STUDIES ON SUSPENSION AND EMULSION .146. MORPHOLOGIES OF MICRON-SIZED MONODISPERSED COMPOSITE POLYMER PARTICLES HAVING CROSS-LINKED STRUCTURES PRODUCED BY SEEDED POLYMERIZATIONS

Three kinds of micron-sized monodispersed polystyrene (PS)/poly(styrene - divinylbenzene) composite particles were produced by two kinds of seeded copolymerizations of styrene (S) and divinylbenzene (DVB) (PS seed/(S+DVB)=2/1, wt. ratio; S/DVB=1/1, molar ratio) in the presence of about 2 mu m-sized monodispersed PS particles, and their morphologies were examined. One was produced by a seeded dispersion copolymerization where almost monomers and initiators exist in an ethanol/water (12.6/4.0, w/w) medium. The others two were produced by seeded copolymerizations with the dynamic swelling method where almost monomers exist in the monomer-swollen particles using 2, 2'-azobisisobutyronitrile in monomer-swollen PS seed particles or using 4, 4'-azobis(4-cyanopentanoic acid) in an ethanol/water (7/43, w/w) medium. In the former polymerization, the produced composite particles had a high dense crosslinked shell, whereas in the latter two polymerizations, they did the comparatively homogeneous crosslinked structures.