The grafting reaction of methyl methacrylate onto polybutadiene (PB) was investigated with different chromatographic techniques, including high-performance liquid chromatography (HPLC) and online coupled two-dimensional liquid chromatography. As a result of the grafting reaction, a complex mixture of nongrafted PB, the graft copolymer PB-g-PMMA [where PMMA is poly(methyl methacrylate)], and the PMMA homopolymer was formed. The complete separation of all the products of the grafting reaction was achieved with gradient HPLC. By the combination of gradient HPLC and size exclusion chromatography in a fully automated two-dimensional chromatography setup, the complex distributions of the chemical composition and molar mass were fingerprinted simultaneously. (C) 2003 Wiley Periodicals, Inc.