Abstract: Methylacryloylpropyl-polyhedraldigomeric silsesquioxanes （MAP-POSS）copolymerized with MMA leading to an organic/inorganic hybrid composite. The copolymerization kinetics of MMA with MAP-POSS was investigated by DSC with polymerization kinetic parameters determined. Mechanical, electrical, and thermal properties of such composite were determined. The impact strength of the composite increased 30 kJ/m2，the thermal degradation temperature increased 34℃ based on neat PMMA, and the electrical property was not affected.

Key words: poly(methyl methacrylate), silsesquioxanes, copolymerization, reaction kinetics, mechanical property