On-demand photo-controlled motion enabled by solvent-driven mesogen alignment switch

Azobenzene mesogen, as a typical photo-responsive material, has potential possibility in the field of soft robots based on its trans-cis isomerization. The alignment of the azobenzene mesogen in a polymer network has a decisive impact on the photo-actuation behavior of the membrane. However, the alignment of mesogens is difficult to change after being determined, which limits the diversity of actuation modes. To solve this problem, this paper proposes a facile solvent treatment approach to reversibly change the alignment of mesogens in the polymer network. The as-prepared membrane demonstrates reversible photo-actuation behavior under UV-vis irradiation based on the strong penetration of the solvent into the polymer network, leading to disruption of the original ordered alignment of the mesogen. Promising application of a photo-driven membrane floating and sinking in the liquid phase is demonstrated. The results of this study are of great significance for the design and fabrication of a novel-type azobenzene actuator in the liquid phase.