GRAFT-POLYMERIZATION OF VINYL MONOMERS FROM INORGANIC ULTRAFINE PARTICLES INITIATED BY AZO GROUPS INTRODUCED ONTO THE SURFACE

The radical graft polymerization of vinyl monomers from inorganic ultrafine particles, such as silica, titanium oxide, and ferrite, by use of azo groups introduced onto their surface was investigated. The introduction of azo groups onto the ultrafine particles was achieved by the reaction of glycidyl groups, which were introduced by the reaction of hydroxyl groups on the surface with 3-glycidoxypropyltrimethoxysilane, with 4,4’-azobis(4-cyanopentanoic acid). The amounts of azo groups introduced onto silica, titanium oxide, and ferrite were determined to be 0.07, 0.05, and 0.03 mmol g-1, respectively. The polymerization of vinyl monomers, such as methyl methacrylate (MMA), styrene, and N-vinylcarbazole (NVC), was found to be initiated by radicals formed by the decomposition of the azo groups. During the polymerization, the polymer was effectively grafted onto these surfaces through propagation from the surfaces; the percentage of grafting of polyMMA onto silica, titanium oxide, and ferrite reached to 45.1, 42.8, and 40.5%, respectively. Polymer-grafted ultrafine particles produced stable dispersions in organic solvents. Furthermore, the dispersion of polymer-grafted ferrite in organic solvent was found to behave like a magnetic fiuid. © 1990, The Society of Polymer Science, Japan. All rights reserved.