The effect of dispersed phase concentration on latex flocculation by a cationic polyelectrolyte

The dependence of fraction phi of flocculated polymer on the concentration of the cationic polyelectrolyte poly(N,N-dimethyl-N,N-diallylammonium chlor ide), C-pe, was studied during polystyrene latex flocculation at various di sperse phase contents C-dp. It was found that the phi-C-pe curves exhibited a maximum (optimum) flocculation at low C-dp values. However, the branches of restabilization in the curves disappear with an increase in C-dp, so th at initially increasing phi reaches its practically constant limiting value with an increase in C-pe. The less the average molecular mass of a polyele ctrolyte, the higher the C-dp value at which flocculation is optimum. The p henomenon found was explained with allowances made for the role of relaxati on processes in polyelectrolyte adsorption layers on the surfaces of latex particles. Because of these processes, polyelectrolyte molecules become inc apable of particle capture according to the bridging mechanism.