Preparation and Properties of a Self-Healing, Multiresponsive Color-Change Hydrogel

Hydrogels are smart materials with a high moisture content, elasticity, and stimuli to pH and temperature and are widely used in drug delivery, wound dressings, tissue engineering, parting materials, and sensors. However, a hydrogel with a multiresponsive feature is desired and challenging to produce. Here, a novel multiresponsive color-change hydrogel, including pH response, light response, and alcohol response, was successfully fabricated by introducing Michler's hydrol blue (MHB) into a semicrystalline hydrophobically associated hydrogel. The color-change function is obtained by a transformation between MHB and protonated Michler's hydrol blue (PMHB) deduced by nucleophilic attack processes. An excellent swelling performance of 2010% of the hydrogel was confirmed by swelling, time-dependent rewetting data, and differential scanning calorimetry (DSC) measurements. Its color change was obvious and fast, within 1 min, when exposed to ultraviolet (UV) light, alcohol, or pH change. In addition, the tensile strength of the hydrogel reached up to 0.9 MPa with loading MHB by 2.0%. The fluorescence and self-healing performances were verified to be good due to the presence of a large delocalized pi-bond and hydrogen bonds. This material fabricated by a facile process might have potential applications in visual fluorescence sensors.