Dynamical clustering of counterions on flexible polyelectrolytes

TL;DR

This study uses molecular dynamics simulations to explore how counterions dynamically cluster around flexible polyelectrolytes, revealing weakly-interacting clusters with slow decay and insensitivity to electric fields, aligning with experimental data.

Contribution

It uncovers the formation and dynamics of counterion clusters on flexible polyelectrolytes, providing insights into their behavior beyond classical theory predictions.

Findings

Counterions form weakly-interacting clusters with short-range order.

Cluster decay is slow and unaffected by electric fields.

Results align with experimental data over longer time scales.

Abstract

Molecular dynamics simulations are used to study the local dynamics of counterion-charged polymer association at charge densities above and below the counterion condensation threshold. Surprisingly, the counterions form weakly-interacting clusters which exhibit short range orientational order, and which decay slowly due to migration of ions across the diffuse double layer. The cluster dynamics are insensitive to an applied electric field, and qualitatively agree with the available experimental data. The results are consistent with predictions of the classical theory only over much longer time scales.