Glass transition temperature of a polymer thin film: Statistical and fitting uncertainties
Glass transition temperature of a polymer thin film: Statistical and fitting uncertainties
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DOI：
10.1016/j.polymer.2020.122433
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发表时间：
2020-05-08
期刊：
影响因子：
4.6
通讯作者：
Johnston, Karen
中科院分区：
文献类型：
--
作者：
McKechnie, David;Cree, Jordan;Johnston, Karen
聚合物的玻璃化转变在广泛的应用中是一种重要的性质。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有很大不同。分子动力学模拟有助于提供分子水平的洞察和预测，特别是在实验上不易观察到的界面上。然而，用分子动力学模拟计算聚合物玻璃化转变温度在方法学上有很大的不确定性。在这项工作中，我们研究了冷却方法、拟合范围和统计变化对计算的聚乙烯玻璃化转变温度的影响。我们发现，有必要进行多个独立的模拟以获得统计上显著的结果，并且必须选择适当的拟合范围。这些方法学的发现被用来研究纯聚乙烯和限制在石墨烯表面之间的聚乙烯薄膜之间的玻璃化转变温度的差异。结果表明，厚度为9 nm的约束膜的玻璃化转变温度比块体聚乙烯高约15K。
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.