Environmentally stable, photochromic and thermotropic organohydrogels for low cost on-demand optical devices

The color-changing ability of creatures widely existed in nature has inspired the development of adaptive allochroic materials, which can respond to various external stimuli. Integrating multi-stimuli responsiveness and long-term stability in allochroic system are urgent for practical applications under complex circumstances.

The photochromic/thermotropic organohydrogels (PTOs) comprised polyacrylamide and cationic cellulose (JR400) were prepared by facile free-radical polymerization and glycerol displacement. The coexisting covalent bonds and noncovalent interactions collaboratively reinforce the networks, endowing the PTOs with boosted stretchability and toughness.

The photochromic ammonium molybdate (Mo₇) and thermo-sensitive poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) (EPE) were made into networks. In these cooperative networks, each constituent performed their own function without disruption, including fast photochromism (10 s) and durable thermo-responsiveness. Importantly, the glycerol-water solvent bestowed the distinct anti-freezing (-30 °C) and anti-dehydration performances on the PTOs. Accordingly, the materials could serve as promising rewritable devices for high-resolution and long-term data storage/encryption. Moreover, on-demand PTO windows integrating UV-prevention and solar energy regulation with T_lum (92.96%) and ΔT_sol (46.02%) could create comfortable and healthy environments for occupants. This work offers a new design strategy for low-cost, environmentally stable smart optical devices.