An end-pi -allylnickel macroinitiator (3) was prepared by the reaction of poly(ethylene glycol) allenyl methyl ether with an excess amount (5 equiv) of [(pi -allyl)NiOCOCF3](2) (1) in the presence of PPh3 ([PPh3]/[1] = 1). The resulting macroinitiator was used as an initiator for the polymerization of l-phenylethyl isonitrile (4a) to give a block copolymer [poly(ethylene glycol)-block-poly(4a)]. The molecular weight and composition of the block copolymers were controlled by the molecular weight of 3 and the ratio of 4a to 3. (C) 2001 John Wiley & Sons, Inc.