Electrical phenomena in a suspension of soft particles

The stability of a suspension of colloidal particles is determined by the interparticle electrostatic interaction, which in turn depends on the particle surface potential. The surface potential or charge of a charged colloidal particle can be evaluated by measuring its electrophoretic mobility. In the present article we focus on soft particles, that is, hard particles covered with an ion-penetrable surface layer of polyelectrolytes and provide various approximate analytic expressions for the electrostatic interaction energy between soft particles and for the electrophoretic mobility of soft particles. These expressions, which depend on the Donnan potential in the surface layer, are quite different from those for hard particles without surface structures.