CN116332800B - Liquid crystal compound, composition and high-frequency component with ultra-low dielectric loss - Google Patents

Abstract

The present invention discloses a liquid crystal compound, a composition and a high-frequency component with ultra-low dielectric loss. The structural formula of the compound is shown in Formula I: Wherein R is selected from an alkyl or alkoxy group having 1 to 10 carbon atoms, an alkenyl or alkenyloxy group having 2 to 10 carbon atoms, a fluorinated alkyl group, a fluorinated alkenyl group and a cycloalkyl group or an alkyl group substituted with a cycloalkyl group; X ₁ to X ₈ are methyl or hydrogen, and at least two substituents in X ₁ to X ₈ are methyl groups; Z ₁ and Z ₂ are respectively selected from a single bond, -C≡C-, -CH=CH-, -CF=CF- and -CH ₂ CH ₂ ; Ring A is a benzene ring, cyclohexane or cyclohexene, wherein the hydrogen atoms on the benzene ring may also be substituted with methyl or halogen; n=0, 1 or 2. The liquid crystal compound and the composition thereof of the present invention not only have ultra-low dielectric loss and high quality factor, but also have a wide nematic phase temperature range and low viscosity, and are suitable for use in fields such as filters, phase shifters, phased array radars and 5G communications.

Description

Liquid crystal compound with ultralow dielectric loss, composition and high-frequency component

Technical Field

The invention belongs to the technical field of liquid crystal materials, and particularly relates to a liquid crystal compound with ultralow dielectric loss, a composition and a high-frequency component, which are mainly applicable to the fields of filters, adjustable frequency selective surfaces, microwave phase shifters, microwave phased array antennas and the like.

Background

Liquid crystal materials are widely used in electro-optical display devices, such as various liquid crystal televisions, desktop liquid crystal displays, mobile display terminals, and the like. By utilizing the property that the effective dielectric constant of the liquid crystal material changes with the action of an external electric field or a magnetic field, novel high-frequency (1 GHz-100 GHz) components based on the liquid crystal material, such as a microwave phase shifter based on the liquid crystal material and the like, are developed.

In these high frequency components based on liquid crystal, the dielectric tuning rate of the liquid crystal material determines the tuning capability of the microwave device. The dielectric tuning rate (τ) of the liquid crystal material is represented by the following formula (1), and is determined by the dielectric anisotropy (Δ∈) of the liquid crystal material at high frequencies and the dielectric constant (ε _∥) in the molecular parallel direction:

τ=Δ∈/ε _∥ formula (1);

Dielectric loss of a liquid crystal material is an important factor affecting the insertion loss of its microwave device. In order to obtain a high performance liquid crystal microwave device, it is necessary to reduce dielectric loss of the liquid crystal material. For liquid crystal materials, the loss tangent (tan δ) varies with the director alignment of the liquid crystal molecules, i.e., the loss tangent values in the major and minor axes of the liquid crystal molecules are different. In calculating the loss of a liquid crystal material, the dielectric loss parameter of the liquid crystal material is typically measured by its maximum loss, i.e., max (tan delta _∥,tanδ_⊥).

In order to evaluate the performance parameters of the liquid crystal material under microwaves, a quality factor (eta) parameter is introduced, and the following formula (2) is shown:

η=τ/max (tan δ _∥,tanδ_⊥) formula (2);

For high frequency device applications, the larger the quality factor (η) is required, the better. This requires a liquid crystal material having a large dielectric tuning rate (τ) and a low dielectric loss tangent (tan δ _∥,tanδ_⊥). However, the dielectric loss tangent (tan delta _∥,tanδ_⊥) of the liquid crystal material for the high-frequency component is larger, so that the insertion loss of the high-frequency component is larger, the working efficiency of the device is low, and the liquid crystal material becomes a technical bottleneck for the application and industrialization of the microwave device based on liquid crystal. Therefore, there is an urgent need to solve the problem of reducing dielectric loss of liquid crystal materials.

For practical applications, there is also a need for an optimized improvement of the liquid crystal material in the following respects.

(1) In order to meet the application of outdoor severe environment, the liquid crystal material is required to have high-definition bright spots and low crystallization temperature, and the fluctuation of high-frequency performance parameters of the liquid crystal material along with the change of the external environment temperature is as small as possible.

