In situ synthesis and self-reinforcement of polymeric composite hydrogel based on particulate macro-RAFT agents

Abstract

Excellent mechanical strength is critical for polymer hydrogels to be successfully applied in the field of mechanical devices and tissue engineering scaffolds. Herein, novel nanoparticle-reinforced polyacrylamide-based hydrogel with high mechanical strength was designed and successfully prepared in this work through the RAFT polymerization of acrylamide (AM) and ethylene glycol dimethacrylate (EGDMA) in the presence of particulate macro-RAFT agents in water. Amphiphilic poly(acrylic acid)-b-polystyrene (PAA-b-PS) copolymer was first synthesized via RAFT copolymerization in methanol. Then the vesicles of about 200 nm in size and decorated with RAFT groups were formed by the self-assembly of PAA-b-PS copolymers during the water dialysis, which can be considered as particulate macro-RAFT agents. After the addition and the polymerization of EGDMA and AM monomers in order, hydrogel filled with uniformly distributed PAA-b-PS nanoparticles was in situ formed, showing an extraordinary compression strength and tensile strength up to 7.0 MPa and 2.0 MPa, respectively, as well as an excellent fatigue resistance under loading-unloading. The self-reinforcement effect of the PAA-b-PS nanoparticles should be related to the strong interaction originating from the chemical and hydrogen bonds between the particulate macro-RAFT agents and polyacrylamide chains. This work provides not only a novel method for macro-RAFT agents, but also opens a new feasible strategy to prepare high-performance hydrogels reinforced by polymeric nanoparticles.