Theory of Crystals and Interfaces in Polyethylene and Isotactic Polypropylene

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• 作者：Jianguang Feng ; Hongfu Zhou ; Xiangdong Wang ; Jianguo Mi
• 刊名：Journal of Physical Chemistry C
• 出版年：2016
• 出版时间：April 28, 2016
• 年：2016
• 卷：120
• 期：16
• 页码：8630-8639
• 全文大小：592K
• 年卷期：0
• ISSN：1932-7455

文摘

We present a three-dimensional density functional method to investigate the crystallization thermodynamics of polyethylene and isotactic polypropylene. Within the theoretical framework, the effects of excluded volume, dispersive attraction, chain connectivity, and conformation are integrated into the nonlocal free-energy functional. Under the condition of crystal–melt phase equilibrium, the crystal lattice parameters as a function of temperature are first determined through the restricted and full free-energy minimizations of crystal cell. The interfacial density profiles and interfacial tensions are then calculated via the restricted and full free-energy minimizations of interfaces. Accordingly, the free-energy barriers and critical sizes during the formation of crystal nuclei are predicted to evaluate the structures and properties of such crystallites. Some results are in good agreement with the available experimental data, indicating that the present theoretical approach could be a good candidate for understanding the molecular mechanism of polymer crystallization.