CN110776396B - Side ethyl tetraphenyl liquid crystal compound and preparation method thereof, liquid crystal composition and microwave device - Google Patents

Abstract

The invention discloses a side ethyl tetrabiphenyl liquid crystal compound and a preparation method thereof, a liquid crystal composition and a microwave device, and relates to the technical field of liquid crystal materials. The pendant ethyl tetraphenyl-based liquid crystal compound has the structure shown in the structural formula (I). The invention aims to provide a side ethyl tetraphenyl nematic liquid crystal compound with high Δn value, stable structure, small microwave absorption coefficient and low dielectric loss. Furthermore, by mixing the side ethyl tetrabiphenyl liquid crystal compound with other four kinds of wide temperature nematic liquid crystal compounds, a nematic liquid crystal composition with high dielectric and low consumption can be prepared which can meet the microwave K-band use, thereby reducing the number of nematic liquid crystals. The microwave dielectric loss improves the microwave phase modulation amount and device quality factor.

Description

Side ethyl tetraphenyl liquid crystal compound and preparation method thereof, liquid crystal composition and microwave device

technical field

The invention relates to the technical field of liquid crystal materials, in particular to a side ethyl tetrabiphenyl liquid crystal compound and a preparation method thereof, a liquid crystal composition and a microwave device.

Background technique

Microwave phase shifter is a key device in the field of microwave K-band (millimeter wave, 0.3-40GHz) communication technology, and has a wide range of applications in many aviation, military and civil fields such as radar systems, satellite antennas, communication systems, electronic countermeasure systems . Nematic liquid crystal is a kind of organic matter that has both the fluidity of liquid and the orderliness and anisotropy of crystal. Under the action of light, electricity, magnetism and other external fields, its molecules will undergo continuous deformation and flow, inducing dielectric The constant and refractive index change periodically and continuously, forming a strong optical nonlinear effect. The microwave liquid crystal phase shifter can be fabricated by using the nematic liquid crystal material as the microwave signal transmission medium.

Dielectric loss refers to the microwave wave frequency loss caused by the wave frequency absorption generated when microwaves (4-40GHz) irradiate or pass through the liquid crystal material, that is, microwave insertion loss. The dielectric loss is usually expressed as the dielectric constant in liquid crystal materials. (Δε _r ), the larger the Δε _r is, the better the microwave phase shift is. At the same time, after the light passes through the liquid crystal material, it is refracted and scattered by the liquid crystal to form ordinary light and extraordinary light. The refractive index of ordinary light means "no", The refractive index of extraordinary light is represented by " _ne ", the birefringence is represented by "Δn", "Δn=n _{o -ne} ", the birefringence "Δn" can reflect the optical anisotropy of liquid crystal compounds and liquid crystal materials, microwave High-frequency devices require Δn value ≥ 0.30. The higher Δn is, the more beneficial it is to improve the microwave phase shift amount.

The earliest liquid crystal materials used are K15 and E7 products of Merck Company in Germany, whose Δn value is lower than 0.2, the Δεr value at high frequency is very small, the dielectric loss is large, the LC cell is too thick (d=254μm), and the response time exceeds 350ms; In 2013, Reuter M. et al. reported the effect of high frequency on the absorption of different end groups such as -F, -CN, -NCS. In recent years, the German Merck Company has reported isothiocyano-polycyclic arylethynyl-based mixed liquid crystal materials with high Δn value. still larger. In 2013 and 2015, Herman J. et al. reported isothiocyano-lateral ethyltetraphenyldiacetylene liquid crystal compounds (Δn≥0.6), the microwave phase shift increased significantly, but the dielectric loss was too large, The material has a high melting point and cannot meet the needs of extreme low temperature environments. However, the research on the influence of low temperature optoelectronic properties of microwave liquid crystals has not been reported yet.

In a word, it is found in the process of a large number of existing researches that there is an urgent need to develop "high dielectric and low consumption" and low melting point microwave liquid crystal materials in practical applications.

SUMMARY OF THE INVENTION

The main purpose of the present invention is to propose a side ethyl tetraphenyl liquid crystal compound and its preparation method, liquid crystal composition and microwave device, aiming to provide a liquid crystal material with high dielectric and low consumption and low melting point.

In order to achieve the above object, the present invention proposes a side ethyl tetrabiphenyl liquid crystal compound, and the side ethyl tetrabiphenyl liquid crystal compound has the structure shown in the following structural formula (I):

Wherein, R ₁ is an alkyl group containing 1-7 carbon atoms or an alkenyl-containing alkyl group containing 3-7 carbon atoms; X ₁ , X ₂ and X ₃ are each independently selected from -H, -F or - Cl; Y is -NCS or -F.

The present invention also provides a method for preparing a side ethyl tetrabiphenyl liquid crystal compound, which is used for synthesizing the above-mentioned side ethyl tetrabiphenyl liquid crystal compound. The preparation method of the side ethyl tetrabiphenyl liquid crystal compound includes the following steps :

Step S10: under nitrogen protection, mix the first reactant, the second reactant, tetrakistriphenylphosphine palladium, potassium carbonate, ethanol, toluene and water, and perform a reflux reaction at 65-85° C. under stirring conditions for 4- After 8h, use TLC to detect and track the reaction, and after the reaction ends, separate, wash, dry and purify to obtain the first intermediate;

Step S20: under ice-salt bath conditions, add hydrobromic acid and tetrahydrofuran to the first intermediate, and after the temperature of the solution drops below 0°C, dropwise add an aqueous solution of sodium nitrite, and then at 5-10°C Insulation and stirring for 50-70min to obtain a reaction solution, another mixture of hydrobromic acid and cuprous bromide and heating to reflux, dropwise addition of the reaction solution, separation, drying and purification to obtain the second intermediate;

Step S30: under nitrogen protection and a temperature not higher than -75°C, add n-butyllithium dropwise to the mixed solution of the second intermediate and tetrahydrofuran, and after constant temperature reaction for 1-1.5h, dropwise add trimethyl borate , continue the constant temperature reaction for 2 to 4 hours, after separation, washing, drying and purification, the third intermediate is obtained;

Step S40: under nitrogen protection, sequentially add the third reactant, tetrakistriphenylphosphine palladium, potassium carbonate, ethanol, toluene and water to the third intermediate, and reflux at 65-80° C. under stirring conditions. The reaction is carried out for 4-6 hours, and the target compound is obtained after separation, washing, drying and purification;

Wherein, the first reactant in step S10 is a compound having the structure represented by the following structural formula (II), the second reactant in step S10 is a compound having the structure represented by the following structural formula (III), step S40 The third reactant in is a compound having the structure shown in the following structural formula (IV):

Wherein, M is _-NH2 or -F.

In addition, the present invention also provides a liquid crystal composition, the liquid crystal composition includes a first component, and the first component is one or more of the above-mentioned side ethyl tetrabiphenyl liquid crystal compounds .

Optionally, each compound component in the liquid crystal composition is a refined product after being purified by an electric field adsorption method.

Optionally, the first component is composed of one to five kinds of side ethyl tetraphenyl liquid crystal compounds represented by structural formula (I), and each of the side ethyl tetraphenyl liquid crystal compounds The weight percentage in the liquid crystal composition is 1-15%.

Optionally, the liquid crystal composition further includes a second component, a third component and a fourth component;

Wherein, the second component includes at least one of the compound represented by the following structural formula (V) and the compound represented by the following structural formula (VI);

The third component includes at least one of the compounds represented by the following structural formula (VII);

The fourth component includes at least one of the compound represented by the following structural formula (VIII) and the compound represented by the following structural formula (IX);

Wherein, in the structural formula (V), R ₂ is a saturated or unsaturated alkyl group containing 2 to 7 carbon atoms; X ₄ , X ₅ , and X ₆ are each independently selected from -H or -F, and Y ₁ is -NCS or -F;

In structural formula (VI), R ₃ is a saturated or unsaturated alkyl group containing 2 to 7 carbon atoms; X ₇ is -H, -F or -Cl, and X ₈ and X ₉ are each independently selected from -H Or -F, Y ₂ is -NCS or -F;

In structural formula (VII), R ₄ and R ₅ are each independently selected from saturated or unsaturated alkyl groups containing 2 to 7 carbon atoms;

In structural formula (VIII), R ₆ is a saturated or unsaturated alkyl group containing 2 to 7 carbon atoms, X ₁₀ and X ₁₁ are each independently selected from -H or -F, and Y ₃ is -NCS or -F ;

In structural formula (IX), R ₇ is a saturated or unsaturated alkyl group containing 2 to 7 carbon atoms; X ₁₂ and X ₁₃ are each independently selected from -H or -F, and Y ₄ is -NCS or -F .

