CN109679666B

CN109679666B - Liquid crystal compound, preparation method thereof, liquid crystal composition and microwave communication device

Info

Publication number: CN109679666B
Application number: CN201910088480.4A
Authority: CN
Inventors: 张智勇; 陈婷; 欧阳慧琦; 关金涛; 汪相如; 乔俊飞; 张海燕; 蔡雄辉; 高时汉; 赵怿哲
Original assignee: Wuhan Polytechnic University
Current assignee: Wuhan Polytechnic University
Priority date: 2019-01-29
Filing date: 2019-01-29
Publication date: 2021-09-17
Anticipated expiration: 2039-01-29
Also published as: CN109679666A

Abstract

The invention discloses a liquid crystal compound and a preparation method thereof, a liquid crystal composition and a microwave communication device. The liquid crystal compound has a structure as shown in structural formula (I). The liquid crystal compound provided by the present invention has a tetrabiphenyl structure in its structure, so it has the advantages of large optical anisotropy and stable structure. Dielectric loss, improve phase modulation capability and increase the quality factor of liquid crystal materials.

Description

Liquid crystal compound, preparation method thereof, liquid crystal composition and microwave communication device

Technical Field

The invention relates to the technical field of organic synthesis, in particular to a liquid crystal compound and a preparation method thereof, a liquid crystal composition and a microwave communication device.

Background

Liquid crystals have been widely used in the display field, however, in some studies liquid crystal media have also been proposed for use in components of microwave technology. The research of the liquid crystal used for the microwave device starts at the end of the last century and develops at a high speed in the beginning of the century; especially, the microwave phase tunable filter has gained worldwide attention in recent years, and is rapidly developed, and researches show that the microwave phase tunable filter can be used in important fields such as tunable filters, reconfigurable antennas, tunable frequency selectors, tunable phase shifters, and the like, for example, in 1993, Lim K.C. et al apply 16V bias voltage according to an electric control birefringence effect by using a commercial liquid crystal K15, obtain 20-degree phase shift at 10.5GHz frequency, and realize microwave phase tunable; in 2002, Germany reports a planar integrated liquid crystal tunable phase shifter, which obtains a phase shift of 53 degrees around the frequency of 18GHz and is generally regarded by the world colleagues.

Nevertheless, there are fundamental problems to be solved in many aspects of the related key technologies, such as liquid crystal materials, alignment, packaging, wiring, device design and functional characterization, and especially there are few research reports on liquid crystal materials. For ease of understanding, the relevant performance parameters for liquid crystal materials are presented below: Δ ∈ represents dielectric anisotropy; Δ n represents optical anisotropy, i.e., refractive index (589nm, 25 ℃); iso, clearing point temperature (deg.c) which is the phase state of the liquid crystal composition; the dielectric anisotropy in the microwave range is defined as: delta epsilon_rTbd (epsilonr | -epsilonr 0); tunability (τ) is defined as: τ ≡ (Δ ε 2r/ε r |); the material quality (η) is defined as: η ≡ (τ/tan ∈ 1r max.), maximum dielectric loss is: tan δ ∈ r max. { tan δ ∈ r | }, tan δ ∈ r | }. The dielectric loss refers to microwave wave frequency loss caused by wave frequency absorption generated when microwaves (4-40 GHZ) irradiate or pass through the liquid crystal material, and is generally called microwave insertion loss; exhibits a dielectric constant 'Delta epsilon' in the liquid crystal material_r", the dielectric constant is divided into a component" ε which is parallel to the long axis of the liquid crystal_r/' and vertical component ∈_rT', the value of the dielectric constant is delta epsilon_r＝ε_r∥-ε_rT, adding a solvent; the physical quantitative expression for microwave "dielectric loss" is: tangent value of dielectric loss (tan. delta. epsilon.)_rT, or tan delta epsilon_{r max}) Is a main performance index parameter reflecting the liquid crystal material in a microwave field and generally requires tan delta epsilon_rT (or tan delta epsilon)_{r max}) A value of less than or equal to about 0.03 and tan delta epsilon_r/value is about 0.006 or less. The birefringence is an expression formula of optical anisotropy of liquid crystal compound and mixed liquid crystal materialThe method is that after passing through a liquid crystal material, light is refracted and scattered by the liquid crystal to form ordinary light and extraordinary light, the refractive index of the ordinary light represents ' no ', and the refractive index of the extraordinary light represents ' n_e", the birefringence is represented by" Δ n ", and" Δ n ═ n_o-n_e", the microwave high frequency device requires the delta n value to be more than or equal to 0.30, and the higher the delta n value is, the more beneficial the microwave phase shift quantity is to be improved. The liquid crystal material with high dielectric anisotropy, high optical anisotropy and low dielectric loss is used as the liquid crystal material with high dielectric anisotropy, high optical anisotropy and low dielectric loss; the microwave has small dielectric loss and tan delta epsilon after being irradiated by the liquid crystal material_rT (or tan delta epsilon)_{r max}) A value lower than about 0.008 and tan delta epsilon_rThe value of | is lower than 0.004. The phase modulation coefficient of the microwave liquid crystal phase shifter is expressed as tau, and reflects the parameter of the phase modulation capability of the liquid crystal material to the microwave frequency, wherein tau is more than or equal to 0.15 and less than or equal to 0.5. The "quality factor" (eta, or FOM) of liquid crystal refers to the comprehensive evaluation result of the performance after microwave passes through the liquid crystal, which reflects the performance and quality of the liquid crystal material, and eta is generally required to be more than or equal to 15.

