CN-117660019-B - Liquid crystal compound with high birefringence, synthesis method, liquid crystal composition and application

Abstract

The invention discloses a liquid crystal compound with high double refractive index, a synthesis method, a liquid crystal composition and application thereof, wherein the structural general formula of the liquid crystal compound is shown as formula I; the liquid crystal compound and the composition thereof not only have ultrahigh double refractive indexes, but also have the advantages of lower viscosity and wide nematic phase temperature range, and can be used for preparing photoelectric devices and microwave devices.

Inventors

• LI JIAN
• SHI FENGJIAO
• WU YIN
• Bai pujiang
• HU MINGGANG
• Wan danyang
• MO LINGCHAO
• CHE ZHAOYI
• LI JUANLI
• YANG CHENG
• ZHANG LU
• HU ZHIGANG

Assignees

• 西安近代化学研究所

Dates

Publication Date

20260505

Application Date

20220823

Claims (10)

1. 1. The liquid crystal compound with high birefringence is characterized in that the structure of the liquid crystal compound is shown as any one of the structures in the general formula I-4~I-5: Wherein R is selected from hydrogen, chlorine or alkyl with 1-10 carbon atoms.
2. 2. A liquid crystal composition comprising a first component comprising one or more liquid crystal compounds selected from the group consisting of claim 1.
3. 3. The liquid crystal composition of claim 2, further comprising a second component comprising one or more liquid crystal compounds of formula II: Wherein R 2 is selected from alkyl with 1-10 carbon atoms, and X 8 and X 9 are independently fluorine or hydrogen.
4. 4. A liquid crystal composition according to claim 3, further comprising a third component comprising one or more liquid crystal compounds of the general structural formula III: Wherein: R 1 is alkyl with 1-10 carbon atoms, alkenyl with 2-10 carbon atoms, fluorinated alkyl with 1-10 carbon atoms, fluorinated alkenyl with 2-10 carbon atoms or cycloalkyl with 3-10 carbon atoms, X 5 、X 6 and X 7 are independently fluorine, chlorine, hydrogen, methyl or ethyl; k. m, n and p are independently 0 or 1; And when R 1 is alkenyl or fluorinated alkenyl and the ring A is a benzene ring, at least one ethylene is separated from the alkene bond in R 1 and the benzene ring.
5. 5. The liquid crystal composition according to claim 2,3 or 4, wherein the first component is 1 to 100% by mass, the second component is 0 to 90% by mass, and the third component is 0 to 90% by mass.
6. 6. The liquid crystal composition of claim 2, 3 or 4, wherein the liquid crystal composition has a birefringence of greater than 0.40 at 25 ℃ and 589 nm.
7. 7. The liquid crystal composition according to claim 2, 3 or 4, characterized in that the liquid crystal composition has a rotational viscosity of less than 500mpa.s at 25 ℃.
8. 8. The liquid crystal composition according to claim 2, 3 or 4, wherein the liquid crystal composition has dielectric anisotropy Δε of 1.4 or more and tunability of 0.34 or more at high frequency of 19 GHz.
9. 9. Use of a liquid crystal composition according to claim 2, 3 or 4 for the preparation of an optical element.
10. 10. Use of a liquid crystal composition according to claim 2, 3 or 4 for the preparation of a microwave assembly.

Description

Liquid crystal compound with high birefringence, synthesis method, liquid crystal composition and application Technical Field The invention belongs to the technical field of liquid crystal materials, and particularly relates to a liquid crystal compound with a wide liquid crystal phase temperature range, a high birefringence and a low viscosity, a synthesis method thereof, a composition containing the liquid crystal compound and related applications. Background Liquid crystal materials are widely used in electro-optical display devices, such as various liquid crystal televisions, desktop liquid crystal displays, mobile display terminals, and the like. Applications other than display of liquid crystals are also important. By utilizing the birefringence characteristics of the liquid crystal, an optical phase modulation device based on the liquid crystal can be manufactured. The method is favorable for dielectric constant difference of liquid crystal at high frequency, and microwave and terahertz phase shifters, metamaterial holographic phased array antennas and the like based on liquid crystal materials are developed. In addition, liquid crystal materials also have great application potential in the field of laser communication, for example, liquid crystal-based wavelength selective switches have been used in 5G/6G optical communication. The development of these new components requires liquid crystal materials with high birefringence, low viscosity and wide liquid crystal temperature range. The higher the birefringence of the liquid crystal material is, the phase modulation amount is increased, and the thickness of the liquid crystal device is reduced, so that the response speed of the liquid crystal is improved. The lower the viscosity of the liquid crystal is, the response time is advantageously shortened, and the response speed is improved. Thus, for new component applications, new liquid crystal materials with birefringence (589 nm) greater than 0.4, and even greater than 0.5, are needed. The liquid crystal having an isothiocyanate group (NCS) at the molecular end has a large birefringence due to a large conjugated group. Literature (Xianyu,H.,Gauza,S.et al.High birefringence and large negative dielectric anisotropy phenyl-tolane liquid crystals.Liquid Crystals,2007,34(12):1473-1478) reports that NCS liquid crystals comprising a phenyldiphenylacetylene backbone, although having a birefringence close to 0.5, have a high rotational viscosity. Literature (Catanescu,C.O.,S.-T.Wu,et al.Tailoring the physical properties of some high birefringence isothiocyanato-based liquid crystals.Liquid Crystals,2004,31(4):541-555) reports that NCS liquid crystal compounds containing an end group conjugated with a benzene ring have higher birefringence, but a nematic liquid crystal phase temperature zone is relatively narrow, and when the liquid crystal compounds are applied to a microwave frequency band, dielectric loss of the liquid crystal structure is found to be larger, and further improvement is needed. Disclosure of Invention In view of the shortcomings or drawbacks of the prior art, the present invention provides, in one aspect, a liquid crystal compound having a high birefringence. Therefore, the structure of the liquid crystal compound provided by the invention is shown as a general formula I: Wherein R is selected from hydrogen, fluorine, chlorine or alkyl with 1-10 carbon atoms; X 1～X4 is independently fluorine, chlorine, hydrogen or methyl, and when X 1 = hydrogen and X 3 = hydrogen, one or both of X 2 and X 4 are not fluorine atoms. Optionally, the structure of the liquid crystal compound is shown as any one of the structures of the general formula I-1~I-5: The invention also provides a synthesis method of the liquid crystal compound. The provided synthesis method comprises the following steps: (1) Reducing the 4-bromophenyl ketone derivative into a 4-bromophenyl alcohol derivative in the presence of a reducing agent sodium borohydride or potassium borohydride; (2) Reacting the 4-bromophenyl alcohol derivative with hydrochloric acid or hydrobromic acid to convert the halogen substituent; (3) Reacting the halogen substituent with a base to eliminate a portion of hydrogen halide and obtain 4-bromobenzene substituted alkene; (4) Reacting 4-bromobenzene substituted alkene with an ethynylation reagent under palladium catalysis to obtain phenylacetylene derivatives, wherein the ethynylation reagent is selected from trimethylsilylacetylene or 2-methylbutynyl alcohol; (5) Under the action of alkali, the phenylacetylene derivative eliminates trimethylsilyl or acetone to obtain phenylacetylene intermediate; (6) Coupling the phenylacetylene intermediate with iodized or brominated aniline under palladium catalysis to obtain a diphenylacetylene intermediate; (7) The reaction of the diphenylacetylene intermediate with thiophosgene gives the liquid crystal compound of claim 1. The synthetic reaction equation is shown as follo