High-Efficiency Circularly Polarized Luminescence from Chiral Luminescent Liquid Crystalline Polymers with Aggregation-Induced Emission Properties
Zhi‐Wang Luo, Lei Tao, Cheng-Long Zhong, Zheng-Xing Li, Kai Lan, Yu Feng, Ping Wang, He‐Lou Xie
Abstract
Circularly polarized luminescent materials play an increasingly important role in display equipment and optical apparatuses. Herein, we design and synthesize a kind of luminescent liquid crystalline polymer with both chirality and aggregation-induced emission groups, namely, poly(4-cholesterol formate-oxygen-tetraphenylethylene-methacrylate) (PT-Chol). Polarized light microscopy and X-ray scattering results show that the polymer forms a layered structure. Because of the existence of the tetraphenylethylene luminogen, the polymer shows highly efficient circularly polarized luminescence (CPL) properties with a luminescence dissymmetry factor (glum) of ∼+0.45 after blending a specified amount of 4-cyano-4′-pentyl biphenyl (5CB), although the pure polymer does not show any CPL behavior in the solid state. A further experimental result shows that the mixture of PT-Chol and 5CB can form a chiral nematic liquid crystal (N*-LC) or smectic C* (Sm C*) phase in low concentration, but the complete dissolution of PT-Chol in 5CB does not result in the development of CPL properties. Gradually increasing the concentration of PT-Chol leads to the development of aggregation-enhanced emission behavior in the 5CB solution, which results in highly efficient CPL properties in the Sm C* phase. At the same time, the obtained circularly polarized luminescent material shows excellent stability, which is conducive to its applications in optoelectronic devices.