The first used liquid crystals were K15, E7 from Merck, germany, with Δ n values below 0.2, small Δ ∈ r values at high frequencies, large dielectric losses, excessively thick LC cells (d ═ 254 μm), response times exceeding 350 ms; then GT3-23001 liquid crystal of Merck company is used, the value of delta n is about 0.3, delta epsilon r reaches 0.8 under high frequency, the dielectric loss is obviously reduced, and the phase shift amount is increased; in recent years, German Merck company reports that an isothiocyanato-polycyclic aromatic acetylene type high-delta n mixed liquid crystal material has a delta n value of about 0.25-0.30, improves the dielectric property of a microwave device, and still has large dielectric loss. Herman J. et al report that in 2013 and 2015, respectively, an isothiocyanato-lateral ethyl tetraphenyl diacetylene liquid crystal compound (delta n is more than or equal to 0.6) is increased in microwave phase shift amount, but the dielectric loss is large and the melting point of the material is high. In 2013, Reuter M. et al report the influence of high frequency on wave absorption of different end groups such as-F, -CN, -NCS and the like. 2017 Dziadiuszek J et al reported that the end groups were NCS, CN, F, OCF₃The influence of these end groups on dielectric anisotropy in GHz and THz bands was analyzed and compared in liquid crystal compositions of 0.45 (. DELTA.n) prepared from equilateral fluorobiphenyl acetylene series compoundsAnd (6) making a response. The change condition of the optical tunability of the fluorine-containing tolane isothiocyanate liquid crystal composition along with the temperature in the 6GHz frequency band is reported by Kowerdziej R.et al in 2018, and the fact that the microwave phase tunability (tau) and the dielectric property (delta n) of the liquid crystal are not obvious along with the temperature change shows that the structural units such as isothiocyanates, ethynyls and the like are stable to microwaves. Recently, Lapanik V. et al, based on Kowerdziej R, adopted the isothiocyanato-polyaromatic ring mixed liquid crystal material, not only reduced the dielectric loss, but also increased the microwave phase shift, revealed the effect of the stability of the groups and bridges in the molecular structure on the dielectric loss, but the melting point of the material was still above 0 deg.C, and could not meet the outdoor use requirements. However, no report has been found on the influence of low-temperature photoelectric properties of microwave liquid crystals.

Further, in the existing large amount of research processes, it is found that the liquid crystal material for microwave mainly has the following problems in practical application: the value of delta n is small, so that the phase shift quantity is insufficient; secondly, the dielectric loss of the liquid crystal material is large due to the wave absorption and polarizability of the structural groups in the liquid crystal molecules; and thirdly, the liquid crystal solvent with high delta n value and low melting point and nematic liquid crystal components are lacked, so that the low-temperature performance of the liquid crystal material is influenced. Therefore, it is desired to provide a novel nematic liquid crystal compound having high stability, Δ n of 0.35 or more, low melting point, high mesomeric property and low consumption.

Disclosure of Invention

The invention mainly aims to provide a liquid crystal compound, a preparation method thereof, a liquid crystal composition and a microwave communication device, and aims to reduce the dielectric loss of a liquid crystal microwave device.

In order to achieve the above object, the present invention provides a liquid crystal compound having a structure represented by the following structural formula (i):

wherein R is₁And R₂Each independently selected from H atoms or unsubstituted alkyl groups containing 1 to 7 carbon atoms, X₁、X₂、X₃、X₄And X₅Each independently selected from a H atom, a F atom or a Cl atom.

Preferably, the liquid crystal compound is at least one of compounds having the structures represented by the following structural formulae (I-1) to (I-6):

wherein R in the structural formulae (I-1) to (I-6)₁And R₂Each independently selected from alkyl groups having 2 to 5 carbon atoms.

Preferably, the liquid crystal compound is at least one of compounds having a structure represented by the following structural formula (I-3-1):

wherein m is 2, 3, 4 or 5.

In order to achieve the above object, the present invention also provides a method for preparing the liquid crystal compound as described above, comprising the steps of:

step S10, under the protection of nitrogen, adding the first reactant, 2-ethyl-4-iodoaniline, palladium catalyst and K₂CO₃Carrying out Suzuki coupling reaction on ethanol, toluene and water for 3.5-4.5 h under the heating and stirring conditions, and then carrying out separation, washing, drying and purification treatment to obtain a first intermediate;

step S20, mixing the first intermediate, concentrated sulfuric acid and tetrahydrofuran, and then dropwise adding NaNO at the temperature of 0-10 DEG C₂Keeping the temperature of the aqueous solution, stirring for 50-70 min, continuously dropwise adding the aqueous solution of KI at the temperature of 0-10 ℃, naturally heating to room temperature after dropwise adding, adding an aqueous solution of sodium thiosulfate, and performing extraction, liquid separation, extraction, drying and purification treatment to obtain a second intermediate;

step S30, under the protection of nitrogen, the second intermediate, the second reactant, the palladium catalyst, K₂CO₃Carrying out Suzuki coupling reaction on ethanol, toluene and water for 3.5-4.5 h under the condition of heating and stirring, and then carrying out separation, washing, drying and purification treatment to obtain a target compound, namely the liquid crystal compound;

wherein the first reactant in step S10 is a compound having a structure represented by the following structural formula (ii), and the second reactant in step S30 is a compound having a structure represented by the following structural formula (iii):

wherein R in the structural formula (II)₁And R in the formula (III)₂Each independently selected from H atom or unsubstituted alkyl containing 1-7 carbon atoms, X in the structural formula (III)₁、X₂、X₃、X₄And X₅Each independently selected from a H atom, a F atom or a Cl atom.

Preferably, in step S10, the first reactant, 2-ethyl-4-iodoaniline, palladium catalyst and K₂CO₃The molar ratio of (1-1.5): 1: (0.01-0.3): (2-5); and/or the presence of a gas in the gas,

in step S20, the first intermediate, concentrated sulfuric acid, NaNO₂And KI in a molar ratio of 1: (1-4): (1-2): (1-3); and/or the presence of a gas in the gas,

in step S30, the second intermediate, the second reactant, the palladium catalyst, and K₂CO₃In a molar ratio of 1: (1-2): (0.1-3): (2-5); and/or the presence of a gas in the gas,

the palladium catalyst is palladium tetratriphenylphosphine; and/or the presence of a gas in the gas,

the reaction temperature of the Suzuki coupling reaction is 40-80 ℃.

