Molecular engineering of a colorless, extremely tough, superiorly self-recoverable, and healable poly(urethane-urea)...

Polyurethane or polyurea elastomers with superb mechanical strength and toughness, good self-recoverability and healable characteristics are of key significance for practical applications. However, some mutually exclusive conflicts among these properties make it challenging to optimize them simultaneously. Herein, we report a facile strategy to fabricate a colorless healable poly(urethane-urea) elastomer with the highest reported mechanical toughness and recoverable energy dissipation capability (503.3 MJ m^-3 and 37.3 MJ m^-3 recovered after 7× stretching). These results were achieved via implanting a large number of irregularly arranged urea H-bonds into units of hard domains of weak and soft, self-healing polymer, which led to a dramatic increase in the Young's modulus, tensile strength, toughness, and fracture energy, while maintaining dynamic adaptiveness and responsiveness. Similar to other external stimuli, such as heat, light, or electricity, etc., trace solvent is capable of dissociating noncovalent crosslinks, promoting the mobility of polymer chains surrounding the fracture surface, and thus endowing the elastomer with healability. Impressively, this elastomer possessed outstanding impact-resistance and energy-absorbing ability, even under relatively high temperature. Moreover, it recovered this functionality even after severe deformation or accidental mechanical damage.