Optionally, the weight percentage of each compound in the second component in the liquid crystal composition is 1-15%;

The weight percentage of each compound in the third component in the liquid crystal composition is 1-20%;

The weight percentage of each compound in the fourth component in the liquid crystal composition is 1-15%.

Optionally, the liquid crystal composition further includes a fifth component, and the fifth component includes at least one of the compounds represented by the following structural formula (X):

Wherein, R ₈ and R ₉ are each independently selected from saturated or unsaturated alkyl groups containing 2 to 7 carbon atoms, and R ₁₀ is -CH ₃ or -C ₂ H ₅ .

Optionally, the weight percentage of each compound in the fifth component in the liquid crystal composition is 1-15%.

In addition, the present invention also provides a microwave device comprising the above-mentioned liquid crystal composition.

In the technical scheme provided by the present invention, a tetraphenyl liquid crystal compound containing a side ethyl branch is designed and synthesized, and fluorine or isothiocyanate group is introduced into its molecular structure, so as to obtain a high Δn value, a stable structure, and a microwave absorption coefficient. Nematic liquid crystal compound with small size and low dielectric loss. Furthermore, by mixing the side ethyl tetrabiphenyl liquid crystal compound with several other wide temperature nematic liquid crystal compounds (II-IV), a low co-freezing point can be prepared, which can meet the requirements of high dielectric and low consumption for microwave K-band. The nematic liquid crystal composition reduces the microwave dielectric loss and improves the microwave phase modulation amount and the device quality factor.

Detailed ways

In order to make the objectives, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be described clearly and completely below. Obviously, the described embodiments are only some, but not all, embodiments of the present invention.

It should be noted that, if the specific conditions are not indicated in the examples, it is carried out according to the conventional conditions or the conditions suggested by the manufacturer. The reagents or instruments used without the manufacturer's indication are conventional products that can be purchased from the market. In addition, the meaning of "and/or" in the whole text includes three parallel schemes. Taking "A and/or B" as an example, it includes scheme A, scheme B, or scheme satisfying both of A and B. In addition, the technical solutions between the various embodiments can be combined with each other, but must be based on the realization by those of ordinary skill in the art. When the combination of technical solutions is contradictory or cannot be achieved, it should be considered that the combination of technical solutions does not exist. , is not within the scope of protection required by the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

The present invention relates to the relevant professional knowledge in the field of liquid crystal materials. For ease of understanding, the relevant performance parameters of the liquid crystal material are introduced as follows:

Δε represents dielectric anisotropy; Δn represents optical anisotropy, that is, birefringence (589nm, 25°C); Iso. is the clearing point temperature (°C) of the phase state of the liquid crystal composition;

The dielectric anisotropy in the microwave range is defined as:

△ε _r ≡(ε _r,|| -ε _r,⊥ ), wherein, the component parallel to the long axis of the liquid crystal “ε _r,|| ”, the component perpendicular to the long axis of the liquid crystal “ε _r,⊥ ”;

Tunability (τ) is defined as: τ≡(Δε _r /ε _r|| );

Material quality (η) is defined as: η≡(τ/tanδε _{r max} .);

The maximum dielectric loss is: tanδε _{r max} .≡max.{tanδε _r⊥ , tanδε _r|| }.

Among them, the dielectric loss is expressed as the dielectric constant “Δε _r ” in the liquid crystal material, and the physical quantitative expression of the microwave “dielectric loss” is: the tangent of the dielectric loss (tanδε _r⊥ , or tanδε _{r max} ), It is the main performance index parameter reflecting the liquid crystal material in the microwave field. Generally, the tanδε _r⊥ (or tanδε _{r max} ) value is less than or equal to 0.03, and the tanδε _{r, ∥} value is less than or equal to 0.005.

The term "high dielectric and low loss" liquid crystal material refers to liquid crystal material with high dielectric anisotropy, high optical anisotropy, and low dielectric loss; after microwave irradiation through the liquid crystal material, the dielectric loss is very small, tanδεr _⊥ (or tanδε _{r max} ) values are lower than about 0.008, and tanδεr|| values are lower than 0.004.

The term "phase modulation coefficient", expressed as "τ", is a parameter that reflects the phase modulation capability of liquid crystal materials to microwave frequencies, 0.15≤τ≤0.5;

The term "quality factor" (η, or FOM) refers to the comprehensive evaluation results of the performance after microwaves pass through the liquid crystal, reflecting the performance and quality of the liquid crystal material, generally requiring η≥15.

The earliest liquid crystal materials used are K15 and E7 products of Merck Company in Germany, whose Δn value is lower than 0.2, the Δεr value at high frequency is very small, the dielectric loss is large, the LC cell is too thick (d=254μm), and the response time exceeds 350ms; In 2013, Reuter M. et al. reported the effect of high frequency on the absorption of different end groups such as -F, -CN, -NCS. In recent years, the German Merck Company has reported isothiocyano-polycyclic arylethynyl-based mixed liquid crystal materials with high Δn value. still larger. In 2013 and 2015, Herman J. et al. reported isothiocyano-side-side ethyl tetraphenyl diacetylene-side-side ethyl tetraphenyl-like liquid crystal compounds (Δn ≥ 0.6), the amount of microwave phase shift increased significantly, However, the dielectric loss is too large and the melting point of the material is high, which cannot meet the needs of extreme low temperature environments. However, the research on the influence of low temperature optoelectronic properties of microwave liquid crystals has not been reported yet.

In a word, it is found in the process of a large number of existing researches that there is an urgent need to develop "high dielectric and low consumption" and low melting point microwave liquid crystal materials in practical applications.

In view of this, the present invention proposes a side ethyl tetrabiphenyl liquid crystal compound, and the side ethyl tetrabiphenyl liquid crystal compound has the structure shown in the following structural formula (I):

Wherein, R ₁ is an alkyl group containing 1-7 carbon atoms or an alkenyl-containing alkyl group containing 3-6 carbon atoms; X ₁ , X ₂ and X ₃ are each independently selected from -H, -F or - Cl; Y is -NCS or -F.

The side ethyl tetraphenyl liquid crystal compound in this embodiment has a tetraphenyl structure with stable structure and low polarizability, and end groups such as -NCS or -F that are stable to microwaves are introduced into the tetraphenyl structure, so that It has the advantages of large optical anisotropy and stable structure. When it is applied to liquid crystal materials with high dielectric anisotropy, it is beneficial to reduce the dielectric loss of liquid crystal microwave devices, improve the phase modulation ability and increase the quality factor of liquid crystal materials; , the side ethyl tetraphenyl type liquid crystal compound in this embodiment is a tetraphenyl type rod-shaped liquid crystal compound containing side ethyl branch chains, and has a relatively low melting point. When it is applied to a liquid crystal composition, it is beneficial to reduce the Co-freezing point, it can adapt to extreme low temperature environment.

