块体聚乙烯相变过程中结构及性质的分子动力学模拟  

Molecular dynamics simulation on structure and properties of bulk polyethylene during phase transition

作　　者：王金剑[1] 周洲[1] 王刚[1] 朱小蕾[1] 

机构地区：[1]南京工业大学化工学院材料化学工程国家重点实验室,江苏南京210009

出　　处：《南京工业大学学报（自然科学版）》2015年第5期34-41,共8页Journal of Nanjing Tech University(Natural Science Edition)

基　　金：国家自然科学基金(21276122;91434109)

摘　　要：通过分子动力学模拟研究不同链长的聚乙烯(PE)块体在熔化和结晶过程中结构和性质的变化。能量分解分析从热力学角度探究不同相互作用在相变中的作用。扩散系数则用于动力学的考察。结构快照、键取向有序参数、键长、键角和二面角分布以及反式构象概率揭示块体结构和链结构的变化。结果表明:不同链长的PE在熔化和结晶过程中表现出不同的相行为。短链PE可生成有序晶体,而长链PE则形成半晶。具有较短链的PE晶体由伸直链和一次折叠链构成。而在较低有序度的半晶中,链的构象主要为自由卷曲链以及包含部分伸直链段的多次折叠链。长链间的缠绕在动力学上阻碍了这些半晶向晶态的转变。Structure and property changes of bulk polyethylene（ PE） with different chain lengths during melting and crystallization were studied in terms of molecular dynamics simulation. Energy component analyses were used to detect the effects of different interactions on phase transition from the viewpoint of thermodynamics. Influences of kinetic factors were measured with diffusion coefficient. Structural snapshot,bond orientation order parameter,bond length,bond angle,and dihedral angle distributions,and percentage of trans conformations revealed the changes in bulk and chain structures. Results demonstrated that the PE polymers with short and long chains had different phase behaviors in melting and crystallization. Ordered crystalline could be formed for short chains,while they were semi-crystalline for the longer ones. The PE crystalline with short chain length consisted of the extended and one-folded chains,while the freely curled and several-folded chains with partly extended segments were the main chain conformations for semi-crystalline with lower order degree. Entanglement between long chains hindered the transition from semi-crystalline to crystalline in kinetics.

关 键 词：聚乙烯 结晶 分子动力学模拟 链构象 

分 类 号：O631.1[理学—高分子化学] O642.4[理学—化学]