Morphology of micron-sized polystyrene particles crosslinked with urethane acrylate

The morphology of micron-sized polystyrene particles crosslinked with a urethane acrylate crosslinker was studied with different concentrations of urethane acrylate and medium solvency by means of simple dispersion polymerization. The urethane acrylate employed as a crosslinker showed an excellent effect on maintaining the monodispersity of the polystyrene particles at a moderate crosslinker concentration (to about 5 wt%) in terms of the monomer-swellable surface of primary particles. By enhancing the medium solvency, the amount of urethane acrylate incorporated was increased, while the monodispersity of the final particles was maintained. It was believed that the increase in solvency on adding xylene to ethanol solution helped the diffusion of the styrene monomers into the primary particles. At high concentration of urethane acrylate, however, nonspherical particles, ellipsoidal or egg-like singlets and asymmetric doublets, were observed. The increased crosslinking density seemed to repel the styrene monomers during particle growth. Received: 30 June 1998 Accepted in revised form: 9 September 1998