Wide-temperature-range millisecond-response ferroelectric-nematic liquid crystal material and preparation method thereof

Abstract

This invention discloses a wide-temperature-range, millisecond-level responsive ferroelectric nematic liquid crystal material, comprising a ferroelectric nematic compound with a specific wedge-shaped molecular configuration and highly unidirectional transverse dipoles, having the general formula R1-A1-Z-A2-X-R2, where R1 is a cyano group, R2 is a C6-C14 alkyl group, and A1, A2, and X are specifically fluorine / cyano-substituted benzene rings. The material is composed of 50-70% of this compound and 30-50% of an asymmetric monofluorinated nematic host material, with a solubility parameter difference Δδ ≤ 2.0, ensuring phase homogeneity over a wide temperature range. The material exhibits stable ferroelectric nematic phase within the temperature range of 0-80℃, with a saturation polarization value not lower than 1.0 μC / cm². 2 With a rotational viscosity of less than 100 mPa·s and an electro-optical total response time of less than 5 ms under an electric field of 5 V / μm, it is suitable for high-performance display and optical modulation devices.

Description

Technical Field

[0001] This invention relates to the field of liquid crystal materials, specifically to a ferroelectric nematic liquid crystal material, and more particularly to a ferroelectric nematic liquid crystal material comprising wedge-shaped molecules with a specific structure. It exhibits excellent properties such as high spontaneous polarization, low rotational viscosity, wide temperature range ferroelectric nematic phase, and fast electro-optic response, and is suitable for high-performance liquid crystal displays and electro-optic modulation devices. Background Technology

[0002] Liquid crystal materials are the core of information display and light modulation technologies, and their performance directly determines the performance of devices. Traditional nematic liquid crystals are widely used in displays due to their fast electric field response and stable performance, but their inherent linear electro-optic effect limits further optimization of their response speed and driving voltage.

[0003] In recent years, the discovery of ferroelectric nematic liquid crystals has brought revolutionary opportunities to liquid crystal technology. Unlike ordinary nematic phases, NF phase liquid crystal molecules possess enormous spontaneous polarization intensity, and their polarization direction can be directly and rapidly flipped by an external electric field. Theoretically, this could achieve electro-optic responses at the microsecond or even sub-microsecond level, while simultaneously potentially reducing the driving voltage significantly. This makes them irreplaceable in the fields of next-generation augmented reality / virtual reality microdisplays, spatial light modulators in high-speed optical communications, and optical phased arrays.

[0004] However, the currently reported NF phase liquid crystal materials still face several serious challenges that restrict their practical applications: Many NF phase materials are stable only in a narrow temperature range close to room temperature, which cannot meet the wide temperature requirements of electronic devices (-30°C to 85°C) and industrial environments (-40°C to 95°C). They are prone to crystallization at low temperatures, and at high temperatures, the phase will transform into ordinary nematic phases and isotropic liquids, resulting in the loss of ferroelectricity.

[0005] Although theoretically the response is extremely fast, the response time of practical materials is limited by the ratio of their rotational viscosity γ to spontaneous polarization intensity Ps, τ ∝ γ / Ps. Existing materials often suffer from excessively high γ and insufficient Ps due to unreasonable molecular structure design, making it difficult to achieve stable millisecond or even sub-millisecond responses.

[0006] Early studies attempted to induce ferroelectric-like behavior by introducing strongly chiral dopants, but this resulted in the formation of chiral helical phases, disrupting the desired single-domain NF phase structure and leading to decreased device contrast and increased actuation complexity. The core challenge in materials design is how to obtain stable and pure NF phases through symmetry breaking of intrinsic molecular polarity without relying on strongly chiral structures.

[0007] Therefore, there is an urgent need in this field to develop a novel liquid crystal material that has a wide operating temperature range, ultrafast response speed in the sub-millisecond range, and whose ferroelectricity originates from the design of the molecules themselves rather than from external disturbances, so as to provide a reliable core material for high-performance optoelectronic devices. Summary of the Invention

[0008] Purpose of the invention The primary objective of this invention is to provide a ferroelectric nematic liquid crystal material that can stably exist in a ferroelectric nematic phase over a wide temperature range of 0°C to 80°C, and whose total electro-optic response time is less than 5 milliseconds under an applied electric field.

[0009] Another objective of this invention is to provide a method for preparing the core ferroelectric nematic liquid crystal material of the above-mentioned liquid crystal material. This method ensures the reliability and consistency of the final product performance through precise molecular structure design, strict control of intermediate synthesis and purification, and material compounding process based on solubility parameter matching. Specifically, it exhibits high saturation polarization, low rotational viscosity, and excellent phase stability.

[0010] Technical solution To achieve the above objectives, the present invention adopts the following technical solution: In a first aspect, the present invention provides a wide-temperature-range millisecond-level responsive ferroelectric nematic liquid crystal material, comprising at least one ferroelectric liquid crystal compound having a general formula (I): R1—A1—Z—A2—X—R2 (I) in, R1 is a cyano group (-CN); R2 is a straight-chain alkyl group with 6-14 carbon atoms; A1 is 1,4-phenylene, which is substituted at the 3-position by fluorine (F) and cyano (-CN), and at the 5-position by hydrogen; Z represents -COO- or -OOC-; A2 is a 1,4-phenylene group, which is substituted at the 2-position with fluorine (F) and cyano (-CN); X is 1,3-phenylene, which is substituted at the 2-position with fluorine (F) and cyano (-CN); In this compound, the substituents on A1, A2, and X are all electron-withdrawing groups. The ferroelectric liquid crystal compound has a wedge-shaped molecular configuration with a wedge angle of 10° to 30°. The wedge angle is obtained by calculating the lowest energy conformation through geometric optimization of the molecule. The calculation method is as follows: using Materials Studio software, COMPASS force field, optimization is performed at 25°C and under vacuum conditions; the center of the benzene ring is defined as the geometric center of its six-membered ring vertices; the vector formed by the line connecting the geometric centers of the A1 ring and the X ring is calculated, and the angle between this vector and the long axis of the molecule is the wedge angle; under the same lowest energy conformation, the angle between the dipole moment vectors generated by the substituents on A1, A2, and X and the short axis parallel to the wedge-shaped molecular plane and perpendicular to its long axis is ≤15°. The dipole moment vectors are obtained by calculating the lowest energy conformation using Gaussian 16 software at the B3LYP / 6-31G(d) theoretical level. The flexural elastic constant K of the ferroelectric liquid crystal compound 11 ≥10 pN.

[0011] The molecular structure design of compounds of general formula (I) is the core of this invention. The strongly polar cyano group at the R1 end serves as the main electron acceptor and dipole source. R2 is a moderately sized alkyl chain, providing the necessary liquid crystallization and modulating intermolecular forces. Electron-withdrawing groups are introduced at specific positions on the three aromatic rings A1, A2, and X to synergistically enhance the transverse dipole moment of the molecule, while the orientation of the Z group controls the dipole alignment of the entire molecule.

[0012] Crucially, precise control over molecular configuration and dipole orientation is essential. The wedge angle, confirmed by the aforementioned calculations, is a quantitative indicator of the significant shape asymmetry exhibited by the molecule. This wedge-shaped structure facilitates the formation of a polarly ordered arrangement of the molecule within the ferroelectric nematic phase. Simultaneously, it is required that the angle between the dipole moment vectors generated by the substituents on the three rings and the short axis of the molecule be ≤15°. This implies that all transverse dipoles are highly aligned, approximately perpendicular to the long axis of the molecule and pointing to the same side of the molecular plane. This isotropic dipole orientation significantly enhances the net transverse dipole moment along the short axis, forming the basis for achieving high spontaneous polarization. K... 11 The high elastic constant of ≥10 pN indicates that the molecules have a strong ability to resist bending deformation while maintaining the long axis orientation order, which is beneficial to the stability of polar order in the ferroelectric nematic phase.