The side ethyl tetraphenyl liquid crystal compound in this embodiment can be any compound having the structure of structural formula (I). In the compound structure, R ₁ can be -CH ₃ , -C ₂ H ₅ , -C ₃ H ₈ , -C ₄ H ₉ , -C ₅ H ₁₁ or -C ₆ H ₁₃ , or one of H An alkyl chain in which an atom is replaced by an alkenyl group, and the alkyl chain is -CH ₃ , -C ₂ H ₅ , -C ₃ H ₈ , -C ₄ H ₉ , for example, -CH ₂ CH=CH ₂ , -CH ₂ CH(CH=CH ₂ )CH ₃ or -CH(CH=CH ₂ )CH ₃ etc.; X ₁ can be -H, -F or -Cl; X ₂ can be -H, -F or -Cl; X ₃ can be -H, -F or -Cl; Y can be -NCS or -F. The groups of R ₁ , X ₁ , X ₂ , X ₃ and Y are chosen not to interfere with each other.

Preferably, at least one of the side groups X ₁ , X ₂ and X ₃ in the structural formula (I) is a F atom. The introduced ethyl and fluorine atoms and their own tetraphenyl structure can make the side ethyl tetraphenyl liquid crystal compound have greater optical anisotropy and better structural stability, which is beneficial to further reduce the liquid crystal material. Dielectric loss and further increase the quality factor of the liquid crystal material.

For ease of expression, the compound structures appearing hereinafter are represented by the structure codes in Table 1 below.

Table 1 Group structure code

In the table, R _n represents an alkyl group with n carbon atoms, and n is an integer; E(n) represents an alkenyl-containing alkyl group with a total carbon number of n, n is an integer; the Arabic numerals shown in the compound code are alkyl groups number of carbon atoms in the chain.

For ease of understanding, the following preferred embodiment I-1 of the ethyl tetrabiphenyl liquid crystal compound is used as an example for illustration. General structure. According to the codes shown in Table 1, the structural formula (I-1) can be named as the liquid crystal compound 3PPI (2) GUF.

As a preferred embodiment, the structural formula of the specific structural formula of the side ethyl tetrabiphenyl liquid crystal compound in the present invention is as follows: 5PP(2)PUF, 3PPI(2)PUF, 5PP(2)PUS, 5PPI(2) PUS, 4PP(2)GGS, 3PPI(2)PUS, 4PPI(2)GUS, 4PPI(2)GUF, 4PP(2)GUS, 3PP(2)JIUF, 4PP(2)PUF, 5PPI(2)GJIS, E(5)PP(2)PUF, E(5)PP(2)PGS, E(5)PPI(2)JUF.

The present invention also provides a method for preparing a side ethyl tetrabiphenyl liquid crystal compound, which is used for synthesizing a target compound product having the structure of structural formula (I), that is, the above-mentioned side ethyl tetrabiphenyl liquid crystal compound.

The synthetic route is:

In this embodiment, the preparation method of the side ethyl tetraphenyl liquid crystal compound includes the following steps:

Step S10: under nitrogen protection, mix the first reactant, the second reactant, tetrakistriphenylphosphine palladium, potassium carbonate, ethanol, toluene and water, and perform a reflux reaction at 65-85° C. under stirring conditions for 4- After 8 hours, the reaction was detected and followed by TLC, and after the reaction was completed, the first intermediate was obtained by separation, washing, drying and purification.

According to the specific structure (structural formula (I)) of the target compound, the first, second and third reactants with different structures are selected. Specifically, in this embodiment, the first reactant is a compound having a structure represented by the following structural formula (II); the second reactant is a compound having a structure represented by the following structural formula (III).

It should be understood that R ₁ in the structural formula of the first reactant is the same as R ₁ of the target compound product; the substitution position of the ethyl group in the second reactant is the same as the substitution position of the pendant ethyl group in the target compound product. For example, when the target compound is 3PPI(2) GUF, R ₁ in the first reactant is -C ₃ H ₉ ; and the second reactant is 3-ethyl-4-iodoaniline.

In step S10, the separation, washing, drying and purification can be carried out according to conventional methods in the field of organic synthesis, such as separating the reaction product by centrifugation or filtration, then extracting with an organic solvent, washing with water, then drying with a desiccant, and finally. Through chromatography, elution, etc., the purified product is obtained. In this embodiment, step S10 can be carried out in the following manner during specific implementation: under nitrogen protection, the first reactant, the second reactant, tetrakistriphenylphosphine palladium (catalyst, Pd( PPh ₃ ) ₄ ), potassium carbonate (K ₂ CO ₃ ), ethanol (EtOH), toluene and water, heated and stirred to reflux, the reflux temperature was 65-85 ℃, after the reflux reaction was 4-8 h, TLC (thin layer Chromatography) to detect and track the reaction, after the reaction is over, stop stirring; after the reaction solution is naturally cooled to room temperature, add hydrochloric acid to neutralize and filter out insolubles, then, add toluene to extract and separate the liquid, and wash the toluene layer to neutrality, Use anhydrous sodium sulfate to dry and filter, the filtrate is rotary evaporated to dryness and then loaded into a chromatography column, eluted with petroleum ether, and then the solvent in the eluent is removed by rotary evaporation to obtain the first intermediate.

Wherein, the molar ratio of the first reactant, the second reactant, tetrakistriphenylphosphine palladium and potassium carbonate is 1:(1-1.05):(0.001-0.003):(2-2.5).

Step S20: under ice-salt bath conditions, add hydrobromic acid and tetrahydrofuran to the first intermediate, and after the temperature of the solution drops below 0°C, dropwise add an aqueous solution of sodium nitrite, and then at 5-10°C Keep stirring for 50 to 70 minutes to obtain a reaction solution. Separately, hydrobromic acid and cuprous bromide are mixed and heated to reflux. The reaction solution is added dropwise, and the second intermediate is obtained through separation, drying and purification.

In the present embodiment, under ice-salt bath conditions, the first intermediate, hydrobromic acid (HBr) and tetrahydrofuran (THF) were successively added to the three-necked flask, and sodium nitrite ( NaNO ₂ ) aqueous solution (the dropwise addition was completed within 1 hour, and the temperature of the solution should not exceed 10°C during the dropwise addition), and the reaction solution was kept at 5-10°C for 50-70min under heat preservation and stirring. To another three-necked flask, add hydrobromic acid and cuprous bromide (CuBr) successively, heat to reflux, then dropwise add the above reaction solution, and keep refluxing all the time during the dropwise addition. After the dropwise addition, the temperature was naturally raised to room temperature, and an aqueous solution of sodium thiosulfate was added for stirring, followed by extraction and separation, followed by extraction with ethyl acetate, drying with anhydrous sodium sulfate, rotary evaporation to remove the solvent, and finally loading into a chromatographic column, The second intermediate is obtained after elution with petroleum ether.

Wherein, the molar ratio of the first intermediate, the hydrobromic acid added for the first time, the hydrobromic acid added again, sodium nitrite and cuprous bromide is 1:(1～4):(2.5～4):( 1 to 2): (0.6 to 3).

Step S30: under nitrogen protection and a temperature not higher than -75°C, add n-butyllithium dropwise to the mixed solution of the second intermediate and tetrahydrofuran, and after constant temperature reaction for 1-1.5h, dropwise add trimethyl borate , continue the constant temperature reaction for 2-4 hours, and obtain the third intermediate after separation, washing, drying and purification.

In this example, under nitrogen protection, the second intermediate and tetrahydrofuran (THF) were sequentially added to the reaction flask, the reaction flask was placed in a low temperature tank, and n-butyllithium was added dropwise after the temperature of the low temperature tank was cooled to -78°C (n-BuLi), the dropwise addition was completed within 1 hour and the temperature was always kept not higher than -75°C during the dropwise addition. After 1-1.5 hours of constant temperature reaction, trimethyl borate (B(OCH ₃ ) ₃ ) was added dropwise, and the temperature was always kept not higher than -75° C. during the dropwise addition. After 2-4 hours of constant temperature reaction, TLC (Thin Layer Chromatography) was used to detect and track the reaction. After the reaction was completed, the stirring was stopped. After the reaction solution was naturally cooled to room temperature, hydrochloric acid was added to neutralize and filter out insoluble matter. Then, acetic acid was added. The ethyl ester was extracted and separated, washed with water until neutral, dried and filtered with anhydrous sodium sulfate, and the filtrate was rotary evaporated to dryness and recrystallized with petroleum ether to obtain the third intermediate.

