Tunable Circularly Polarized Luminescence Enabled by Photo-Induced Phase Transition in a Blue-Phase Liquid Crystal with a Wide Room-Temperature Window.

Abstract

Chiral luminescent liquid crystal (LC) materials with switchable circularly polarized luminescence (CPL) signals have received extensive attention, in which the use of light stimulation to achieve different CPL states is of great significance. However, there are very few reports on the generation and regulation of CPL signals enabled by blue phase LC (BPLC). Herein, achieving CPL signal inversion based on the phase transition induced by light/temperature stimulation in a BPLC system with a wide room-temperature window is reported. A binaphthalene azo-based chiral photoswitch (S)-switch 3 with high helical twisted power (HTP) and large HTP variation is synthesized, and a BP system with a wide room temperature range is further fabricated by doping (S)-switch 3 and a fluorescence molecule into a bulk LC. By regulating the doping amount of (S)-switch 3, a phase transition from BP to cholesteric (Ch) phase at room temperature is observed upon 365 nm UV light irradiation or during cooling process, and the polarization inversion of CPL signal is correspondingly found due to the different CPL generation mechanisms of BPLC and CLC. This study provides a new strategy for the flexible regulation of CPL signals in a BPLC system.