A New heterobifunctional poly(ethylene glycol) (PEG) having a polymerizable acryloyl group at one end and an isocyanate group at the other end was prepared in three efficient steps from commercially available t-Boc-PEG-NH2. The end groups were characterized by H-1 NMR and MALDI-TOF-MS spectroscopy. Conjugation of the resulting PEG onto dextran via stable urethane linkage gave the PEG graft polymer with an acryloyl group at the free end of the graft chain.