标题： 聚合物在不同氧气浓度下氧化老化的粗粒度分子动力学模拟 显示英文标题

标题： Coarse-Grained Molecular Dynamics Simulations for Oxidative Aging of Polymers under Various O2 Concentration

摘要： 自20世纪90年代以来，聚合物氧化老化的建模研究一直受到广泛关注。 这些研究的见解表明，氧气和自由基的传输显著影响老化异质性，同时涉及化学反应动力学。 一项最近的模拟研究 [Ishida 等，Macromolecules, 56(21), 8474-8483, 2023] 表明，当H原子抽取反应比聚合物链的松弛时间更快时，会引发介观尺度的异质性。 在本研究中，通过模拟氧气添加到聚合物自由基的速率（k_2）来扩展模拟，以反映O2浓度的影响。 发现三个关键方面受O2添加速率的影响：(i) 反应动力学，(ii) 异质性的程度，以及(iii) 交联的数量。 也就是说，降低O2浓度会减缓聚合物自由基转化为可抽取H的过氧自由基的转化速度。 这种减速会延迟H原子抽取反应，增加聚合物自由基的数量，并促进两个聚合物自由基之间的交联反应。 显示英文摘要

摘要： Modeling of polymer oxidative aging has been actively studied since the 1990s. Insights from these studies suggest that the transport of oxygen and radicals significantly influences aging heterogeneity, alongside chemical reaction kinetics. A recent simulation study [Ishida et al., Macromolecules, 56(21), 8474-8483, 2023] demonstrated that mesoscale heterogeneity arises when the H-abstraction reaction occurs faster than the relaxation times of polymer chains. In this study, the simulations were extended by modeling the rate of oxygen addition to polymer radicals (k_2) to reflect the effects of the O2 concentration. Three key aspects of oxidative aging behavior were found to be influenced by the O2 addition rate: (i) reaction kinetics, (ii) the degree of heterogeneity, and (iii) amount of crosslinking. Namely, reducing O2 concentration slows the conversion of polymer radicals into H-abstractable peroxyl radicals. This deceleration delays H-abstraction reactions, increases the number of polymer radicals, and promotes crosslinking reactions between two polymer radicals.