A Strong Adhesive with High Switching Ratio Achieved by Phototriggered Azobenzene-Terminated Hyperbranched Polymer

Photoswitchable adhesives realized by azobenzene groups exhibit important applications in flexible electronics, micro/nanotransfer printing, and soft robots. Such phototriggered reversible adhesives, however, suffered from a contradiction between adhesion strength and switchability. Here, we present a hyperbranched polymer with terminal groups of azobenzene as a photoswitchable adhesive. This adhesive demonstrates both a high adhesion strength and a high switching ratio after UV light irradiation. By introducing abundant hydrogen bonds into the hyperbranched polymer through selecting the appropriate monomer, the cohesive strength and interfacial interactions were enhanced, thereby improving the adhesion strength of the adhesive. Simultaneously, due to the presence of azobenzene groups, the hyperbranched polymer underwent a significant solid-liquid phase transition under UV irradiation, disrupting its cohesive strength and achieving strong switchability. On the basis of the comprehensive evaluation of both adhesion strength (8.07 MPa) and switching ratio (53.80) on glass, our optimal adhesive outperforms previously reported azobenzene-based reversible adhesives. This hyperbranched polymer provides an alternative to developing switchable adhesives for advanced manufacturing.