Debonding-on-demand adhesives based on photo-reversible cycloaddition reactions

Debonding-on-demand (DoD) adhesives, which have the ability to repeatedly adhere and release in response to external stimuli, are attracting attention as sustainable functional materials. DoD adhesives can be designed by fabricating dynamic covalent bonds and using polymer cleavage and flow generation by dynamic mechanisms that respond autonomously to external stimuli, such as heat and light. However, the typical DoD adhesives using dynamic covalent bonds mainly utilize heat-induced systems, and the practical application of these adhesives at room temperature and ambient pressure is challenging. In this study, we report a DoD adhesive system based on a polymer that is fabricated by the reversible cycloaddition reaction of coumarin-terminated four-arm siloxane monomers. Thermophysical property analysis of the obtained polymers confirmed that photoinduced fluidization was based on the reversible crosslinking and decrosslinking reactions of the monomers. These thermophysical properties can directly control the stiffness of the polymers, providing mechanistic evidence of DoD adhesion. This simple siloxane-based reversible cycloaddition system exhibits significant potential as a DoD adhesive that functions at room temperature.