A smart spiropyran-containing cellulose material for photopatterning, temperature and humidity sensing†

Abstract

Based on their stimuli-responsiveness, smart materials are able to undergo controllable physicochemical changes. As compared to the responsiveness to one specific stimulus, multiple stimuli-responsiveness would make smart materials adaptable to diverse environments, which is highly desired in the design of smart materials but appreciably more difficult to realize. Herein, an ammonium surfactant (SPA) based on spiropyran is designed for complexing with carboxymethylcellulose through an electrostatic route, affording a soft cellulose material (CMC–SPA) in solvent-free conditions. Thanks to the molecular design of SPA and the anisotropic arrangement of cellulose on SPA molecules, CMC–SPA exhibits triple stimuli-responsiveness by responding to light, heat and humidity. With good thermodynamic stabilities of different color states, CMC–SPA could well record optical information by changing colors under UV and visible irradiations. More interestingly, linear relationships between UV-visible absorption and temperature/humidity are established, endowing CMC–SPA with the functions of recording ceiling temperatures in inaccessible scenarios and indicating real-time environmental humidity. This study provides a design strategy for fabricating multiple stimuli-responsive materials, affording a new route for gaining smart biomaterials from biomacromolecules.