Effective Interactions Between Rigid Polyelectrolytes and Like-charged Planar Surfaces

TL;DR

This study uses Brownian dynamics simulations to explore how various factors like counterion valence and macroion charge density influence the effective interactions between rigid polyelectrolytes and charged surfaces in salt-free conditions.

Contribution

It provides new insights into the effects of counterion valence, macroion charge density, and surface charge discretization on polyelectrolyte-surface interactions without prior experimental data.

Findings

Divalent and monovalent counterions can mediate both attractive and repulsive interactions.

Adjusting macroion charge density or rod radius changes the nature of the interaction.

Surface charge discretization and electrostatic images significantly affect the interaction forces.

Abstract

We study the effective interaction between a planar array of uniformly negatively charged, stiff rods parallel to a negatively charged planar substrate in the absence of salt in a continuous, isotropic dielectric medium. Using Brownian dynamics simulations, we examine the general effects of counterion valence, rod spacing, macroion charge densities, and the rod size on the attractive rod-surface interaction force. At room temperature divalent as well as monovalent counterions mediate an interaction that can be repulsive or attractive upon adjusting either the macroion charge densities or the rod radius. Finally, we examine the effects of discretizing the surface charge as laterally mobile monovalent anions and of electrostatic images in the substrate.