A simple PVA/Cu(OAc)2 thermogel with an inherent near-infrared light response and its applications in smart windows and photoresistors

Thermogels are one kind of smart materials, characterized by the in situ sol–gel transition upon temperature increase. Currently, most of them are constructed using thermosensitive polymers, which often require tedious chemical synthesis. Besides, it is difficult to precisely control the gel properties through remote stimuli like near-infrared (NIR) light. In this work, we have prepared a thermogel with inherent NIR photothermal responsive features by simply mixing hydrophilic polyvinyl alcohol (PVA) with Cu(OAc)2 in deionized water. Without the incorporation of extra reagents and the chemical modification of PVA, the PVA/Cu(OAc)2 thermogel exhibited high photothermal conversion efficiency and reversible sol–gel transition behavior. Because of the inherent NIR absorption and optical conversion abilities, the PVA/Cu(OAc)2 thermogel can be used as a smart window material to effectively absorb sunlight and prevent the rise of indoor temperature. In addition, its photosensitive conductivity also gave it the potential to act as a photoresistor. As far as we know, this is the first PVA-tailored thermogel with an inherent NIR light response, which provides an innovative strategy to construct smart materials.