Unilever Research Vlaardingen, P.O. Box 114, 3130 AC Vlaardingen, The Netherlands.
J Chem Phys. 2013 Jun 14;138(22):224903. doi: 10.1063/1.4808199.
The endpoint distribution and dynamics of semiflexible fibers are studied by numerical simulation. A brief overview is given over the analytical theory of flexible and semiflexible polymers. In particular, a closed expression is given for the relaxation spectrum of wormlike chains, which determines polymer diffusion and rheology. Next a simulation model for wormlike chains with full hydrodynamic interaction is described, and relations for the bending and torsion modulus are given. Two methods are introduced to include torsion stiffness into the model. The model is validated by simulating single chains in a heat bath, and comparing the endpoint distribution of the chains with established Monte Carlo results. It is concluded that torsion stiffness leads to a slightly shorter effective persistence length for a given bending stiffness. To further validate the simulation model, polymer diffusion is studied for fixed persistence length and varying polymer length N. The diffusion constant shows crossover from Rouse (D [proportionality] N(-1)) to reptation behaviour (D [proportionality] N(-2)). The terminal relaxation time obtained from the monomer displacement is consistent with the theory of wormlike chains. The probability for chain crossing has also been studied. This probability is so low that it does not influence the present results.
通过数值模拟研究了半刚性纤维的末端分布和动力学。简要概述了柔性和半柔性聚合物的分析理论。特别是，给出了蠕虫链的弛豫谱的封闭表达式，该表达式决定了聚合物的扩散和流变性质。接下来，描述了具有完全流体动力相互作用的蠕虫链的模拟模型，并给出了弯曲和扭转模量的关系。介绍了两种将扭转刚度纳入模型的方法。通过在热浴中模拟单链并将链的末端分布与已建立的蒙特卡罗结果进行比较，对模型进行了验证。结论是，扭转刚度导致给定弯曲刚度的有效持久长度略有缩短。为了进一步验证模拟模型，研究了固定持久长度和变化聚合物长度 N 下的聚合物扩散。扩散常数从 Rouse 行为（D [与] N（-1））转变为 reptation 行为（D [与] N（-2））。从单体位移获得的末端松弛时间与蠕虫链理论一致。还研究了链交叉的概率。这种概率非常低，不会影响目前的结果。
