Anomalous bending of a polyelectrolyte

TL;DR

This paper investigates the unique bending behavior of charged rods, revealing that electrostatic forces cause them to flatten internally and bend at the ends, differing from neutral rods, with implications for understanding polyelectrolyte elasticity.

Contribution

It introduces a novel perspective on the electrostatic persistence length and analyzes how charge influences the shape and statistical properties of stiff rods.

Findings

Charged rods tend to flatten internally and bend at the ends.

A new definition for electrostatic persistence length is proposed.

The new length measure aligns with end-to-end distribution data.

Abstract

We report on a study of the shape of a stiff, charged rod that is subjected to equal and opposite force couples at its two ends. Unlike a neutral elastic rod, which forms a constant curvature configuration under such influences, the charged rod tends to flatten in the interior and accumulate the curvature in the end points, to maximally reduce the electrostatic self-repulsion. The effect of this nonuniform bending on the effective elasticity and on the statistical conformations of a fluctuating charged rod is discussed. An alternative definition for the electrostatic persistence length is suggested. This new definition is found to be consistent with a corresponding length that can be deduced from the end-to-end distribution function of a fluctuating polyelectrolyte.