Azobenzene-Based Light-Sensitive Polyurethane Elastomers with Enhanced Self-Healing and Soft–Hard Switching Proerties

Developing intelligent polyurethane elastomers with balanced high mechanical strength and rapid self-healing capability remains a critical challenge in advanced functional materials. Herein, we designed a kind of polyurethane elastomer of PU-A1D2 by incorporating the azobenzene compound of 3-(4-(p-tolyldiazenyl)phenoxy)propane-1,2-diol (Azo-2) and dimethylglyoxime into the polyurethane matrix as components of the chain extender, where the dual functional groups synergistically contribute to self-healing performance. Dynamic oxime-urethane bonds construct a covalent adaptable network, enabling excellent self-healing in PU-A1D2 via reversible dissociation-association, while light-responsive Azo-2 units undergo photoisomerization, inducing topology transition and reversible soft–hard switching. The resultant PU-A1D2 exhibited a tensile strength of 13 MPa, toughness of 50 MJ m–3, and 95% self-healing efficiency after heat treatment at 80 °C for 12 h, achieving a favorable balance between mechanical robustness and self-healing efficiency. Moreover, PU-A1D2 achieved complete scratch self-healing within 2 h under the synergistic effect of ultraviolet (UV) irradiation and 90 °C. In addition, the 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide (EMIM·TFSI)-doped PU-A1D2-ET achieved almost 100% self-healing efficiency within merely 10 min under room-temperature UV irradiation. This work clarifies the regulatory mechanism of azobenzene on polyurethane self-healing and provides a promising design strategy for fabricating high-performance polymer elastomers integrated with outstanding mechanical properties and rapid light-controlled self-healing, which holds great potential in flexible electronics and smart wearable devices.