Trifunctional Disulfide-Cross-Linked Polyurethane Networks: Balancing Mechanical Robustness and Dynamic Exchange for Functional Thermoacoustic Restoration

Intrinsic self-healing polyurethanes (PUs) based on dynamic covalent chemistries offer great promise for extending the operational lifespan of flexible electronic devices. However, simultaneously achieving high mechanical robustness and efficient self-healing remains a fundamental challenge due to the inherent trade-off between network cross-linking density and polymer chain mobility. Herein, we report a robust, transparent, and intrinsically self-healing polyurethane elastomer featuring a dynamic junction architecture constructed via a trifunctional disulfide-containing cross-linker (Tri-HEDS). By strategically positioning dynamic disulfide units at network junction points, we systematically modulated the network topology, cross-linking density, and intermolecular hydrogen-bonding interaction. Increasing the cross-linker (Tri-HEDS) significantly enhanced the Young’s modulus and thermal rigidity while maintaining dynamic exchangeability, leading to a nonmonotonic dependence on cross-linker content. Crucially, moving beyond conventional morphological and mechanical healing metrics, the developed SHPU network was integrated into flexible, transparent thermoacoustic(TA) loudspeakers to evaluate functional durability. The device demonstrated full restoration of electrical continuity and acoustic sound pressure level (SPL) output following surface scratch damage and subsequent thermal healing. This study establishes a rational molecular design strategy for dynamic covalent polymer networks, bridging the gap between topological cross-linking control and functional device reliability.