The transformation of ring opening polymerization into an initer process is reported For the preparation of the block copolymer of epsilon-caprolactone (CL) with styrene (St). In the first step, ring opening polymerization of CL was carried out by using triphenyl methanol (TPM) as the initiator and aluminum alkoxide as the promoter, respectively, to give a triphenylmethyl (trityl)-terminated polymer. UV and H-NMR studies show that the trityl group associated with the active alkoxy group of the initiator is selectively attached to one chain end. In the second step, the trityl-terminated polymer served as a thermal 'initer' for the polymerization of styrene and this makes it possible to prepare a block copolymer. (C) 2000 Elsevier Science Ltd. All rights reserved.