原子模拟与使用时间-温度叠加的实验相结合，用于交联环氧树脂网络,Macromolecular Theory and Simulations

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原子模拟与使用时间-温度叠加的实验相结合，用于交联环氧树脂网络
Macromolecular Theory and Simulations ( IF 1.8 ) Pub Date : 2020-03-01 , DOI: 10.1002/mats.201900032
Ketan S. Khare _{1,

2} , Frederick R. Phelan ₁

Affiliation

对于形成玻璃的聚合物，原子详细分子动力学模拟与热机械实验的直接定量比较受到可访问时间尺度之间巨大不匹配的阻碍。最近，我们展示了时间温度叠加 (TTS) 原理的成功应用，可以对环氧树脂网络的体积特性进行这样的比较。在这里，我们在计算上跟进并研究同一网络的局部平移动力学。在跨越玻璃化转变的温度范围内计算网络中选定原子的均方位移 (MSD) 和时间尺度指数趋势。使用 TTS，这两种趋势都会折叠到主曲线上，该曲线将降低的 MSD 和时标指数与参考温度下的减少时间相关联。由于这些计算主曲线的缩短时间延长至 109 秒，因此它们可以直接与文献中相同材料的实验蠕变柔量进行比较。对三个主曲线进行定量比较，以提供将原子级动力学与宏观热力学联系起来的综合视图。模拟中 TTS 所需的时移因子与文献中的实验非常吻合，进一步证明了我们方法的准确性。

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Integration of Atomistic Simulation with Experiment Using Time−Temperature Superposition for a Cross‐Linked Epoxy Network

For glass-forming polymers, direct quantitative comparison of atomistically detailed molecular dynamics simulations with thermomechanical experiments is hindered by the vast mismatch between the accessible timescales. Recently, we demonstrated the successful application of the timetemperature superposition (TTS) principle to perform such a comparison for the volumetric properties of an epoxy network. Here, we follow-up and study the local translational dynamics of the same network computationally. The mean squared displacement (MSD) and time-scaling exponent trends of select atoms of the network are calculated over a temperature range that spans the glass transition. Using TTS, both trends collapse onto master curves that relate the reduced MSD and time-scaling exponent to the reduced time at a reference temperature. Because the reduced time of these computational master curves extends to 109 s, they can be directly compared with experimental creep compliance for the same material from the literature. A quantitative comparison of the three master curves is performed to provide an integrated view that relates atomic-level dynamics with macroscopic thermomechanics. The timeshift factors needed for TTS in simulation show excellent agreement with experiment in the literature, further establishing the veracity of our approach.

更新日期：2020-03-01

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