High-Efficiency Circularly Polarized Luminescence from Chiral Luminescent Liquid Crystalline Polymers with Aggregation-Induced Emission Properties

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.