Synthesis of well-defined amphiphilic poly(d,l-lactide)-b-poly(N-vinylpyrrolidone) block copolymers using ROP and xanthate-mediated RAFT polymerization

Abstract

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 1H NMR spectroscopy and GPC. Spherical micelles of ∼30.2 nm diameter were formed from the aqueous solution of amphiphilic diblock copolymer PDLLA42-b-PNVP63 as revealed by TEM and supported by 1H 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 (Rh) 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.