Attractive Interactions Between Rod-like Polyelectrolytes: Polarization, Crystallization, and Packing

TL;DR

This paper investigates how multivalent counterions induce attractive interactions between rod-like polyelectrolytes, leading to polarization, crystallization, and specific packing arrangements influenced by counterion valence and volume constraints.

Contribution

It introduces a model accounting for counterion volume and angular distribution, revealing mechanisms behind attraction and ordering in polyelectrolyte systems with multivalent counterions.

Findings

Attractive interactions are strongest with multivalent counterions.

Counterions condense more and form packing structures at short distances.

Hard-core volume constraints suppress longitudinal charge fluctuations.

Abstract

We study the attractive interactions between rod-like charged polymers in solution that appear in the presence of multi-valence counterions. The counterions condensed to the rods exhibit both a strong transversal polarization and a longitudinal crystalline arrangement. At short distances between the rods, the fraction of condensed counterions increases, and the majority of these occupy the region between the rods, where they minimize their repulsive interactions by arranging themselves into packing structures. The attractive interaction is strongest for multivalent counterions. Our model takes into account the hard-core volume of the condensed counterions and their angular distribution around the rods. The hard core constraint strongly suppresses longitudinal charge fluctuations.