Metal–ligand-based thixotropic self-healing poly (vinyl alcohol) metallohydrogels: Their application in pH-responsive drug release and selective adsorption of dyes

This work reports in situ fabrication of biocompatible metallohydrogels composed of polyvinyl alcohol (PVA) polymer crosslinked via coordination complexation between polymeric O− and Mn+ (Mn+ = Ni2+, Fe3+ and Cu2+ ions) at room temperature. The obtained metallohydrogels exhibited the remarkable thixotropic and rapid self-healing properties. Among the three metallogels, Cu-PVA hydrogel exhibited high mechanical strength, elasticity, fatigue resistance, and self-healing ability due to stronger bonding followed by Fe-PVA and Ni-PVA metallohydrogels. Furthermore, these metallohydrogels depicted pH-responsive drug release with sustained release at basic pH while a burst release at neutral and acidic pH values. In addition, they exhibited selective adsorption towards anionic dyes in a mixture of cationic, anionic, and neutral dyes, thereby making them suitable candidates as dye separation agents. Hence, the as-prepared metallohydrogels are promising and potential materials with biocompatibility, high mechanical strength, elasticity, thixotropy, and quick self-healing properties for biomedical and environmental remediation fields.