Poly(divinylbenzene-alt-maleic anhydride) Microgels: Intermediates to Microspheres and Macrogels in Cross-Linking Copolymerization

Three distinct copolymer morphologies were observed during the cross-linking copolymerization of divinylbenzene-55 and maleic anhydride at low monomer concentrations in methyl ethyl ketone/heptane mixtures: microspheres, microgels, and macrogels. These morphologies depended primarily upon solvent composition and changed from microspheres and microgels to macrogels with increasing methyl ethyl ketone volume fractions. The effects of solvent composition and cross-linker concentration on the observed morphologies were investigated using electron microscopy, viscosity, and light scattering experiments. Microgels were found to be precursors to both macrogels and microspheres, and mechanisms for the formation of each morphology are proposed.