Dual physically crosslinked healable polyacrylamide/cellulose nanofibers nanocomposite hydrogels with excellent mechanical properties

To develop healable hydrogels with excellent mechanical properties is still a challenge topic. In this study, a novel class of physically crosslinked polyacrylamide based nanocomposite hydrogels reinforced with cellulose nanofibers (CNF) were fabricated using radical polymerization, followed by further strengthening through ferric ions via strong ionic coordination interactions between Fe³⁺ and carboxyls on CNF surfaces. Then the obtained gels were characterized by FTIR, tensile and compressive measurements as well as healing experiments. The increase of CNF amount or Fe³⁺ concentration generated positive effect on the improvement of hydrogel mechanics, demonstrating facilely modulatable mechanical properties through simply changing CNF dosages in formulations and/or Fe³⁺ concentrations in posttreatment. The obtained nanocomposite hydrogels show remarkable mechanical properties with high stiffness and toughness, quick recovery and healing abilities owing to the distinctive roles of dual physical crosslinks. This work provides a promising view for designing novel high strength hydrogels with fully physical crosslinks.