The polymer glass transition is an important property in a wide variety of applications. The glass transition temperature of a polymer composite or confined thin film can be significantly different to the pure polymer. Molecular dynamics simulations are useful for providing molecular level insight and prediction, particularly at interfaces, that are not easily observable experimentally. However, there are significant methodological uncertainties in calculating the polymer glass transition temperature using molecular dynamics simulations. In this work we investigate how the cooling method, fitting range and statistical variation affects the calculated glass transition temperature of polyethylene. We found that it is necessary to perform multiple independent simulations to obtain statistically significant results, and that appropriate fitting ranges must be chosen. The methodological findings were used to investigate the difference in glass transition temperature between pure polyethylene and a polyethylene film confined between graphene surfaces. It was found that the glass transition temperature of a 9 nm thick confined film was higher than bulk polyethylene by approximately 15 K.

在多种应用中，聚合物玻璃化转变是重要的特性。聚合物复合材料或受限薄膜的玻璃化转变温度可能与纯聚合物明显不同。分子动力学模拟可用于提供分子水平的见解和预测，尤其是在界面上，这在实验中不易观察到。但是，在使用分子动力学模拟计算聚合物玻璃化转变温度时，存在很大的方法学不确定性。在这项工作中，我们研究了冷却方法，拟合范围和统计变化如何影响聚乙烯的玻璃化转变温度。我们发现有必要执行多个独立的模拟以获得具有统计意义的结果，并且必须选择合适的配合范围。方法学上的发现用于研究纯聚乙烯和石墨烯表面之间的聚乙烯薄膜之间的玻璃化转变温度差异。发现9nm厚的限制膜的玻璃化转变温度比本体聚乙烯高约15K。