Wherein, the molar ratio of the second intermediate, n-butyllithium and trimethyl borate is 1:(1.0-1.5):(1.5-2).

Step S40: under nitrogen protection, sequentially add the third reactant, tetrakistriphenylphosphine palladium, potassium carbonate, ethanol, toluene and water to the third intermediate, and reflux at 65-80° C. under stirring conditions. The reaction was carried out for 4-6 hours, and the target compound was obtained after separation, washing, drying and purification.

Similarly, according to the specific structure of the target compound (see structural formula (I)), the third reactant with different structure, ie, brominated biphenyl containing different substituent groups, is selected. Specifically, in this embodiment, the third reactant is a compound having a structure represented by the following structural formula (IV).

Wherein, M may be -F or -NH ₂ . It should be understood that X ₁ , X ₂ , X ₃ and M in the structural formula of the third reactant are all the same as X ₁ , X ₂ , X ₃ and Y in the structural formula of the target compound regardless of the selected group structure or substitution position. correspond. For example, when the target compound is 3PPI(2) GUF, the structural formula of the third reactant is as follows. However, it should be noted that, in view of the fact that when Y in structural formula (I) is -NCS, the brominated biphenyl containing -NCS substitution is not easy to react, in order to promote the smooth progress of the reaction, M can be selected as the third reactant of _-NH2 .

Third reactant:

Wherein, the molar ratio of the third intermediate, the third reactant, tetrakistriphenylphosphine palladium and potassium carbonate is 1:(1-1.05):(0.001-0.003):(2-4).

During specific implementation, step S40 can be performed by the following operations: under nitrogen protection, sequentially add the third intermediate, the third reactant, tetrakistriphenylphosphine palladium, potassium carbonate, ethanol, toluene and water into the reaction flask, heat Stir to reflux, the reflux temperature is 65 ~ 80 ℃, after the reflux reaction is 4 ~ 6h, use TLC (thin layer chromatography) to detect and track the reaction, after the reaction is over, stop stirring; after the reaction solution is naturally cooled to room temperature, add Toluene was extracted and separated, washed with water until neutral, dried and filtered using anhydrous sodium sulfate, the filtrate was rotary evaporated to dryness and then loaded into a chromatography column, eluted with petroleum ether, and the solvent was removed by rotary evaporation, and then recrystallized with petroleum ether. The target compound, that is, the crude product of the pendant ethyl tetraphenyl-based liquid crystal compound having the structure represented by the structural formula (I) is obtained.

In another embodiment of the preparation method of the present invention, when Y ₁ in the structural formula (I) of the target compound is -NCS, a brominated biphenyl in which Y is -NH ₂ is selected as the third reactant. Of course, the third reaction The X ₁ , M ₁ , and N ₁ of the compound are still in one-to-one correspondence with X ₁ , M ₁ , and N ₁ in the structural formula of the target compound. In this embodiment, the product of step S40, calcium carbonate, water and dichloromethane are mixed at 0-5°C, and then carbon dichlorosulfide is added dropwise, and the reaction is performed at a constant temperature of 0-5°C for 1.5 hours, and the temperature rises to the temperature naturally. The reaction was carried out at room temperature for 0.5h, and then heated and refluxed for 0.5h. After separation and purification, the target compound in which Y ₁ was -NCS could be obtained.

In order to further improve the resistivity of the side-ethyl tetraphenyl-based liquid crystal compound, the crude product of the side-ethyl tetraphenyl-based liquid crystal compound can also be subjected to power plant adsorption purification and removal of trace ions after step S40. Specifically, the electric field adsorption method can be used: the crude product is dissolved in toluene to make a solution to be treated; toluene, the solution to be treated and nano-silica are respectively added to the cathode solvent chamber and the sample of the three-slot ionic membrane purifier respectively. In the chamber and the anode solvent chamber, oxide film electrodes are used, the electrode spacing is 6-15mm, the electric field intensity is 1.0-4kV/cm, and the refined product is obtained after purifying for 30min.

In addition, the present invention also provides a liquid crystal composition, the liquid crystal composition includes a first component, and the first component includes one or more of the above-mentioned side ethyl tetrabiphenyl liquid crystal compounds , that is, the first component includes at least one of the side ethyl tetraphenyl liquid crystal compounds with the structure represented by the structural formula (I) provided above in the present invention, for example, the liquid crystal composition of this embodiment may include 5PP(2 )PUF, may also include 5PP(2)PUF, 5PPI(2)PUF, and may also include three or more side ethyl tetraphenyl liquid crystal compounds having the structure represented by structural formula (I). The liquid crystal composition can also be obtained by combining the side ethyl tetrabiphenyl liquid crystal compound with any existing liquid crystal compound, all of which have dielectric properties brought about by the structural characteristics of the side ethyl tetrabiphenyl liquid crystal compound. Advantages of lower loss and higher quality factor.

Further, in this embodiment, each compound component in the liquid crystal composition is a refined product after being purified by an electric field adsorption method. In this way, a product with lower dielectric loss and higher quality factor can be obtained. combination. The purification treatment by the electric field adsorption method has been described above, and will not be repeated here.

As a more preferred embodiment of the liquid crystal composition of the present invention, the liquid crystal composition of this embodiment includes a first component, and the first component may be composed of one to five compounds represented by the structural formula (I), and each The weight percent content of one of the compounds in the liquid crystal composition is 1-15%, preferably 5-10%. For example, the liquid crystal composition includes a first component and other existing liquid crystal compounds, the first component is composed of 5PP(2)PUF and 5PPI(2)PUF, then in the liquid crystal composition of this embodiment, 5PP(2) ) The weight percentage of PUF is 1-15%, and the weight percentage of 5PPI (2) PUF is 1-15%.

Further, in an embodiment of the liquid crystal composition provided by the present invention, the liquid crystal composition further includes a second component, a third component and a fourth component.

Wherein, the second component includes at least one of the compound represented by the following structural formula (V) and the compound represented by the following structural formula (VI). That is, the second component can be selected from one or more of the compounds with the structure represented by the structural formula (V); one or more of the compounds with the structure represented by the structural formula (VI) can also be selected; A compound having the structure represented by the structural formula (V) and at least one compound having the structure represented by the structural formula (VI).

In structural formula (V), R ₂ is a saturated or unsaturated alkyl group containing 2 to 7 carbon atoms, X ₄ , X ₅ , and X ₆ are each independently selected from -H or -F, and Y ₁ is -NCS or -F; in structural formula (VI), R ₃ is a saturated or unsaturated alkyl group containing 2 to 7 carbon atoms, X ₇ is -H, -F or -Cl, X ₈ and X ₉ are each independently Selected from -H or -F, Y ₂ is -NCS or -F.

The third component includes at least one of the compounds represented by the following structural formula (VII).

In structural formula (VII), R ₄ and R ₅ are each independently selected from saturated or unsaturated alkyl groups containing 2 to 7 carbon atoms.

The fourth component includes at least one of the compound represented by the following structural formula (VIII) and the compound represented by the following structural formula (IX).

In structural formula (VIII), R ₆ is a saturated or unsaturated alkyl group containing 2 to 7 carbon atoms, X ₁₀ and X ₁₁ are each independently selected from -H or -F, and Y ₃ is -NCS or -F ; In structural formula (IX), R ₇ is a saturated or unsaturated alkyl group containing 2 to 7 carbon atoms; X ₁₂ and X ₁₃ are each independently selected from -H or -F, and Y ₄ is -NCS or - F.

It can be understood that, in this embodiment, the liquid crystal composition includes a first component, a second component, a third component and a fourth component; wherein, the first component can be selected from the group having the structural formula (I) At least one of the compounds of the structure shown, the second component can be selected from at least one of compounds with structures such as structural formula (V) and structural formula (VI), and the third component can be selected from compounds with structures such as At least one of the compounds represented by the structural formula (VII), the fourth component can be selected from at least one of the compounds represented by the structural formula (VIII) and the compounds represented by the structural formula (IX), and the fifth component can be selected from At least one of the compounds represented by the structural formula (X). In the liquid crystal composition of this embodiment, the weight percentage of each compound in the second component is 1-15%, preferably 5-10%; the weight percentage of each compound in the third component is 100% The component content is 1-20%, preferably 5-15%; the weight percentage of each compound in the fourth component is 1-15%, preferably 2-8%.

