Amphiphilic, biocompatible poly(N-vinylpyrrolidone)-b-poly(l-lactide) (PVP-b-PLLA) block polymers were synthesized at 60 degrees C using a hydroxyl-functionalized N,N-diphenyldithiocarbamate reversible addition-fragmentation chain transfer (RAFT) agent, 2-hydroxyethyl 2-(N,N-diphenylcarbamothioylthio)propanoate (HDPCP), as a dual initiator for RAFT polymerization and ring-opening polymerization (ROP) in a one-step procedure. 4-Dimethylamino pyridine was used as the ROP catalyst for l-lactide. The two polymerization reactions proceeded in a controlled manner, but their polymerization rates were affected by the other polymerization process. This one-step procedure is believed to be the most convenient method for synthesizing PVP-b-PLLA block copolymers. HDPCP can also be used for the one-step synthesis of poly(N-vinylcarbazole)-b-PLLA block copolymers. (c) 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014, 52, 1607-1613