Recyclable Base-Triggered "Debond-on-Demand" Aliphatic Polyurethane Adhesives: Engineering Adhesion for Use in Inkjet Formulations.

While strong polymeric adhesives are widely valued, their removal can present a significant challenge where substrate recycling is concerned. Recent advancements in "debond-on-demand" adhesives have shown promising enhancements in adhesive strength and debondability. However, they often face a choice between increased adhesive strength or the rate and degree of debonding. Here we report using a rapidly base degradable chain-extender within a series of polyurethanes which possess tailorable adhesive characteristics. These chain-extended polyurethanes (CEPUs) possess high shear strength (8.20 MPa) which upon exposure to base solutions depolymerise (up to 88% loss in ) facilitating up to 92% loss in shear strength after only 30 min. Formulation of the CEPUs into inks suitable for continuous inkjet (CIJ) printing produced defined images which upon treatment with base solutions could be removed from the substrate. Having been engineered for circularity, the parent CEPUs can be recycled postdegradation into daughter CEPUs, maintaining their depolymerizable and "debond-on-demand" properties. This work highlights how commercially available starting materials can be utilized to generate highly tailorable polymeric adhesives and inkjet binders capable of rapid depolymerization, ultimately providing an industrially attractive system to increase the recyclability and sustainability of waste materials.