Regulating the Photodeformation Behavior of Azobenzene-Containing Polyimide via Thermal Treatment

Photodeformable polymers have significant potential for untethered smart actuation due to their rapid response and versatile deformation behaviors. However, altering deformation behaviors typically requires preparing materials with different macromolecular structures. Here, we achieved controllable reversal of photodeformation behaviors (bending away from or toward the light source) in side-chain azobenzene polyimides by adjusting the thermal treatment conditions. Different thermal treatments introduced variations in the internal free volume of the material, leading to two distinct deformation mechanisms under blue light exposure and resulting in opposite macroscopic deformation behaviors. By choosing appropriate thermal treatment methods, we fabricated actuators with specific functionalities and utilized the correlation between deformation behavior and thermal treatment to demonstrate a detector for thermal history. This postsynthesis regulation of the photodeformation behavior offers a convenient and repeatable manner to engineer actuation on demand.