ABSTRACT Molecular dynamics simulations have been performed with chemically realistic coarse-grained potentials to assess the effects of molecular weight on the glass transition temperatures (Tg ) of single-chain particle of poly(ethylene oxide) in a vacuum. It is found that all the long isolated chains form impact globule like configurations, and higher molecular weight and lower temperature lead to more perfect sphericity. With increasing molecular weight, the simulated Tg of the isolated chain tends to increase whereas the Tg of the bulk undergoes a slight change. The confinement effects are associated with localisation of chain ends at the surface and specific surface areas. More importantly, the Tg shift can be quantified by the solubility parameter that includes the contribution of conformational change. As compared to the conventional definition that only sums intermolecular interactions, such solubility parameter is a better metric in simulations to explain the confinement effects since it does not depend upon the degree of equilibration as the Tg . These results can be quite valuable to clarifying glass transition behaviour of polymers films.

中文翻译：

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孤立的聚（环氧乙烷）链的模拟玻璃化转变温度的分子量依赖性

摘要 分子动力学模拟已使用化学上真实的粗粒电位进行，以评估分子量对真空中聚（环氧乙烷）单链粒子的玻璃化转变温度 (Tg) 的影响。发现所有孤立的长链形成撞击球状构型，较高的分子量和较低的温度导致更完美的球形度。随着分子量的增加，孤立链的模拟 Tg 趋于增加，而本体的 Tg 发生轻微变化。限制效应与链端在表面和比表面积的定位有关。更重要的是，Tg 变化可以通过包括构象变化贡献的溶解度参数来量化。与仅对分子间相互作用求和的传统定义相比，这种溶解度参数是模拟中更好的度量来解释限制效应，因为它不依赖于平衡度，如 Tg。这些结果对于阐明聚合物薄膜的玻璃化转变行为非常有价值。