Soft-Segment-Tuned Dynamic Polyurethanes With Low Compression Set and Recyclability

High-performance polyurethane (PU) elastomers fundamentally suffer from a trade-off between structural resilience and recyclability. Herein, we propose a strategy to reconcile this dichotomy by developing Diels-Alder (DA) dynamic covalently cross-linked PU elastomers (DAPU-EEs) with precisely tailored polyether-to-polyester soft segment ratios. Systematically modulating this composition elucidates the structure-property relationship, enabling the programmable optimization of mechanical robustness, thermal stability, and dynamic responsiveness. Empowered by the thermoreversible DA network, the optimized elastomer (DAPU-EE2) exhibits efficient recyclability, retaining pristine mechanical properties after multiple hot-pressing cycles. Crucially, DAPU-EE2 demonstrates a remarkably low compression set of 15%, representing a 40% improvement over typical commercial TPU sealing materials. Furthermore, it exhibits superior solvent resistance and highly efficient processability with significantly reduced complex viscosities. Ultimately, this work provides a practical material design strategy that balances demanding mechanical performance with sustainable reprocessing, demonstrating promising potential for advanced sealing applications.