(2) To meet the need for fast response of high frequency components, lower rotational viscosity of the liquid crystal material is required.

(3) In order to meet the requirement that the high frequency components operate under electric field driving, it is also required that the liquid crystal material has a suitable dielectric anisotropy value at low frequencies, for example 1 KHz.

Commercial high-birefringence Liquid crystal materials are reported in Molecular CRYSTALS AND Liquid Crystals,2011,542 (1): 196/[718] -203/[725], the paper entitled "Characterisation and Applications of Nematic Liquid CRYSTALS IN Microwave devices," for high frequency performance and applications, wherein Liquid crystal materials containing cyanobiphenyl, e.g., E7, E44, etc., have the disadvantages of low tunability at high frequencies and large losses.

For high frequency applications, a liquid crystal medium comprising a bis-diphenylacetylene based liquid crystal material is disclosed in patent CN103443245A, for example, having the structure shown in the following formula:

Although the compound has a relatively high quality factor at high frequency, a relatively low dielectric loss tangent, tan delta _⊥ =0.0064 at 30GHz, the tuning rate is smaller, τ=0.242. The dielectric constant of the compound is small at low frequency and is only 0.8.

Patent CN107955630A, CN105368465A discloses a liquid crystal composition having a molecular terminal NCS group and a molecular skeleton fluorine substituted benzene ring, which has a large dielectric constant and a large tuning rate at high frequency but a large dielectric loss value, and in the disclosed embodiment, the dielectric loss tan delta _⊥ (19 GHz) is all 0.01 or more.

Patent CN110499163A, US2019292458A1 discloses a liquid crystal composition having a molecular terminal NCS group and a molecular skeleton of fluorine substituted benzene ring, and in the disclosed embodiment, the dielectric loss tan δ _⊥ (19 GHz) > 0.083.

Disclosure of Invention

In order to overcome the drawbacks or deficiencies of the prior art, it is an object of the present invention to provide a liquid crystal compound, composition and high frequency component with ultra low dielectric loss, which has ultra low dielectric loss at high frequencies, large dielectric tunability, wide nematic temperature range, low rotational viscosity and/or large dielectric constant at low frequencies.

In order to achieve the above task, the present invention adopts the following technical solutions:

A liquid crystal compound with ultralow dielectric loss has a structure shown in a general formula I:

Wherein R is selected from alkyl or alkoxy with 1-10 carbon atoms, alkenyl or alkenyloxy with 2-10 carbon atoms, fluorinated alkyl, fluorinated alkenyl and cycloalkyl or alkyl substituted by cycloalkyl;

X ₁～X₈ is methyl or hydrogen, and at least two substituents in X ₁～X₈ are methyl;

Z ₁ and Z ₂ are each independently selected from the group consisting of a single bond, -C≡C-, -CH=CH-, -CF=CF-, and-CH ₂CH₂ -;

ring A is benzene ring, cyclohexane or cyclohexene, wherein hydrogen atoms on the benzene ring can be substituted by methyl or halogen;

n=0, 1 or 2.

The preferred structures of the liquid crystal compounds according to the invention are shown in Table 1:

TABLE 1

The liquid crystal compound introduces two or more methyl substituents in the short axis direction of molecules, has the unexpected effect that compared with the known liquid crystal containing lateral fluorine substituents and lateral one methyl, the liquid crystal compound has the advantages that the dielectric loss value at high frequency is greatly reduced, the high-frequency dielectric anisotropy is kept, the working requirement of a microwave device is greatly facilitated, and meanwhile, the liquid crystal phase region can be obviously regulated and controlled along with the different number and positions of the methyl substituents. For example, compared with the known one lateral methyl or lateral fluorine substituted compound, the two methyl substituent groups are favorable for obtaining nematic liquid crystal phase and inhibiting smectic phase region, when the two methyl groups are respectively on different benzene rings, the two methyl groups can play a role of greatly reducing the melting point of the liquid crystal, the low-temperature performance of the liquid crystal composition is favorable for improving, when the two methyl groups are positioned on the same side of the benzene rings connected with NCS groups, for example, the 2, 3-dimethyl substituted compound is greatly improved compared with the known one methyl substituted compound, and the clearing point of the liquid crystal composition can be adjusted.

