Salt-induced collapse and reexpansion of highly charged flexible polyelectrolytes

TL;DR

This study uses computer simulations to explore how dilute flexible polyelectrolytes change conformation with varying salt concentrations, revealing collapse and reexpansion behaviors influenced by ion size and charge overcompensation.

Contribution

It provides detailed insights into salt-dependent conformational transitions of polyelectrolytes, highlighting the role of multivalent ions and ion size in overcharging and reexpansion.

Findings

Low salt induces chain collapse

Higher salt causes reexpansion of chains

Multivalent counterions can overcharge the chain

Abstract

We study the salt-dependent conformations of dilute flexible polyelectrolytes in solution via computer simulations. Low concentrations of multivalent salt induce the known conformational collapse of individual polyelectrolyte chains, but as the salt concentration is increased further this is followed by a reexpansion. We explicitly demonstrate that multivalent counterions can overcompensate the bare charge of the chain in the reexpansion regime. Both the degree of reexpansion and the occurrence of overcharging sensitively depend on ion size. Our findings are relevant for a wide range of salt-induced complexation phenomena.