TEMPO-oxidized cellulose nanofibers/polyacrylamide hybrid hydrogel with intrinsic self-recovery and shape memory properties

Shape memory hydrogels attract increasing attention due to their promising applications as intelligent biomaterials for actuators, biomedicine and sensory applications. Nonetheless, the integration of synergistic characteristics providing good mechanical properties and ideal self-recovery rate still remains a challenge. To tackle this, we develop a novel nanocomposite hydrogel by radical polymerization. TEMPO-oxidized cellulose nanofibers (TOCNs) with high strength and ultra-high aspect ratio were introduced to improve the energy dissipation mechanism and enhance the fatigue resistance of polyacrylamide (PAAM) hydrogel. Interestingly, the nanocomposite hydrogel displays unprecedented shape memory properties through coordination with Fe3+. The resulting TOCN/PAAM hydrogel achieves excellent energy dissipation capability (9.68 MJ m−3 at 60% strain), satisfactory viscoelasticity (51.1 kPa) and good self-recovery rate (about 93.2% after 30 min recovery). In particular, the 3% TOCN/PAAM-Fe3+ hydrogel exhibits better tensile performance. This nanocomposite hydrogel with good shape memory properties and excellent mechanical strength has broad application prospects in soft actuators and sensory research.