A novel, well-defined graft copolymer (polystyrene (PS)-g-poly(methyl methacrylate) (PMMA)) with control over the length of both the backbone and the side chain was synthesized by the coupling reaction of living PMMA with bromomethylated PS. The backbone polymer was prepared by the anionic polymerization of styrene with n-butyllithium followed by bromomethylation using C8H17OCH2Br/SnCl4 The living PMMA was prepared by the group transfer polymerization of MMA. Graft copolymers with a narrow molecular weight distribution, D = 1.2 similar to 1.4 at an (M) over bar(n), of around 3 x 10(4)-7 x 10(4) were obtained. The reactivity of the bromomethylated PS and the living PMMA decreased with increase in their molecular weight; the favoured reaction temperature was -20 degrees C. Characterization of the product was performed by methods including H-1 n.m.r., g.p.c. and d.s.c.. Compared with the homopolymers PS and PMMA, the copolymer had a lower glass transition temperature.