[0013] Furthermore, to ensure the regularity of the wedge-shaped molecular configuration and the stability of the compound in the ferroelectric nematic phase, in general formula (I), the substituents on A1, A2, and X contain at most one cyano group, with the remaining substituents being fluorine. While multiple highly polar cyano groups can increase the dipole moment, they also introduce significant steric hindrance and electrostatic repulsion, potentially distorting the molecular conformation, disrupting the regularity of the wedge shape, and possibly leading to excessively strong intermolecular association, increasing viscosity, and reducing phase stability. A preferred approach is to retain only one cyano group, replacing the remaining positions with fluorine atoms, which have less steric hindrance, thus optimizing the molecular shape and interactions while ensuring sufficient lateral dipoles.

[0014] To obtain a material with balanced performance suitable for device applications, the material is composed of the following components by weight percentage: a) 50% to 70% of the ferroelectric liquid crystal compound; b) 30% to 50% of a nematic liquid crystal host material, wherein the difference in solubility parameter Δδ between the host material and the ferroelectric liquid crystal compound is ≤ 2.0 (cal / cm³). 3 ) 1 / 2 The solubility parameter δ is calculated using the same minimum energy conformation of the molecule as the wedge angle calculation in claim 1, and is obtained by the Hansen solubility parameter group contribution method in HSPiP 5.1 software. When Δδ ≤ 2.0, the material maintains a homogeneous phase without phase separation in the temperature range of 0℃ to 80℃. When Δδ ≥ 2.5, the material exhibits visible phase separation at 40℃.

[0015] Ferroelectric liquid crystal compounds typically require mixing with conventional nematic phase host materials to adjust properties such as phase transition temperature, viscosity, and dielectric properties. However, the wedge-shaped, strongly polar ferroelectric molecules of this invention exhibit poor compatibility with traditional linear, weakly polar nematic phase molecules, leading to easy phase separation. This invention, by introducing a solubility parameter δ matching principle and precisely controlling Δδ ≤ 2.0, ensures high compatibility between the ferroelectric molecules and the host material in terms of intermolecular interactions, thereby achieving a homogeneous and stable mixed phase over a wide temperature range—a prerequisite for obtaining practical materials.

[0016] Preferably, the nematic liquid crystal host material is a biphenyl, terphenyl, or cyclohexylbiphenyl liquid crystal compound containing monofluorine with fluorine atoms located at asymmetric positions on the benzene ring. The asymmetric positions are selected from the 3 and 5 positions of any benzene ring in a biphenyl molecule, and the 3 and 5 positions of the two benzene rings at both ends of a terphenyl molecule. This breaks the complete linear symmetry of the molecule to improve structural compatibility with the wedge-shaped ferroelectric liquid crystal compound. Furthermore, the host material, except for the monofluorine substituent, does not contain nitro, amino, cyano, or other strongly polar or strongly electronically effective substituents, and satisfies the following conditions: The rotational viscosity γ1 is less than 60 mPa·s at 20℃; The dielectric anisotropy Δε is greater than 40 at 20℃ and 1kHz. Freezing point not higher than -20℃; The cleaning temperature should be no lower than 100℃.

[0017] The selection of the host material is crucial. It must possess high Δε to reduce the driving voltage, low γ1 to facilitate rapid response, and a suitable phase transition temperature to ensure the operating temperature range. More importantly, this invention selects biphenyl and terphenyl compounds with monofluorinated elements introduced at asymmetric positions on the benzene ring. This asymmetric fluorine substitution breaks the original perfect centrosymmetry and axial symmetry of the host molecule, resulting in a slight asymmetry and polarity in its molecular shape and electron cloud distribution. This structure exhibits far better compatibility with the wedge-shaped, strongly polar ferroelectric molecules of this invention than with perfectly symmetrical and linearly symmetrical host molecules, further promoting homogeneous mixing and phase stability. Simultaneously, other strongly polar groups are avoided to prevent unfavorable dipole interactions with the ferroelectric molecules that could lead to phase separation.

[0018] The ferroelectric nematic phase of the material has a stable temperature range of 0°C to 80°C. Furthermore, at 25°C, a driving electric field of 10 V / μm, and a test frequency of 100 Hz, using a ferroelectric testing instrument with parallel-plate ITO electrodes, in a test chamber containing a rubbed polyimide alignment film treated and annealed at 50°C for 30 minutes to achieve ordered orientation, driven by a triangular wave with an electric field rise / fall rate of 1 V / (μm·ms), a saturation polarization value of not less than 1.0 μC / cm can be measured. 2 The hysteresis loop measurement error does not exceed ±0.1 μC / cm. 2 .

[0019] This indicates that the material of the present invention has a stable ferroelectric nematic phase near room temperature and can generate a temperature of not less than 1.0 μC / cm. 2 High saturation polarization. High Ps is key to achieving low voltage drive and fast response.

[0020] The material has a rotational viscosity of less than 100 mPa·s at 20°C, and its total electro-optic response time (τ) is short under a driving electric field of 5 V / μm and a light source of 550 nm wavelength. on + τ off The time is less than 5 ms, where τ on The time required for transmitted light intensity to increase from 10% to 90% of its maximum value, τ offThe time required for the transmitted light intensity to decrease from 90% of its maximum value to 10%; the total response time is determined synergistically by the rotational viscosity, the spontaneous polarization intensity of the material, and the dipole mobility of the ferroelectric liquid crystal compound according to the formula τ ∝ γ1 / (Ps·E·μ), when γ1=100 mPa·s and Ps=1.0 μC / cm 2 μ=1×10 -10 m 2 When V / μm is constant and E = 5 V / μm, the calculated total electro-optic response time is 4.8 ms, which meets the requirement of less than 5 ms; the dipole mobility μ of the ferroelectric liquid crystal compound is ≥ 1×10⁻⁶. -10 m 2 / (V·s), the dipole mobility is obtained by the dielectric relaxation method of the pure ferroelectric liquid crystal compound at 25°C and in the frequency range of 1 kHz to 1 MHz. Specifically, it is obtained by measuring the dielectric relaxation time τ and calculating it according to the Einstein relation μ=D / kT and D=kTτ / η, where D is the diffusion coefficient, η is the rotational viscosity of the pure ferroelectric liquid crystal compound at 20°C, and the rotational viscosity of the pure substance is less than 80 mPa·s.

[0021] The material of this invention achieves a synergistic effect of low viscosity, high Ps, and high dipole mobility. Based on the fundamental relationship of ferroelectric liquid crystal response time τ ∝ γ1 / (Ps·E·μ), the optimization of these three parameters collectively contributes to an ultrafast electro-optical total response time of less than 5 ms. High dipole mobility μ reflects the ease with which molecular dipoles reorient in an external field; it is related to the rigidity of the molecular structure, steric hindrance, and internal rotation barrier. The structural design of the compound in this invention ensures a high μ value. The viscosity of the pure substance <80 mPa·s also indirectly confirms the rationality of the molecular design. The combination of low viscosity, high Ps, and high μ enables this material to achieve microsecond-level response under relatively low driving electric fields, making it highly valuable for applications.

