Synthesis of latices with polystyrene cores and poly(vinyl acetate) shells. 1. Use of polystyrene seeds

Strategies for avoiding secondary particle formation in seeded emulsion polymerisation, based on a simple model for particle nucleation [Macromol. Symp. 92 (1995) 13], are discussed and exemplified in the context of growing latex particles with polystyrene cores and poly(vinyl acetate) shells. With a polystyrene seed of unswollen radius 44 nm, core–shell polymerisation was easily achieved. However, when the same recipes were used with a polystyrene seed of unswollen radius 200 nm, excessive new particle formation occurred and no poly(vinyl acetate) shells could be detected. A wide selection of the suggested strategies for overcoming this were implemented, but always either extensive secondary nucleation occurred or the system became colloidally unstable. These results are in full accord with the predictions of the simplified nucleation model.