Preferably, in step S10, the compound E, 2-ethyl-4-iodoaniline, palladium catalyst and K₂CO₃The molar ratio of (1-1.2): 1: (0.1-0.3): (2-4); and/or the presence of a gas in the gas,

in step S20, the intermediate I and concentrated sulfuric acid、NaNO₂And KI in a molar ratio of 1: (1.2-2): (1-1.5): (1-2); and/or the presence of a gas in the gas,

in step S30, the intermediate II, compound F, palladium catalyst and K₂CO₃In a molar ratio of 1: (1-1.2): (0.5-1.5): (2-4).

The invention further provides a liquid crystal composition which comprises a first compound, wherein the first compound is the liquid crystal compound.

Preferably, the liquid crystal composition further comprises at least one second type compound having a structure shown in the following structural formula (IV), at least one third type compound having a structure shown in the following structural formula (V), and at least one fourth type compound having a structure shown in the following structural formula (VI):

wherein n in the structural formulas (IV), (V) and (VI) is independently selected from 3, 4, 5 or 6, and m in the structural formulas (IV), (V) and (VI) is independently selected from 2, 3, 4 or 5.

Preferably, the mass fractions of the first, second, third and fourth compounds in the liquid crystal composition are 1-40%, 1-80%, 1-50% and 1-50%, respectively.

Preferably, the mass fractions of the first, second, third and fourth compounds in the liquid crystal composition are 3-30%, 10-80%, 5-40% and 3-40%, respectively.

Preferably, the mass fractions of the first, second, third and fourth compounds in the liquid crystal composition are 5-20%, 20-70%, 5-30% and 5-30%, respectively.

The invention also provides a microwave communication device, which comprises the liquid crystal composition.

Preferably, the microwave communication device is a microwave liquid crystal phase shifter, a tunable filter or a phased array antenna.

In the technical scheme provided by the invention, the liquid crystal compound has a structure of the quaterphenyl structure, so that the liquid crystal compound has the advantages of large optical anisotropy and stable structure, and when the liquid crystal compound is applied to a liquid crystal material with high dielectric anisotropy, the dielectric loss of a liquid crystal microwave device is favorably reduced, the phase modulation capability is improved, and the quality factor of the liquid crystal material is increased.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other related drawings can be obtained according to the drawings without creative efforts.

Fig. 1 is a schematic flow chart of an embodiment of a method for preparing a liquid crystal compound according to the present invention.

The implementation, functional features and advantages of the objects of the present invention will be further explained with reference to the accompanying drawings.

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. The examples, in which specific conditions are not specified, were conducted under conventional conditions or conditions recommended by the manufacturer. The reagents or instruments used are not indicated by the manufacturer, and are all conventional products available commercially.

The invention aims to develop the liquid crystal material with the molecular structure with small microwave absorption coefficient and small polarizability by researching the influence of the liquid crystal molecular structure on the dielectric property of a microwave K frequency band, particularly the dielectric loss effect; developing molecular compounds of 'high delta n value liquid crystal solvent' and 'low melting point liquid crystal component', designing and synthesizing novel nematic phase liquid crystal molecules with high delta n value, low melting point, low dielectric loss and high stable structure; and the nematic phase liquid crystal material which meets the requirements of microwave devices and has high dielectric constant, low consumption and stable low-temperature performance is prepared by mixing the liquid crystal compounds.

The invention provides a liquid crystal compound with a structure shown as the following structural formula (I):

The liquid crystal compound provided by the invention has a structure of the quaterphenyl structure, so that the liquid crystal compound has the advantages of large optical anisotropy and stable structure, and when the liquid crystal compound is applied to a liquid crystal material with high dielectric anisotropy, the dielectric loss of a liquid crystal microwave device is reduced, the phase modulation capability is improved, and the quality factor of the liquid crystal material is increased. Wherein, the side group X in the structural formula (I)₁、X₂、X₃、X₄And X₅More preferably, at least one of the side chains is a F atom, so that the side chain of the liquid crystal compound contains both ethyl and fluorine atoms, and the liquid crystal compound has a quaterphenyl structure, so that the liquid crystal compound has larger optical anisotropy and better structural stability, and is favorable for further reducing the dielectric loss of the liquid crystal material and further increasing the quality factor of the liquid crystal material.

As a preferred embodiment of the present invention, the liquid crystal compound is at least one of compounds having the structures represented by the following structural formulae (I-1) to (I-6):

As the most preferable embodiment of the present invention, the liquid crystal compound is at least one of compounds having a structure represented by the following structural formula (I-3-1):

wherein m is 2, 3, 4 or 5. The compound shown in the structural formula (I-3-1) has larger optical anisotropy and better stability, and when the compound is applied to a liquid crystal material, the improvement effect on the optical anisotropy and the quality factor of the liquid crystal material is more obvious.

Furthermore, the invention also provides a preparation method of the liquid crystal compound, and the synthetic route is as follows:

fig. 1 shows an embodiment of a method for preparing a liquid crystal compound according to the present invention. Referring to fig. 1, in the present embodiment, the method for preparing the liquid crystal compound includes the following steps:

the separation, washing, drying and purification processes in step S10 may be performed according to a conventional method in the field of organic synthesis, for example, by separating the reaction product by centrifugation or filtration, followed by extraction with an organic solvent, washing with water, drying with a drying agent, and finally performing chromatography, elution and the like to obtain a purified product. In this embodiment, step S10 can be implemented in the following manner: under the protection of nitrogen, a first reactant, 2-ethyl-4-iodoaniline, a palladium catalyst and K are sequentially added into a reaction bottle₂CO₃And carrying out reflux reaction on ethanol, toluene and water under heating and stirring for 3.5-4.5 h, stopping stirring, naturally cooling the reaction solution to room temperature, then adding hydrochloric acid for neutralization, filtering to remove insoluble substances, then adding toluene for extraction and separation, washing with water to be neutral, drying with anhydrous sodium sulfate, filtering, drying the filtrate by rotary evaporation, then loading into a chromatographic column, eluting with petroleum ether, and removing the solvent in the eluent by rotary evaporation to obtain the first intermediate. The reaction bottle can be a conical flask, a three-neck flask or an organic synthesis reaction kettle and other containers, and is determined according to the dosage of reaction raw materials or the yield requirement of reaction products during specific operation.