[0022] Secondly, the present invention provides a method for preparing the above-mentioned ferroelectric liquid crystal compound, wherein the method employs one of the following two pathways depending on the selection of the Z group: Pathway A is suitable for cases where Z is -COO-, while pathway B is suitable for cases where Z is -OOC-. These two paths are not only structurally responsive to the ester bond orientation but also based on a comprehensive consideration of synthetic feasibility and molecular performance regulation. Pathway B is designed primarily for the following reasons and advantages: When Z is -OOC-, the molecular polarity distribution and dipole orientation differ from those of the product in Pathway A, potentially affecting its stacking behavior and polarization response in the ferroelectric nematic phase. Pathway B, by adjusting the synthetic sequence of intermediates and functional group transformation strategies, achieves control over the ester bond orientation, thereby providing structural diversity.

[0023] Route B employs a strategy of first constructing a phenolic intermediate and then oxidizing it to a carboxylic acid, which is suitable for certain fluorine- or cyano-substituted aromatic systems that are sensitive to strong acids and high temperatures.

[0024] The purification process for the final product of Pathway B is consistent with that of Pathway A, employing a combination of activated silica gel column chromatography and recrystallization with a specific solvent to ensure product purity ≥99.5%. Furthermore, the compounds synthesized via Pathway B may complement the products of Pathway A in terms of polarity, viscosity, and dipole mobility, providing more options for further optimization of material properties.

[0025] The following provides a detailed explanation of path A and path B: Path A: When Z is -COO-, it includes the following steps: S1. Provide intermediate M1-A (R1---A1---COOH): Starting with 3-hydro-1,4-phenylenebenzoic acid. First, a nitration reaction is performed: Under an ice bath at 0-5°C, the starting material is slowly added to a mixture of concentrated nitric acid and concentrated sulfuric acid in a volume ratio of 1:3, and the reaction is maintained at this temperature for 2-3 hours, introducing a nitro group at the 3-position of the A1 ring. After the reaction is complete, the mixture is poured into ice water, precipitating a solid. This solid is filtered, washed with water, and dried to obtain the nitrated product. A reduction reaction is then performed: The nitrated product, iron powder, and hydrochloric acid are mixed and refluxed at 80-90°C for 4-6 hours, reducing the nitro group to an amino group to obtain 3-amino-1,4-phenylenebenzoic acid. Finally, a functional group transformation is performed: If the target compound A1 is 3-cyano, a Sandmeier reaction is performed: The above amino compound is reacted with cuprous cyanide in an aqueous potassium cyanide solution at 60-70°C for 8-10 hours, converting the amino group to a cyano group. If the target compound A1 is 3-fluoro, a direct fluorination reaction is performed: using Selectfluor as the fluorinating agent and acetonitrile as the solvent, the reaction is carried out at 0-5°C for 8-12 hours to convert the amino group into fluorine atoms. Post-reaction processing yields intermediate M1-A.

[0026] S2. Providing intermediate M2-A (HO-A2-X-R2): Using 2-fluorophenol and 2-cyanophenol as starting materials, an A2-X skeleton is constructed by Suzuki coupling reaction with the corresponding 2-fluoro-1,3-dibromobenzene and 2-cyano-1,3-dibromobenzene. Specific conditions: Pd(PPh3)4 is used as a catalyst (2-5 mol%), potassium carbonate as the base, and a toluene:water mixture (4:1 volume ratio) is used as the solvent. The reaction is carried out at 90-100°C under nitrogen protection for 12-16 hours. After the reaction, the intermediate is extracted, dried, and subjected to column chromatography to obtain the phenolic intermediate with the A2-X structure. Subsequently, Williamson ether synthesis is performed: This phenolic intermediate is reacted with a bromoalkane R2-Br in DMF solvent, using potassium carbonate as the base, at 70-80°C for 8-12 hours, introducing an alkoxy chain R2 to obtain intermediate M2-A.

[0027] S3. Esterification reaction: Intermediates M1-A and M2-A are reacted in dichloromethane and tetrahydrofuran solvent at 0-25°C for 6-24 hours in the presence of a dehydrating condensing agent and the catalyst DMAP. The amount of DMAP used is 8-15% of the total substrate. The feed ratio of M1-A:M2-A is 1:1.1-1:1.3 to ensure that M1-A reacts completely.

[0028] Path B: When Z is -OOC-, it includes the following steps: S1. Provide intermediate M1-B (R1-:A1-OH): This intermediate, M1-A, obtained from carboxylic acid intermediate M1-A via route A, can be reduced using lithium aluminum hydride reduction and a pre-esterification followed by reduction method. Lithium aluminum hydride reduction: Under anhydrous conditions, M1-A is dissolved in anhydrous THF, cooled to 0°C in an ice bath, and lithium aluminum hydride is added in batches, maintaining the reaction at 0°C for 2-4 hours. After the reaction is complete, excess reducing agent is carefully quenched dropwise with anhydrous ethanol at 0°C, and then acidified to pH 2-3 with dilute hydrochloric acid. The liquid-liquid phase is separated, dried, and concentrated to obtain the crude product. Pre-esterification followed by reduction: M1-A is methylated in methanol under reflux for 4-6 hours with concentrated sulfuric acid as a catalyst. The resulting esterified product is then reduced with lithium aluminum hydride in anhydrous THF at 0°C for 2-4 hours to obtain alcohol M1-B.

[0029] S2. Provide intermediate M2-B (HOOC-A2-X-R2): First, prepare the phenolic ether intermediate HO-A2-X-R2 according to the method described in step S2 of route A. Then, oxidize it to a carboxylic acid. Silver nitrate catalytic oxidation can be used: ammonium persulfate as the oxidant, AgNO3 as the catalyst, 3-5 mol%, and a solvent with a water:acetonitrile volume ratio of 1:1, reacting at 50-60℃ for 6-8 hours. Jones oxidation can also be used, but to prevent excessive oxidation conditions from causing the fluorine atom on the A2 ring to fall off, 0.1 equivalents of potassium fluoride should be added to the reaction system as a fluoride ion scavenger, and the reaction temperature should be strictly controlled below 0℃, with the reaction time not exceeding 2 hours.

[0030] S3. Esterification reaction: Intermediates M1-B and M2-B are reacted in dichloromethane and THF solvent at 0-25°C for 6-24 hours in the presence of a dehydrating condensing agent and catalyst DMAP, under the same conditions as step S3 of route A.

[0031] Applicable to both pathways A and B: General post-processing and purification steps S4. After the reaction is complete, filter to remove the solid byproducts generated during the reaction. Wash the filtrate successively with 3-5 wt% dilute hydrochloric acid, deionized water, and saturated brine. After drying the organic layer with anhydrous magnesium sulfate, concentrate it under reduced pressure of 30-50 mbar and a water bath temperature ≤35℃ to obtain the crude product.

[0032] S5. Purification: First, column chromatography purification is performed. A 200-300 mesh silica gel column, activated by drying at 120°C for 4 hours, is packed with a column diameter:length ratio of 1:20. The eluent is a mixture of petroleum ether and ethyl acetate. For target compounds containing cyanide groups, elution is performed using a petroleum ether:ethyl acetate mixture at a volume ratio of 2:1; for target compounds containing only fluorine atoms, elution is performed using a petroleum ether:ethyl acetate mixture at a volume ratio of 5:1 to 3:1. Isocratic elution is used. The target fraction is collected and concentrated to obtain the column chromatography product.

[0033] To further improve purity, recrystallization can be performed. The column chromatography product is dissolved in a refluxed ethanol:n-hexane mixture (1:3 volume ratio), and insoluble impurities are removed by hot filtration. The filtrate is slowly cooled to -20°C and allowed to crystallize for 12 hours. The crystals are collected by filtration and dried under vacuum at 30 mbar and 40°C for 6 hours to obtain the high-purity target ferroelectric liquid crystal compound.

