Engineered Functional Segments Enabled Mechanically Robust, Intrinsically Fire‐Retardant, Switchable, Degradable PolyureThane Adhesives

Adhesives are being used ubiquitously, such as automotive, building, electronics, and beyond. Due to the lack of rational design strategies, they have yet to achieve a performance portfolio: mechanically robust, highly adhesive, fire‐retardant, switchable, and sustainable (e.g., biobased, reusable, biodegradable) to ensure their practical applications. Herein, a fire‐retardant phosphorus‐containing pimaric acid bio‐derivative, AD, as functional segments, is rationally engineered to prepare biobased polyurethane (PU) adhesive that realizes such an integrated performance portfolio. Because of dynamic hydrogen‐bonding and π–π stacking of polar AD, the as‐prepared PU adhesive exhibits an ultrahigh adhesion force of 38.8 N cm–1. As‐prepared adhesive can be readily reused benefiting from its good solubility in ethanol and exhibits temperature‐responsive switchable adhesion without degraded adhesion. Also, the adhesive shows intrinsic fire retardance due to its biphasic modes of action. The labile ester bonds in the structure enable the adhesive to completely degrade in the presence of lipase or dilute acid. Further demonstration of its promising applications as an adhesive for nanocomposite heat dissipators shows superior dissipating efficiencies to commercial heat sinks. This work offers a novel design approach for creating next‐generation sustainable high‐performance adhesives with functional integration and circular life cycles, which are anticipated to find extensive real‐world applications. By introducing a unique hard segment combining acrylic pimaric acid and 9,10‐dihydro‐9‐oxa‐10‐phospaphenantrene‐10‐oxide, a robust, fire‐retardant, switchable, and sustainable polyurethane adhesive is developed, demonstrating a superhigh adhesion force, a fully recovered adhesion using ethanol, an on‐demand debonding ability, a dual‐mode degradability and a self‐extinguishing ability, holding great potential as next‐generation functional sustainable adhesives.