摘要本文首先运用Material Studio软件构造了乙烷、丁烷和2,6-辛二烯分子，模拟其分子中单键内旋转，比较其旋转能垒，从能量的角度说明因结构差异而导致的长链柔性的差异，从分子运动的机理上说明分子链上含有非共轭双键的分子链柔性更大；其次，本文运用经典分子动力学模拟方法，在NPT系综下，5个不同温度下的凝聚态聚乙烯进行分子动力学模拟，分析了聚乙烯链的均方末端距、均方旋转半径、密度、力学性能与温度的关系。结果表明，随着温度的升高，链的均方末端距、均方旋转半径增大，密度降低。由模拟计算得出聚乙烯的玻璃化转变温度Tg为-75。3℃。在力学性能研究上，拉伸模量（E）、体积模量（K）、剪切模量（G）随着温度的升高而减小，体积模量与剪切模量比值K/G随着温度的升高而增大，聚乙烯刚性减小，延展性增大。73337

毕业论文关键词  链柔性  分子动力学模拟  聚乙烯  均方末端距  均方旋转半径  力学性能

毕业设计说明书外文摘要

Title     The molecular dynamics simulation of single chain polyethylene and condensed state of polyethylene

Abstract In this paper, we use Material Studio to build ethane, butane and 2,6-ocdiene and simulate their internal rotation of carbon bond。 By comparing the potential barrier of internal rotation of these molecules, we can speculate how the molecular structures influence the long chain flexibility from the view of energy so that we can explain the mechanism that the long chain containing non-conjugated double bond is more flexible than the single long chain。 Next, we use classical molecular dynamics simulation method to study condensed polyethylene on five different temperatures with NPT ensemble。 We calculate the mean square end-to-end distance and the mean square radius of gyration of the PE chain, density and some mechanical parameters。 The results show that the relationship between these parameters and temperature, with the temperature rising, the mean square end-to-end distance and the mean square radius of gyration increase, the density decreases, and the tensile modulus(E)、bulk modulus(K)and shear modulus(G) increase, but the ratio K/G decreases。 The calculated glass-transition temperature(Tg) is -75。3℃。The changes of mechanical properties indicate that the rigidity of PE weakens and the ductility strengthens。 

Key Words  Chain flexibility  Molecular dynamics simulation  Polyethylene  Mean square end-to-end distance  Mean square radius of gyration ` Mechanical property 

目   次

1  绪论 1

1。1  分子模拟的发展历史 1

1。2  分子模拟在高分子材料中的应用 2

1。3  本文研究意义，背景，方法 2

2  聚乙烯单链相对柔顺性的模拟研究 4

2。1  引言 4

2。2  单体分子的旋转势能分析 4

3  凝聚态聚乙烯结构的模拟研究 15

3。1  引言 15

3。2  聚乙烯单链的初始模型构建 15

3。3  凝聚态聚乙烯分子动力学模拟 16

3。4  凝聚态聚乙链尺寸的模拟计算 19

3。5  结果与讨论 19

3。6  本章小结