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Prediction of glass-melt behavior and penetrant sorption thermodynamics in vinyl polymers via molecular simulations.

机译：通过分子模拟预测乙烯基聚合物中的玻璃熔体行为和渗透剂吸附热力学。

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Molecular simulations are quickly emerging as a predictive tool in materials engineering. This dissertation describes the development of efficient molecular simulation techniques for the prediction and better understanding of bulk polymer properties in the glass and melt states, as well as of penetrant sorption thermodynamics in such systems.; Efficient Monte Carlo algorithms were developed for simulating dense polymer melts and glasses. A relatively simple system, atactic polypropylene (aPP), was used to test the methodologies, which are general for any vinyl polymer. Predictions of aPP glass/melt structure and thermodynamics compared well with experiment. Signatures of a glass-melt transition were captured and molecular motions and modes of sampling configuration space that distinguish glass from melt were investigated.; An efficient Monte Carlo methodology was also developed for simulating the sorption of penetrants in a host polymer phase. Predictions of the sorption thermodynamics of methane in aPP exhibited qualitative agreement with experimental evidence, but were generally too high, due to overly attractive (un-optimized) potentials and ill-relaxed representative glassy structures. Sorption isotherms in the glass exhibited dual mode behavior, but the simulated polymer-penetrant interaction energetics did not support the existence of only two distinct sorption environments, postulated in the dual mode theory. Instead, a distribution of sub-populations was evident.; The predictive tools developed in the thesis can provide insights at a molecular level into how details of the molecular structure and specific chemical interactions are manifested in the final material properties.
机译：分子模拟正在迅速成为材料工程中的一种预测工具。本文描述了有效的分子模拟技术的发展，以预测和更好地了解玻璃态和熔融态下的本体聚合物性能，以及此类体系中的渗透性吸附热力学。开发了有效的蒙特卡洛算法来模拟稠密的聚合物熔体和玻璃。使用一种相对简单的系统，无规聚丙烯（aPP），来测试任何乙烯基聚合物通用的方法。对aPP玻璃/熔体结构和热力学的预测与实验比较。捕获了玻璃熔体转变的特征，并研究了区分玻璃与熔体的分子运动和采样配置空间的模式。还开发了一种有效的蒙特卡洛方法，用于模拟渗透剂在主体聚合物相中的吸附。对aPP中甲烷吸附热力学的预测与实验证据显示出定性的一致性，但是由于过于诱人（未优化）的电势和松弛的代表性玻璃状结构，因此预测值通常过高。玻璃中的吸附等温线表现出双模式行为，但模拟的聚合物-渗透剂相互作用能学不支持双模式理论中假设的仅存在两种不同的吸附环境。相反，明显的是亚群的分布。本文开发的预测工具可以在分子水平上提供有关分子结构细节和特定化学相互作用如何在最终材料特性中体现的见解。

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