Molecular dynamics (MD) simulations are conducted to systematically benchmark the effects of molecular weight, chain number, and cooling rate on the glass transition temperature (Tg) and coefficient of thermal expansion (CTE) of poly(ethylene oxide) (PEO). Hyperbolic regression as an objective identified method is used to extract Tg and CTE. The results show that for a cooling rate higher than 5 × 1013 K/min, Tg and CTE are both strongly affected by rapid quenching. For a cooling rate lower than 5 × 1013 K/min, Tg and CTE in the high-temperature domain still slightly depend on the cooling rate. Eventually, to eliminate the finite size effect of the model, a threshold molecular weight of 11,240 g/mol should be satisfied in the system. In addition, the chain number must be more than 10, at least for an oligomer system (50 monomers). This study comprehensively reveal the critical parameters of poly(ethylene oxide) (PEO) in the MD simulation that causes the numerical effect on polymer simulation and the variation of thermodynamics property. The threshold value of total molecular weight of 11,240 g/mol must be satisfied, which leads the polymer that exhibits its steady state bulk properties. For the oligomer system (Mw < 2248 g/mol per chain (50 monomers)), the total chain number must be more than 10 at least. The cooling rate must be lower than 5 × 1013 K/min for the structural equilibrium.

中文翻译：

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分子动力学模拟中聚合物热力学的分子量和冷却速率依赖性

进行分子动力学 (MD) 模拟以系统地衡量分子量、链数和冷却速率对聚环氧乙烷 (PEO) 的玻璃化转变温度 (Tg) 和热膨胀系数 (CTE) 的影响。双曲线回归作为一种客观识别方法用于提取 Tg 和 CTE。结果表明，当冷却速度高于 5 × 1013 K/min 时，Tg 和 CTE 都受到快速淬火的强烈影响。对于低于 5 × 1013 K/min 的冷却速率，高温域中的 Tg 和 CTE 仍然略微取决于冷却速率。最终，为了消除模型的有限尺寸效应，系统中应满足 11,240 g/mol 的阈值分子量。此外，链数必须大于 10，至少对于低聚物系统（50 个单体）。该研究全面揭示了聚（环氧乙烷）（PEO）在MD模拟中的关键参数，这些参数对聚合物模拟的数值影响和热力学性质的变化。必须满足 11,240 g/mol 的总分子量阈值，这导致聚合物表现出其稳态整体特性。对于低聚物体系（Mw < 2248 g/mol 每条链（50 个单体）），总链数必须至少大于 10。冷却速度必须低于 5 × 1013 K/min 以达到结构平衡。这导致聚合物表现出其稳态整体特性。对于低聚物体系（Mw < 2248 g/mol 每条链（50 个单体）），总链数必须至少大于 10。冷却速度必须低于 5 × 1013 K/min 以达到结构平衡。这导致聚合物表现出其稳态整体特性。对于低聚物体系（Mw < 2248 g/mol 每条链（50 个单体）），总链数必须至少大于 10。冷却速度必须低于 5 × 1013 K/min 以达到结构平衡。