Photoresponsive Polymers for Debonding-on-Demand Pressure-Sensitive Adhesives

An ideal adhesive requires strong adhesion during usage and simple removal on demand, but obtaining these striking features has been a perpetual impediment in the design of pressure-sensitive adhesives (PSAs). To overcome this continuous challenge, a photoresponsive coumarin containing PSA was designed that enables an increase in cross-link density through cycloaddition in the presence of UV light. The PSA was based on either permanent static covalent bonds or dynamic metal ligand coordination bonds. Thermal and rheological experiments revealed the photoinduced cycloaddition, which induced higher cross-link density leading to increased stiffness and ultimately substantially reduced adhesion and debonding. This presented practical evidence to demonstrate debond-on-demand (DoD) adhesion. The lap shear experiment highlights the improved adhesive strength of the PSAs especially for networks with metal ligand dynamic but a persistent cross-linker, while still retaining debonding ability after UV exposure. Considering these results, the simple photoresponsive PSA designed herein demonstrates outstanding potential as a DoD PSA.