Switchable photochromic transparent wood as smart packaging materials

Transparent wood (TW) has been developed to combine the optical and functional aspects of wood. Many efforts have been dedicated to adding quantum dots, nanoparticles, or dyes to TW to provide additional functionalities, such as luminescent, electrochromic, thermochromic, and photo-switchable TW. However, the UV shielding performance and its new application of transparent wood are needed to explore. Herein, we report a photochromic transparent wood (PTW) by incorporating poly(methyl methacrylate) and UV/visible light switchable molecules into the delignified wood template. The focus is to investigate the relationship of process-structure-property of the PTW. The dispersion of photochromic molecules in PTW is shown by using energy-dispersive X-ray spectroscopy. The transmittance and the color of the PTW are switchable under UV and visible light excitation due to a change from the closed-ring to the open-ring form. Moreover, the PTW was found to possess, UV shielding performance, favorable thermal and mechanical properties, as well as excellent dimensional stability. We also demonstrate the potential smart packaging application of the UV-blocking PTW. We envision this PTW could be utilized for anti-counterfeit materials, intelligent sensors, and smart indicators.