Smart healable polyurethanes: sustainable problem solvers based on constitutional dynamic chemistry

Abstract

As a kind of polymeric material with high flexibility and durability, polyurethanes (PUs) are widely used in industry, electronic products, construction, transportation and medical fields. The introduction of healing ability can greatly enhance the service lives and recyclability of PUs. Over the past decade, this dream has come closer to reality with the development of polymer networks containing dynamic bonds, which are capable of healing their physical properties and unique functions after damage to polyurethane materials. However, high chain mobility is frequently required to achieve restoration in healable PUs, which inevitably leads to degradation of intrinsic mechanical properties, especially the tensile stress and Young's modulus. Herein, the synthesis, mechanical properties, healing performance of intrinsic healable PUs based on different types of supramolecular interactions and reversible covalent bonds are discussed, aiming at summarizing some strategies to resolve the tradeoff between mechanical properties and healable performances. Moreover, various PU-based nanomaterials have been summarized to improve the mechanical properties, to facilitate the healing process by stimulation, and to endow them with special functions. Finally, the potential applications, challenges and prospects in the field of healable PU composites are also elaborated in the final part of this paper.