The synthesis of the liquid crystal compound can adopt a palladium catalytic coupling reaction strategy to establish a basic molecular skeleton, and then obtain a target product through proper functional group conversion. Specifically, for the compounds of the general structural formula I:

when Z ₂ = single bond, using palladium catalyzed Suzuki coupling reaction, building molecular skeleton by aryl boric acid and bromo or iodo aniline derivative coupling, then converting aniline derivative intermediate into isothiocyanate target product:

scheme 1;

When Z ₂ = -c≡c-, a palladium-catalyzed Sonogashira coupling reaction is employed to build a molecular framework by aryl acetylene and bromo or iodo aniline derivatives coupling, and then the aniline derivative intermediate is converted into isothiocyanate target product:

scheme 2;

When Z ₂ = -ch=ch-, -cf=cf-, a palladium-catalyzed Heck coupling reaction is used to build a molecular framework by coupling aryl ethylene and bromo-or iodo-aniline derivatives, and then the aniline derivative intermediate is converted into an isothiocyanate target product:

scheme 3;

When Z ₂＝-CH₂CH₂ -, an aniline derivative containing acetylene or ethylene bridge bonds can be hydrogenated to saturated ethylene under palladium catalysis, and then an aniline intermediate is converted into an isothiocyanate target product through a functional group.

Scheme 4;

Another object of the present invention is to provide a liquid crystal composition with ultra low dielectric loss, comprising 1 or more compounds of the general structural formula I.

The liquid crystal composition of the invention may further comprise 1 or more compounds selected from the group consisting of compounds represented by the structural formula II as a second component:

Wherein R ₁、R₂ is alkyl with 1-10 carbon atoms, alkenyl with 2-10 carbon atoms, fluorinated alkyl, fluorinated alkenyl, cycloalkyl, halogen and NCS, and ring A and ring B are benzene ring, cyclohexane and cyclohexene, wherein hydrogen atoms on the benzene ring can be replaced by fluorine atoms;

comprising as a third component 1 or more compounds selected from the group consisting of the general structural formula III:

Wherein R ₁ is alkyl with 1-10 carbon atoms, alkenyl with 2-10 carbon atoms, fluorinated alkyl and fluorinated alkenyl, X ₉～X₁₃ is H, methyl and ethyl, one of X ₉～X₁₃ is methyl or ethyl, k, m and n are respectively 0 or 1, and ring A is benzene ring, cyclohexane or cyclohexene;

Comprising as a fourth component 1 or more compounds selected from the group consisting of the general structural formula IV:

Wherein R ₁ is alkyl with 1-10 carbon atoms, alkenyl with 2-10 carbon atoms, fluorinated alkyl and fluorinated alkenyl, X ₁₄～X₁₇ is H, methyl and ethyl, one of X ₁₄～X₁₇ is methyl or ethyl, and the rest is H.

In the composition of the present invention, the compounds of the general structural formula I further preferably have the structure shown in table 2:

TABLE 2

Compared with the high-frequency liquid crystal composition based on isothiocyanato, the compound with the structural general formula I disclosed by the invention is characterized in that lateral fluorine atom substituent groups are not in molecules, but methyl with larger volume and no polarity is adopted as the lateral substituent groups, and after 2 lateral methyl substituent groups are introduced into the molecules, the dielectric loss value of the liquid crystal material under high frequency is greatly reduced.

The preferred specific structure of the components of the composition of the present invention of formula II is as follows:

The molecular structure of the structural general formula II is composed of 2 rings, has the characteristics of low viscosity, low melting point and low dielectric loss, can further improve the low-temperature compatibility of the liquid crystal composition, greatly reduces the viscosity of the liquid crystal composition, and simultaneously reduces the dielectric loss.

The structural general formula II-A of the present invention is more preferably a specific compound of the following formula:

wherein II-B is further preferably a compound of the following structure:

wherein II-C is further preferably a compound of the following structure:

The preferred specific structure of the compound of the general structural formula III in the composition of the invention is as follows:

the compound with the structural general formula III in the composition has a wider liquid crystal phase range, lower viscosity and larger dielectric constant, and can play a role in adjusting the liquid crystal phase range and the dielectric constant of the composition under low frequency.

