UV Reconfigurable Shape Memory Polyurethane with a High Recovery Ratio under Large Deformation

The shape memory thermoplastic polyurethane (TPU) generally exhibits a phase-separated structure, in which the hard segments form the hard domains via hydrogen bonds, and plays an important role in shape recovery. However, the physical interaction in the hard domains is always weak, resulting in a permanent deformation and thus decreasing the shape-recovery ability of TPU significantly. In this research, a new type of diol chain extender containing anthracene groups was synthesized, and the photoresponsive anthracene groups were incorporated into the hard segment of TPU. The stability in hard domains and recoverability could be tailored by different UV irradiation times via the photodimerization of anthracene groups, and the shape-recovery ratio and the shape-fixing ratio were still both above 93%, even when the strain reached 270%. More importantly, the shape-free reconfiguration is achieved through the dimerization of anthracene groups under UV irradiation, which achieved free construction of three-dimensional (3D) shapes without templates. Thus, the spontaneous shape change from two-dimensional (2D) to 3D was realized, in combination with melting transition, and the dedimerization of anthracene ensured the recyclability of polyurethane at T = 150 °C. This simple and facile strategy could be used to fabricate the recyclable and photoplasticity shape memory TPU with a high shape-fixing/recovery ratio at large deformation, and it would have a wider range of potential application in stents.