The first reactant is a compound having a structure represented by the following structural formula (II):

wherein R in the structural formula (II)₁Is H atom or unsubstituted alkyl group containing 1 to 7 carbon atoms.

Further, in this example, the first reactant, 2-ethyl-4-iodoaniline, palladium catalyst and K in step S10₂CO₃The molar ratio of (1-1.5): 1: (0.01-0.3): (2-5), more preferably (1-1.2): 1: (0.1-0.3): (2-4).

the extraction, liquid separation, purification, drying, purification, and the like can be performed by a method commonly used in the organic synthesis technology field, and further, a specific implementation step of step S20 is provided in this embodiment: adding the first intermediate, concentrated sulfuric acid and tetrahydrofuran into a reaction vessel in sequence, placing the reaction vessel in a salt bath with ice, and waiting for the materialsAfter the temperature is reduced to below 0 ℃, NaNO is dripped into the materials₂And (2) ensuring that the dropping is finished within 1h and the temperature of the material is kept to be not more than 10 ℃ in the whole dropping process (namely, the temperature of the material is kept to be 0-10 ℃ in the dropping process), keeping the temperature and stirring for 1h after the dropping is finished, dropping the KI aqueous solution and keeping the temperature of the material to be not more than 10 ℃ in the whole dropping process, naturally heating to room temperature after the dropping is finished, adding the sodium thiosulfate aqueous solution, stirring, extracting, separating liquid, extracting with ethyl acetate, drying with anhydrous sodium sulfate, performing rotary evaporation to remove the solvent, finally loading into a chromatographic column, and eluting with petroleum ether to obtain the second intermediate.

In this embodiment, the first intermediate, concentrated sulfuric acid, NaNO in step S20₂And KI in a molar ratio of 1: (1-4): (1-2): (1-3), more preferably 1: (1.2-2): (1-1.5): (1-2).

Step S30, under the protection of nitrogen, the second intermediate, the second reactant, the palladium catalyst and K are mixed₂CO₃Carrying out Suzuki coupling reaction on ethanol, toluene and water for 3.5-4.5 h under the condition of heating and stirring, and then carrying out separation, washing, drying and purification treatment to obtain a target compound, namely the liquid crystal compound;

likewise, the separation, washing, drying and purification processes in step S30 can also be performed by conventional methods in the field of organic synthesis, and a specific embodiment of step S30 is provided in this example: under the protection of nitrogen, a second intermediate, a second reactant, a palladium catalyst and K are sequentially added into a reaction bottle₂CO₃And carrying out reflux reaction on ethanol, toluene and water under heating and stirring for 3.5-4.5 h, stopping stirring, naturally cooling the reaction liquid to room temperature, then adding hydrochloric acid for neutralization, filtering to remove insoluble substances, then adding toluene for extraction and separation, washing with water to be neutral, drying by using anhydrous sodium sulfate, filtering, drying the filtrate by rotary evaporation, then filling into a chromatographic column, and leaching by using petroleum ether to obtain the target compound, namely the liquid crystal compound.

The second reactant is a compound having a structure represented by the following structural formula (III):

wherein R in the structural formula (III)₁Is H atom or unsubstituted alkyl group containing 1 to 7 carbon atoms, X in the structural formula (III)₁、X₂、X₃、X₄And X₅Each independently selected from a H atom, a F atom or a Cl atom.

Further, in the present embodiment, the second intermediate, the second reactant, the palladium catalyst and K in step S30₂CO₃In a molar ratio of 1: (1-2): (0.1-3): (2-5), more preferably 1:1: (1-1.2): (0.5-1.5): (2-4).

Suzuki coupling reaction is also called Suzuki reaction, which means that aryl or alkenyl boric acid or boric acid ester and chlorine, bromine, iodo arene or olefin are subjected to cross coupling under the catalysis of a zero-valent palladium complex, and the Suzuki coupling reaction is commonly used for synthesizing derivatives of polyene, styrene and biphenyl. The catalysts for the Suzuki coupling reaction mainly fall into two main categories: palladium catalysts, which can be used in aqueous systems, are tolerant of a large number of functional groups, and nickel catalysts, which must be anhydrous and oxygen-free in the reaction. In this embodiment, a palladium catalyst containing an organophosphorus ligand is selected as a catalyst for the Suzuki coupling reaction, and tetratriphenylphosphine palladium is more preferable, so that the catalyst is more widely used, and has better stability and better catalytic effect. In other embodiments of the invention, the palladium catalyst may also be selected from, for example, Ph₃P、n-Bu₃P or (MeO)₃P, and so on. Further, in the present embodiment, the reaction temperature of the Suzuki coupling reaction is 40-80 ℃.

By adopting the preparation method of the liquid crystal compound, the liquid crystal compound with the side chain containing ethyl and the quaterphenyl structure can be prepared in batch and stably through the coupling reaction of the alkyl-containing biphenyl boric acid and the side ethyl-containing biphenyl bromide, has the advantages of large optical anisotropy and stable structure, and can reduce the dielectric constant of the liquid crystal material when being applied to the liquid crystal materialLoss and improved tunability, and provides a liquid crystal material with better performance for developing microwave communication devices. It will be appreciated that when it is desired to prepare liquid crystal compounds having different substituents, a corresponding selection of the first reactant having a substituent and the second reactant can be achieved, for example, when R is the target product of the liquid crystal compound₁Is alkyl of 5 carbon atoms, R₂Is alkyl of 3 carbon atoms, X₃Is F atom, the remainder being X₁To X₅When the atom is H, correspondingly selecting 4-n-pentylphenylboronic acid as the first reactant, selecting 3-fluoro-4' n-alkylbiphenyl boric acid as the second reactant, and so on to obtain the liquid crystal polymer with different substituents, which will be further exemplified by combining with specific examples.

