Counterion desorption and globule-coil transition of a polyelectrolyte under tension

TL;DR

This paper investigates how a single polyelectrolyte chain responds mechanically under tension, revealing a force-induced globule-coil transition in poor solvents linked to counterion release, supported by simulations and theory.

Contribution

It introduces a combined simulation and theoretical analysis of counterion desorption and globule-coil transition under tension in polyelectrolytes.

Findings

Globule-coil transition occurs at a critical force.

Counterion release accompanies the transition.

Transition is discontinuous in polymer size.

Abstract

We explore the mechanical response of a single polyelectrolyte chain under tension in good and poor solvents using a combination of simulation and theory. In poor solvents, where the equilibrium state of the chain is a collapsed globule, we find that the chain undergoes a globule-coil transition, as the magnitude of the force is increased beyond a critical value. This transition, where the polymer size changes discontinuously from a small to a large value, is accompanied by release of bound counterions from the chain. We explain these results by adhering to a statistical mechanical theory of counter-ion condensation on flexible polyelectrolytes.