Morphology of micron-sized monodispersed poly(butyl methacrylate)/polystyrene composite particles produced by seeded dispersion polymerization

In order to develop the seeded dispersion polymerization technique for the production of micron-sized monodispersed core shell composite polymer parti cles the effect of polymerization temperature on the core,;shell morphology was examined, Micron-sized monodispersed composite particles were produced by seeded dispersion polymerizations of styrene with about 1.4-mu m-sized monodispersed poly(n-butyl methacrylate) (Pn-BMA) and poly(i-butyl methacry late) (Pi-BMB) particles in a methanol/water (4/1, w/w) medium in the tempe rature range from 20 to 90 degrees C. The composite particles, PBMA/polysty rene (PS) (2/1, w/w), consisting of a PBMA core and a PS shell were produce d with 2,2'-azobis(4-methoxy-2,4-dimethyl valeronitrile) initiator at 30 de grees C for Pn-BMA seed and with 2,2'-azobis(isobutyronitrile) initiator at 60 degrees C for Pi-BMA seed. The polymerization temperatures were a littl e above the glass-transition temperatures (T-g) of both Pn-BMA (20 degrees C) and PI-BMA (40 degrees C). On the other hand, when the seeded dispersion polymerizations were carried out at much higher temperatures than the T-g of the seed polymers, composite particles having a polymeric oil-in-oil str ucture were produced.