Emulsion crosslinking polymerization of allyl methacrylate

In the emulsion polymerization of allyl methacrylate (AMA), no gelation occurred, whereas gelation occurred easily at about 4% conversion in the bulk polymerization. Thus, the reactive cross-linked-polymer microspheres as microgel-like polymers with abundant pendant allyl groups were easily obtained in the emulsion polymerization because AMA possesses two types of vinyl groups, methacrylic and allylic double bonds, having greatly different reactivities. The weight-average molecular weights, the r.m.s. radii of gyration, the second virial coefficients, the intrinsic viscosities, and H-1-NMR spectra of the resulting allyl-type reactive microspheres were characteristic of microgel-like polymers as compared with those of the branched-polymer-like prepolymers obtained in bulk. The precopolymers prepared from the emulsion copolymerization of AMA with methyl methacrylate and ethylene dimethacrylate in order to obtain the crosslinked-polymer microspheres having different crosslinking densities were also characterized, although the results obtained are not in conformity with our expectation.