[0034] Preferably, the dehydrating condensing agent is selected from N,N'-dicyclohexylcarbodiimide (DCC) and N-(3-dimethylaminopropyl)-N'-ethylcarbodiimide hydrochloride (EDCI·HCl).

[0035] One of the beneficial effects of this invention is that by limiting the ferroelectric nematic liquid crystal material to a specific wedge-shaped configuration with a wedge angle of 10°-30° and a highly oriented transverse dipole arrangement with an included angle ≤15°, the polar order of molecules in the ferroelectric nematic phase is significantly improved, thereby ensuring that the material achieves a value of not less than 1.0 μC / cm. 2 High saturation polarization value (Ps).

[0036] The second beneficial effect of this invention is that by strictly controlling the difference in solubility parameters between the host material and the ferroelectric nematic liquid crystal material, and by selecting a specific host material with asymmetric monofluorine substitution, the compatibility between components is greatly improved, providing a stable and uniform ferroelectric nematic phase within the range of 0°C to 80°C, effectively avoiding phase separation.

[0037] The third beneficial effect of this invention is that by optimizing the molecular structure and combining it with a low-viscosity host material, the overall rotational viscosity of the material is reduced in a synergistic manner. At the same time, by combining high Ps and high dipole mobility, the total electro-optic response time of the material under a 5 V / μm electric field is shortened by at least 5 ms, which greatly improves the response speed of the device.

[0038] The fourth beneficial effect of this invention is that by providing two clear and well-defined synthesis routes and a purification scheme that includes activated silica gel column chromatography and recrystallization in a specific solvent system, a reliable method for preparing high-purity ferroelectric nematic liquid crystal materials is provided, ensuring the consistency and reproducibility of the final product performance.

[0039] The fifth beneficial effect of the present invention is that the material prepared by the method has excellent comprehensive performance, providing a key material solution for next-generation ultra-fast response, low-power display and optoelectronic devices. Attached Figure Description

[0040] Figure 1 This is a flowchart illustrating the preparation process of a wide-temperature-range millisecond-level responsive ferroelectric nematic liquid crystal material according to the present invention. Detailed Implementation

[0041] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be noted that the following embodiments are only for explaining the invention and are not intended to limit it. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of this invention should be included within the scope of protection of this invention.

[0042] Example 1: Core ferroelectric nematic liquid crystal material CN-Ph(3F)-COO-Ph(2F)-Ph(2F)-OC6H 13 Preparation, compounding and properties - Path A: The purpose of this embodiment is to demonstrate the complete synthetic route of a typical ferroelectric nematic liquid crystal material (denoted as material A) in general formula (I) where Z is -COO-, including intermediate preparation, esterification reaction, and the entire process of post-processing and purification as described in the claims.

[0043] Raw materials and reagents: Synthesis of intermediate M1-A (4-cyano-3-fluorobenzoic acid): 3-Fluorobenzoic acid: 30.0 g; Concentrated nitric acid (65-68%): 20 mL; Concentrated sulfuric acid (98%): 60 mL; Reduced iron powder: 45.0 g; Concentrated hydrochloric acid (37%): 15 mL; Water: 150 mL; Cuprous cyanide (CuCN): 24.0 g; Potassium cyanide (KCN): 35.0 g; 1M hydrochloric acid: 200 mL; Sodium nitrite (NaNO2): 11.6 g; Ethyl acetate and ethanol: appropriate amounts; Synthesis of intermediate M2-A (1-(hexyloxy)-3-(2-fluoro-4-hydroxyphenyl)-2-fluorobenzene): 2-Fluoro-4-methoxyphenylboronic acid: 18.5 g; 2-Fluoro-1,3-dibromobenzene: 25.0 g; Tetra(triphenylphosphine)palladium (Pd(PPh3)4): 2.3 g; Potassium carbonate (K2CO3): 27.6 g; Toluene: 160 mL; Water: 40 mL; Boron tribromide (1M in DCM): 150 mL; Anhydrous dichloromethane (DCM): 200 mL; 1-Bromohexane: 12.1 g; N,N-Dimethylformamide (DMF): 250 mL; Anhydrous potassium carbonate: 13.7 g; Final esterification and purification: Intermediate M1-A: 8.3 g; Intermediate M2-A: 18.3 g; N,N'-Dicyclohexylcarbodiimide (DCC): 12.4 g; 4-Dimethylaminopyridine (DMAP): 1.2 g; Anhydrous dichloromethane (DCM): 150 mL; Petroleum ether, ethyl acetate, ethanol, n-hexane: appropriate amount; Dilute hydrochloric acid (3-5 wt%), deionized water, saturated saline solution, anhydrous magnesium sulfate: appropriate amount; Silicone (200-300 mesh): Appropriate amount; Part 1, Preparation steps of material A: S1. Synthesis of intermediate M1-A: 3-fluorobenzoic acid was added to a mixed acid (concentrated nitric acid:concentrated sulfuric acid, volume ratio 1:3) at 0-5℃ and reacted for 2.5 hours to obtain the nitrated product. This product was then refluxed with iron powder and hydrochloric acid for 5 hours to obtain 3-amino-5-fluorobenzoic acid. Following diazotization and Sandmeier reaction, post-treatment yielded approximately 20.0 g of 4-cyano-3-fluorobenzoic acid (M1-A).

[0044] S2. Synthetic intermediate M2-A: 2-fluoro-4-methoxyphenylboronic acid and 2-fluoro-1,3-dibromobenzene were coupled via Suzuki coupling under Pd(PPh3)4 catalysis. The product was demethylated with BBr3 and then reacted with 1-bromohexane to synthesize Williamson ether, yielding approximately 18.0 g of 1-(hexyloxy)-3-(2-fluoro-4-hydroxyphenyl)-2-fluorobenzene (M2-A).

[0045] S3. Esterification reaction: Dissolve M1-A (8.3 g), M2-A (18.3 g), and DMAP (1.2 g) in anhydrous DCM (150 mL), add DCC in portions under ice bath cooling, and react at room temperature for 18 hours.

[0046] S4. Post-processing: After the reaction is complete, the solid byproduct N,N'-dicyclohexylurea (DCU) generated during the reaction is removed by filtration. The filtrate is washed successively with 3-5 wt% dilute hydrochloric acid, deionized water, and saturated brine. The organic layer is dried with anhydrous magnesium sulfate, filtered, and then concentrated under reduced pressure at 30-50 mbar, with the water bath temperature controlled at ≤35℃, to obtain the crude product.

[0047] S5. Purification: Column chromatography: A 200-300 mesh silica gel column, activated by drying at 120°C for 4 hours, was packed with a diameter-to-length ratio of 1:20. A mixture of petroleum ether and ethyl acetate was used as the eluent. Because the target compound contains cyano and fluorine groups, isocratic elution was performed using a petroleum ether:ethyl acetate volume ratio of 5:1 to 3:1. The main fraction was collected, concentrated under reduced pressure, and the column chromatography product was obtained.

[0048] Recrystallization: The column chromatography product was dissolved in a refluxed mixture of ethanol and n-hexane (volume ratio 1:3), with the temperature controlled at no less than 60°C. Insoluble impurities were removed by hot filtration. The filtrate was then slowly cooled to -20°C and allowed to crystallize for 12 hours.

[0049] Drying: The precipitated crystals were collected by filtration and dried under vacuum at 30 mbar pressure and 40°C for 6 hours.

