Overcharging, charge inversion and reentrant condensation: Using highly-charged polyelectrolytes in tetravalent salt solutions as an example of study

TL;DR

This study uses computer simulations to explore how highly-charged polyelectrolytes interact with tetravalent salt solutions, revealing complex behaviors like charge inversion, reentrant condensation, and the influence of ion size and excluded volume.

Contribution

It provides new insights into salt-induced charge overcompensation and charge inversion, emphasizing the role of ion size and excluded volume effects in polyelectrolyte behavior.

Findings

Reentrant condensation occurs at intermediate salt concentrations.

Charge inversion does not always coincide with overcharging.

Ion size influences the occurrence of charge inversion.

Abstract

We study salt-induced charge overcompensation and charge inversion of flexible polyelectrolytes via computer simulations and demonstrate the importance of ion excluded volume. Reentrant condensation takes place when the ion size is comparable to monomer size, and happens in a middle region of salt concentration. In a high-salt region, ions can overcharge a chain near its surface and charge distribution around a chain displays an oscillatory behavior. Unambiguous evidence obtained by electrophoresis shows that charge inversion does not necessarily appear with overcharging and occurs when the ion size is not big. These findings suggest a disconnection of resolubilization of polyelectrolyte condensates at high salt concentration with charge inversion.