Electrostatic interaction between two interpenetrating soft particles

A three-stage model of the electrostatic interaction between two interpenetrating charged spherical soft particles with no particle core (space-charged porous spheres) in an electrolyte solution is presented. That is, (i) interaction before contact of the two spheres, (ii) partial interpenetration, and (iii) full interpenetration, i.e., engulfing of one sphere by the other. This is an extension of the work of Dähnert and Rödenbeck (J. Colloid Interface Sci., 163 (1994) 229), who considered the interaction between two interpenetrating vesicle-like surface-charged particles, to the case of the interaction of space-charge porous spheres. Analytic expressions for the interaction energy and force between two interpenetrating weakly charged porous spheres as a function of particle separation are derived for the respective stages on the basis of the linearized Poisson–Boltzmann equations for the electric potential distribution.