Synthesis and self-assembly of amphiphilic and biocompatible poly(vinyl alcohol)-block-poly(L-lactide) copolymer

Well-defined amphiphilic and biocompatible poly(vinyl alcohol)block-poly(L-lactide) copolymers (PVA-b-PLLA) were synthesized by the combination of reversible addition-fragmentation chain transfer (RAFT), ring opening polymerization (ROP), and click chemistry. First, an innovative azide-functionalized xanthate mediated chain transfer agent (CTA) [S-(3-azidopropyl propanamide)-(O-butyl xanthate)] was synthesized and used for vinyl acetate (VAc) polymerization through RAFT. Then, azide-terminated poly(vinyl acetate) (azide-PVAc) was converted to the corresponding azide-terminated poly(vinyl alcohol) (azide-PVA) through hydrolysis. Alkyne-terminated poly (L-lactide) (alkyne-PLLA) was synthesized via ROP using a bifunctional initiator, having an alkyne and a hydroxyl group. Finally, azide-PVA and alkyne-PLLA were coupled by 1,3 cycloaddition click reaction to get PVA-b-PLLA. Synthesized azide-PVAc, azide-PVA, alkyne-PLLA and PVA-b-PLLA were characterized by size exclusion chromatography and H-1 NMR spectroscopy. The self-assembly of PVA-b-PLLA in water was investigated by transmission electron microscope, atomic force microscopy, dynamic light scattering and H-1 NMR spectroscopy. Spherical micelles in water were clearly observed. The critical micelle concentration of PVA-b-PLLA in water was determined by fluorescence spectroscopy, and it was decreased with increasing the molecular weight of PLLA block. PVA-b-PLLA exhibited low cytotoxicity which could be used in biomedical application. (C) 2016 Elsevier Ltd. All rights reserved.