Coumarin-based polyurethane with triple-shape memory effect, photo-responsive self-healing, photolithography, and dual-mode encoding/decoding for smart data transfer

Human future needs are moving toward the use of intelligent materials providing multiple smart functionalities in a single system. Herein, thermo and photo-responsive shape memory polyurethanes (SMPUs) with several smart functionalities were developed for different applications, including sensors and actuators, anti-counterfeiting inks, ink-free rewritable media, self-healing coatings, and smart data transfer. The SMPUs were prepared based on semi-crystalline polycaprolactone soft segments, as the thermo-responsive shape memory switches, and coumarin-based chain extenders, as the photo-responsive groups. The photo-induced reversible cycloaddition reactions of the coumarin groups upon UV light irradiation provides a photo-responsive shape memory effect. Moreover, the diverse fluorescence emission intensities of the dimerized and undimerized coumarin groups presented the photolithography ability of the samples. Fourier-transform infrared spectroscopy and differential scanning calorimetry studies showed that the presence of coumarin bulky groups and their dimerization under UV irradiation substantially changed the microphase separation of SMPUs. The mechanical studies showed that the morphological variation in SMPUs structure transforms the mechanical behavior of the samples from highly cross-linked mechanical behavior to a more ductile one. In addition, the photo-induced cross-linking of PU chains results in a 3D network with high coumarin content, which improved mechanical strength of the samples. Resistance against swelling in hot dimethylformamide verified dimerization of the coumarin groups. This study follows a complete report on the synthesis, characterization, and some smart functionalities of the coumarin-based SMPUs.