Multi-responsive, self-healing and adhesive PVA based hydrogels induced by the ultrafast complexation of Fe³⁺ ions

Herein, a PVA (polyvinyl alcohol)-based multi-responsive hydrogel was prepared by introducing the dynamic and reversible supramolecular complexation between polyvinyl alcohol acetoacetate (PVAA) and Fe3+ ions within 20 s at room temperature. PVAA-Fe hydrogels could be achieved by the simple mixing process of a PVAA aqueous solution with FeCl3 aqueous solution. The soluble PVAA was synthesized by the reaction of PVA with tert-butyl acetoacetate (t-BAA) via transesterification in dimethyl sulfoxide (DMSO). The chemical structure of PVAA was systematically characterized by FT-IR and 1H NMR spectroscopy. The resulting hydrogel showed excellent self-healing behavior without other external stimuli. It was also demonstrated that the PVAA-Fe hydrogel exhibited multi-responsive properties, such as responsiveness to pH, redox, light irradiation and temperature. In addition, the presence of Fe3+ ions and Cl- ions in the gel imparted the PVAA-Fe hydrogel with favorable conductivity. Therefore, the strategy for the facile preparation of the hydrogel in this work could provide a benign and versatile method for achieving multi-functional soft materials for various applications such as smart devices, logic gates, and sensors.