THE EFFECT OF NEUTRAL POLYMERS AND ELECTROLYTE ON THE STABILITY OF AQUEOUS POLYSTYRENE LATEX

The stability of polymer-coated latex suspensions was investigated by stopped flow turbidimetry and measurement of the diffusion coefficient of the flocculating suspension by dynamic light scattering. The maximum polymeric flocculation efficiency was observed for double layer and adsorbed polymer layer thicknesses on the order of 1 nm for a carboxylate modified polystyrene latex and neutral water soluable polymers. The effect of polymer polydispersity on the initial rate of coagulation was found to be unimportant at coverages below the optimal value, but measureable at higher coverages. A simple model governing the optimal surface coverage and maximum polymeric capture efficiency was found qualitatively to give the right trends, but gave somewhat erroneous quantitative predictions, with the measured optimal coverage being lower and the maximum capture efficiency somewhat higher than predicted. Measurements on the evolution of particle size during flocculation of initially uncoated spheres in saline polymer solution indicated that the initial rapid flocculation could be self-reversing due to ongoing adsorption and rearrangement of polymer.