Micron-size monodisperse polymer microspheres having chloromethyl groups thereon were prepared by two-step polymerization process as follows. First, micron-size monodisperse polystyrene particles were prepared by dispersion polymerization with 2,2'-azobisisobutyronitrile as initiator in ethanol-water medium in the presence of poly(acrylic acid) as stabilizer under various conditions. Secondly, in the presence of the 1.9-Fm monodisperse polystyrene particles produced under the optimum conditions, seeded copolymerization for styrene and chloromethyl styrene was carried out. The seeded copolymerization proceeded smoothly without producing new particles, and it was confirmed by x-ray photoelectron spectroscopy that the chloromethyl group existed more at the surface of the produced microsphere than at that of film cast from the benzene solution in which the microspheres were dissolved.

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SynopsisIn order to reduce the internal stress in a cured epoxy resin, submicrometer-sized poly(buty1 acrylate) (PBA)/poly(methyl methacrylate) (PMMA) core-shell particles having cross-links were dispersed in the .resin prior to curing. For the introduction of cross-links, monoethylene glycol dimethacrylate or glycidyl methacrylate monomer was copolymerized. Cross-links in the PBA core reduced the shrinkage of the cured epoxy resin, and cross-links at the PMMA shell produced a strong interaction with the epoxy matrix. The internal stress was reduced effectively by the introduction of cross-links.