INSTABILITIES IN DISPERSIONS OF HAIRY PARTICLES ON ADDING SOLVENT-MISCIBLE POLYMERS

This paper outlines some recent experimental observations regarding de pletion flocculation in dispersions of particles carrying terminally a nchored polymer chains. Two types of model experimental system are use d: (1) dispersions in various non-aqueous media (primarily dioxan) of silica particles carrying terminally grafted poly(methyl methacrylate) chains; (2) aqueous dispersions of polystyrene latex particles carryi ng terminally grafted poly(ethylene oxide) chains. A number of specifi c effects are investigated: (1) the role of surface coverage of the gr afted chains in controlling the efficacy of the depletion interaction; (2) the possible role of electrostatic forces emanating from surface charge groups on the particles, particularly with regard to non-aqueou s systems and how these may offset the depletion interaction; (3) for aqueous systems, the role of polyelectrolytes in depletion flocculatio n.