The preferred specific structure of the compound of formula IV in the composition of the invention is as follows:

the compound with the structural general formula IV in the composition has a wider liquid crystal phase range, high double refractive index and large dielectric constant, and can play a role in adjusting the liquid crystal phase range and the dielectric constant of the composition under low frequency.

In a preferred embodiment of the invention, the liquid crystal composition comprises one or more compounds selected from the group consisting of the compounds of the general structural formula (I) and one or more compounds selected from the group consisting of the compounds of the general structural formula (II). In another preferred embodiment of the invention, the liquid crystal composition comprises one or more compounds of the general structural formula (I), one or more compounds of the general structural formula (II) and one or more compounds of the general structural formula (III). In another preferred embodiment of the invention, the liquid crystal composition comprises one or more compounds of the general structural formula (I), one or more compounds of the general structural formula (II) and one or more compounds of the general structural formula (III) and one or more compounds of the general structural formula IV.

The liquid crystal composition according to the invention comprises 1% -100%, preferably 10% -90%, more preferably 20% -80% of the compound of formula I based on the total amount of the mixture. The liquid crystal composition of the present invention may further contain 0 to 40%, preferably 5 to 30%, particularly preferably 10 to 20% of a compound of the general structural formula II based on the total amount of the mixture. The liquid crystal composition of the present invention may further comprise 0 to 90%, preferably 10 to 80%, particularly preferably 20 to 70% of a compound of the general structural formula III based on the total amount of the mixture. The liquid crystal composition of the present invention may further contain 0 to 50%, preferably 10 to 40%, particularly preferably 15 to 30% of a compound of the structural formula IV based on the total amount of the mixture.

The liquid crystal composition of the invention can further comprise 0.001% -1% of additives, such as hindered phenol antioxidants, amine light stabilizers and the like. Wherein the hindered phenolic antioxidant is preferably selected from the following structures:

wherein R is alkyl or alkoxy with 1-9 carbon atoms.

The hindered amine light stabilizer is preferably selected from the following structures:

the preferable addition amount of the hindered phenol antioxidant and the amine light receiving stabilizer is 0.01% -0.5%, and more preferable 0.02% -0.2%.

The liquid crystal composition of the invention can also contain one or more chiral additives, and the content of the chiral additives is 0.01% -1%, preferably 0.1% -0.5%. The chiral additive is preferably selected from the following structures:

Wherein the alkyl or alkoxy is C1-9.

The liquid crystal composition according to the present invention is composed of a plurality of compounds, preferably 3 to 20 compounds, more preferably 5 to 18 compounds. The compounds can be obtained by mixing the above materials in a conventional manner, weighing the above materials according to a predetermined mass ratio, heating, homogenizing and mixing by magnetic stirring or ultrasonic stirring to completely dissolve the above materials, and filtering. The liquid crystal compositions may also be prepared in other conventional ways, for example using so-called premixes, or using so-called "multi-bottle" systems in which the ingredients themselves are ready-to-use mixtures.

Test method for liquid crystal performance under high frequency by adopting literature report ：Penirschke,A.(2004).Cavity perturbation method for characterization of liquid crystals up to 35GHz.Microwave Conference,2004.34thEuropean.

Liquid crystal is poured into Polytetrafluoroethylene (PTFE) or fused quartz capillaries, and the capillaries filled with liquid crystal are inserted into the middle of the resonance chamber. The input signal source is then applied and the result of the output signal is recorded with a vector network analyzer. The change in the resonance frequency and Q factor between the capillary filled with liquid crystal and the blank capillary was measured, and the dielectric constant and loss tangent were calculated. The permittivity components perpendicular and parallel to the liquid crystal directors are obtained by the orientation of the liquid crystal in a magnetic field, the direction of which is set accordingly, and then rotated by 90 ° accordingly.

The tuning rate tau of the liquid crystal composition is more than or equal to 0.25, more preferably tau is more than or equal to 0.28, the dielectric loss tan delta _⊥ of the liquid crystal material in the vertical direction is more than or equal to 0.006, more preferably tan delta _⊥ is more than or equal to 0.005, and the material quality factor eta is more than or equal to 50, preferably eta is more than or equal to 60. The nematic phase temperature range of the liquid crystal composition is 0-90 ℃ or more, preferably-10-100 ℃ or more, and more preferably-20-120 ℃. The dielectric constant of the liquid crystal composition is more than or equal to 6.0 at low frequency of 1KHz, and more preferably more than or equal to 7.0.

