A Self-Healing\nCellulose Nanocrystal-Poly(ethylene\nglycol) Nanocomposite Hydrogel via Diels–Alder Click Reaction

Abstract

Self-healing\nhydrogels are particularly desirable for increased\nsafety and functional lifetimes because of stress-induced deformation\nand propagation of cracks. In this paper, we report a tough, highly\nresilient, fast self-recoverable, and self-healing nanocomposite hydrogel,\nwhich builds an interpenetrated network encapsulating rod-like cellulose\nnanocrystals (CNCs) by flexible polymer chains of poly­(ethylene glycol)\n(PEG). A thermally reversible covalent Diels–Alder click reaction\nbetween furyl-modified CNCs and maleimide-end-functionalized PEG was\nconfirmed by Fourier transform infrared spectroscopy. Uniaxial tensile\ntests and unconfined compression tests displayed outstanding mechanical\nproperties of the hydrogels with a high fracture elongation up to\n690% and a fracture strength up to 0.3 MPa at a strain of 90%. Cyclic\nloading–unloading tests showed excellent self-recovery and\nantifatigue properties of the nanocomposite hydrogels. The self-healing\ncapability of nanocomposite hydrogels assessed by tension tests was\nfound to be as high as 78%. The self-healing CNC-PEG nanocomposite\nhydrogels would shed insight into designing reusable and renewable\npolymeric hydrogels.