The invention also provides a liquid crystal composition, which comprises the first compound, wherein the first compound is the liquid crystal compound, namely the liquid crystal compound with the structure shown in the structural formula (I), and the liquid crystal composition can be obtained by combining the liquid crystal compound with any existing liquid crystal compound and has the advantages of low dielectric loss and high quality factor caused by the structural characteristics of the liquid crystal compound.

In an embodiment of the liquid crystal composition provided by the present invention, the liquid crystal composition further includes at least one second compound having a structure represented by the following structural formula (iv), at least one third compound having a structure represented by the following structural formula (v), and at least one fourth compound having a structure represented by the following structural formula (vi):

It is understood that, in the liquid crystal composition, the first type of compound may be at least one selected from compounds having a structure shown in a structural formula (I), the second type of compound may be at least one selected from compounds having a structure shown in a structural formula (IV), the third type of compound may be at least one selected from compounds having a structure shown in a structural formula (V), and the fourth type of compound may be at least one selected from compounds having a structure shown in a structural formula (VI). Preferably, the first compound, the second compound, the third compound and the fourth compound are all selected from a mixture of 2-5 compounds in the compounds with structures shown in corresponding structural formulas, and the liquid crystal composition obtained by combination has large optical anisotropy, low dielectric loss and large quality factor when applied.

Further, in this embodiment, the mass fractions of the first type of compound, the second type of compound, the third type of compound, and the fourth type of compound in the liquid crystal composition are 1 to 40%, 1 to 80%, 1 to 50%, and 1 to 50%, respectively, and the liquid crystal composition obtained by combining the first type of compound, the second type of compound, the third type of compound, and the fourth type of compound has better application performance.

As a preferable embodiment of the liquid crystal composition provided by the invention, the mass fractions of the first compound, the second compound, the third compound and the fourth compound in the liquid crystal composition are 3-30%, 10-80%, 5-40% and 3-40%, respectively, and the application performance of the liquid crystal composition obtained by combining the first compound, the second compound, the third compound and the fourth compound is further improved.

As another more preferred embodiment of the liquid crystal composition provided by the present invention, the mass fractions of the first, second, third and fourth compounds in the liquid crystal composition are 5-20%, 20-70%, 5-30% and 5-30%, respectively, and the liquid crystal composition obtained by the combination has excellent application performance.

The liquid crystal composition provided by the invention can further improve the optical anisotropy and the stability of the conventional liquid crystal composition under microwave, has the effect of reducing dielectric loss, and can be applied to the field of microwave communication devices.

Further, the invention also provides a microwave communication device, which comprises the liquid crystal composition. The microwave communication device can be a component or a device which can be tuned by applying a magnetic field and/or an electric field, such as a tunable filter, a reconfigurable antenna, a tunable frequency selector or a tunable phase shifter, and the like.

The technical solutions of the present invention are further described in detail below with reference to specific examples and drawings, it should be understood that the following examples are merely illustrative of the present invention and are not intended to limit the present invention.

In order to facilitate the distinction of the structures of the first compound (the liquid crystal compound having the structure shown in the structural formula (i)), the second compound (the compound having the structure shown in the structural formula (iv)), the third compound (the compound having the structure shown in the structural formula (v)) and the fourth compound (the compound having the structure shown in the structural formula (vi)) in the liquid crystal composition, the first compound is named as the liquid crystal compound nPP (2) GIPm, the second compound is named as the compound nPTP (2) TPm, the third compound is named as the compound ntup (1) TPm, and the fourth compound is named as the compound ntugtpm, which are all described in further detail below in combination with the abbreviation of the above-mentioned naming.

TABLE 1 element Classification

Example 1 synthesis of liquid crystal compound 5PP (2) GIP4, structural formula:

the preparation process comprises the following steps:

(1) to a 250mL four-necked flask were added 4-n-pentylphenylboronic acid (0.04mol, 7.68g), 2-ethyl-4-iodoaniline (0.04mol, 9.88g), and K in this order₂CO₃(0.10mol, 13.8g), 80mL of ethanol, 60mL of toluene and 30mL of water, replacing with nitrogen for 4 times, adding a catalyst of palladium tetratriphenylphosphine (0.01mol, 0.46g), heating and stirring to keep the liquid phase temperature at 70 ℃, refluxing for 4 hours, stopping stirring, naturally cooling the reaction solution to room temperature, adding hydrochloric acid for neutralization, filtering to remove insoluble substances, adding toluene (3X 50mL), extracting, separating, washing with water to neutrality, and using anhydrous Na to wash the washing product₂SO₄Drying, filtering, evaporating filtrate to dryness, loading into chromatographic column, eluting with petroleum ether, and removing solvent by rotary evaporation to obtain intermediate 5PP (2) NH₂8.5g of brown liquid was obtained in 80.3% yield.

(2) To a 250mL three-necked flask was added the intermediate 5PP (2) NH in sequence₂(0.035mol, 9.3g), concentrated sulfuric acid (98%, 0.044mol, 4.4g) and Tetrahydrofuran (THF)100mL, placed in an ice-salt bath until the temperature drops to 0 ℃, and then 20mL of NaNO was added dropwise₂(2.4g, 0.035mol) aqueous solution, after finishing dropping within 1 hour, keeping the temperature of the reaction solution not to exceed 10 ℃ in the dropping process, keeping the temperature to be stirred for 1 hour after finishing dropping, then dropping 50mL of KI (0.042mol, 6.9g) aqueous solution, keeping the temperature not to exceed 10 ℃ in the dropping process, naturally rising to room temperature after finishing dropping, then adding 50mL of sodium thiosulfate (0.042mol, 6.6g) aqueous solution, extracting and separating after stirring, extracting by ethyl acetate (3X 50mL), drying by anhydrous sodium sulfate, removing the solvent by rotary evaporation to obtain 8.3g of reddish brown liquid, then loading into a chromatographic column, and leaching by petroleum ether to obtain an intermediate 5PP (2) I, thus obtaining 7.6g of yellow liquid, and the yield of 57.6%.

