Preparation of Poly(methyl acrylate)/TiO_2 Composites by Potassium Diperiodatocuprate- initiated Grafting Copolymerization

摘要

The effective chemical binding of polymeric chain with inorganic materials has a crucial impact on improving the integrative property of the composite. In this study, potassium diperiodatocuprate (Cu~(3+)) was used as an initiator to prepare poly(methyl acrylate)/TiO_2 composites (PMA/TiO_2) by in situ graft copolymerization in an alkaline medium. TiO_2 particles were at first modified by aminopropyltriethoxysilane (KH550) before polymerization process in order to obtain the covalent bonds of PMA chain with TiO_2 particles. The three synthetic parameters including the monomer conversion, grafting percentage and grafting efficiency were systematically evaluated as functions of temperature, initiator concentration, pH and reaction time. The graft parameters were increased first and then decreased with increases in temperature, Cu~(3+) concentration and pH value of polymerization. It was also found from the experimental results that Cu~(3+) was a highly efficient grafting initiator for the copolymerization. The grafting efficiency was as high as 95% and the graft percentage was readily controlled within 460%. In addition, the highest graft parameters were observed at pH 13.08 when the temperature was controlled at 30-40℃. The structure of PMA/TiO_2 composite was characterized using the thermal gravimetric analysis (TGA), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). The IR measurements clearly suggested that the PMA chains were effectively grafted onto TiO_2 surface. A single-electron-transfer mechanism was proposed to illustrate the generation of radicals by the redox reaction and the formation of PMA/TiO_2 composite.