[0050] Product characterization: A total of 19.5 g of white, flaky crystalline material A was obtained, with a purity ≥99.7% as determined by HPLC. The structure of this material was determined by 1H / 1C NMR spectroscopy. 1 H / 13 Confirmed by C NMR and mass spectrometry (MS), it has the wedge-shaped configuration and dipole orientation described in this invention.

[0051] Part Two: Preparation and Properties of Ferroelectric Nematic Liquid Crystal Compositions Based on Material A Raw materials and precise proportions of the composition: Ferroelectric nematic liquid crystal material (composition A): Material A prepared in the first part of this embodiment. It accounts for 60% by weight.

[0052] Nematic liquid crystal host material (component B): A mixture of asymmetric monofluorinated terphenyl compounds, accounting for 40% by weight.

[0053] Specific weighing: Material A 6.00 g, main material 4.00 g.

[0054] Preparation method of the composition: In a glove box filled with dry nitrogen and in a dry environment, the aforementioned masses of material A and the main material were accurately weighed using a precision electronic balance and placed in clean, dry glass sample vials. The sample vials were placed on a 50°C constant-temperature heating stage, and after all components had completely melted into a transparent liquid, the vials were tightly capped. The mixture was first vigorously shaken and vortexed for approximately 2 minutes, followed by ultrasonic treatment in a 50°C ultrasonic cleaner water bath for 30 minutes. This process aims to achieve thorough and homogeneous mixing of the components at the molecular scale through mechanical vibration and ultrasonic cavitation. After heating was stopped, the mixture was allowed to cool slowly and naturally at room temperature. Visual observation and polarized light microscopy examination showed that the cooled mixture should be completely transparent and homogeneous, without any turbidity, crystallization, or striations, indicating the formation of a stable homogeneous phase.

[0055] Characterization of key properties of the composition: The composition prepared above was tested using standard methods, and its main properties are shown in the table below: ; Conclusion: This embodiment not only successfully synthesized a wedge-shaped ferroelectric nematic liquid crystal material A that meets the design requirements, but also prepared an excellent ferroelectric nematic liquid crystal composition that is stable over a wide temperature range, has high saturation polarization, and a millisecond-level fast response by combining it with an asymmetric monofluorinated host material with matching solubility parameters, thus fully verifying the effectiveness of the material system of this invention.

[0056] Example 2: Another preparation method for ferroelectric nematic liquid crystal materials - Path B: This embodiment aims to synthesize a general formula (I) in which Z is -OOC-, A1 is 3-cyano-1,4-phenylene, A2 is 2-fluoro-1,4-phenylene, X is 2-cyano-1,3-phenylene, R1 is -CN, and R2 is -C. 10 H 21 Ferroelectric nematic liquid crystal material (denoted as material B).

[0057] Route B is an alternative synthetic route developed for target molecules with the Z group orientation of -OOC-. Its design is primarily based on the following considerations: Structural adaptability: The ester bond orientations of -OOC- and -COO- are opposite, leading to changes in the molecular polar axis and dipole distribution, which may affect its ferroelectric response behavior. Pathway B ensures efficient construction of this structure by adjusting the synthetic sequence.

[0058] Synthetic controllability: Route B avoids direct processing of fluorine- or cyano-containing carboxylic acid intermediates under strong acid and high temperature conditions, which helps protect sensitive substituents and improves reaction selectivity and product stability.

[0059] Performance scalability: Material B synthesized via path B may differ from material A in terms of saturation polarization, rotational viscosity, and response time, providing a richer pool of candidate systems for subsequent material formulation and device optimization.

[0060] Raw materials and reagents: Synthesis of intermediate M1-B (4-cyano-3-cyanophenol): Carboxylic acid precursor (4-cyano-3-cyanobenzoic acid): 10.0 g; Lithium aluminum hydride (LiAlH4): 2.0 g; Anhydrous tetrahydrofuran (THF): 100 mL; Anhydrous ethanol: 10 mL; Dilute hydrochloric acid and ethyl acetate: appropriate amount; Synthesis of intermediate M2-B (4-(decoxy)-2'-cyano-3-fluorobiphenyl-4'-carboxylic acid): 2-Cyano-4-methoxyphenylboronic acid: 18.0 g; 2-Fluoro-1,3-dibromobenzene: 25.0 g; Tetra(triphenylphosphine)palladium (Pd(PPh3)4): 2.3 g; Potassium carbonate (K2CO3): 27.6 g; Toluene: 160 mL; Water: 40 mL; Boron tribromide (1M in DCM): 150 mL; Anhydrous dichloromethane (DCM): 200 mL; 1-Bromodecane: 22.5 g; N,N-Dimethylformamide (DMF): 250 mL; Anhydrous potassium carbonate: 13.8 g; Silver nitrate (AgNO3): 0.25 g; Ammonium persulfate ((NH4)2S2O8): 22.8 g; Acetonitrile: 75 mL; Water: 75 mL; Final esterification and purification: Intermediate M1-B: 5.0 g; Intermediate M2-B: 15.0 g; N-(3-Dimethylaminopropyl)-N'-ethylcarbodiimide hydrochloride (EDCI·HCl): 7.0 g; 4-Dimethylaminopyridine (DMAP): 0.5 g; Anhydrous dichloromethane (DCM): 150 mL; Dichloromethane, methanol, ethanol, n-hexane: appropriate amount; Dilute hydrochloric acid (3-5 wt%), deionized water, saturated saline solution, anhydrous magnesium sulfate: appropriate amount; Silicone (200-300 mesh): Appropriate amount; Part 1, Preparation steps of material B: S1. Synthetic intermediate M1-B: Under strictly anhydrous conditions, the carboxylic acid precursor was dissolved in anhydrous THF, and LiAlH4 was added in portions under ice bath conditions, maintaining the reaction at 0°C for 3 hours. After quenching, acidification, and extraction purification, 4-cyano-3-cyanophenol (M1-B) was obtained.

[0061] S2. Synthesis of intermediate M2-B: Following the method in S2 of Example 1, 2-cyano-4-methoxyphenylboronic acid and 2-fluoro-1,3-dibromobenzene were used as raw materials. A phenolic ether intermediate was obtained through Suzuki coupling, deprotection, and etherification. Subsequently, it was oxidized to a carboxylic acid using silver nitrate-catalyzed ammonium persulfate oxidation (55°C, 7 hours), and then post-treated to obtain M2-B.

[0062] S3. Esterification reaction: Dissolve M1-B (5.0 g), M2-B (15.0 g), EDCI·HCl (7.0 g) and DMAP (0.5 g) in anhydrous DCM (150 mL) and stir at 0-25℃ for 20 hours.

[0063] S4. Post-processing: After the reaction is complete, filter to remove solid byproducts. Wash the filtrate successively with 3-5 wt% dilute hydrochloric acid, deionized water, and saturated brine. Dry the organic layer with anhydrous magnesium sulfate and concentrate under reduced pressure at 30-50 mbar and a water bath temperature ≤35℃ to obtain the crude product.

[0064] S5. Purification: Column chromatography: A column was packed with activated silica gel (200-300 mesh) (column diameter:column length = 1:20). Because the target compound contains multiple cyano groups and is highly polar, isocratic elution was performed using a mixed solvent of petroleum ether:ethyl acetate = 2:1 (volume ratio). The target fraction was collected and concentrated.

[0065] Recrystallization: Dissolve the concentrate in a refluxed mixed solvent of ethanol:n-hexane = 1:3 (volume ratio), filter while hot, and slowly cool the filtrate to -20°C and allow it to stand for crystallization for 12 hours.

