Effect of polymer adsorption on PEO-coated latex particles during salt-induced aggregation

The salt-induced aggregation of polystyrene particles in dilute aqueous sol utions has been studied by means of dynamic light scattering measurements a nd the hydrodynamic radius of the resulting aggregates has been evaluated d uring the time evolution of the whole process. Poly(ethylene oxide) (PEO) p olymer adsorbed on the particle surface at different amounts has been used to modify the inter-particle interactions resulting in the formation of clu sters of increasing size or in the stabilization of the suspension, dependi ng on the polymer molecular weight. The aggregation regime, i.e. a diffusio n limited cluster aggregation (DLCA) occurring in the polymer-free latex su spension, is partially modified according to the polymer percentage adsorbe d on the particle surface. At high polymer content, the polystyrene latex u ndergoes a complete steric stabilization. The deviation from a DLCA regime has been observed for different polymer contents and for polymers of differ ent molecular weights, from 1.5 to 2000 kD. The alterations of the aggregat ion rates, induced by the polymer interactions, are presented and briefly d iscussed. (C) 1999 Elsevier Science B.V. All rights reserved.