The liquid crystal composition according to the present application is very suitable for preparing a microwave component, and can operate in UHF-band (0.3-1 GHz), L-band (1-2 GHz), S-band (2-4 GHz), C-band (4-8 GHz), X-band (8-12 GHz), ku-band (12-18 GHz), K-band (18-27 GHz), ka-band (27-40 GHz), V-band (50-75 GHz), W-band (75-110 GHz) and at most 1 THz. The construction of the phase shifter according to the application is known to the expert. Typically a loaded line shifter, inverted microstrip, fin (Finline) shifter, preferably antipodal (Antipodal) fin shifter, slotted shifter, microstrip shifter or coplanar waveguide (CPW) shifter is used. These components may implement a reconstructed antenna array.

By adopting the technical scheme, the invention has the technical advantages that:

the liquid crystal compound and the composition thereof have ultralow dielectric loss, larger dielectric tuning rate and very high quality factor at high frequency, and have wider liquid crystal working temperature area.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention will be described in further detail with reference to the following examples, and it is apparent that the described examples are only some of the examples of the present invention, but not all of the examples. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.

The present invention will be described in further detail with reference to specific examples.

And testing physical properties and photoelectric properties of the mixed liquid crystal. The invention relates to a detailed test method for physical properties and photoelectric properties, which comprises the following steps:

(1) Clearing point (Tni):

the polarized light heat stage method is to coat a liquid crystal sample on a glass slide and place the liquid crystal sample in an orthogonal polarized light microscopic heat stage, and the temperature rising rate is set to be 2 ℃ per minute. And observing the temperature of the liquid crystal sample from a bright state to black in a polarizing microscope, namely, a clear point.

Or adopting differential scanning calorimetry, and setting the temperature rise rate to be 2 ℃ per minute under the nitrogen atmosphere.

(2) Low temperature storage temperature (LTS) is prepared by filling about 1mL of the mixed liquid crystal into a transparent glass bottle and placing the bottle in a low temperature refrigerator. The temperature was set at-20 ℃, -30 ℃, -40 ℃, and the mixture was stored for 10 days, and the presence or absence of crystal precipitation or smectic phase was observed. If no crystal is precipitated at-30 ℃, LTS is less than or equal to-30 ℃.

(3) Birefringence (Δn) the refractive indices of the ordinary (n _o) and extraordinary (n _e) rays were measured separately using an abbe refractometer at a constant temperature of 25 ℃ with a light source of 589nm, the birefringence Δn=n _e－n_o.

(4) Dielectric constant (. DELTA.. Epsilon.) under constant temperature conditions of 25℃the test was carried out using an LCR meter. Delta epsilon=epsilon _∥-ε_⊥, i.e., the difference between the molecular long axis dielectric constant (epsilon _∥) and the molecular short axis dielectric constant (epsilon _⊥).

(5) Elastic constant (K ₁₁,K₃₃) under the constant temperature condition of 25 ℃, K ₁₁ and K ₃₃ are obtained by fitting the curves of liquid crystal capacitance-voltage (C-V).

(6) Rotational viscosity (gamma ₁) by applying voltage to the liquid crystal test cell under constant temperature condition of 25 deg.C, testing transient current value Ip of liquid crystal molecule deflected along with movement of electric field, and calculating to obtain rotational viscosity gamma ₁.

The code numbers and descriptions are shown in tables 3-5:

TABLE 3 physical parameters

Table 4 Structure abbreviations

Table 5 abbreviations for example

The liquid crystal phase transition temperature is C representing the melting point, S representing the smectic phase, N representing the nematic phase, and Iso representing the liquid state.

