Biocompatible poly(epsilon-caprolactone)-b-poly(vinyl alcohol) (PCL-b-PVA), poly(o-valerolactone)-b-PVA, and poly(trimethylene carbonate)-b-PVA block copolymers were synthesized at 30 degrees C using a hydroxylfunctionalized xanthate reversible addition-fragmentation chain transfer (RAFT) agent, 2-hydroxyethyl 2-(ethoxycarbonothioylthio)propanoate, as a dual initiator for ring-opening polymerization (ROP) and RAFT polymerization in a one-pot procedure. The ROP of epsilon-caprolactone, 6-valerolactone, and trimethylene carbonate was first performed using diphenyl phosphate as the ROP catalyst followed by the RAFT polymerization of vinyl chloroacetate after quenching the ROP with 4-dimethyamino pyridine. The resulting block copolymers were aminolyzed directly to the PVA-based biocompatible block copolymers by adding hexylamine to the reaction mixture. To the best of our knowledge, this is the most convenient method for synthesizing PVA-based biocompatible block copolymers. (C) 2013 Elsevier Ltd. All rights reserved.