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Tacticity Effects on the Bulk Modulus of Poly(methyl methacrylate) Explored by Coarse-Grained Simulations
The Journal of Physical Chemistry B ( IF 2.8 ) Pub Date : 2020-11-11 , DOI: 10.1021/acs.jpcb.0c06596 Chaofu Wu 1
The Journal of Physical Chemistry B ( IF 2.8 ) Pub Date : 2020-11-11 , DOI: 10.1021/acs.jpcb.0c06596 Chaofu Wu 1
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It has long been realized that stereochemistry is quite important to the mechanical properties of relevant polymers, but it still remains far from complete understanding. In this work, the tacticity dependences of the bulk modulus (B) of two stereoregular poly(methyl methacrylate) bulks have been extensively studied. Both equilibrium (EQ) and nonequilibrium (NE) molecular dynamics (MD) simulations are employed with chemically specific coarse-grained models. The fluctuation equation seems to be a simple route to calculate the B, but the result can significantly depend upon the barostat mass. The thermodynamics relation is valuable to disclosing the entropy contribution, but the result can suffer from great errors in nonlinear fitting. In particular, the instantaneous pressures and volumes during the EQ MD simulations in the “true” NPT ensemble are thus proposed to calculate the B via the definition formula. It is demonstrated in both case-by-case and averaged ways that the effects of tacticity on the B of the polymer are very slight. The identified trend is well explained as one competitive consequence of intermolecular interactions and conformational flexibility.
中文翻译：
粗粒模拟研究的规整度对聚甲基丙烯酸甲酯本体模量的影响
早已认识到，立体化学对相关聚合物的机械性能非常重要，但仍远未完全理解。在这项工作中，对两种立构规整的聚（甲基丙烯酸甲酯）块体的体积模量（B）的立构规整度进行了广泛的研究。平衡（EQ）和非平衡（NE）分子动力学（MD）模拟都可用于化学特定的粗粒度模型。波动方程似乎是计算B的简单方法，但结果可能很大程度上取决于恒压器的质量。热力学关系对于揭示熵的贡献很有价值，但是结果可能会在非线性拟合中遭受很大的误差。尤其是，因此建议在“真实” NPT集合中进行EQ MD仿真期间的瞬时压力和体积，以通过定义公式计算B。以逐例和平均的方式证明，立构规整度对聚合物B的影响很小。所确定的趋势被很好地解释为分子间相互作用和构象灵活性的竞争结果之一。
更新日期：2020-11-25
中文翻译：
粗粒模拟研究的规整度对聚甲基丙烯酸甲酯本体模量的影响
早已认识到，立体化学对相关聚合物的机械性能非常重要，但仍远未完全理解。在这项工作中，对两种立构规整的聚（甲基丙烯酸甲酯）块体的体积模量（B）的立构规整度进行了广泛的研究。平衡（EQ）和非平衡（NE）分子动力学（MD）模拟都可用于化学特定的粗粒度模型。波动方程似乎是计算B的简单方法，但结果可能很大程度上取决于恒压器的质量。热力学关系对于揭示熵的贡献很有价值，但是结果可能会在非线性拟合中遭受很大的误差。尤其是，因此建议在“真实” NPT集合中进行EQ MD仿真期间的瞬时压力和体积，以通过定义公式计算B。以逐例和平均的方式证明，立构规整度对聚合物B的影响很小。所确定的趋势被很好地解释为分子间相互作用和构象灵活性的竞争结果之一。
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