Overaging in Glassy Polymers within a Wide Range of Temperature

IF 5.1 1区化学 Q1 POLYMER SCIENCE Macromolecules Pub Date : 2024-10-23 DOI:10.1021/acs.macromol.4c01274

Tingyu Xu, Yunhan Zhang, Fan Peng, Renkuan Cao, Ziwei Liu, Hao Sun, Liangbin Li

引用次数: 0

Abstract

Mechanical deformation is known to affect the stability of glassy systems. Some studies report that small-amplitude loading leads to overaging, while large-amplitude loading rejuvenates the system. Recent experiments, however, have shown no overaging effect in lightly cross-linked poly(methyl methacrylate) (PMMA) glasses, raising concerns about previous simulation results. Given the importance of understanding physical aging, this work uses coarse-grained molecular dynamics simulations to examine the impact of cyclic loading/unloading on glassy polymers. The results indicate that overaging occurs in glassy polymer systems only below the Vogel–Fulcher–Tammann temperature (T_VFT). Above T_VFT, mechanical perturbations with amplitudes below the critical strain significantly accelerate the structural relaxation. Counterintuitively, these perturbations have minimal effect on inherent energy and all examined structural parameters, while particle mobility shows a clear proportional enhancement and increased spatial correlation.

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玻璃态聚合物在宽温度范围内的过老化现象

众所周知，机械变形会影响玻璃态系统的稳定性。一些研究报告称，小振幅加载会导致过老化，而大振幅加载则会使系统恢复活力。然而，最近的实验表明，轻度交联的聚甲基丙烯酸甲酯（PMMA）玻璃没有过老化效应，这引起了人们对之前模拟结果的担忧。鉴于了解物理老化的重要性，本研究利用粗粒度分子动力学模拟来研究循环加载/卸载对玻璃态聚合物的影响。结果表明，玻璃态聚合物体系只有在 Vogel-Fulcher-Tammann 温度（TVFT）以下才会发生超老化。在 TVFT 以上，振幅低于临界应变的机械扰动会显著加速结构松弛。与直觉相反的是，这些扰动对固有能量和所有检测结构参数的影响微乎其微，而粒子流动性则明显呈比例增强，空间相关性也有所提高。

本文章由计算机程序翻译，如有差异，请以英文原文为准。

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来源期刊

Macromolecules 工程技术-高分子科学

CiteScore

9.30

自引率

16.40%

发文量

942

审稿时长

2 months

期刊介绍： Macromolecules publishes original, fundamental, and impactful research on all aspects of polymer science. Topics of interest include synthesis (e.g., controlled polymerizations, polymerization catalysis, post polymerization modification, new monomer structures and polymer architectures, and polymerization mechanisms/kinetics analysis); phase behavior, thermodynamics, dynamic, and ordering/disordering phenomena (e.g., self-assembly, gelation, crystallization, solution/melt/solid-state characteristics); structure and properties (e.g., mechanical and rheological properties, surface/interfacial characteristics, electronic and transport properties); new state of the art characterization (e.g., spectroscopy, scattering, microscopy, rheology), simulation (e.g., Monte Carlo, molecular dynamics, multi-scale/coarse-grained modeling), and theoretical methods. Renewable/sustainable polymers, polymer networks, responsive polymers, electro-, magneto- and opto-active macromolecules, inorganic polymers, charge-transporting polymers (ion-containing, semiconducting, and conducting), nanostructured polymers, and polymer composites are also of interest. Typical papers published in Macromolecules showcase important and innovative concepts, experimental methods/observations, and theoretical/computational approaches that demonstrate a fundamental advance in the understanding of polymers.