单链聚乙烯在石墨烯二维表面结晶的分子模拟

Molecular Simulation of Single Shain Polyethylene Crystallization on Two-Dimensional Surface of Graphene

目前对于石墨或石墨烯等片层结构对共聚聚乙烯结晶行为的影响研究相对较少,尚未系统揭示其结晶机制。采用分子动力学模拟方法,研究单链聚乙烯在二维石墨烯表面受限状态下的结晶过程。结果发现,与聚乙烯单链结晶不同,聚乙烯沿石墨烯(001)表面发生表面吸附-链折叠取向有序形成层状晶体,结晶过程由表面吸附和链折叠共同控制,随等温结晶温度变化分为3个区域。另外,支链不利于结晶,但当支链长度大于10时,即开始发生吸附或折叠进入晶区,与主链形成共晶,从而减缓了结晶度随支链长度而下降的趋势,并且支链主要进入石墨层界面附近的晶区。

Few studies on the influence of lamellar structure like graphite or graphene on crystallization behavior of PE copolymer were reported, and the crystallization mechanism had not yet revealed systematically. In this paper,the crystallization process of single chain PE induced by graphene surface was investigated with molecular dynamics simulation. It turned out that PE tended to crystalize into lamellar structure on the surface of graphene （001） through surface absorption-chain folding-orientation process. This process, controlled by both of surface adsorption and chain folding, could be divided into three temperature regimes in the progress of isothermal crystallization. In addition, chain branches restrained crystallization,however,they would be adsorbed into the graphene surface or folded into crystalline field to co-crystallize with main chain when the length of chain branch was more than 10. This transformation slowed down the trend that crystallinity decreased with the length of chain branch. Moreover, chain branches tended to fold into crystalline field near the graphene surface.