(3) Under the protection of nitrogen, an intermediate 5PP (2) I (0.0185mol, 7.0g), 3-fluoro-4' -n-butylbiphenylboronic acid (0.0185mol, 5.03g) and K are sequentially added into a 250mL four-neck flask₂CO₃(0.0555mol, 7.6g), ethanol 60mL, toluene 50mL and water 15mL, the nitrogen was replaced 4 times, then the catalyst palladium tetrakistriphenylphosphine (0.01mol, 0.21g) was added, the mixture was heated and stirred to maintain the liquid phase temperature at 70 ℃, and the reaction was refluxed for 4 hours, and then the reaction was stoppedStirring, naturally cooling the reaction solution to room temperature, adding hydrochloric acid for neutralization, filtering to remove insoluble substances, adding toluene (3 × 50mL), extracting, separating, washing with water to neutrality, and adding anhydrous Na₂SO₄Drying, filtering, evaporating filtrate, loading into chromatographic column, eluting with petroleum ether, evaporating solvent, recrystallizing to obtain target compound 5PP (2) GIP4, and obtaining white solid 4.7g with yield 53.4%, phase transition temperature Cr 56.3 deg.C, Sm 73.8 deg.C, N110.3 deg.C I, and Δ N (optical anisotropy, i.e. birefringence (589nm, 25 deg.C)) of 0.295.

The structure detection is carried out by hydrogen-nuclear magnetic resonance spectroscopy and fluorine-nuclear magnetic resonance spectroscopy, and the test result is as follows:

¹H-NMR(CDCl₃，400MHz)δ(ppm)：7.35～7.66(m，14H)，2.72～2.77(m， 6H)，1.72～1.77(m，4H)，1.45～1.49(m，6H)，0.99～1.26(m，9H)；

13C-NMR(100MHz，CDCl₃)δ(ppm)：14.050，14.132，15.273，22.478， 22.656，26.490，31.267，31.663，33.665，35.390，35.690，113.73，122.36， 124.33，126.88，127.35，128.88，129.07，130.81，132.04，133.73，137.02， 138.46，141.15，142.21，158.84，161.28；

¹⁹F-NMR(376.29MHz，CDCl₃)δ(ppm)：-114.34。

the structure of the prepared target compound is consistent with the structure shown in the structural formula.

Example 2 synthesis of liquid crystal compound 5PP (2) GIP5, structural formula:

the preparation process comprises the following steps:

(1) to a 250mL four-necked flask were added 4-n-pentylphenylboronic acid (0.08mol, 15.36g), 2-ethyl-4-iodoaniline (0.08mol, 19.76g), and K in this order₂CO₃(0.24mol, 33.12g), ethanol 100mL, toluene 60mL and water 35mL, replaced with nitrogen for 4 times, and then added with palladium tetrakistriphenylphosphine (0.01 mo) as a catalystl, 1.24g), heating and stirring, keeping the liquid phase temperature at 70 ℃, carrying out reflux reaction for 4 hours, stopping stirring, naturally cooling the reaction liquid to room temperature, adding hydrochloric acid for neutralization, filtering to remove insoluble substances, adding toluene (3X 50mL) for extraction, separating liquid, washing with water to neutrality, and using anhydrous Na to wash the washing product₂SO₄Drying, filtering, evaporating filtrate to dryness, loading into chromatographic column, eluting with petroleum ether, and removing solvent by rotary evaporation to obtain intermediate 5PP (2) NH₂16.94g of brown liquid was obtained in 79.3% yield.

(2) To a 250mL three-necked flask was added the intermediate 5PP (2) NH in sequence₂(0.05mol, 13.35g), concentrated sulfuric acid (98%, 0.075mol, 7.5g) and Tetrahydrofuran (THF)150mL, placing in a ice salt bath until the temperature is reduced to 0 ℃, and then dropwise adding 30mL of NaNO₂(4.14g, 0.06mol) of the aqueous solution, dropwise adding the aqueous solution within 1 hour, keeping the temperature of the reaction solution not to exceed 10 ℃ in the dropwise adding process, keeping the temperature and stirring the solution for 1 hour after dropwise adding, then dropwise adding 50mL of KI (0.10mol, 16.6g) aqueous solution, keeping the temperature not to exceed 10 ℃ in the dropwise adding process, naturally raising the temperature to room temperature after dropwise adding, then adding 50mL of sodium thiosulfate (0.10mol, 15.8g) aqueous solution, stirring the solution, extracting and separating the solution, extracting the solution by ethyl acetate (3X 50mL), drying the solution by anhydrous sodium sulfate, performing rotary evaporation to remove the solvent to obtain a reddish brown liquid, then loading the reddish brown liquid into a chromatographic column, and performing drip washing by using petroleum ether to obtain an intermediate 5PP (2) I, thus obtaining 9.26g of a yellow.

