Depletion flocculation in dispersions of sterically-stabilised particles (“soft spheres”)
A new approach is described for calculating the depletion interaction in systems of sterically-stabilised particles (“soft spheres”) plus added free polymer. By combining the depletion interaction with the steric interaction, the overall interparticle pair potential is calculated. Variations in the amount of free polymer required to induce flocculation is predicted for these systems, in particular as a function of the nature of the solvent (through the Ï parameter) and the properties of the adsorbed polymer layer (through the thickness and the average segment volume fraction). Some experimental results are presented for the system silica—g—polystyrene plus solvent plus free polystyrene, which confirm, at least in a qualitative way, the predictions of the new theory.