Synthesis of novel temperature responsive PEG-b-[PCL-g-P(MEO2MA-co-OEGMA)]-b-PEG (tBG) triblock-graft copolymers and preparation of tBG/graphene oxide composite hydrogels via click chemistry

Novel triblock-graft copolymers, poly ethylene glycol-b-[poly(epsilon-caprolactone)-g-poly(2-(2-methoxyethoxy) ethyl methacrylate-co-oligo (ethylene glycol) methacrylate)]-b-poly ethylene glycol (PEG-b-[PCL-g-P(MEO(2)MA-co-OEGMA)]-b-PEG) (tBG), were synthesized via ring-opening polymerization (ROP) and atom transfer radical polymerization (ATRP). In the synthesis process, temperature responsive P(MEO(2)MA-co-OEGMA) chains were grafted onto the PCL block of triblock copolymer PEG-b-Pa-b-PEG to improve its hydrophilicity. This method succeeded in increasing the solubility of PEG-b-PCL-b-PEG in water, and more importantly, endowing PEG-b-PCL-b-PEG with temperature sensitivity. By adjusting the feed ratio of 2-(2-methoxy ethoxy) ethyl methacrylate (MEO(2)MA) and oligo (ethylene glycol) methacrylate (OEGMA) monomers, the lower critical solution temperature (LCST) of the tBG can be realized at about 37 degrees C. Taking advantage of the excellent mechanical property of graphene sheets, alkyne-functionalized graphene oxide (alkyne-GO) was introduced to cross-link tBGs and prepare tBG/GO composite hydrogel through click reaction between tBG-N-3 and alkyne-GO. Different from traditional cross-linkers, alkyne-GO acts as reinforcing filler in the composite hydrogel. Benefiting from superior properties of PCL, PEG, P(MEO(2)MA-co-OEGMA) and GO, the as-prepared temperature responsive tBG/GO hydrogel exhibits excellent mechanical strength and toughness, demonstrating future potential applications in tissue engineering and biotechnology fields. (C) 2015 Elsevier B.V. All rights reserved.