(3) Under the protection of nitrogen, sequentially adding an intermediate 5PP (2) I (0.0085mol, 3.2g), 3-fluoro-4' -n-butylbiphenyl boric acid (0.0085mol, 2.4g), K2CO3 (0.021mol, 2.9g), 60mL of ethanol, 40mL of toluene and 15mL of water into a 250mL four-neck flask, replacing for 4 times by nitrogen, adding a catalyst of tetratriphenylphosphine palladium (0.01mol, 0.098g), heating and stirring, keeping the liquid phase temperature at 70 ℃, stopping stirring after refluxing for 4 hours, naturally cooling the reaction liquid to room temperature, adding hydrochloric acid for neutralization, filtering to remove insoluble substances, adding toluene (3 x 50mL) for extraction, separating, washing with water, drying a washing product with anhydrous Na2SO4, filtering, evaporating the filtrate to dryness, loading into a chromatographic column, eluting with petroleum ether, evaporating to remove a solvent by rotary evaporation, recrystallizing to obtain a target compound 5PP (2) GIP5, 1.9g of a white solid was obtained in a yield of 45.4%, a phase transition temperature of Cr75.8 ℃ N112.5 ℃ I,. DELTA.n of 0.301.

¹H-NMR(CDCl₃，400MHz)δ(ppm)：7.35～7.66(m，14H)，2.72～2.77(m， 6H)，1.45～1.79(m，10H)，0.99～1.26(m，9H)；

¹³C-NMR(100MHz，CDCl₃)δ(ppm)：14.050，14.132，15.273，22.478，22.656，26.490，31.267，31.663，32.452，33.665，35.390，35.690，113.73， 122.36，124.33，126.88，127.35，128.88，129.07，130.81，132.04，133.73， 137.02，138.46，141.15，142.21，158.84，161.28；

¹⁹F-NMR(376.29MHz，CDCl₃)δ(ppm)：-114.34。

Example 3 synthesis of liquid crystal compound 5PP (2) GIP2, structural formula:

the procedure was as in example 1, except that 3-fluoro-4 '-n-butylbiphenyl boronic acid in the step (3) was replaced with 3-fluoro-4' -ethylbiphenyl boronic acid.

The detection of hydrogen-nuclear magnetic resonance spectrum and fluorine-nuclear magnetic resonance spectrum proves that the structure of the prepared target compound is consistent with the structure shown in the structural formula.

Example 4 synthesis of liquid crystal compound 5PP (2) GIP3, structural formula:

the procedure was as in example 1, except that 3-fluoro-4 '-n-butylbiphenylboronic acid in the step (3) was replaced with 3-fluoro-4' -propylbiphenylboronic acid.

Example 5

The procedure is the same as in example 1, except that:

4-n-pentylphenylboronic acid, 2-ethyl-4-iodoaniline, palladium tetratriphenylphosphine and K in step (1)₂CO₃In a molar ratio of 1.2:1:0.1: 4;

the intermediate 5PP (2) NH in the step (2)₂Concentrated sulfuric acid, NaNO₂The molar weight ratio of the KI to the KI is 1:2:1.5: 1;

the intermediates 5PP (2) I, 3-fluoro-4' -n-butylbiphenylboronic acid, tetratriphenylphosphine palladium and K in the step (3)₂CO₃In a molar ratio of 1:1.2:1.5: 2.

The detection of hydrogen-nuclear magnetic resonance spectrum and fluorine-nuclear magnetic resonance spectrum proves that the structure of the prepared target compound is consistent with the structure shown in the structural formula in the example 1.

Example 6

The procedure is the same as in example 1, except that:

4-n-pentylphenylboronic acid, 2-ethyl-4-iodoaniline, palladium tetratriphenylphosphine and K in step (1)₂CO₃In a molar ratio of 1.1:1:0.3: 2;

the intermediate 5PP (2) NH in the step (2)₂Concentrated sulfuric acid, NaNO₂The molar weight ratio of the KI to the KI is 1:1.2:1.3: 1.5;

the intermediates 5PP (2) I, 3-fluoro-4' -n-butylbiphenylboronic acid, tetratriphenylphosphine palladium and K in the step (3)₂CO₃In a molar ratio of 1:1.1:0.8: 4.

Example 7

The procedure is the same as in example 1, except that:

4-n-pentylphenylboronic acid, 2-ethyl group in step (1)4-iodoaniline, palladium tetratriphenylphosphine and K₂CO₃In a molar ratio of 1.5:1:0.01: 5;

the intermediate 5PP (2) NH in the step (2)₂Concentrated sulfuric acid, NaNO₂The molar weight ratio of the KI to the KI is 1:3:1.8: 3;

the intermediates 5PP (2) I, 3-fluoro-4' -n-butylbiphenylboronic acid, tetratriphenylphosphine palladium and K in the step (3)₂CO₃In a molar ratio of 1:1.5:0.1: 3.5.

Example 8

The procedure is the same as in example 1, except that:

4-n-pentylphenylboronic acid, 2-ethyl-4-iodoaniline, palladium tetratriphenylphosphine and K in step (1)₂CO₃In a molar ratio of 1.3:1:0.05: 3.5;

the intermediate 5PP (2) NH in the step (2)₂Concentrated sulfuric acid, NaNO₂The molar weight ratio of the KI to the KI is 1:4:2: 2.5;

the intermediates 5PP (2) I, 3-fluoro-4' -n-butylbiphenylboronic acid, tetratriphenylphosphine palladium and K in the step (3)₂CO₃In a molar ratio of 1:2:3: 5.

Example 9

The procedure was as in example 1 except that the reflux reaction temperature in step (1) and step (3) was 80 ℃.

Example 10

The procedure was the same as in example 1 except that the reflux reaction temperature in step (1) and step (3) was 55 ℃.

Example 11

The procedure was the same as in example 1 except that the reflux reaction temperature in step (1) and step (3) was 40 ℃.

Example 12

The mass fractions (Wt%) of the components and the performance parameters of the liquid crystal composition are shown in table 2.

TABLE 2 Mass fractions and Performance parameters of the components of the liquid crystal composition of example 12

Example 13

The mass fractions (Wt%) of the components and the performance parameters of the liquid crystal composition are shown in table 3.

TABLE 3 Mass fractions and Performance parameters of the components of the liquid crystal composition of example 13

Example 14

The mass fractions (Wt%) of the components and the performance parameters of the liquid crystal composition are shown in table 4.

