Abstract
Adhesives are essential in the manufacturing of modern technological devices for various application fields, ranging from transportation to communications, to aerospace and energy generation and storage. Their adhesion strength and stability are critical for the device's development and performance; however, they pose significant challenges to disassembly and recycling. These challenges can be overcome by introducing user-defined debondable or reversible technologies into structural adhesives. Herein, a new adhesive formulation is reported that can be bonded and detached by blue light (lambda = 410-450 nm) and ultraviolet (UV) light (lambda = 340-355 nm), respectively. The adhesive platform is prepared by incorporating acrylamidyl pyrene moieties into polyethylenimine, enabling reversible photocrosslinking by redshifted [2 + 2] photocycloaddition. The photophysical properties and switching mechanisms between the monomeric and dimeric forms of the acrylamidyl pyrene are thoroughly investigated by spectroscopic measurements and complemented by comprehensive quantum chemical calculations. Under selective irradiation of low-energy blue and UV light, the reversible photocycloaddition [2 + 2] facilitates dynamic bonding and debonding of the crosslinked networks, enabling reversible adhesion between a range of solid substrates. Critically, the adhesives are stable at elevated temperatures above 70 degrees C and in aqueous environments, thereby providing a new strategy for the development of next-generation debonding on-demand adhesives.