Charge Regulation Effect on Nanoparticles Interaction Mediated by Polyelectrolyte

TL;DR

This study investigates how charge regulation influences nanoparticle interactions mediated by polyelectrolytes, revealing that charge regulation enhances polymer adsorption and alters the nature of interparticle forces, especially at low salt concentrations.

Contribution

It introduces a hybrid simulation framework to systematically analyze charge regulation effects on nanoparticle interactions mediated by polyelectrolytes, comparing with constant charge models.

Findings

Charge regulation enhances polymer adsorption onto nanoparticles.

CR leads to weak net repulsion due to osmotic forces.

At high salt, counterion screening diminishes CR effects.

Abstract

The ability to precisely control surface charge using charged polymers is fundamental to many nanotechnology applications, enabling the design and fabrication of materials with tailored properties and functionalities. Here, we study the effect of charge regulation (CR) on the interaction between two nanoparticles (NPs) mediated by an oppositely charged polyelectrolyte (PE) in an electrolyte solution. To this end, we employ a hybrid CR Monte Carlo / molecular dynamics simulation framework to systematically explore the effects of pH, salt concentration, and polymer chain length on NP surface charge behavior. For comparison, we also conduct molecular simulations under constant charge (CC) conditions. Our results reveal that CR enhances PE adsorption onto NP surfaces compared to the CC case, where polymer bridging dominates across a wide range of NP intersurface separations. This enhanced adsorption under CR leads to a weak net repulsion driven by osmotic forces. In contrast, the CC model yields a stronger net attraction due to the bridging force. Furthermore, we find that the CR effects are more pronounced at low salt concentration, whereas at high salt concentration, counterion screening dominates in both CR and CC cases, diminishing the CR effect. These findings highlight the importance of incorporating charge regulation in characterizing nanoparticle interactions within a complex biochemical environment, particularly in low salt concentrations.