As a preferred embodiment of the present invention, the liquid crystal composition further includes a fifth component, that is, the liquid crystal composition in this embodiment is composed of a first component, a second component, a third component, a fourth component and a fifth component point. Wherein, the fifth component includes at least one of the compounds represented by the following structural formula (X):

Wherein, R ₈ and R ₉ are each independently selected from saturated or unsaturated alkyl groups containing 2 to 7 carbon atoms, and R ₁₀ is -CH ₃ or -C ₂ H ₅ .

In the liquid crystal composition of this embodiment, the weight percentage of each compound in the fifth component in the liquid crystal composition is 1-15%, preferably 2-5%.

In addition, the present invention also provides a microwave device comprising the above-mentioned liquid crystal composition.

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

The technical solutions of the present invention will be described in further detail below with reference to specific embodiments. It should be understood that the following embodiments are only used to explain the present invention, and are not intended to limit the present invention.

Example of preparation method

Example 1 Synthesis of side ethyl tetraphenyl liquid crystal compound 5PP(2)PUF

The molecular structure of 5PP(2)PUF is as follows:

Its synthetic route is:

(1) 7.6g (0.04mol) of 4-n-pentylphenylboronic acid, 9.88g (0.04mol) of 2-ethyl-4-iodoaniline, 13.8g (0.10mol) of potassium carbonate were added successively in a 250mL four-necked flask, 80 mL of ethanol, 60 mL of toluene and 30 mL of water; after 6 times of nitrogen replacement, 0.46 g (1% mol) of catalyst tetrakistriphenylphosphine palladium was added under nitrogen protection; heated and stirred, the temperature was controlled at 70 °C, and the reaction was refluxed for 4 h, using TLC Follow-up detection, after the reaction is complete, stop stirring; cool down to room temperature, neutralize 5% hydrochloric acid and filter out insolubles, add toluene to extract the liquid, wash with water until neutral, dry with anhydrous sodium sulfate, filter, and evaporate the filtrate to dryness It was loaded into a chromatography column, eluted with petroleum ether, and the solvent was removed by rotary evaporation to obtain 8.7g of the intermediate 4-(4'-n-pentyl)-2-ethylaniline [5PP(2)NH ₂ ] in brown color Liquid, 82.2% yield.

(2) 8g (0.03mol) of compound 5PP(2)NH ₂ , 24.3g (40%, 0.12mol) of hydrobromic acid and 100ml of tetrahydrofuran (THF) were successively added to a 250mL three-necked flask, ice-salt bath, and the temperature dropped to After 0 °C, add 20 mL of sodium nitrite (2.4 g, 0.035 mol) aqueous solution dropwise. The dropwise addition is completed within 1 hour, and the solution temperature cannot exceed 10 °C during the dropwise addition. Stir at 5 °C for 60 minutes, and store at low temperature for later use. ; In another there-necked flask, add 15.2g (40%, 0.075mol) hydrobromic acid successively, 2.88g (0.02mol) cuprous bromide, be heated to reflux, add the step reaction solution dropwise again, in the dropping process Always keep refluxing. After the dropwise addition, the temperature was naturally raised to room temperature, and an aqueous solution of sodium thiosulfate was added for stirring, followed by extraction and separation, followed by extraction with ethyl acetate, drying with anhydrous sodium sulfate, rotary evaporation to remove the solvent, and finally loading into a chromatographic column, Rinse with petroleum ether (60℃～90℃); after removing the solvent, 6.9 g of intermediate 5PP(2)Br (yellow liquid) is obtained, and the yield is 70.0%.

(3) 5.6g (0.016mol) 5PP(2)Br and 100ml tetrahydrofuran (THF) were added successively in a 250ml four-necked flask, the reaction flask was placed in a low temperature tank, and the dripping started after the temperature of the low temperature tank was cooled to -78°C 1.1 g (0.02 mol) of n-butyllithium was added, and the dropwise addition was completed for 1 h, and the temperature of the reaction solution was always kept below -75°C during the dropwise addition. After 1 h of constant temperature reaction, 2.5 g (0.024 mol) of trimethyl borate was added dropwise (the temperature of the reaction solution should not exceed -75°C during the process). After 2 hours of constant temperature reaction, TLC followed the reaction process. After the reaction was completed, the stirring was stopped. After the reaction solution was naturally cooled to room temperature, 5% hydrochloric acid was added to neutralize it. , dried and filtered with anhydrous sodium sulfate, the filtrate was evaporated to dryness and recrystallized with petroleum ether to obtain 3.1 g of white solid amylbiphenylboronic acid with a yield of 65.2%.

(4) Under nitrogen protection, 2.9g (0.01mol) intermediate amylbiphenylboronic acid, 2.86g (0.01mol) brominated biphenyl, 5.5g (0.04mol) potassium carbonate powder solid were successively added to the 250mL four-necked flask , 60 mL of ethanol, 50 mL of toluene and 15 mL of water, replaced with nitrogen for 6 times, and 0.12 g (1% mol) of catalyst tetrakistriphenylphosphine palladium was added. Heating and stirring to reflux under nitrogen protection, the reflux temperature is 70 ℃, after the reaction is refluxed for 4 hours, use TLC to track and detect, after the reaction is complete, stop stirring; the reaction solution is naturally cooled to room temperature, neutralized with hydrochloric acid, filtered to remove insolubles, and added Toluene was extracted and separated, washed with water until neutral, dried with anhydrous sodium sulfate and filtered. The filtrate was evaporated cleanly, separated by column chromatography, eluted with petroleum ether (60℃～90℃), and most of the solvent was removed by rotary evaporation. , and crystallized by cooling to obtain 3.4 g of the target compound 5PP(2)PUF as a white solid, with a yield of 75.2% and a phase transition temperature of Cr 72°C N 185°C Iso.

The molecular structure identification data are as follows:

¹ H-NMR (CDCl ₃ , 400MHz) δ (ppm): 7.31～7.68 (m, 13H), 2.65～2.68 (t, 4H), 2.51～2.54 (m, 2H), 1.68～1.82 (m, 4H) ,1.45～1.49(m,6H),0.99～1.26(t,9H);

¹³ C-NMR (100MHz, CDCl ₃ )δ(ppm): 14.050, 14.132, 15.273, 22.478, 22.656, 26.490, 31.267, 31.663; ,130.81,132.04,133.73,137.02,138.46,141.15,142.21,158.84,161.28;

19F-NMR (376.29 MHz, CDCl ₃ ) δ (ppm): -114.34.

Example 2 Synthesis of side ethyl tetraphenyl liquid crystal compound 5PPI (2) PUF

The molecular structure of 5PPI(2)PUF is as follows:

(1) 7.6g (0.04mol) of 4-n-pentylphenylboronic acid, 9.88g (0.04mol) of 3-ethyl-4-iodoaniline, 13.8g (0.10mol) of potassium carbonate were added successively in a 250mL four-necked flask, 80 mL of ethanol, 60 mL of toluene and 30 mL of water; after 6 times of nitrogen replacement, 0.46 g (0.1% mol ratio) of catalyst tetrakistriphenylphosphine palladium was added under nitrogen protection; heated and stirred, the temperature was controlled at 85 ° C, and the reaction was refluxed for 4 h, using TLC tracking detection, after the reaction is complete, stop stirring; cool to room temperature, neutralize with 5% hydrochloric acid, filter out insolubles, add toluene to extract the liquid, wash with water until neutral, dry with anhydrous sodium sulfate, filter, and evaporate the filtrate to dryness After purification by column chromatography, eluting with petroleum ether (60 ℃ ~ 90 ℃), rotary evaporation to remove the solvent to obtain 7.8g of intermediate 4-(4'-n-pentyl)-2-ethylaniline [5PPI (2 ) _NH2 ] as a brown liquid in 74.5% yield.