EXAMPLE 1 Synthesis of 1-isothiocyanate-2, 3-dimethyl-4- ((4-n-butylphenyl) ethynyl) benzene

The synthesis method is as follows:

abbreviated as 5PTP (M-2, 3) S;

Synthesis step 1, under the protection of nitrogen, 24.7g of 2, 3-dimethyl-4-iodoaniline, 200mL of triethylamine, 2.1g of diphenylphosphine palladium chloride and 1.1g of cuprous iodide are added into a three-neck flask, stirred and heated to be higher than 40 ℃, and 100mL of triethylamine solution in which 17.2g of 4-n-pentylphenyl acetylene is dissolved is slowly added dropwise. After the dripping is finished, the temperature is raised to 50-60 ℃ and the stirring reaction is continued for 2 hours. Cooling to room temperature, filtering to remove salt produced by the reaction, and distilling under reduced pressure to remove triethylamine. 200mL of toluene was added and the mixture was washed with water to neutrality. The solvent was removed by concentration and the resulting product was recrystallized from petroleum ether to give 27g of brown solid.

And 2, adding 27g of the brown solid obtained in the previous step into a three-necked flask, adding 200mL of chloroform and 50mL of water, cooling to below 5 ℃, and slowly and dropwise adding 15.5g of thiophosgene. After the completion of the dropwise addition, the temperature was raised to reflux for 2 hours. Cooling to room temperature, separating, washing the organic layer with sodium bicarbonate aqueous solution, and washing with water to neutrality. The solvent was distilled off under reduced pressure, and the obtained product was subjected to a silica gel column and eluted with n-heptane. The product was recrystallized from n-heptane to give 23.4g of white solid with a gas chromatography purity of 99.8%.

The structural identification data are as follows:

¹H NMR(500MHz,CDCl₃)δ(ppm):0.89(d,J＝7.5Hz,3H),1.32–1.33(m,4H),1.61(m,2H),2.31(s,3H),2.47(s,3H),2.59-2.62(m,2H),7.04–7.07(m,1H),7.14–7.17(m,2H),7.30–7.33(m,1H),7.41–7.44(m,2H).

¹³C NMR(125MHz,CDCl₃)δ(ppm):14.1,15.6,18.3,22.7,31.0,31.6,36.1,87.7,95.0,120.5,123.0,123.9,128.7,130.2,130.3,133.5,140.3,143.9.

MS m/z(RI,%):333.2(M⁺,100),276.1(89),202.1(17),121.5(2).

DSC:C 64.39N(59.78)Iso。

EXAMPLE 2 Synthesis of 1-isothiocyanate-2, 6-dimethyl-4- ((4-n-pentylphenyl) ethynyl) benzene

Abbreviated as 5PTP (M-2, 6) S;

the same procedures used in example 1 were repeated except for using 2, 6-dimethyl-4-iodoaniline instead of 2, 3-dimethyl-4-iodoaniline used in example 1 to give 1-isothiocyanate-2, 6-dimethyl-4- ((4-n-pentylphenyl) ethynyl) benzene.

The structural identification data are as follows:

¹H NMR(500MHz,CDCl₃)δ(ppm):0.89(t,J＝7Hz,3H),1.28–1.38(m,4H),1.57–1.63(m,2H),2.34(s,6H),2.59(t,J＝7.5Hz,2H),7.19(d,J＝8Hz,2H),7.47(d,2H),7.56(s,2H).

¹³CNMR(125MHz,CDCl₃)δ(ppm)：14.1,17.7,20.1,22.6,30.9,31.5,35.9,86.9,95.2,120.4,122.6,126.7,128.6,131.5,133.7,136.2,138.9,143.7.

MS m/z(RI,%):333.3(M⁺,100),276.2(90),244.2(2),202.1(18),189.1(3).

DSC:C 43.26Iso。

EXAMPLE 3 Synthesis of 4- ((4-isothiocyanato-3, 5-dimethylphenyl) ethynyl) -4' -n-pentylbiphenyl

Abbreviated as 5PPTP (M-2, 6) S;

The same procedures used in example 1 were repeated except for using 4 '-n-pentyl-4-ethynyl biphenyl instead of 4-n-pentylphenyl acetylene and 2, 6-dimethyl-4-iodoaniline instead of 2, 3-dimethyl-4-iodoaniline in example 1 to give 4- ((4-isothiocyanato-3, 5-dimethylphenyl) ethynyl) -4' -n-pentylbiphenyl.

