Effect of Mono- and Multivalent Salts on Angle-dependent Attractions between Charged Rods

TL;DR

This study uses molecular dynamics simulations to explore how salt valency and concentration influence the angle-dependent effective interactions between charged rods, revealing complex aggregation behaviors.

Contribution

It provides new insights into how multivalent and monovalent salts modulate electrostatic interactions and aggregation configurations of charged rods.

Findings

Multivalent salt induces a transition from isolated to aggregated perpendicular and parallel rods.

High multivalent salt concentration can reduce attraction between rods.

Monovalent salt affects attraction depending on multivalent salt levels.

Abstract

Using molecular dynamics simulations we examine the effective interactions between two like-charged rods as a function of angle and separation. In particular, we determine how the competing electrostatic repulsions and multivalent-ion-induced attractions depend upon concentrations of simple and multivalent salt. We find that with increasing multivalent salt the stable configuration of two rods evolves from isolated rods to aggregated perpendicular rods to aggregated parallel rods; at sufficiently high concentration, additional multivalent salt reduces the attraction. Monovalent salt enhances the attraction near the onset of aggregation, and reduces it at higher concentration of multivalent salt.