(2) 8g (0.03mol) of compound 5PPI (2) NH ₂ , 24.3g (40%, 0.12mol) of hydrobromic acid and 100ml of tetrahydrofuran (THF) were successively added to a 250mL three-necked flask, ice-salt bath, and the temperature dropped to After 0 °C, add 20 mL of sodium nitrite (2.4 g, 0.035 mol) aqueous solution dropwise. The dropwise addition is completed within 1 hour, and the solution temperature cannot exceed 10 °C during the dropwise addition. Stir at 7 °C for 70 minutes, and store at low temperature for later use. In another there-necked flask, add 15.2g (40%, 0.075mol) hydrobromic acid with this, 2.88g (0.02mol) cuprous bromide, be heated to reflux, add the step reaction solution dropwise again, dripping process Keep refluxing all the time, after the dropwise addition is completed, the temperature is naturally raised to room temperature, the aqueous solution of sodium thiosulfate is added for stirring, and the liquid is extracted and separated, and then extracted with ethyl acetate, dried with anhydrous sodium sulfate, and the solvent is removed by rotary evaporation. In the chromatographic column, petroleum ether (60℃～90℃) was used for elution; after the solvent was removed, 6.7g of intermediate 5PPI(2)Br (yellow liquid) was obtained, and the yield was 69.5%.

(3) add 5.6g (0.016mol) 5PPI (2) Br, 100ml tetrahydrofuran (THF) with this in the 250ml four-necked flask, the reaction flask is placed in the low temperature tank, and the temperature of the low temperature tank is cooled to -78 ℃ and then starts 1.1 g (0.02 mol) of n-butyllithium was added dropwise, the dropwise addition was completed for 1 h, and the temperature of the reaction solution was always kept below -75°C during the dropwise addition. After 1.5 hours of constant temperature reaction, 2.5 g (0.024 mol) of trimethyl borate was added dropwise (the temperature of the reaction solution should not exceed -75°C during the process). After 2.2 hours of constant temperature reaction, TLC followed the reaction process. After the reaction was completed, the stirring was stopped. After the reaction solution was naturally cooled to room temperature, 5% hydrochloric acid was added to neutralize it. , dried over anhydrous sodium sulfate, filtered, the filtrate was rotary evaporated to dryness and recrystallized with petroleum ether to obtain 3.7 g of white solid amylbiphenylboronic acid with a yield of 68.2%.

(4) Under nitrogen protection, 2.9g (0.01mol) intermediate amylbiphenylboronic acid, 2.86g (0.01mol) brominated biphenyl, 5.5g (0.04mol) potassium carbonate powder solid were successively added to the 250mL four-necked flask , 60 mL of ethanol, 50 mL of toluene and 15 mL of water, replaced with nitrogen for 6 times, and 0.12 g (0.1% mol ratio) of catalyst tetrakistriphenylphosphine palladium was added. Heat and stir to reflux under nitrogen protection, the reflux temperature is 65 ℃, after the reaction is refluxed for 6 hours, use TLC to track and detect, after the reaction is complete, stop stirring; Add toluene for extraction and separation, wash with water until neutral, dry with anhydrous sodium sulfate and filter, the filtrate is rotary evaporated to clean, separated by column chromatography, eluted with petroleum ether (60 ℃ ~ 90 ℃), and rotary evaporated to remove most of the solvent , and crystallized by cooling to obtain 3.6g of the target compound 5PPI(2)PUF as a white solid with a yield of 80.3%. The phase transition temperature is Cr65℃N 180℃Iso; Δn is 0.385.

The molecular structure identification data are as follows:

¹ H-NMR (CDCl ₃ , 400MHz) δ (ppm): 7.25-7.88 (m, 13H), 2.71-2.73 (t, 2H), 2.64-2.67 (t, 2H), 2.53-2.56 (m, 2H) ,1.61～0.65(m,4H),1.45～1.54(m,6H),0.98～1.25(m,9H);

¹³ C-NMR (100MHz, CDCl ₃ )δ(ppm): 14.050, 14.132, 15.273, 22.478, 22.656, 26.490, 31.267, 31.663; ,130.81,132.04,133.73,137.02,138.46,141.15,142.21,158.84,161.28;

¹⁹ F-NMR (376.29 MHz, CDCl ₃ ) δ (ppm): -115.45.

Example 3 Synthesis of side ethyl tetraphenyl liquid crystal compound 5PP(2)PUS

The molecular structure of 5PP(2)PUS is as follows:

(1) 7.6g (0.04mol) of 4-n-pentylphenylboronic acid, 9.88g (0.04mol) of 2-ethyl-4-iodoaniline, 13.8g (0.10mol) of potassium carbonate were added successively in a 250mL four-necked flask, 80mL of ethanol, 60mL of toluene and 30mL of water; after 6 times of nitrogen replacement, 0.46g (0.1% mol ratio) catalyst tetrakistriphenylphosphine palladium was added under nitrogen protection; heated and stirred, the temperature was controlled at about 65°C, and the reaction was refluxed for 8h, Use TLC to track and detect, after the reaction is complete, stop stirring; cool to room temperature, neutralize with 5% hydrochloric acid, filter out insolubles, add toluene to extract and separate, wash with water until neutral, dry with anhydrous sodium sulfate and filter, and the filtrate is rotary evaporated After drying, it was purified by column chromatography, eluted with petroleum ether (60℃～90℃), and the solvent was removed by rotary evaporation to obtain 8.7g of intermediate 4-(4'-n-pentyl)-2-ethylaniline [5PP( 2) _NH2 ] as a brown liquid in 82.2% yield.

(2) 8g (0.03mol) of compound 5PP(2)NH ₂ , 24.3g (40%, 0.12mol) of hydrobromic acid and 100ml of tetrahydrofuran (THF) were successively added to a 250mL three-necked flask, ice-salt bath, and the temperature dropped to After 0 °C, add 20 mL of sodium nitrite (2.4 g, 0.035 mol) aqueous solution dropwise. The dropwise addition is completed within 1 hour, and the solution temperature cannot exceed 10 °C during the dropwise addition. Stir at 10 °C for 50 minutes, and store at low temperature for use. ; In another there-necked flask, add 15.2g (40%, 0.075mol) hydrobromic acid successively, 2.88g (0.02mol) cuprous bromide, be heated to reflux, add the step reaction solution dropwise again, in the dropping process Always keep refluxing. After the dropwise addition, the temperature was naturally raised to room temperature, and an aqueous solution of sodium thiosulfate was added for stirring, followed by extraction and separation, followed by extraction with ethyl acetate, drying with anhydrous sodium sulfate, rotary evaporation to remove the solvent, and finally loading into a chromatographic column, Rinse with petroleum ether (60℃～90℃); after removing the solvent, 6.9 g of intermediate 5PP(2)Br (yellow liquid) is obtained, and the yield is 70.0%.

(3) add 5.6g (0.016mol) 5PP (2) Br, 100ml tetrahydrofuran (THF) with this in the 250ml four-necked flask, the reaction flask is placed in the low temperature tank, and the temperature of the low temperature tank is cooled to -78 ℃ and then starts 1.1 g (0.02 mol) of n-butyllithium was added dropwise, the dropwise addition was completed for 1 h, and the temperature of the reaction solution was always kept below -75°C during the dropwise addition. After 1.2 hours of constant temperature reaction, 2.5 g (0.024 mol) of trimethyl borate was added dropwise (the temperature of the reaction solution should not exceed -75°C during the process). After 3 hours of constant temperature reaction, TLC followed the reaction process. After the reaction was completed, the stirring was stopped. After the reaction solution was naturally cooled to room temperature, 5% hydrochloric acid was added to neutralize it. After drying over anhydrous sodium sulfate, the solution was filtered, and the filtrate was rotary evaporated to dryness and recrystallized with petroleum ether to obtain 3.1 g of a white solid with a yield of 65.2%.

