Eco-friendly and photo-switchable smart adhesives from biomass-based copolymers with acid azobenzene functions

Conventional adhesives is recently emerging as an environmental concern, while they need to be more specialized for advanced applications. In response, a biomass-based tetrahydrogeraniol methacrylate monomer (TGMM) and an acid azobenzene-based methacrylate monomer (AAMM) are newly synthesized and subsequently copolymerized to produce eco-friendly and photo-switchable smart adhesives. The resultant copolymer as targeted adhesive exhibits great adhesion to a wide range of substrates, including metals, plastics, and rubber. When exposed to UV and visible lights, the adhesive on transparent substrates exhibits a reversible change in adhesion strength due to the photoisomerization behavior of azobenzene moiety. In addition to the photo-responsive behavior, the adhesive is highly reusable and recyclable through solvent, heat, and light treatments, while maintaining its adhesion performance across repeated usage cycles. The newly developed adhesives were successfully integrated into smart UV sensors, acting as UV light-sensitive switches in electrical circuits. With the unique combination of photo-switchable adhesion and reusability, this versatile and sustainable adhesive can make a significant contribution to smart sensing and next-generation adhesive applications.