Electric double layer of spherical pH-responsive polyelectrolyte brushes in an electrolyte solution: a strong stretching theory accounting for excluded volume interaction and mass action law

TL;DR

This study develops a strong stretching theory to analyze the electrostatics of pH-responsive spherical polyelectrolyte brushes, incorporating excluded volume effects and chargeable site density, revealing how core size and interactions influence brush structure.

Contribution

It introduces a comprehensive theoretical framework accounting for excluded volume and pH effects on spherical polyelectrolyte brushes, advancing understanding of their electrostatic behavior.

Findings

Smaller core radius leads to longer brush height.

Increased excluded volume causes brush swelling.

pH, ionic concentration, and chain separation effects depend on core size and interactions.

Abstract

In this paper, we study the electrostatics of pH-responsive polyelectrolyte-grafted spherical particles by using a strong stretching theory that takes into account the excluded volume interaction and the density of chargeable sites on the polyelectrolyte molecules. Based on the free energy formalism, we obtain self-consistent field equations for determining the structure and electrostatics of spherical polyelectrolyte brushes. First, we find that the smaller the radius of the inner core, the longer the height of the polyelectrolyte brush. Then, we also prove that an increase in excluded volume interaction yields an swelling of the polyelectrolyte brush height. In addition, we demonstrate how the effect of pH, bulk ionic concentration, and lateral separation between adjacent polyelectrolyte chains on the electrostatic properties of a spherical polyelectrolyte brush is affected by the radius of inner core, the excluded volume interaction and the chargeable site density.