Self-Healable and Reprocessable Cross-Linked Poly(urea-urethane)\nElastomers with High Mechanical Performance Based on Dynamic Oxime–Carbamate\nBonds

Abstract

Owing\nto excessive energy consumption and environmental deterioration,\nthermosets with permanent covalent crosslinks have encountered unprecedented\nchallenge in the sustainable development. An effective method to address\nthis intractable problem is to construct covalent adaptive networks\nthat contain dynamic covalent bonds. Herein, self-healable and reprocessable\ncross-linked poly­(urea-urethane) elastomers with high mechanical performance\nwere simply developed by introducing dynamic oxime–carbamate\nbonds (POUUs). The studies on nuclear magnetic resonance indicated\nthat the sufficient exchange rather than the reversible dissociation\nof oxime–carbamate bonds was the key to network arrangement\nat elevated temperatures. Due to the incorporation of strong polar\nurea bonds, POUUs showed excellent mechanical performance with a tensile\nstrength of 27.8 MPa and toughness of 52.5 MJ m^–3. The good self-healing ability of POUUs was demonstrated by the\ndisappearance of scratches at 80 °C after 15 h. All POUUs were\neasily remolded (130 °C, 5 MPa) into transparent films with a\nmaximum recovery efficiency of 80%. Furthermore, complete dissolution\nin <i>N</i>,<i>N</i>-dimethylformamide was achieved\nat 100 °C after 4 h, exhibiting high recyclability of the cross-linked\nPOUUs.