Well-defined amphiphilic poly(D,L-lactide)-b-poly(N-vinylpyrrolidone) (PDLLA-b-PNVP) block copolymers were successfully prepared using ring-opening polymerization (ROP) and xanthate-mediated reversible addition-fragmentation chain transfer (RAFT) polymerization. Synthesized PDLLA-b-PNVP block copolymers were characterized by H-1 NMR spectroscopy and GPC. Spherical micelles of similar to 30.2 nm diameter were formed from the aqueous solution of amphiphilic diblock copolymer PDLLA42-b-PNVP63 as revealed by TEM and supported by H-1 NMR and light scattering. The critical micelle concentration value of the block copolymers, determined by fluorescence spectroscopy using pyrene as probe, increased with the increase in the chain length of PNVP block. The average hydrodynamic radius (R-h) of the micelles remained almost constant above the cmc value over the angles of scattering measurement. Thermal properties of these block copolymers were studied by TGA, DTA and DSC. Crystalline properties of these block copolymers were studied by WXRD. (C) 2012 Elsevier Ltd. All rights reserved.