Development of semi-crystalline polyurethane with self-healing and body temperature-responsive shape memory properties

Recently, polyurethane (PU) with multifunctionality has attracted significant attention in biomedical applications. This study reports semi-crystalline PUs with both shape memory and self-healing effects, which are composed of poly(ε-caprolactone) diol (PCL), isophorone diisocyanate (IPDI), and 1, 4-butanediol (BDO). The hard segment content greatly influences the structure, morphology and properties, and the increasing hard segment content promotes the phase separation and reduces the crystallizability of the soft segments. Herein, a new self-healing morphology of the semi-crystalline SMPUs is observed, and the self-healing mechanism is ascribed to the diffusion of soft segments and the stability of the hard domains. The relationship between the self-healing efficiency and the stability of hard domains is also explored. Furthermore, the shape memory mechanism of IPDI-based PU is clarified. Based on the partial melting state of the soft segment crystals, the PUs feature relatively good shape memory properties, and the response temperature can be designed as body temperature (37 °C). As the hard segment content increases, the value of shape fixity increases, while that of shape recovery decreases, which is related to hydrogen bonding between polymer chains. Considering the excellent biocompatibility, the as-designed semi-crystalline SMPUs are expected to be used as smart biomaterials in biomedical devices.