The destabilisation of anionic polystyrene particles by solutions of vinyl-pyridine/acrylamide copolymers

Abstract

Vinyl-pyridine and acrylamide homopolymers and random copolymers have been synthesised and their flocculating action against anionic polystyrene latices measured. A two-stage mixing technique was adopted. On a mass basis, the optimum flocculation concentration of poly(2-vinyl-pyridine) is the same whether the low or high molecular weight polymer is employed: the larger polymer is sufficiently expanded to bridge between particles and destabilises a greater proportion of the solid particles. Although the saturation adsorption of the copolymers increases with acrylamide content, the concentration required for flocculation is inversely related to the vinyl-pyridine content. Neither homopolyacrylamide nor an anionic copolymer destabilise the polystyrene latices. Increase of the pH from 3 to 4 reduces the cationic charge on the copolymers and increases the amount required for destabilisation. Destabilisation, albeit of low efficiency, is possible at pH 9 when the particles are negative and the copolymers uncharged. In general, addition of univalent electrolyte reduces the critical polymer concentration but broadens the range of action.