Cholesteric Liquid Crystal Polymer Networks Doped with an Axially Chiral Fluorescent Dye: Circularly Polarized Luminescence and Anti‐Counterfeiting Applications

Abstract Circularly polarized luminescence (CPL) of chiral luminescent materials has gained increasing attention because of their significant applications in 3D displays, chiral optoelectronics, anti‐counterfeiting, and encryption. A strongly emissive chiral dye BAcT is synthesized using (R)‐BINOL as the chiral source and a tetraphenylethene group as the fluorophore. Upon the addition of BAcT to the nematic liquid crystal, a left‐handed cholesteric structure is induced. Different concentrations of R/S5011 as chiral co‐dopants are added to prepare a series of structurally colored cholesteric liquid crystal polymer network (CLCN) films. CPL bands are detected for these green emissive CLCN films, and relatively high |glum| values (up to 0.48) are obtained. Furthermore, a fluorescent PMMA‐BAcT layer is prepared by embedding the dye in the PMMA matrix and stacked with a CLCN layer to construct a composite film. Because of the chiral filtering effect of the CLCN film, a high |glum| value up to 1.41 is successfully achieved. Colorful CLCN patterns are prepared, and clear pictures are observed in both reflective and fluorescent modes, contributing to optical anti‐counterfeiting with enhanced security. This work not only provides a deeper understanding of CPL, but also establishes a practical strategy to prepare colorful CLCN patterns for anti‐counterfeiting using inkjet printing technology.