High-performance easy-degradable and recyclable thermosetting polyurethanes via dynamic cross-linking and abundant hydrogen bonding for foam sensor applications

Developing degradable and recyclable thermosetting polyurethanes represents a significant step toward environmental protection and resource conservation. However, achieving these properties often compromises mechanical performance and thermal stability. To address this challenge, we developed a high-performance degradable and recyclable thermosetting polyurethane (IP-AD-BA1) by integrating dynamic cross-linkers with abundant hydrogen bonding. First, a polyurethane prepolymer was synthesized using adipic dihydrazide (AD), a chain extender enriched with hydrogen bond donors and acceptors, to generate abundant hydrogen bonding within the polyurethane structure. This prepolymer was then cross-linked to form IP-AD-BA1 using boric acid as the dynamic cross-linker. Comparisons with other polyurethanes of the same type reveal that IP-AD-BA1 exhibits excellent comprehensive performance. This includes outstanding mechanical properties (tensile strength of 51.1 MPa and toughness of 152.1 MJ m −3 ), as well as thermal stability (5% weight loss temperature of 322.5 °C). Moreover, IP-AD-BA1 offers rapid recyclability under mild conditions (110 °C, 15 MPa) while maintaining its mechanical and thermal properties after recycling. It can also be degraded in ethanol, enabling recovery as a linear polyurethane oligomer. Finally, we utilized IP-AD-BA1 to fabricate recyclable foam sensors capable of effectively detecting strain and stress, thereby broadening the potential applications of thermosetting polyurethanes.