Induction of a helical superstructure in photoresponsive liquid crystals: switching from linearly polarized to circularly polarized luminescence

Abstract

Polarized luminescence materials with switchable handedness or emission characteristic have garnered much attention due to their enormous potential applications in new photonic and photoelectric fields. Here a novel α-cyanodiarylethene-based chiral fluorescent photoswitch, namely switch 1, is firstly designed and synthesized. To our surprise, the helical twisting power (HTP) of switch 1 shows an obvious increasing trend during the irradiation of visible light (450 nm) and it can recover partly under ultraviolet light (UV, 365 nm) exposure. On the basis of this observation, light-induced formation of a cholesteric superstructure is proposed in a photoluminescent liquid crystal (LC) doped with switch 1. Correspondingly, switching from linearly polarized to circularly polarized luminescence happens during the induction of the cholesteric superstructure since the HTP of switch 1 sharply increases upon irradiation with visible or ultraviolet light. Furthermore, an ingenious approach of “dual-polarization fluorescence mode” information storage combining photoalignment and the blue-light-input way is demonstrated, which possesses potential value for advanced information encryption applications.