The structural identification data are as follows:

¹H NMR(500MHz,CDCl₃)δ(ppm):0.90(t,J＝7Hz,3H),1.33–1.37(m,4H),1.61-1.67(m,2H),2.34(s,6H),2.63(t,J＝8Hz,2H),7.21(s,2H),7.24(d,J＝8Hz,2H),7.50(d,J＝8Hz,2H),7.53–7.56(m,4H).

¹³C NMR(125MHz,CDCl₃)δ(ppm):14.1,18.7,22.7,31.2,31.7,35.8,89.3,91.0,121.7,122.1,127.0,129.1,129.7,131.3,132.2,135.4,136.8,137.8,141.4,141.8,142.9.

MS m/z(RI,%):MS m/z(RI,%):409.2(M⁺,100),352.1(73),320.1(4),277.1(3),175.9(10).

DSC:C 121.99N 153.19Iso。

EXAMPLE 4 Synthesis of 4- ((4-isothiocyanato-2, 3-dimethylphenyl) ethynyl) -4' -n-pentylbiphenyl

Abbreviated as 5PPTP (M-2, 3) S;

The same procedures used in example 1 were repeated except for using 4 '-n-pentyl-4-ethynyl biphenyl instead of 4-n-pentylphenyl acetylene in example 1 to give 4- ((4-isothiocyanato-2, 3-dimethylphenyl) ethynyl) -4' -n-pentylbiphenyl.

The structural identification data are as follows:

¹H NMR(500MHz,CDCl₃)δ(ppm):0.90(t,J＝7Hz,3H),1.33–1.37(m,4H),1.50–1.52(m,2H),2.33(s,2H),2.49(s,2H),2.64(d,J＝7.5Hz,2H),7.07(t,J＝8Hz,1H),7.24–7.26(m,3H),7.34(d,J＝8.5Hz,1H),7.50–7.52(m,1H),7.53–7.58(m,4H).

¹³C NMR(125MHz,CDCl₃)δ(ppm):14.1,15.6,18.4,22.7,31.2,31.7,35.8,88.9,94.8,121.9,122.9,123.9,127.0,127.0,129.1,130.4,130.6,132.1,133.5,136.0,137.8,140.4,141.4,142.9.

MS m/z(RI,%):409.2(M⁺,100),377.1(6),352.1(61),294.1(18),253.0(6),176.2(9).

DSC:C 99.31S 194.30N 254.89 Iso。

EXAMPLE 5 Synthesis of 4- ((4-isothiocyanato-2, 5-dimethylphenyl) ethynyl) -4' -n-pentylbiphenyl

Abbreviated as 5PPTP (M-2, 5) S;

The same procedures used in example 1 were repeated except for using 4 '-n-pentyl-4-ethynyl biphenyl instead of 4-n-pentylphenyl acetylene in example 1 and 2, 5-dimethyl-4-iodoaniline instead of 2, 3-dimethyl-4-iodoaniline in example 1 to give 4- ((4-isothiocyanato-2, 5-dimethylphenyl) ethynyl) -4' -n-pentylbiphenyl.

The structural identification data are as follows:

¹H NMR(500MHz,CDCl₃)δ(ppm):0.91(t,J＝7Hz,3H),1.31–1.38(m,4H),1.63–1.69(m,2H),2.34(s,3H),2.46(s,3H),2.65(t,J＝8Hz,2H),7.07(s,1H),7.26(d,J＝8Hz,2H),7.35(s,1H),7.52(d,J＝8.5Hz,2H),7.55–7.59(m,4H).

¹³C NMR(125MHz,CDCl₃)δ(ppm):14.1,17.9,20.2,22.7,31.3,31.7,35.8,88.2,95.1,121.9,122.6,127.0,127.0,127.1,129.1,130.0,132.1,132.3,133.9,136.3,137.8,139.2,141.5,142.9.

MS m/z(RI,%):409.2(M⁺,100),352.1(57),294.1(14),204.5(4),175.9(11).

DSC:C 97.66N 153.60 Iso。

EXAMPLE 6 Synthesis of 4- ((4-isothiocyanato-2-methylphenyl) ethynyl-3-methyl) -4' -n-pentylbiphenyl

Is abbreviated as 5PP (M-2) TP (M-3) S;

the same procedures used in example 1 were repeated except for using 4 '-n-pentyl-3-methyl-4-ethynyl biphenyl instead of 4-n-pentylphenyl acetylene and 3-methyl-4-iodoaniline instead of 2, 3-dimethyl-4-iodoaniline in example 1 to give 4- ((4-isothiocyanato-2-methylphenyl) ethynyl-3-methyl) -4' -n-pentylbiphenyl.

