Mechanically Robust yet Body-Temperature Self-Healable Polyurethane Elastomer via the Cross-Linking of Dynamic Boroxines

It has been a long-standing goal to develop self-healable polyurethane elastomers with desirable mechanical strength and toughness to satisfy the needs of practical applications. However, the conflict between mechanical strength and self-healing efficiency makes the development of such materials very challenging. Here, we have developed a mechanically robust and body-temperature self-healable polyurethane elastomer via the synergy of multiple dynamic reversible non- and covalent interactions in the polymer networks. The design selects flexible 1,4-butanediol bis(3-aminopropyl) ether (BBE) as the chain extender to endow the elastomer with toughness and chain flexibility to benefit its self-healing at body temperature. In addition, 4-formylphenylboronic acid (4-FPBA) was used to cross-link the polyurethane prepolymer to enhance the mechanical properties by the dehydration of phenylboronic acids. Therefore, the as-prepared boroxine cross-linked poly(urethane-urea) (PUUI-Boroxine) elastomer exhibited high mechanical strength and toughness of ∼49.2 MPa and ∼162.9 MJ m –3, respectively. Importantly, the damaged PUUI-Boroxine elastomer can be healed with a high healing efficiency of 91% at 37 °C for 15 h. The PUUI-Boroxine elastomer can also be solution reprocessed for at least three cycles with only a minimal decline in its mechanical properties. Finally, the PUUI-Boroxine elastomer can be employed to fabricate a body-temperature self-healable watchband. This work provides a facile strategy for the development of body-temperature self-healable polyurethane elastomers with outstanding mechanical strength and toughness.