稀溶液中大幅拉伸高分子单链的弛豫动力学

Relaxation Dynamics of a Highly Stretched Single Polymer Chain in a Dilute Solution

针对大幅拉伸的高分子单链在Θ溶剂和良溶剂中的弛豫过程,分别通过解析理论和分子动力学模拟方法研究了弛豫动力学.对比研究发现,相对于研究高分子链在平衡态下的弛豫动力学(利用有关物理量的自关联函数),本文的非平衡态方法可以明确地揭示弛豫时间与简正模式之间标度行为的动态演化.结果表明,相关的物理量在弛豫初期均受到非平衡态的影响,而在较长时间后,高分子链的弛豫动力学则与平衡态下的结果相吻合;在高分子链的最长弛豫时间与链长的标度关系方面,平衡态和非平衡态两种方法的研究结果也一致.研究结果表明,高分子链在非平衡态下的短时和长时弛豫动力学可以更加细致地阐明弛豫全过程,给出更加丰富的结构-特征关系,从而为深入探讨高分子链的非平衡弛豫提供可借鉴的线索.

For the relaxation of a highly stretched single polymer chain in dilute solutions of various solvent quali⁃ties,the relaxation dynamics was investigated through the methods of analytical theory and molecular dynamics(MD)simulation.To facilitate the comparison,the equilibrium and non-equilibrium routes were employed in the simula⁃tions,where the equilibrium route is performed by using the self-correlation function of related physical quantities.The reason for using the non-equilibrium route is that it is directly related to many practical processes,and the dynamic evolution of the scaling behavior between the relaxation time and normal modes can be present clearly.Consequently,it is found that at the initial stage of relaxation,some physical quantities would be influenced by the non-equilibrium initial state of the polymer chain, while after a certain time, the relaxation dynamics is consistent with that predicted the equilibrium state. Meanwhile, the two routes showed the same scaling behavior between the longest relaxation time and chain length. The non-equilibrium route is therefore helpful to investigate the whole relaxation process of a polymer chain, thereby giving more information of structure-property. It is expected that such an effort can provide some useful clues to pertinent topics.