Three-dimensional Brownian diffusion of rod-like macromolecules in the presence of randomly distributed spherical obstacles: Molecular dynamics simulation

TL;DR

This study uses molecular dynamics simulations to analyze how rod-like polymers diffuse in a medium with spherical obstacles, revealing a power-law dependence of diffusion on available volume and a transition from Rouse to reptation dynamics.

Contribution

It provides new insights into the diffusion behavior of rod-like macromolecules in obstructed environments, highlighting the transition from anomalous to normal diffusion and the crossover in dynamic regimes.

Findings

Diffusion coefficient follows a power law with available volume fraction.

Diffusion exhibits anomalous behavior at short times and normal at long times.

Transition from Rouse to reptation dynamics with increasing obstacle density.

Abstract

Brownian diffusion of rod-like polymers in the presence of randomly distributed spherical obstacles is studied using molecular dynamics (MD) simulations. It is observed that dependence of the reduced diffusion coefficient of these macromolecules on the available volume fraction can be described reasonably by a power law function. Despite the case of obstructed diffusion of flexible polymers in which reduced diffusion coefficient has a weak dependence on the polymer length, this dependence is noticeably strong in the case of rod-like polymers. Diffusion of these macromolecules in the presence of obstacles is observed that is anomalous at short time scales and normal at long times. Duration time of the anomalous diffusion regime is found that increases very rapidly with increasing both the polymer length and the obstructed volume fraction. Dynamics of diffusion of these polymers is observed that crosses over from Rouse to reptation type with increasing the density of obstacles.