A new way to control particle morphology in heterophase polymerizations

The formation of microphase separated structures in the confined space of l atex particles is reported. Three different systems are investigated: emuls ion polymerizations started either with polymeric radicals or with persulfa te in the presence of ionic chain transfer agents, aqueous dispersions of w ell defined polystyrene model oligomers with sulfonate end groups, and mini emulsion polymerization in the presence of large amounts of preformed polym er in the droplets. In any of these cases microphase separation leads to th e formation of inhomogeneities in the particles. Electron microscopy, atomi c force microscopy, and X-ray absorption microscopy show identical structur es and hence prove that the inhomogeneities already exit in the dispersed s tate.