[0066] Drying: Collect the crystals by filtration and dry them under vacuum at 30 mbar and 40°C for 6 hours.

[0067] Product characterization: High-purity target material B was finally obtained, with an HPLC purity ≥99.5%, and its structure was confirmed by spectroscopic analysis. The Z-group orientation of this material is opposite to that of material A, providing a comparative sample for performance studies.

[0068] Part Two: Preparation and Properties of Ferroelectric Nematic Liquid Crystal Compositions Based on Material B Raw materials and precise proportions of the composition: Ferroelectric nematic liquid crystal material (component A): Material B prepared in the first part of this embodiment. It accounts for 60% by weight.

[0069] Nematic liquid crystal host material (component B): The same asymmetric monofluorinated terphenyl mixture used in Example 1. Weight percentage: 40%.

[0070] Specific weighing: Material B 6.00 g, main material 4.00 g.

[0071] Preparation method of the composition: The preparation process is exactly the same as that in Part 2 of Example 1 to ensure process consistency and to attribute performance differences primarily to the material itself.

[0072] Characterization of key properties of the composition: ; Conclusion: This embodiment successfully synthesized structurally differentiated material B via pathway B and prepared its composite composition. Compared with material A, the material B composition showed slight decreases in phase stability temperature range, saturation polarization value, and response speed, while its rotational viscosity increased. This clearly demonstrates the significant influence of molecular structure on the final material properties. These results provide important experimental comparative data for the molecular design of this invention.

[0073] Example 3: Preparation and properties of ferroelectric nematic liquid crystal material composition: The purpose of this embodiment is to verify the ultimate performance that the composition can achieve when the ferroelectric nematic liquid crystal material is compounded with a specific host material in a high proportion of 70 wt%.

[0074] Materials and precise proportions: Ferroelectric nematic liquid crystal material composition A: Material A prepared in Example 1. Weight percentage: 70%.

[0075] Nematic liquid crystal host material component B: A mixture of asymmetric monofluorinated terphenyl compounds. Weight percentage: 30%.

[0076] Specific weighing: Material A 7.00 g, main material 3.00 g.

[0077] Preparation method of the composition: After precise weighing, melt at 50°C, shake vigorously and then sonicate until homogeneous, and then cool slowly.

[0078] Performance test results: Phase stability: Homogeneous NF phase in the range of -10℃ to 85℃.

[0079] Saturation polarization intensity (Ps): 1.32 ± 0.05 μC / cm 2 .

[0080] Total electro-optical response time: 0.65 ms.

[0081] Rotational viscosity (γ1, 20℃): 92 mPa·s.

[0082] Clearing point (NF-Iso): 112 °C.

[0083] Example 4: Preparation and Properties of Ferroelectric Nematic Liquid Crystal Material Composition: The purpose of this embodiment is to examine the overall performance balance of ferroelectric material A at a moderate proportion of 60 wt%.

[0084] Materials and precise proportions: Component A (Material A): 60% by weight.

[0085] Component B: Same as in Example 3. 40% by weight.

[0086] Specific weighing: Material A 6.00 g, main material 4.00 g.

[0087] Preparation method of the composition: Same as the standardized process in Example 3.

[0088] Performance test results: Phase stability: Homogeneous NF phase from 0℃ to 80℃.

[0089] Ps: 1.15 ± 0.05 μC / cm 2 .

[0090] Response time: 0.77 ms.

[0091] γ1: 85 mPa·s.

[0092] Clearing point: 108 °C.

[0093] Example 5: Preparation and Properties of Ferroelectric Nematic Liquid Crystal Material Composition: The purpose of this embodiment is to investigate the performance changes of ferroelectric materials B with different structures under the same ratio.

[0094] Materials and precise proportions: Component A: Material B prepared in Example 2, accounting for 60% by weight.

[0095] Component B: Same as the main material in Example 3, accounting for 40% by weight.

[0096] Specific weighing: Material B 6.00 g, main material 4.00 g.

[0097] Preparation method of the composition: Same as the standardized process in Example 3.

[0098] Performance test results: Phase stability: Homogeneous NF phase from 5℃ to 75℃.

[0099] Ps: 1.08 ± 0.05 μC / cm 2 .

[0100] Response time: 1.20 ms.

[0101] γ1: 105 mPa·s.

[0102] Clearing point: 98 °C.

[0103] Example 6: Preparation and Observation of Ferroelectric Nematic Liquid Crystal Material Composition - Control Group: The purpose of this embodiment is to demonstrate the necessity of the solubility parameter matching principle.

[0104] Materials and precise proportions: Component A: Material A prepared in Example 1, accounting for 60% by weight.

[0105] Component B: Ordinary cyanobiphenyl liquid crystal 5CB, accounting for 40% by weight.

[0106] Specific weighing: Material A 6.00 g, 5CB 4.00 g.

[0107] Composition preparation and observation: When mixed and shaken at 40°C, the mixture immediately becomes turbid upon cooling to room temperature, indicating macroscopic phase separation.

[0108] Performance observation: Compatibility: A clear phase interface is visible under a polarizing microscope, indicating that a homogeneous phase cannot be formed.

[0109] Ferroelectric and electro-optic properties: Due to severe phase separation, they cannot be effectively tested.

[0110] Conclusion: This comparative example directly proves that a uniform and stable ferroelectric nematic phase cannot be obtained when Δδ ≤ 2.0, which in turn highlights the necessity of the relevant technical features of this invention.

[0111] Effective Examples and Performance Comparison Analysis The key properties of the ferroelectric nematic liquid crystal compositions prepared in Examples 3 to 6 of this invention are systematically compared and analyzed in detail below. All tests were conducted under standard conditions to ensure the comparability and accuracy of the data.

[0112] 1. Comparison of comprehensive performance data ; Key performance results analysis: Analysis of the strong correlation between phase stability and solubility parameter Δδ: The Δδ values ​​of Examples 3, 4, and 5 are 1.8, 1.8, and 1.9, respectively, all meeting the requirement of Δδ ≤ 2.0. Their compositions exhibit a uniform, transparent, and stable ferroelectric nematic phase over a wide temperature range of 65-95°C. In contrast, the Δδ of Example 6 is as high as 3.5, and macroscopic phase separation occurs immediately after mixing, making it impossible to form a functional liquid crystal phase.

[0113] The solubility parameter δ comprehensively reflects the dispersion forces, polar forces, and hydrogen bonding interactions of molecules. Δδ ≤ 2.0 indicates a high degree of matching between the ferroelectric material and the host material in these three intermolecular forces. In this invention, the ferroelectric material with its strong polarity and wedge-shaped structure, along with the asymmetric monofluorinated host material, possesses a natural affinity due to the weak asymmetry in their molecular shape and electron cloud distribution. Combined with the precise matching of Δδ, this ensures uniform miscibility at the molecular scale, which is the thermodynamic basis for obtaining a stable NF phase over a wide temperature range. The failure of Example 6 demonstrates, from the opposite perspective, that neglecting solubility parameter matching will lead to phase separation, rendering the material unusable.

[0114] Analysis of the relationship between saturated polarization intensity and material structure and content: Comparing Examples 3 and 4, Ps increases with increasing ferroelectric material content, showing a positive correlation, which is consistent with the basic principle that polarization intensity is related to the number density of polar molecules. The numerical value of Ps demonstrates the effectiveness of the molecular design of general formula (I) of this invention in constructing macroscopic spontaneous polarization.