(4) Under nitrogen protection, 2.9g (0.01mol) intermediate amylbiphenylboronic acid, 2.86g (0.01mol) brominated biphenyl, 5.5g (0.04mol) potassium carbonate powder solid were added successively to the 250mL four-necked flask , 60 mL of ethanol, 50 mL of toluene and 15 mL of water, replaced with nitrogen 6 times, and added 0.12 g (0.1% mol ratio) catalyst tetrakistriphenylphosphine palladium. Heating and stirring to reflux under nitrogen protection, the reflux temperature was 80 °C, after the reaction was refluxed for 6 hours, followed by TLC detection, after the reaction was completed, stop stirring; Toluene was extracted and separated, washed with water until neutral, dried over anhydrous sodium sulfate and filtered. The filtrate was evaporated cleanly, separated by column chromatography, eluted with petroleum ether (60°C to 90°C), and most of the solvent was removed by rotary evaporation. Crystallization by cooling gave 3.4 g of pale yellow solid 5PP(2)PUNH ₂ with a yield of 75.2%.

(5) Into a 250ml three-necked flask, 3.6g of the previous product 5PP( ₂ ) _PUNH2 , 2g of CaCO3 powder, 5ml of water and 50ml of _{CH2Cl2 were} sequentially added. Control the temperature at about 0-5°C, then inject 2ml of carbon dichlorosulfide into the constant pressure dropping funnel, slowly add dropwise to the control temperature not exceeding 5°C, keep the temperature constant for 1.5h, naturally rise to room temperature for 0.5h, and then heat to reflux Reaction 0.5h. Use TLC to track and detect, after the reaction is complete, stop stirring; the reaction solution is naturally cooled to room temperature, the insolubles are filtered off, ethyl acetate is added to extract the liquid, washed with water until neutral, dried over anhydrous sodium sulfate, filtered, and the filtrate is rotary evaporated. After separation by column chromatography, eluting with petroleum ether (60°C-90°C), and removing most of the solvent by rotary evaporation, 3.4 g of white solid 5PP(2)PUS was obtained by cooling and crystallization, and the yield was about 78%. The phase transition temperature is Cr 108°C N 185°C Iso.

The molecular structure identification data are as follows:

¹ H-NMR (CDCl ₃ , 400MHz) δ (ppm): 7.31～7.68 (m, 13H), 2.65～2.68 (t, 4H), 2.51～2.54 (m, 2H), 1.68～1.82 (m, 4H) ,1.45～1.49(m,6H),0.99～1.26(t,9H);

¹³ C-NMR (100MHz, CDCl ₃ )δ(ppm): 14.050, 14.132, 15.273, 22.478, 22.656, 26.490, 31.267, 31.663; ,130.81,132.04,133.73,137.02,138.46,141.15,142.21,158.84,161.28;

19F-NMR (376.29 MHz, CDCl ₃ ) δ (ppm): -114.34.

Example 4 Synthesis of side ethyl tetraphenyl liquid crystal compound 5PPI (2) PUS

The molecular structure of 5PPI(2)PUS is as follows:

(1) 7.6g (0.04mol) of 4-n-pentylphenylboronic acid, 9.88g (0.04mol,) of 3-ethyl-4-iodoaniline, 13.8g (0.10mol) of potassium carbonate were added successively in a 250mL four-necked flask , 80mL of ethanol, 60mL of toluene and 30mL of water; after 6 times of nitrogen replacement, 0.46g (0.1% mol ratio) catalyst tetrakistriphenylphosphine palladium was added under nitrogen protection; heating and stirring, the temperature was controlled at about 85 ℃, and the reflux reaction was carried out for 5h After the reaction is complete, stop stirring; cool to room temperature, neutralize with 5% hydrochloric acid, filter out insolubles, add toluene (3×50ml) to extract and separate, wash with water until neutral, and dry with anhydrous sodium sulfate After filtering, the filtrate was rotary evaporated to dryness and purified by column chromatography, eluted with petroleum ether (60℃～90℃), and 8.7g of intermediate 4-(4'-n-pentyl)-2- was obtained after rotary evaporation to remove the solvent. Ethylaniline [5PPI(2) _NH2 ] as a brown liquid in 82.2% yield.

(2) 8g (0.03mol) of compound 5PPI (2) NH ₂ , 24.3g (40%, 0.12mol) of hydrobromic acid and 100ml of tetrahydrofuran (THF) were successively added to a 250mL three-necked flask, ice-salt bath, and the temperature dropped to After 0 °C, add 20 mL of sodium nitrite (2.4 g, 0.035 mol) aqueous solution dropwise. The dropwise addition is completed within 1 hour, and the solution temperature cannot exceed 10 °C during the dropwise addition. Stir at 5 °C for 70 minutes, and store at low temperature for later use. In another there-necked flask, add 15.2g (40%, 0.075mol) hydrobromic acid with this, 2.88g (0.02mol) cuprous bromide, be heated to reflux, add the step reaction solution dropwise again, dripping process Keep refluxing all the time, after the dropwise addition is completed, the temperature is naturally raised to room temperature, the aqueous solution of sodium thiosulfate is added for stirring, and the liquid is extracted and separated, and then extracted with ethyl acetate, dried with anhydrous sodium sulfate, and the solvent is removed by rotary evaporation. In the chromatographic column, petroleum ether (60℃～90℃) was used for elution; after the solvent was removed, 6.9 g of intermediate 5PPI(2)Br (yellow liquid) was obtained with a yield of 70.0%.

(3) Add 5.6g (0.016mol) of 5PPI (2) Br, 100ml of tetrahydrofuran (THF) to the 250ml four-necked flask, and start to drop 1.1g (0.02mol) of n-butyl after the low temperature tank is cooled to -78°C Lithium was added dropwise for 1 hour (the temperature of the reaction solution should not exceed -75°C during the process), and after 1 hour of constant temperature reaction, 2.5g (0.024mol) trimethyl borate was added dropwise (the temperature of the reaction solution should not exceed -75°C during the process). After 4 hours of constant temperature reaction, TLC followed the reaction process. After the reaction was completed, the stirring was stopped. After the reaction solution was naturally cooled to room temperature, 5% hydrochloric acid was added to neutralize it. After drying over anhydrous sodium sulfate, the solution was filtered, and the filtrate was rotary evaporated to dryness and recrystallized with petroleum ether to obtain 3.1 g of a white solid with a yield of 65.2%.

(4) Under nitrogen protection, 2.9g (0.01mol) intermediate amylbiphenylboronic acid, 2.86g (0.01mol) brominated biphenyl, 5.5g (0.04mol) potassium carbonate powder solid were added successively to the 250mL four-necked flask , 60 mL of ethanol, 50 mL of toluene and 15 mL of water, replaced with nitrogen 6 times, and added 0.12 g (0.1% mol ratio) catalyst tetrakistriphenylphosphine palladium. Heat and stir to reflux under nitrogen protection, the reflux temperature is 70 ℃, after the reaction is refluxed for 5 hours, use TLC to track and detect, after the reaction is complete, stop stirring; the reaction solution is naturally cooled to room temperature, neutralized with hydrochloric acid, filtered to remove insolubles, and added Toluene was extracted and separated, washed with water until neutral, dried over anhydrous sodium sulfate and filtered. The filtrate was evaporated cleanly, separated by column chromatography, eluted with petroleum ether (60°C to 90°C), and most of the solvent was removed by rotary evaporation. Crystallization by cooling gave 3.4 g of pale yellow solid 5PPI(2)PUNH ₂ with a yield of 75.2%.