TABLE 4 Mass fractions and Performance parameters of the components of the liquid crystal composition in example 14

Example 15

The mass fractions (Wt%) of the components and the performance parameters of the liquid crystal composition are shown in table 5.

TABLE 5 Mass fractions and Performance parameters of the components of the liquid crystal composition of example 15

Example 16

The mass fractions (Wt%) of the components and the performance parameters of the liquid crystal composition are shown in table 6.

TABLE 6 Mass fractions and Performance parameters of the components of the liquid crystal composition of example 16

Example 17

The mass fractions (Wt%) of the components and the performance parameters of the liquid crystal composition are shown in table 7.

TABLE 7 Mass fractions and Performance parameters of the components of the liquid crystal composition of example 17

From the results of the performance parameters of the liquid crystal compositions in the above embodiments, it can be seen that the liquid crystal composition provided by the embodiments of the present invention has a large optical anisotropy, a low dielectric loss and a large quality factor under microwave, can be used as a liquid crystal material in microwave communication devices, especially as a nematic liquid crystal material for microwave phase shifters, and is a nematic liquid crystal material with a high Δ n value, a low melting point, a low dielectric loss and a high stable structure.

The above is only a preferred embodiment of the present invention, and it is not intended to limit the scope of the invention, and various modifications and changes will occur to those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention shall be included in the scope of the present invention.

Claims

1. A liquid crystal composition, characterized in that it comprises a first type of compound, and the first type of compound is a liquid crystal compound having a structure represented by the following structural formula (I);

The liquid crystal composition also includes at least one compound of the second type having the structure represented by the following structural formula (IV), at least one compound of the third type having the structure represented by the following structural formula (V), and at least one compound having the following structural formula ( VI) The fourth class of compounds of the structure shown:

Wherein, R ₁ and R ₂ in structural formula (I) are each independently selected from H atoms or unsubstituted alkyl groups containing 1 to 7 carbon atoms, and X ₁ , X ₂ , X ₃ , X ₄ and X ₅ are each independently independently selected from H atoms, F atoms or Cl atoms;

n in structural formula (IV), (V) and (VI) are each independently selected from 3, 4, 5 or 6, m in structural formula (IV), (V) and (VI) are each independently selected from 2, 3, 4 or 5;

The mass fractions of the first type of compound, the second type of compound, the third type of compound and the fourth type of compound in the liquid crystal composition are correspondingly 1-40%, 1-80%, 1-50% and 1-40%. 50%.

2. The liquid crystal composition according to claim 1, wherein the first type of compound is at least one of the compounds having the structures represented by the following structural formula (I-1) to structural formula (I-6):

Wherein, R ₁ and R ₂ in structural formula (I-1) to structural formula (I-6) are each independently selected from alkyl groups containing 2 to 5 carbon atoms.

3. The liquid crystal composition according to claim 2, wherein the first type of compound is at least one of the compounds having the structure represented by the following structural formula (I-3-1):

where m is 2, 3, 4 or 5.

4. liquid crystal composition as claimed in claim 1 is characterized in that, described first kind of compound is made by following steps:

Step S10: Under the protection of nitrogen, the first reactant, 2-ethyl-4-iodoaniline, palladium catalyst, K ₂ CO ₃ , ethanol, toluene and water are subjected to Suzuki coupling reaction under heating and stirring conditions for 3.5-4.5 h, then through separation, washing, drying and purification to obtain the first intermediate;

Step S20, after mixing the first intermediate, concentrated sulfuric acid and tetrahydrofuran, add the aqueous solution of NaNO ₂ dropwise at a temperature of 0～10°C, keep stirring for 50～70min, and continue to add KI dropwise at a temperature of 0～10°C The aqueous solution is naturally warmed to room temperature after the dropwise addition, and then the sodium thiosulfate aqueous solution is added, and then the second intermediate is obtained through extraction and separation, extraction drying and purification;

Step S30: Under nitrogen protection, the second intermediate, the second reactant, the palladium catalyst, K ₂ CO ₃ , ethanol, toluene and water are subjected to a Suzuki coupling reaction under heating and stirring conditions for 3.5-4.5 h, and then After separation, washing, drying and purification, the target compound is obtained, that is, the liquid crystal compound is obtained;

Wherein, the first reactant in step S10 is a compound having a structure represented by the following structural formula (II), and the structural formulas of the first intermediate in step S10 and the second intermediate in step S20 are as follows As shown, the second reactant in step S30 is a compound having the structure represented by the following structural formula (III):

Wherein, R 1 in the structural formula (II), the structural formula of the first intermediate, and the structural formula of the _{second intermediate and R 2} _in the structural formula (III) are each independently selected from H atoms or unsubstituted ones containing 1 to 7 carbons. The alkyl group of the atom, X ₁ , X ₂ , X ₃ , X ₄ and X ₅ in the structural formula (III) are each independently selected from H atom, F atom or Cl atom.

5. The liquid crystal composition according to claim 4, wherein in step S10, the molar ratio of the first reactant, 2-ethyl-4-iodoaniline, palladium catalyst and K ₂ CO ₃ is (1 to 1.5): 1: (0.01 to 0.3): (2 to 5); and/or,

In step S20, the molar ratio of the first intermediate, concentrated sulfuric acid, NaNO ₂ and KI is 1:(1~4):(1~2):(1~3); and/or,

In step S30, the molar ratio of the second intermediate, the second reactant, the palladium catalyst and the K ₂ CO ₃ is 1:(1~2):(0.1~3):(2~5); and/ or,

The palladium catalyst is tetrakistriphenylphosphine palladium; and/or,

The reaction temperature of the Suzuki coupling reaction is 40-80°C.

6 . A microwave communication device, characterized in that, the microwave communication device comprises the liquid crystal composition according to any one of claims 1 to 5 .

7. The microwave communication device according to claim 6, wherein the microwave communication device is a microwave liquid crystal phase shifter, a tunable filter or a phased array antenna.