Preparation, photo-induced deformation behavior and application of hydrogen-bonded crosslinked liquid crystalline elastomers based on α-cyanostilbene

Abstract

Photoresponsive liquid crystalline elastomers have seen significant advancements in the past decades owing to their significant value in the design of light-driven soft actuators. At present, almost all the reported photochemical-responsive liquid crystalline elastomers were constructed using azobenzene as the photoresponsive group. The choice of the photochemical-responsive group is limited. In this article, a series of α-cyanostilbene liquid crystalline elastomers with different flexible spacer lengths (LCE-mCS, m = 0, 2, 4, 6, 8, and 10) cross-linked by multiple hydrogen bonds were successfully synthesized. The phase structures have been investigated by the combination of differential scanning calorimetry (DSC), polarized optical microscopy (POM) and 1D wide-angle X-ray diffraction (1D WAXD). The research results show that LCE-mCS exhibit a smectic phase. The influence of spacer length on the photo-driven bending behavior of LCE-mCS was also studied. The results show that under UV irradiation, the uniaxially oriented LCE-mCS fibers bend toward the light source along the fiber axis, and show a fast photoresponse speed and large deformation. Their maximum bending angles and bending speed increase with the increasing spacer length. The trans–cis isomerization of α-cyanostilbene mesogens and their photothermal effect act together on the deformation of fibers, which leads to excellent photoinduced deformation properties of LCE-mCS fibers. In addition, the application of LCE-mCS in information encryption materials was also studied.