Strongly Charged, Flexible Polyelectrolytes in Poor Solvents -- Molecular Dynamics Simulations

TL;DR

This study uses molecular dynamics simulations to explore how strongly charged, flexible polyelectrolyte chains behave in poor solvents, revealing diverse structures influenced by density and electrostatic screening.

Contribution

It provides detailed insights into the structural transitions of polyelectrolytes under poor solvent conditions, highlighting the role of free charge density in their behavior.

Findings

Low-density chains form stretched, necklace-like structures.

High-density chains are highly collapsed without phase separation.

Free charge density critically influences chain conformation.

Abstract

We present a set of molecular dynamics (MD) simulations of strongly charged, flexible polyelectrolyte chains under poor solvent conditions in a salt free solution. Structural properties of the chains and of the solutions are reported. By varying the polymer density and the electrostatic interaction strength we study the crossover from a dominating electrostatic interaction to the regime of strong screening, where the hydrophobic interactions dominate. During the crossover a multitude of structures is observed. In the limit of low polymer density strongly stretched, necklace like conformations are found. In the opposite limit of high polymer density which is equivalent to strongly screened electrostatic interactions, we find that the chains are extremely collapsed, however we observe no agglomeration or phase separation. The investigations show that the density of free charges is one of the relevant parameters which rules the behavior of the system and hence should be used as a parameter to explain experimental results.