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首页> 外文期刊>Mechanics of time-dependent materials >Static and dynamic scaling of semiflexible polymer chains--a molecular dynamics simulation study of single chains and melts
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Static and dynamic scaling of semiflexible polymer chains--a molecular dynamics simulation study of single chains and melts

机译：半柔性聚合物链的静态和动态缩放-单链和熔体的分子动力学模拟研究

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摘要

A molecular dynamics study of the effect of increasing molecular chain stiffness on the dynamic properties of single linear chains and polymer melts is presented. The chain stiffness is controlled by a bending potential. By means of a normal mode analysis the systematic crossover behavior of coarse-grained linear polymer systems from Rouse modes to bending modes with increasing mode number p is presented systematically for the first time via simulation data. The magnitude and the onset of the region where crossover behavior occurs is investigated in dependence of a systematic variation of the chains' persistence lengths. For long wavelength modes the well-known p~(-2) behavior is observed which represents the Rouse scaling, whereas for the bending modes one observes a distinct p~(-4) scaling of the mean square mode amplitudes and the relaxation times. Additionally, the effect of this crossover behavior on the monomer dynamics given by their mean square displacements is investigated. The findings are contrasted with previous simulation studies of semiflexible chain behavior and it is shown that those studies-due to too small persistence lengths L_P-were actually limited to the crossover regime where both, Rouse and bending modes contribute to the chain dynamics, and no distinct p~(-4) scaling can be observed. Using an expansion of the monomer position vector, a simple theory of the observed scaling behavior is proposed which allows for deriving analytic expressions that describe the presented simulation data very well.
机译：提出了分子动力学研究，该分子动力学研究了增加分子链刚度对单线性链和聚合物熔体动力学特性的影响。链条刚度由弯曲电位控制。通过常规模态分析，首次通过仿真数据系统地提出了粗粒线性聚合物系统从Rouse模态到弯曲模态的系统交叉行为，其中Rouse模态随着弯曲模数p的增加而弯曲。根据链的持续长度的系统变化，研究发生交叉行为的区域的大小和开始时间。对于长波长模式，观察到了代表Rouse缩放的众所周知的p〜（-2）行为，而对于弯曲模式，则观察到了均方模振幅和弛豫时间的明显p〜（-4）缩放。另外，研究了这种交联行为对单体均方位移给定的单体动力学的影响。这些发现与先前对半柔韧性链行为的模拟研究形成对比，结果表明，由于持久长度L_P太小，这些研究实际上仅限于交叉机制，在这种情况下，唤醒模式和弯曲模式均对链的动力学有贡献，而没有可以观察到明显的p〜（-4）标度。利用单体位置矢量的展开，提出了观察到的缩放行为的简单理论，该理论允许推导能够很好地描述所呈现的仿真数据的解析表达式。

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