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

- Azide-functionalized xanthate mediated chain transfer agent [S-(3-azidopropyl propanamide)-(O-butyl xanthate)].
- Synthesis of azide terminated polyvinyl alcohol with less than PDI of 1.25.
- Well-defined amphiphilic and biocompatible poly(vinyl alcohol)-block-poly(l-lactide) copolymers.
- Self-assembly of PVA-b-PLLA in water is investigated.

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 1H NMR spectroscopy.The self-assembly of PVA-b-PLLA in water was investigated by transmission electron microscope, atomic force microscopy, dynamic light scattering and 1H 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.

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