Smart Shape Memory Polyurethane with Photochromism and Mechanochromism Properties

The combination of shape memory effects and multi-functionalities in smart materials is becoming one of the hottest research directions in the field of actuators and robotics. In this study, N-hydroxyethyl-3,3-dimethyl-6-nitroindoline spiropyran (SP) is chemically grafted into a polyurethane matrix to prepare ultraviolet light-actuated shape memory thermoplastic polyurethane, which first integrates three unique properties including shape memory, photochromism, and mechanochromism. The FTIR, WAXD, SAXS, DSC, TGA, and shape memory tests reveal that the shape memory transformation temperature of 4.6 wt% SP-based shape memory polyurethane is 41.2 °C, and it has the highest shape memory performance, as indicated by shape fixation and shape recovery ratios of 97.4% and 93.7%, respectively. Furthermore, “bionic fingers” with diversely selective actuation properties are fabricated, which exhibit a series of programmable multi-segment motions to meet potential applications in the field of soft actuators.