Self-Healing and Multistimuli-Responsive Hydrogels Formed via a Cooperation Strategy and Their Application in Detecting Biogenic Amines

We reported here a new platform of supramolecular hydrogels cross-linked by the cooperation of metal–ligand coordination and hydrophobic interaction. A salicylaldehyde benzoyl hydrazone-terminal poly(ethylene glycol) (2SBH-PEG) was synthesized and formed small micelles in an aqueous environment. Addition of Ni2+ connected the low-molecular-weight 2SBH-PEG into a metallopolymer via metal–ligand coordination and led to micelle aggregation, resulting in gelation due to the enhancement of hydrophobic interaction. The forming hydrogel, Ni–PEGel, exhibited rapid self-healing ability and reversible pH-responsive property. Because of the containing metal coordination bond, it was also sensitive to the strong competing ligands, such as ethylenediaminetetraacetic acid (EDTA) and pyridine. In addition, Ni–PEGel showed colorimetric changes when exposed to biogenic amine (BA) vapor. The color development of Ni–PEGel toward BAs makes it a good candidate in monitoring food spoilage.