(5) To a 250ml three-necked flask, 2.5g of the product of the previous step 5PPI(2) PUNH ₂ , 1.4g of CaCO ₃ powder, 5ml of water and 50ml of CH ₂ Cl ₂ were sequentially added. Control the temperature at about 0-5°C, then inject 2ml of carbon dichlorosulfide into the constant pressure dropping funnel, slowly add dropwise to the control temperature not exceeding 5°C, keep the temperature constant for 1.5h, naturally rise to room temperature for 0.5h, and then heat to reflux Reaction 0.5h. Use TLC to track and detect, after the reaction is complete, stop stirring; the reaction solution is naturally cooled to room temperature, the insolubles are filtered off, ethyl acetate is added to extract the liquid, washed with water until neutral, dried over anhydrous sodium sulfate, filtered, and the filtrate is rotary evaporated. After separation by column chromatography, petroleum ether (60℃～90℃) eluted, most solvent was removed by rotary evaporation, 2.1g of white solid 5PPI(2)PUS was obtained by cooling and crystallization, and the yield was about 75%. The phase transition temperature is Cr 68℃N 185℃Iso; Δn is 0.44.

¹ H NMR (400 MHz, CDCl ₃ ) δ 7.78 (d, J=8.2 Hz, 2H), 7.72-7.58 (m, 3H), 7.58-7.46 (m, 2H), 7.32 (dt, J=11.9, 8.8 Hz, 6H), 2.92–2.64 (m, 3H), 1.70 (dd, J=35.6, 28.2Hz, 2H), 1.52–1.33 (m, 4H), 1.23 (t, J=7.5Hz, 3H), 0.98 (t,J=6.6Hz,3H).

¹³ C NMR (101MHz, CDCl ₃ ) δ 159.54(s, 1H), 157.05(s, 1H), 144.95(s, 1H), 142.38(s, 1H), 141.73(d, J=4.0Hz, 2H) ,141.37(s,1H),140.66(s,1H),138.94(s,2H),138.64(s,1H),136.49(s,1H),130.81(s,3H),129.07(s,5H), 128.18(s, 5H), 127.81(s, 5H), 127.24(d, J=10.3Hz, 8H), 124.25(s, 3H), 110.29(s, 3H), 110.07(s, 3H), 35.74(s ,2H),31.70(s,3H),31.22(s,2H),26.36(s,2H),22.64(s,2H),15.79(s,2H),14.12(s,2H).

¹⁹ F-NMR (376.29 MHz, CDCl ₃ ) δ (ppm): -116.41.

Examples of liquid crystal compositions

Example 5

Select different liquid crystal compounds of the first component, the second component, the third component, the fourth component and the fifth component, sample and weigh them according to a certain mass ratio, mix, heat and stir for 0.5 hours to prepare a liquid crystal combination material (M-1). Its microwave dielectric properties were tested by Chengdu Enchi Microwave Technology Co., Ltd. using the rectangular resonant cavity perturbation method. The specific component content (Wt%) and high-frequency dielectric properties are shown in Table 2 below:

Table 2 Composition and dielectric properties of liquid crystal composition material (M-1)

Example 6

Select different liquid crystal compounds of the first component, the second component, the third component and the fourth component, sample and weigh them according to a certain mass ratio, mix, heat and stir for 0.5 hours to prepare a liquid crystal composition (M-2 ). Its microwave dielectric properties were tested by Chengdu Enchi Microwave Technology Co., Ltd. using the rectangular resonant cavity perturbation method. The specific component content (Wt%) and high-frequency dielectric properties are shown in Table 3 below:

Table 3 Liquid crystal composition material (M-2) composition and dielectric properties

Example 7

Mix the various liquid crystal compounds of the first component, the second component, the third component, the fourth component and the fifth component, sample and weigh according to a certain mass ratio, heat and stir for 0.5 hours to prepare a liquid crystal combination material (M-3). Its microwave dielectric properties were tested by Chengdu Enchi Microwave Technology Co., Ltd. using the rectangular resonant cavity perturbation method. The specific component content (Wt%) and high-frequency dielectric properties are shown in Table 4 below:

Table 4 Composition and dielectric properties of liquid crystal composition material (M-3)

Comparative ratio

The components shown in the following table 5 are mixed and formulated into liquid crystal composition M6-2 as a comparative example. The specific component content and high-frequency dielectric properties of the liquid crystal composition M6-2 of the comparative example are shown in Table 5:

Table 5 Composition and dielectric properties of mixed liquid crystal material (M6-2) in comparative examples

Composition M6-2 as a comparative example for comparison of dielectric properties is a liquid crystal composition to which the first component liquid crystal compound (I) is not added. After the microwave dielectric performance test, it was found that under high frequency, the compositions M-1, M-2, and M-3 in the examples of the present invention were all added with the first component compound (I), which made the high-frequency dielectric The performance is better than that of M6-2, the dielectric loss at high frequency is lower than that of M6-2, and the quality factor of liquid crystal material is better than that of M6-2.

The above are only preferred embodiments of the present invention, and are not intended to limit the scope of the present invention. For those skilled in the art, the present invention may have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the scope of patent protection of the present invention.

Claims (7)

1. A liquid crystal composition, characterized in that the liquid crystal composition comprises a first component, and the first component is one or more of side ethyl tetrabiphenyl liquid crystal compounds, and the side The ethyl tetraphenyl liquid crystal compound has the structure shown in the following structural formula (I):

Wherein, R ₁ is an alkyl group containing 1-7 carbon atoms or a C _n H _2n+1 chain in which one H atom is substituted by -CH=CH ₂ , and n=1-4; X ₁ , X ₂ and X ₃ are each independently selected from -H, -F or -Cl; Y is -NCS or -F; The liquid crystal composition further includes a second component, a third component and a fourth component; Wherein, the second component includes at least one of the compound represented by the following structural formula (V) and the compound represented by the following structural formula (VI); The third component includes at least one of the compounds represented by the following structural formula (VII); The fourth component includes at least one of the compound represented by the following structural formula (VIII) and the compound represented by the following structural formula (IX);

Wherein, in structural formula (V), R ₂ is a saturated alkyl group containing 2 to 7 carbon atoms; X ₄ , X ₅ , and X ₆ are each independently selected from -H or -F, and Y ₁ is -NCS or -F ; In structural formula (VI), R ₃ is a saturated alkyl group containing 2 to 7 carbon atoms; X ₇ is -H, -F or -Cl, X ₈ and X ₉ are independently selected from -H or -F, Y ₂ is -NCS or -F; In structural formula (VII), R ₄ and R ₅ are each independently selected from saturated alkyl groups containing 2 to 7 carbon atoms; In structural formula (VIII), R ₆ is a saturated alkyl group containing 2 to 7 carbon atoms; X ₁₀ and X ₁₁ are each independently selected from -H or -F, and Y ₃ is -NCS or -F; In structural formula (IX), R ₇ is a saturated alkyl group containing 2-7 carbon atoms; X ₁₂ and X ₁₃ are each independently selected from -H or -F, and Y ₄ is -NCS or -F. 2 . The liquid crystal composition according to claim 1 , wherein each compound component in the liquid crystal composition is a refined product after being purified by an electric field adsorption method. 3 . 3. The liquid crystal composition according to claim 1, wherein the first component is composed of one to five kinds of side ethyl tetraphenyl liquid crystal compounds represented by structural formula (I), and each The weight percentage of the side ethyl tetraphenyl liquid crystal compound in the liquid crystal composition is 1-15%. 4. The liquid crystal composition according to claim 1, wherein the weight percentage of each compound in the second component in the liquid crystal composition is 1-15%; The weight percentage of each compound in the third component in the liquid crystal composition is 1-20%; The weight percentage of each compound in the fourth component in the liquid crystal composition is 1-15%. 5. The liquid crystal composition according to claim 4, wherein the liquid crystal composition further comprises a fifth component, and the fifth component comprises at least one of the compounds represented by the following structural formula (X):

Wherein, R ₈ and R ₉ are independently selected from saturated alkyl groups containing 2 to 7 carbon atoms, and R ₁₀ is -CH ₃ or -C ₂ H ₅ . 6. The liquid crystal composition according to claim 5, wherein the weight percentage of each compound in the fifth component in the liquid crystal composition is 1-15%. 7 . A microwave device, characterized in that, the microwave device comprises the liquid crystal composition according to any one of claims 1 to 6 .