This report describes a new route to covalently bonded polymer-graphene nanocomposites and the subsequent enhancement in thermal and mechanical properties of the resultant nanocomposites. At first, the graphite is oxidized by the modified Hummers method followed by functionalization with Octadecylamine (ODA). The ODA functionalized graphite oxides are reacted with methacryloyl chloride to incorporate polymerizable -C=C-functionality at the nanographene platelet surfaces, which were subsequently employed in in situ polymerization of methylmethacrylate to obtain covalently bonded poly(methyl methacrylate) (PMMA)-graphene nanocomposites. The obtained nanocomposites show significant enhancement in thermal and mechanical properties compared with neat PMMA. Thus, even with 0.5 wt % graphene nanosheets, the T-g increased from 119 degrees C for neat PMMA to 131 degrees C for PMMA-graphene nanocomposite, and the respective storage modulus increased from 1.29 to 2 GPa. (c) 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 4262-4267, 2010