Counterion distributions and effective interactions of spherical polyelectrolyte brushes

Abstract

We consider the electrosteric repulsion of colloidal particles whose surface carries a dense layer of long polyelectrolyte chains (“spherical polyelectrolyte brushes”). The theory of electrosteric repulsion of star polyelectrolytes developed recently is augmented to include particles with a finite core radius. It is shown that most of the counterions are confined within the brush layer. The strong osmotic pressure thus created within the brush layer dominates the repulsive interaction between two such particles. Because of this the pair interaction potential between spherical polyelectrolyte brushes can be given in terms of an analytic expression. The theoretical predictions are compared with available experimental data and semi-quantitative agreement between the two is found.