高分子熔体的空间密度关联

Spatial Density Correlation in Polymer Melts

利用分子动力学模拟方法,以不同链结构的高分子熔体为对象,研究了高分子熔体的空间密度关联.链节的局域结构性质通过Voronoi分割方法得到.结果表明,链端链节的平均局域体积更大,运动能力也更强;不同构造及链不同部位链节的局域体积大小具有统一的分布规律,表明在链节尺度上,熔体具有相似的无定形结构.通过局域体积来划分疏堆积和密堆积链节,2种链节均倾向于形成团簇.疏堆积链节形成的团簇更大,并且团簇大小的温度依赖性也更显著.模拟结果表明疏堆积链节的空间关联更强.

The spatial density correlation in glass-forming polymer melt with different chain architectures was investigated using molecular dynamics simulation.The local environment of each bead was identified.Using the Voronoi construction,the results indicate that the chain ends have more local volume in the average level and the mobility of chain ends is higher.Moreover,the distributions of local volume become narrow when decreasing temperature and the rescaled distributions follow a master curve,implying that the melts have qualitatively similar amorphous structure for different chain architectures.The loosely and densely packed particles were identified according to their local volume.Both loosely and densely packed particles tend to form clusters,and the loosely packed particles was larger than that by densely packed particles.The simulation results demonstrate the spatial correlation of loosely packed particles is stronger,which might help to understand the glass forming behavior of polymer melts.