Dual-Functional Biopolyurethane Blends with Shape-Memory and Self-Healing Properties: Effects of Mixed Hard Domains on Structures and Properties

Thermoplastic biopolyurethanes (bio-TPUs) with shape-memory and self-healing properties exhibit promising application in smart medical devices. The phase structure plays a crucial role in designing dual-functional bio-TPUs, and the stability of the hard domain can directly affect the structure and properties of bio-TPUs. It is of high application value to simultaneously optimize the shape-memory and self-healing properties of TPUs by adjusting the composition of the hard domain. In this study, two kinds of TPUs containing either alicyclic isocyanate [isophorone diisocyanate (IPDI)] or aliphatic isocyanate [hexamethylene diisocyanate (HDI)] were prepared, and tunable thermoresponsive shape-memory and self-healing dual-function blends were constructed by solution blending of IPDI-based PU (I-PU) and HDI-based PU (H-PU). Based on the hydrogen bonding between the urethane groups, the two types of hard segments in the blend could self-assemble into mixed hard domains, and the phase-transition temperature of hard domains could be increased from 130 to 163 degree celsius with the addition of H-PU. It is worth noting that the self-assembly of the hard segments weakened the effect on the chain motion of the soft segments, resulting in an increased crystallized ability of the soft segments. Hence, the shape-memory behavior of the blends could be modified according to the H-PU content. The increase of the H-PU content decreased the shape fixity (100-93.1%) and recovery ratios (96.2-76.7%) of the blends but increased the stability of the shape-memory process. Meanwhile, the mixed hard domains served as the stationary phase, and the chain motion of the soft segments at 60 degree celsius imparted self-healing properties to the blends. Combined with excellent biocompatibility, the designed blends are promising to be used in various cutting-edge applications, such as tissue scaffolds, smart clothing, and wearable devices.