Collapse of Stiff Polyelectrolytes due to Counterion Fluctuations

TL;DR

This paper investigates how counterion fluctuations can induce collapse in stiff, highly charged polyelectrolytes, revealing mechanisms for instability and collapse states influenced by salt conditions and electrostatic screening.

Contribution

It introduces a theoretical framework for understanding the collapse of stiff polyelectrolytes due to counterion density fluctuations, including effects of added salt and electrostatic persistence length.

Findings

Counterion fluctuations can cause instability and collapse of stiff polyelectrolytes.

Collapse can lead to globule or necklace states depending on length scales.

Electrostatic persistence length depends nontrivially on Debye screening length.

Abstract

The effective elasticity of highly charged stiff polyelectrolytes is studied in the presence of counterions, with and without added salt. The rigid polymer conformations may become unstable due to an effective attraction induced by counterion density fluctuations. Instabilities at the longest, or intermediate length scales may signal collapse to globule, or necklace states, respectively. In the presence of added-salt, a generalized electrostatic persistence length is obtained, which has a nontrivial dependence on the Debye screening length.