Ghasemi Arman, Liao Yangchao, Li Zhaofan, Xia Wenjie, Gao Wei
Department of Mechanical Engineering, University of Texas at San Antonio, San Antonio, TX 78249, USA.
Department of Civil, Construction and Environmental Engineering, North Dakota State University, Fargo, ND 58108, USA.
Nanoscale. 2023 Jul 27;15(29):12235-12244. doi: 10.1039/d3nr00817g.
This study employs all-atomistic (AA) molecular dynamics (MD) simulations to investigate the crystallization and melting behavior of polar and nonpolar polymer chains on monolayers of graphene and graphene oxide (GO). Polyvinyl alcohol (PVA) and polyethylene (PE) are used as representative polar and nonpolar polymers, respectively. A modified order parameter is introduced to quantify the degree of two-dimensional (2D) crystallization of polymer chains. Our results show that PVA and PE chains exhibit significantly different crystallization behavior. PVA chains tend to form a more rounded, denser, and folded-stemmed lamellar structure, while PE chains tend to form an elongated straight pattern. The presence of oxidation groups on the GO substrate reduces the crystallinity of both PVA and PE chains, which is derived from the analysis of modified order parameter. Meanwhile, the crystallization patterns of polymer chains are influenced by the percentage, chemical components, and distribution of the oxidation groups. In addition, our study reveals that 2D crystalized polymer chains exhibit different melting behavior depending on their polarity. PVA chains exhibit a more molecular weight-dependent melting temperature than PE chains, which have a lower melting temperature and are relatively insensitive to molecular weight. These findings highlight the critical role of substrate and chain polarity in the crystallization and melting of polymer chains. Overall, our study provides valuable insights into the design of graphene-based polymer heterostructures and composites with tailored properties.
本研究采用全原子（AA）分子动力学（MD）模拟来研究极性和非极性聚合物链在石墨烯和氧化石墨烯（GO）单层上的结晶和熔化行为。分别使用聚乙烯醇（PVA）和聚乙烯（PE）作为代表性的极性和非极性聚合物。引入了一个修正的序参量来量化聚合物链的二维（2D）结晶程度。我们的结果表明，PVA和PE链表现出显著不同的结晶行为。PVA链倾向于形成更圆润、更致密且具有折叠茎状的层状结构，而PE链倾向于形成细长的直线图案。GO基底上氧化基团的存在降低了PVA和PE链的结晶度，这是通过对修正序参量的分析得出的。同时，聚合物链的结晶模式受氧化基团的百分比、化学成分和分布的影响。此外，我们的研究表明，二维结晶的聚合物链根据其极性表现出不同的熔化行为。PVA链比PE链表现出更依赖分子量的熔化温度，PE链的熔化温度较低且对分子量相对不敏感。这些发现突出了基底和链极性在聚合物链结晶和熔化中的关键作用。总体而言，我们的研究为设计具有定制性能的基于石墨烯的聚合物异质结构和复合材料提供了有价值的见解。
