A synthetic technique is presented for the preparation of a novel type of arborescent copolymer containing polyisoprene (PIP) segments. Isoprene is polymerized with sec-butyllithium in cyclohexane or tetrahydrofuran, to yield a predominantly cis-1,4- or a mixed microstructure, respectively. The graft copolymers are obtained by capping the polyisoprenyl anions with 1,1-diphenylethylene and titration with a solution of a chloromethylated polystyrene substrate. Copolymers containing PIP side chains of different molecular weights are prepared by grafting onto linear, comb-branched (GO) and twice-grafted (G1) chloromethylated polystyrenes. The samples with short (M-w approximate to 5000) PIP branches contain 77-83% w/w polyisoprene. For PIP side chains with M-w approximate to 30 000 and 90 000, the polystyrene content is negligible. A low apparent polydispersity (M-w(app)/B-n(app) less than or equal to 1.15) is maintained after grafting. Characterization of these materials using size exclusion chromatography and light scattering indicates that they have a highly compact structure. Scanning force microscopy measurements in the phase contrast mode show that the copolymers display phase-separated morphologies (glassy core surrounded by a rubbery shell) to different extents, depending on their structure.