Fabrication of dual dynamic crosslinking polyurethane networks towards self-healing, resist fatigue, and highly stretchable ionic skins

The limited anti-fatigue performance of self-healing polyurethane elastomers under high-strain conditions restricts their application in high-performance ionic skins. Herein, a polyurethane network (PU-DDN) synergistically reversibly crosslinked by dynamic thiourethane bonds and hydrogen bonds was synthesized successfully. This dual reversibly crosslinking strategy not only endowed the polyurethane network with an excellent fatigue resistance (showing a residual strain of only 63 % after 10 uninterrupted cyclic tensile tests at 400 % strains), but also imparted it with a high strength (6.12 MPa) and stretchability (611.42 %). Owing to the thermo-reversibility of dual dynamic networks, the damaged PU-DDN heated at 100 °C for 3h could fully restore its initial mechanical properties. Subsequently, transparent stretchable ionic skins were fabricated by mixing the PU-DDN with ionic liquids. A resulting highly-sensitive ionic skin (GF₁ = 1.25, GF₂ = 2.01) named PU-DDN/IL20 demonstrated exceptional durability, which could produce repeatable electrical signals even after 2000 cycles of stretching to an extensive deformation of 400 %. Meanwhile, it can also monitor human motions, showcasing its promising potential in the realm of intelligent wearable applications.