Mesoscale simulation of semiflexible chains. I. Endpoint distribution and chain dynamics

TL;DR

This paper presents a numerical simulation study of semiflexible polymer chains, focusing on endpoint distribution and dynamics, validating the model against theoretical predictions, and exploring effects of torsion stiffness and chain length on diffusion and relaxation.

Contribution

It introduces a comprehensive simulation model for wormlike chains with hydrodynamic interactions, including torsion stiffness, and validates it through comparison with analytical and Monte Carlo results.

Findings

Torsion stiffness slightly shortens the effective persistence length.

Polymer diffusion exhibits crossover from Rouse to reptation behavior.

Terminal relaxation times align with wormlike chain theory.

Abstract

The endpoint distribution and dynamics of semiflexible fibers is 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 to reptation behaviour. 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.