Poly(methyl methacrylate) chains were grafted onto the surfaces of silica nanoparticles successfully via the direct facile esterification reaction under such mild conditions as ambient temperature, moisture and atmospheric pressure. The resulting composite nanoparticles were characterized by XPS, FTIR, Si-29 NMR, TEM, TGA, and DSC techniques. Results showed that this facile graft method had high graft efficiency and the grafted polymers accounted for about 55 wt% of the composite nanoparticles. Meanwhile, the resulting nanoparticles had core-shell structure while PMMA molecules and nanoparticles combined with covalent ester bonds, and which led to the PMMA segments attached on the nanoparticle surfaces with better thermal stability and higher glass transition temperature than that of the pristine carboxyl-terminated PMMA. (C) 2009 Elsevier B.V. All rights reserved.