Facile synthesis of thiol-functionalized amphiphilic polylactide-methacrylic diblock copolymers
- Publisher: RSC Publishing
Biodegradable amphiphilic diblock copolymers based on an aliphatic ester block and various hydrophilic\ud methacrylic monomers were synthesized using a novel hydroxyl-functionalized trithiocarbonate-based\ud chain transfer agent. One protocol involved the one-pot simultaneous ring-opening polymerization\ud (ROP) of the biodegradable monomer (3S)-cis-3,6-dimethyl-1,4-dioxane-2,5-dione (L-lactide, LA) and\ud reversible addition–fragmentation chain transfer (RAFT) polymerization of 2-(dimethylamino)ethyl\ud methacrylate (DMA) or oligo(ethylene glycol) methacrylate (OEGMA) monomer, with 4-\ud dimethylaminopyridine being used as the ROP catalyst and 2,20-azobis(isobutyronitrile) as the initiator for\ud the RAFT polymerization. Alternatively, a two-step protocol involving the initial polymerization of LA\ud followed by the polymerization of DMA, glycerol monomethacrylate or 2-(methacryloyloxy)ethyl\ud phosphorylcholine using 4,40-azobis(4-cyanovaleric acid) as a RAFT initiator was also explored. Using a\ud solvent switch processing step, these amphiphilic diblock copolymers self-assemble in dilute aqueous\ud solution. Their self-assembly provides various copolymer morphologies depending on the block\ud compositions, as judged by transmission electron microscopy and dynamic light scattering. Two novel\ud disulfide-functionalized PLA-branched block copolymers were also synthesized using simultaneous ROP\ud of LA and RAFT copolymerization of OEGMA or DMA with a disulfide-based dimethacrylate. The disulfide\ud bonds were reductively cleaved using tributyl phosphine to generate reactive thiol groups. Thiol–ene\ud chemistry was utilized for further derivatization with thiol-based biologically important molecules and\ud heavy metals for tissue engineering or bioimaging applications, respectively.
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