Novel photo-thermal staged-responsive supramolecular shape memory polyurethane complex

Abstract

Photo-responsive polymers attracted a great deal of interest in recent years. This paper reports a facile preparation of supramolecular shape memory polyurethane complexes from the pyridine-containing polyurethanes and azobenzene-containing mesogens. The results showed that the azobenzene-containing mesogens are grafted on the polyurethane networks via hydrogen bonds between pyridine rings and carboxyl of mesogens. The addition of azobenzene-containing mesogens greatly affected the intermolecular interactions, increasing the glass transition temperature, thermal stability, and storage modulus while promoting the micro-phase separation. The complexes exhibited multi-shape memory properties and excellent photo-thermal staged-responsive shape memory properties showing photo-responsive deformation, temporary shape fixation under visible light irradiation at room temperature and thermal-responsive shape recovery. Particularly, the photo-deformation was achieved even at 2 wt % mesogens added to the polymer network. However, the photo-response greatly increased when the content of mesogen reached 6 wt%. Finally, the proposed mechanism of photo-deformation revealed that this property is due to the photo-isomerization of azobenzene groups of the mesogens, whereas the shape recovery was ascribed to the thermal-responses of polymer networks. It is thus anticipated that these supramolecular polyurethane complexes could be widely applied in smart devices, photo-thermal sensors, and other fields.