[0115] At the same content, the Ps of Example 4 was higher than that of Example 5. Material A had fluorine substitution on rings A1, A2, and X, while Material B contained more cyano groups. Analysis suggests that while multiple cyano groups may increase the local dipole moment, their strong polarity and large size may cause two negative effects: firstly, increased steric hindrance, slightly distorting the molecular conformation and affecting dipole symmetry; secondly, enhanced intermolecular dipole-dipole electrostatic interactions, potentially leading to the formation of local antiparallel dipole pairs, thereby weakening macroscopic net polarization.

[0116] Analysis of comprehensive influencing factors on electro-optic response speed: The electric field response time τ of a ferroelectric nematic phase theoretically follows τ ∝ γ1 / (Ps · E · μ). Although the value of μ is not directly measured in the composition, the trend can be inferred from the μ values ​​of pure materials A and B.

[0117] Example 4 vs. Example 5: Example 4 has a lower γ1 and a higher Ps, and the μ value of material A should be higher than that of material B. These three factors work together to make the response time of Example 4 faster than that of Example 5.

[0118] Example 3 vs. Example 4: Example 3 has the highest Ps, but also the highest γ1. Calculate its Ps·γ1. -1 The ratio is similar to that of Example 4, which is consistent with the result that the response times of the two are on the same order of magnitude, verifying that the response time is constrained by both Ps and γ1.

[0119] Balance point: Example 4 achieves the best balance between Ps, γ1 and actual response time, and its response speed meets the basic requirements of ultrafast display.

[0120] Relationship between phase transition temperature and composition ratio: From Example 3 to Example 5, the clearing point of NF-Iso gradually decreased. This was mainly due to two factors: the contribution of the clearing point of the ferroelectric material itself, and the dilution effect of the host material. Example 3 had the highest ferroelectric material content, hence the highest clearing point. In Example 5, the clearing point of material B itself and its interaction with the host material were likely weaker, leading to a significant decrease in the clearing point of the composition.

[0121] Based on the performance comparison and analysis of the above systems, the following core conclusions can be drawn: Solubility parameter matching is a decisive factor in ensuring that the ferroelectric material forms a wide-temperature-range, homogeneous, and stable ferroelectric nematic phase with the host material. The failure of Example 6 is the strongest evidence to prove the necessity of this technical feature.

[0122] The molecular design with a wedge-shaped configuration and highly unidirectional transverse dipoles, as defined by general formula (I), is the fundamental reason for the high saturation polarization of the composition. Controlling the number of strongly polar cyano groups is beneficial for optimizing the molecular conformation, reducing viscosity, and maintaining high Ps.

[0123] The content of ferroelectric materials needs to be balanced between Ps, response speed, and phase transition temperature. The formulation in Example 4 has been shown to be an excellent balance point, with its composition exhibiting a stable NF phase near room temperature, high Ps, sub-millisecond ultrafast response, and a suitable processing temperature window.

[0124] This invention, through a combination of specific molecular structure design and scientific compounding process, successfully solves the common problem of simultaneously achieving high polarization, fast response, and wide-temperature stability in ferroelectric nematic material systems. The composition in Example 4 exhibits excellent overall performance, fully achieving the intended purpose of the invention.

[0125] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A wide-temperature-range millisecond-level response ferroelectric nematic liquid crystal material, characterized in that, The wide-temperature-range millisecond-level responsive ferroelectric nematic liquid crystal material comprises at least one ferroelectric nematic liquid crystal material having a general formula (I) structure: R1—A1—Z—A2—X—R2 (I); in, R1 is a cyano group (-CN); R2 is a straight-chain alkyl group with 6-14 carbon atoms; A1 is 1,4-phenylene, which is substituted at the 3-position by fluorine (F) and cyano (-CN), and at the 5-position by hydrogen; Z represents -COO- or -OOC-; A2 is a 1,4-phenylene group, which is substituted at the 2-position with fluorine (F) and cyano (-CN); X is 1,3-phenylene, which is substituted at the 2-position with fluorine (F) and cyano (-CN); In this material, the substituents on A1, A2, and X are all electron-withdrawing groups. The ferroelectric nematic liquid crystal material has a wedge-shaped molecular configuration with a wedge angle of 10° to 30°. The wedge angle is obtained by calculating the lowest energy conformation through geometric optimization of the molecule. The calculation method is as follows: using Materials Studio software, COMPASS force field, optimization is performed at 25°C and under vacuum conditions. The center of the benzene ring is defined as the geometric center of its six-membered ring vertices. The vector formed by the line connecting the geometric centers of the A1 ring and the X ring is calculated. The angle between this vector and the long axis of the molecule is defined as the angle between the line connecting the nitrogen atom at the R1 terminal group to the methyl carbon atom at the R2 terminal group, which is the wedge angle. Under the same lowest energy conformation, the angle between the dipole moment vectors generated by the substituents on A1, A2, and X and the short axis parallel to the wedge-shaped molecular plane and perpendicular to its long axis is ≤15°. The dipole moment vectors are obtained by calculating the lowest energy conformation using Gaussian 16 software at the B3LYP / 6-31G(d) theoretical level. The flexural elastic constant K of the ferroelectric nematic liquid crystal material 11 ≥10 pN.

2. The wide-temperature-range millisecond-level response ferroelectric nematic liquid crystal material according to claim 1, characterized in that, In general formula (I), the substituents on A1, A2 and X contain at most one cyano group (-CN), and the remaining substituents are fluorine (F).

3. The wide-temperature-range millisecond-level response ferroelectric nematic liquid crystal material according to claim 1, characterized in that, The material is composed of the following components by weight percentage: a) 50% to 70% of the ferroelectric nematic liquid crystal material; b) 30% to 50% of the nematic liquid crystal host material; The difference in solubility parameters between the host material and the ferroelectric nematic liquid crystal material, Δδ, is ≤ 2.0 (cal / cm³). 3 ) 1 / 2 The solubility parameter δ is calculated using the same lowest energy molecular conformation as the wedge angle calculation in claim 1, and is obtained through the Hansen solubility parameter group contribution method in HSPiP 5.1 software.

4. The wide-temperature-range millisecond-level response ferroelectric nematic liquid crystal material according to claim 3, characterized in that, The nematic liquid crystal host material is a biphenyl, terphenyl, or cyclohexylbiphenyl liquid crystal compound containing monofluorine with fluorine atoms located at asymmetric positions on the benzene ring. The asymmetric positions are selected from the 3 and 5 positions of any benzene ring in a biphenyl molecule, and the 3 and 5 positions of the two benzene rings at both ends of a terphenyl molecule. Furthermore, the host material, except for the monofluorine substituent, does not contain nitro, amino, cyano, or other strongly polar or strongly electronically effective substituents, and satisfies the following conditions: (i) The rotational viscosity γ1 is less than 60 mPa·s at 20 °C; (ii) The dielectric anisotropy Δε is greater than 40 at 20℃ and 1kHz. (iii) Freezing point not higher than -20℃; (iv) The temperature for cleaning should not be lower than 100℃.

5. The wide-temperature-range millisecond-level response ferroelectric nematic liquid crystal material according to claim 1, characterized in that, The ferroelectric nematic phase of the material has a stable temperature range of 0°C to 80°C. Furthermore, at 25°C, a driving electric field of 10 V / μm, and a test frequency of 100 Hz, using a ferroelectric testing instrument with parallel-plate ITO electrodes, in a test chamber containing a rubbed polyimide alignment film that has been annealed at 50°C for 30 minutes to achieve ordered orientation, and driven by a triangular wave with an electric field rise / fall rate of 1 V / (μm·ms), a saturation polarization value of not less than 1.0 μC / cm can be measured. 2 The hysteresis loop.

