Research On The Properties Of CPL Materials Based On Luminescent Liquid Crystal

Circularly polarized luminescence（CPL）materials exhibit unequal emission intensity of left-and right-circularly polarized light under light radiation.When used in liquid crystal displays or other devices,it can achieve high-contrast three-dimensional image display effect,so it has broad application prospects.However,it is still a great challenge to obtain CPL materials with high g_em and high luminescence quantum efficiency(Ф_FL).Liquid crystal is a kind of soft material with both anisotropy and fluidity.In this paper,CPL material systems were constructed with luminescent liquid crystal molecules.Through efficient self-assembly process of liquid crystal,the system obtained a more orderly spiral structure,realized the transfer and amplification of chirality,and finally obtained excellent CPL performance.The main research contents include:1.Doped liquid crystal CPL material based on fluorescent liquid crystal polymerChiral binaphthyl derivative molecules（Guest-1）and achiral fluorescent liquid crystal polymer（Guest-2）were designed and synthesized.Guest-1 were doped into commercial liquid crystal 5CB to form binary cholesteric liquid crystal with the highest g_em value of 0.17andФ_FL of 19.2%.Subsequently,Guest-1 and Guest-2 were incorporated into 5CB together,and the resulting ternary dispersed cholesteric liquid crystal was induced to show stronger CPL signal,g_em was as high as 0.97,andФ_FL was 52.2%.The results show that in the new ternary dispersed cholesteric liquid crystal,the chirality of binaphthyl derivative molecules was effectively transferred to fluorescent liquid crystal polymer.Due to strong interaction between molecules,a more ordered spiral arrangement structure and chiral amplification effect were formed.It provides a new strategy for preparing doped liquid crystal CPL material with high g_em and highФ_FL.2.Non-doped liquid crystal CPL material based on organic fluorine boron compoundIn order to simplify liquid crystal CPL system and improve its practicability,non-doped liquid crystal CPL material has been further explored.Combining chirality of 1,2-cyclohexanediamine and luminescence properties of fluoroboron compounds,a class of Schiff base fluoroboron compounds with chirality,luminescence and liquid crystallinity were synthesized,named R/S-Salen BF₂.The research results show that R/S-Salen BF₂exhibted obvious thermotropic liquid crystal properties under polarizing microscope,and the clear point is 233℃.Thanks to the high-order self-assembly in liquid crystal state,g_em of neat liquid crystal film was significantly enlarged from 2.8×10^-4（before annealing）to 1.0×10^-2（after annealing at 230℃）.This type of non-doped liquid crystal CPL material is expected to be further applied to preparation of organic light-emitting diodes and other optoelectronic devices.