Toward Sustainable Optics: Fully Biomass-Based Vitrimer Film for Near-Infrared Transparency

Materials that are opaque to visible light yet transparent to near-infrared (NIR) light are highly desirable for applications in security imaging, night vision, and anticounterfeiting. However, these materials are mainly based on inorganic compounds or petroleum-derived polymers doped with dyes, which face challenges related to sustainability, reprocessability, and environmental compatibility. Herein, we report a fully biomass-derived NIR-transparent vitrimer film from diglycidyl ether of daidzein (DGED), dimer fatty acid (DFA), and lignin. The resulting film exhibits >80% transmittance in the NIR region while blocking over 90% of visible light at 650 nm. In addition, it also demonstrates high mechanical strength, excellent stability against water, solvents, and heat, as well as remarkable self-healing and reprocessing capabilities. Benefiting from its biomass-derived composition, dynamic covalent network, and simple preparation process without toxic organic solvents, this film represents a sustainable and versatile candidate for advanced NIR optical applications, including privacy protection, secure anticounterfeiting, and night vision imaging.