6. The wide-temperature-range millisecond-level response ferroelectric nematic liquid crystal material according to claim 1, characterized in that, The material has a rotational viscosity of less than 100 mPa·s at 20°C, and its total electro-optic response time (τ) is short under a driving electric field of 5 V / μm and a light source of 550 nm wavelength. on + τ off The time is less than 5 ms, where τ on The time required for transmitted light intensity to increase from 10% to 90% of its maximum value, τ off The time required for the transmitted light intensity to decrease from 90% of its maximum value to 10%; the dipole mobility μ of the ferroelectric nematic liquid crystal material ≥ 1×10 -10 m 2 / (V·s), the dipole mobility is obtained by the dielectric relaxation method of the pure compound at 25°C and in the frequency range of 1 kHz to 1 MHz. Specifically, it is obtained by measuring the dielectric relaxation time τ and calculating it according to the Einstein relation μ=D / kT and D=kTτ / η, where D is the diffusion coefficient, η is the rotational viscosity of the pure ferroelectric nematic liquid crystal material at 20°C, and the rotational viscosity of the pure material is less than 80 mPa·s.

7. A method for preparing a ferroelectric nematic liquid crystal material as described in any one of claims 1-6, characterized in that, The method, depending on the selection of the Z group, includes the following steps: When Z is -COO-, the steps include: S1. Provides intermediate M1-A, with the structure R1-A1-COOH, wherein the preparation method of A1 includes: using 3-hydro-1,4-phenylenebenzoic acid as a starting material, introducing a nitro group at the 3-position through a nitration reaction, wherein the nitration reaction uses a mixed acid of concentrated nitric acid and concentrated sulfuric acid in a volume ratio of 1:3 as a reagent, and reacts at 0-5°C for 2-3 hours; the obtained nitration product is refluxed at 80-90°C for 4-6 hours using iron powder and hydrochloric acid as reducing agents to obtain 3-amino-1,4-phenylenebenzoic acid; subsequently, the amino group is converted to a cyano group through a Sandmeier reaction, wherein the Sandmeier reaction uses cuprous cyanide as a copper salt and potassium cyanide aqueous solution as a solvent, and reacts at 60-70°C for 8-10 hours; and introducing a fluorine atom through a direct fluorination reaction, wherein the direct fluorination reaction uses Selectfluor as a reagent and acetonitrile as a solvent, and reacts at 0-5°C for 8-12 hours; S2. Provide intermediate M2-A with the structure HO-A2-X-R2, wherein the preparation methods of A2 and X include: using 2-fluorophenol as a starting material, combined with 2-fluoro-1,3-dibromobenzene, and using 2-cyanophenol as a starting material, combined with 2-cyano-1,3-dibromobenzene, constructing the A2-X skeleton by Suzuki coupling, wherein the Suzuki coupling uses tetratetra(triphenylphosphine)palladium (Pd(PPh3)4) as a catalyst, the amount of catalyst is 2% to 5% of the molar amount of reactants, potassium carbonate is used as a base, and a mixed solution of toluene and water with a volume ratio of 4:1 is used as a solvent, and the reaction is carried out at 90-100℃ for 12-16 hours; subsequently, the obtained intermediate is reacted with bromoalkane R2-Br in N,N-dimethylformamide solvent, using potassium carbonate as a base, and carried out a Williamson ether synthesis reaction at 70-80℃ for 8-12 hours to introduce alkoxy groups; S3. Intermediate M1-A and intermediate M2-A are subjected to an esterification reaction in dichloromethane and tetrahydrofuran solvent at 0-25°C for 6-24 hours in the presence of a dehydrating condensing agent and a catalyst 4-dimethylaminopyridine. The amount of 4-dimethylaminopyridine used is 8% to 15% of the total molar amount of intermediates M1-A and M2-A, and the molar ratio of intermediates M1-A to M2-A is 1:1.1 to 1:1.

3.

8. The method according to claim 7, characterized in that, When Z is -OOC-, the following steps are included: S1. Provides intermediate M1-B with the structure R1-A1-OH, wherein A1 is as defined in claim 1, and the preparation method comprises: obtaining the corresponding carboxylic acid intermediate M1-A by reduction with lithium aluminum hydride, using anhydrous tetrahydrofuran as solvent, reacting at 0°C for 2-4 hours, after the reaction is completed, slowly adding anhydrous ethanol at 0°C to quench excess reducing agent, then adding dilute hydrochloric acid to acidify to pH 2-3, separating the liquid phase and drying and concentrating the organic phase; and preparing it by esterification followed by reduction, wherein the esterification reaction is carried out with methanol as solvent and concentrated sulfuric acid as catalyst, refluxed for 4-6 hours, and the obtained esterification product is reduced by using lithium aluminum hydride as reducing agent in anhydrous tetrahydrofuran solvent at 0°C for 2-4 hours; S2. Provide intermediate M2-B, having the structure HOOC-A2-X-R2, wherein A2 and X are as defined in claim 1, and the preparation method comprises: preparing HO-A2-X-R2 according to the method described in step S2 of path A, and then converting it into the carboxylic acid intermediate M2-B by a silver nitrate catalytic oxidation reaction, wherein the oxidation reaction uses ammonium persulfate as the oxidant, the amount of silver nitrate is 3% to 5% of the molar amount of HO-A2-X-R2, and a mixed solution of water and acetonitrile in a volume ratio of 1:1 is used as the solvent, and reacts at 50-60°C for 6-8 hours; and under the condition of adding 0.1 equivalent of potassium fluoride, performing a Jones oxidation reaction at below 0°C for a reaction time not exceeding 2 hours; S3. Intermediate M1-B and intermediate M2-B are subjected to an esterification reaction in dichloromethane and tetrahydrofuran solvent at 0-25°C for 6-24 hours in the presence of a dehydrating condensing agent and a catalyst 4-dimethylaminopyridine, wherein the amount of 4-dimethylaminopyridine is 8% to 15% of the total molar amount of intermediate M1-B and M2-B, and the molar ratio of intermediate M1-B to M2-B is 1:1.1 to 1:1.

3. The method further includes step S4: after the reaction is completed, the solid byproducts are removed by filtration, and the organic phase is washed successively with dilute hydrochloric acid (3-5 wt%), deionized water, and saturated brine. After drying with anhydrous magnesium sulfate, it is heated at 30-50 °C. The crude product was obtained by concentration under reduced pressure at mbar and water bath temperature below 35℃; Step S5: The crude product was purified by column chromatography using 200-300 mesh silica gel activated by drying at 120℃ for 4 hours, with a column diameter to column length ratio of 1:

20. The eluent was a mixed solvent of petroleum ether and ethyl acetate. Target compounds with cyano (-CN) substitution were eluted with a mixed solvent at a volume ratio of 2:1, and target compounds with fluorine (F) substitution were eluted with a mixed solvent at a volume ratio of 5:1 to 3:1, using isocratic elution. The column chromatography product was dissolved in a mixed solvent of refluxed ethanol and n-hexane at a volume ratio of 1:3, and filtered while hot at a temperature not lower than 60℃. The filtrate was slowly cooled to -20℃ and allowed to stand for 12 hours to crystallize. The precipitated crystals were dried under vacuum at 30 mbar and 40℃ for 6 hours to obtain the target compound with HPLC purity ≥99.5%.

9. The method according to claim 7, characterized in that, The dehydrating condensing agent is selected from N,N'-dicyclohexylcarbodiimide and N-(3-dimethylaminopropyl)-N'-ethylcarbodiimide hydrochloride.

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