Revealing the enhanced structural recovery and gelation mechanisms of cation-induced cellulose nanofibrils composite hydrogels.

In this study, we fabricate physically dual-crosslinked cellulose-based hydrogels by varying coordination bonding effects with the addition of either divalent or trivalent metal cations. The first crosslinked network is created by metal-carboxylate coordination bonds between the cellulose nanofibrils that have abundant carboxyl groups and the metal cations. The second crosslinked network is formed by the reaction of tetra-functional borate ion complex and the hydroxyl groups in polyvinyl alcohol. These physically dual-crosslinked networks are strongly interwoven by non-sacrificial hydrogen bonds, this dual-crosslinked network leads to enhanced recovery characteristics in the resulting hydrogels. We use three interval thixotropic testing to investigate the deformation and recovery behaviors of the hydrogels and plot their structural deformation parameters in phase diagrams to understand the underlying complexity of energy dissipation and viscoelastic dynamics of the dual-crosslinked hydrogels.