Reversible White-Light-Driven Photochromic Polymer Hydrogels with High Stretchability and Adhesiveness

Photochromic materials that reversibly change color by light stimulus are of interest for developing sensors and optoelectronics. A design of Ag+-containing photochromic polymer hydrogel showing reversible photochromism, high stretchability, and high adhesiveness is reported. The polymer hydrogel is fabricated using the Ag+/ammonium persulfate (APS) fast gelation system, which initiates the fast gelation of the acrylic acid (AA) and 3-iminodiacetate-2-hydroxypropyl methacrylate (IDHPMA) aqueous solution. The iminodiacetate (IDA) ligands from the copolymer bind with Ag+ ions to form Ag+–IDA coordination cross-links, contributing to the high stretchability of the hydrogel. The Ag+–IDA complexes also impart a high adhesion performance to the hydrogel through the formation of Mn+–IDA complexes on various metal surfaces. The Ag+ ions in the hydrogel undergo a reversible transition between the ionic and Ag nanoparticle states when subjected to switchable white-light irradiation and incubation in the dark. It is demonstrated that this photochromic hydrogel was suitable for photopatterning with a controllable storage time. This photochromic hydrogel illustrates a pathway to make soft wearable devices for controllable information storage and anticounterfeiting, where high stretchability and adhesiveness are required.