Stimuli-Responsive Polyurethane Actuator Triggered by Light and Heat Reinforced With Disulfide Bonds

The photoisomerization behavior of mesogenic azobenzene makes it possible to convert light energy into mechanical action. However, achieving durability, configurability, and flexibility of light-responsive actuators for artificial intelligence applications remains challenging. Here, a light responsive polyurethane (AzoPU-SS) with remarkable anti-fatigue and anti-stress properties has been synthesized through the combination of dynamic disulfide bonds and mesogenic azobenzene functional groups. The AzoPU-SS film demonstrated excellent photo-induced bending, under ultraviolet (UV) light exposure, indicating effective transfer of molecular deformation from the microscopic to the macroscopic level. Moreover, the AzoPU-SS material's elongation at break was greatly increased, due to the dynamic and reversible nature of the flexible S-S and H bonds, enabling the coordinated motion of azobenzene groups and producing significant deformation. Such a reinforced strategy could be used to design smart actuators with superior stretchability and toughness, helping to broaden the applications of light-responsive actuator materials.