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.