Two polyisobutylene-grafted graphene nanocomposites were prepared by CuBr-catalyzed atom transfer nitroxide radical coupling (ATNRC) and Cu-catalyzed single electron transfer-nitroxide radical coupling (SET-NRC) chemistry under mild conditions, respectively, through the grafting-onto strategy. Graphene oxide was first reduced to graphene by diazonium addition reaction followed by treating graphene with ethyl 2-bromoisobutyrate for introducing Br-containing groups onto the surface to give G-Br. The presynthesized well-defined functional polyisobutylene (PIB) possessing 2,2,6,6-tetramethylpiperidine-1-oxyl terminal group obtained via cationic polymerization of isobutylene was then coupled with G-Br through ATNRC or SET-NRC at room temperature to afford polymer-modified graphene, G-PIB. SET-NRC method has a faster coupling rate using cheaper reagent (Cu wire instead of CuBr) in comparison with ATNRC approach. Detailed characterizations including FT-IR, Raman, H-1 NMR, TGA, AFM, and TEM assured us of successful anchoring of PIB chains onto the surface of graphene sheets. The resulting G-PIB nanocomposites still maintain the separated single layers in dispersion and the dispersibilities in organic solvents are significantly improved. (c) 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 4505-4514