Synthesis And Properties Of Heterocyclic Liquid Crystal And Dichroic Liquid Crystal Dyes

With the continuous development of display technology,people have increasingly high requirements for the quality of LCD display screens.As a key optoelectronic material for liquid crystal displays,the performance of liquid crystal materials determines the quality of liquid crystal displays.Introducing heteroatoms into liquid crystal molecules greatly affects the physical properties of liquid crystals by changing dipole moments,conjugated electrons,and dielectric constants,demonstrating good application potential in display devices.In addition,adding dichroic dyes to liquid crystals is an important way to improve the contrast of liquid crystal displays,with advantages such as high brightness,low power consumption,and bright colors.In order to improve the outstanding problems of the current display devices,such as slow response speed,high driving voltage and low contrast,two series of dibenzo heterocyclic liquid crystals and a series of anthraquinone dichoroic liquid crystal dyes were designed and synthesized with dibenzofuran,dibenzothiophene and anthraquinone as the parent body.The structure of the intermediate and target compound was identified through nuclear magnetic resonance spectroscopy,infrared spectroscopy,and mass spectrometry,and the properties of the synthesized target compound were studied and analyzed.The specific research content were as follows:(1)Using 2-bromo-6-fluorophenol and 2,3-difluoro-4-ethoxyphenylboronic acid as raw materials,a series of dibenzofuran compounds(Series A)were designed and synthesized through suzuki coupling,williamson etherification,oxidation and other reactions.Compounds A3 and A4 have two types of liquid crystal textures: smetic and nematic,with liquid crystal phase ranges exceeding 80 ℃.The dielectric anisotropy value of compound A4 is-11.62,and the optical anisotropy value is 0.179.After the combination of A3 and A4 with liquid crystal XH3002,the response time of liquid crystal XH3002 was reduced by 6.5 ms and 8.2 ms,and the threshold voltage was reduced by 0.398 V and 0.453 V.(2)Using 2-bromo-6-fluorophenol and 2,3-difluoro-4-ethoxyphenylboronic acid as raw materials,a series of di Benzothiophene compounds(B series)were designed and synthesized through suzuki coupling,nucleophilic substitution,esterification and other reactions.This series of compounds all have liquid crystal phase and exhibit two types of liquid crystal textures:smetic and nematic.The liquid crystal phase range exceeds 100 ℃,and compound B1 has a widest liquid crystal phase range of 117.3 ℃.Compound B2 maintains a wide liquid crystal phase range,with a dielectric anisotropy value of-12.1 and an optical anisotropy value of 0.186.After the combination of B1-B3 with liquid crystal XH3002,both can reduce the response time and threshold voltage of liquid crystal XH3002.Among them,the addition of B2 reduces the response time of liquid crystal XH3002 by 9.0 ms and the threshold voltage by 0.510 V.(3)Using 2-methylanthraquinone as raw material,three anthraquinone dye compounds containing different carbon chain lengths(C series)were designed and synthesized through nitrification,oxidation,reduction and other reactions.The maximum absorption wavelength of this series of compounds in dichloromethane solvent is about 627 nm,located in the visible light region,and appears blue in the solid state.The ordered parameters of compounds C1-C3 are all greater than 0.65,with the highest order parameter of C3 reaching 0.75.The display device prepared based on C series compounds as guest bodies dissolved in the main liquid crystal XH3032 has a display contrast range of 1.41-1.67,which is up to 29.46% higher than the existing blue anthraquinone liquid crystal dyes.