类型：
--
作者：
Jiping Wang;Wenbing Hu
应力松弛是块体非晶聚合物最基本的力学响应。我们用四组相互作用参数分别表征了聚合物重复单元，分别代表了局部链内和链间相互作用的热力学和动力学方面，并通过动力学蒙特卡罗模拟评估了它们在高温下线性粘弹性应力松弛中的相对重要性（DOI: 10.1016/j.p olm .2021.123740）。在此，我们继续评价它们在低温下非线性粘弹性起始和偏离程度中的相对重要性。我们观察到热力学相互作用似乎没有效果，而其他三个局部相互作用延缓了非线性粘弹性应力松弛的后期阶段，导致聚合物橡胶状态的KWW指数在0.5左右。链内和链间相互作用的动力学方面都决定了非线性粘弹性的起始温度，它们的高势垒抑制了非线性粘弹性向金属和陶瓷等强液体的偏离程度，而它们的低势垒则使脆性液体向更热动力学刚性的聚合物倾斜。我们的工作有助于更好地理解非线性非晶聚合物的结构-性能关系。
Stress relaxation manifests itself as the most fundamental mechanical response of bulk amorphous polymers. We characterized polymer repeating units with four-set interaction parameters separately representing the thermodynamic and kinetic aspects of local intrachain and interchain interactions, and evaluated their relative importance in stress relaxation with linear viscoelasticity at high temperatures by means of kinetic Monte Carlo simulations (DOI: 10.1016/j.polym.2021.123740). Hereby we continued to evaluate their relative importance in the initiation and the deviation extent of nonlinear viscoelasticity at low temperatures. We observed that thermodynamic interchain interactions seem no effective, while the other three local interactions retard the later stage of stress relaxation for nonlinear viscoelasticity, responsible for the KWW indexes of polymer rubbery states around 0.5. Both the kinetic aspects of intrachain and interchain interactions dominate the initiation temperatures of nonlinear viscoelasticity, and their high barriers suppress the deviation extent of nonlinear viscoelasticity towards the strong liquids like metals and ceramics, while their low barriers leave the fragile liquids to more thermodynamically rigid polymers. Our work facilitates a better understanding of structure-property relationship in nonlinear viscoelasticity of bulk amorphous polymers.