Liquid Crystals Doped with Chiral Fluorescent Polymer: Multi‐Color Circularly Polarized Fluorescence and Room‐Temperature Phosphorescence with High Dissymmetry Factor and Anti‐Counterfeiting Application

Abstract

AbstractChiral nematic liquid crystals (N*‐LCs) can tremendously amplify circularly polarized luminescence (CPL) signals. Doped emissive N*‐LCs have been substantially explored. However, their CPL performances still need to be improved, mainly due to the unsatisfying helical twisting power (HTP) of commonly used chiral fluorescent dopants. Chiral fluorescent helical polymers (CFHPs) have outstanding optical activity and CPL performance. The present contribution reports the first success in constructing emissive N*‐LCs by doping CFHP into nematic liquid crystals (5CB, N‐LCs). The helical assembly structures of N*‐LCs effectively amplify the CPL signals of the CFHP. Owing to the high HTP of CFHP, the selective reflection band of N*‐LC can be adjusted to fully cover its emission band. A nearly pure CPL with a dissymmetry factor (glum) up to −1.87 is realized at 9 wt% doping concentration. Taking advantage of the selective reflection mechanism, multi‐color CPL‐active N*‐LCs with high glum are fabricated via further adding achiral fluorophores. Also noticeably, circularly polarized room‐temperature phosphorescence with glum up to −1.57 is achieved. Anti‐counterfeiting application is demonstrated by exploiting multi‐mode optical characteristics of the created N*‐LCs. The established strategy for constructing emissive N*‐LCs provides a platform for future exploring of CPL‐active N*‐LCs.