4'-azobis(4-cyanopenlanoic acid) (ACPA) onto nanometer silica and radical graft polymerization of methyl methacrylate (MMA) from the modified silica throush emulsion polymerization were investigated.The anchoring of ACPA onto silica was achieved by treating of silica with glycidoxypropyl-trimethoxysilane and reacting with ACPA.The anchoring of ACPA was confirmed by DSC and element analysis.Poly (methyl methacrylate) (PMMA) was effectively grafted onto nanometer silica throughe initiation of anchored ACPA during emulsion polymerization.The grafting percentnge and efficiency of PMMA were 23.2% and 36.1% determined by TGA.Furthermore
the aggregation degree of the original nanometcr silica was decreased by in-situ polymerization
and the stability of PMMA/nano-silica composite latex was good.