The structural identification data are as follows:

¹H NMR(500MHz,CDCl₃)δ(ppm):0.91(t,J＝7Hz,3H),1.31–1.40(m,4H),1.62–1.68(m,2H),2.51(s,3H),2.57(s,3H),2.65(t,J＝7.5Hz,2H),7.04(dd,J₁＝8Hz,J₂＝1.5Hz,1H),7.12(s,1H),7.25(d,J＝8Hz,2H),7.41(dd,J₁＝8Hz,J₂＝1.5Hz,1H),7.47-7.55(m,5H).

¹³C NMR(125MHz,CDCl₃)δ(ppm):14.2,21.0,21.2,22.7,31.3,31.7,35.8,91.9,94.6,121.6,123.0,123.2,124.4,126.9,127.0,128.3,129.1,132.5,133.0,137.9,140.5,141.6,141.8,142.8.

MS m/z(RI,%):409.2(M⁺,100),352.1(52),294.1(13),277.1(4),204.7(3),176.0(7).

DSC:C 78.21N 183.71 Iso。

EXAMPLE 7 1-isothiocyanate-2, 3-dimethyl-4- ((4- (4-n-pentylcyclohexyl) phenyl) ethynyl) benzene

Is abbreviated as 5CPTP (M-2, 3) S;

The same procedures used in example 1 were repeated except for using 4- (4-n-pentylcyclohexyl) phenylacetylene instead of 4-n-pentylphenylacetylene used in example 1 to give 1-isothiocyanate-2, 3-dimethyl-4- ((4- (4-n-pentylcyclohexyl) phenyl) ethynyl) benzene.

¹H NMR(500MHz,CDCl₃)δ(ppm):0.89(t,3H),0.99–1.08(m,2H),1.20–1.45(m,11H),1.87-1.90(m,4H),2.31(s,3H),2.44(t,J＝12Hz,1H),2.47(s,3H),7.04–7.07(m,1H),7.14–7.17(m,2H),7.30–7.33(m,1H),7.41–7.44(m,2H).

¹³C NMR(125MHz,CDCl₃)δ(ppm):14.2,18.7,22.9,26.8,32.4,33.7,34.4,37.5,39.1,44.8,87.7,95.0,120.5,123.0,123.9,128.7,130.2,130.3,133.5,140.3,143.9.

MS m/z(RI,%):415.4(M⁺,100),302.2(8),276.2(19),229.2(13).

DSC:C 105.96N 244.02 Iso。

EXAMPLE 8 2-isothiocyanato-1, 3-dimethyl-5- ((4- (4-n-pentylcyclohexyl) phenyl) ethynyl) benzene

Is abbreviated as 5CPTP (M-2, 6) S;

The same procedures used in example 1 were repeated except for using 4- (4-n-pentylcyclohexyl) phenylacetylene instead of 4-n-pentylphenylalcetylene and 2, 6-dimethyl-4-iodoaniline instead of 2, 3-dimethyl-4-iodoaniline in example 1 to give 2-isothiocyanate-1, 3-dimethyl-5- ((4- (4-n-pentylcyclohexyl) phenyl) ethynyl) benzene.

The structural identification data are as follows:

¹H NMR(500MHz,CDCl₃)δ(ppm):0.89(t,3H),0.98–1.05(m,2H),1.19–1.44(m,11H),1.88-1.91(m,4H),2.31(s,6H),2.44(t,J＝12Hz,1H),7.13–7.15(m,4H),7.38–7.39(d,J＝8Hz,2H).

¹³C NMR(125MHz,CDCl₃)δ(ppm):14.2,18.7,22.9,26.8,32.4,33.7,34.4,37.5,39.1,44.8,88.1,91.3,120.5,122.3,127.1,129.5,131.2,131.8,135.3,136.7,148.8.

MS m/z(RI,%):415.4(M⁺,100),302.2(6),276.1(16),229.1(10),215.1(2).

DSC:C 81.87N 158.72 Iso。

EXAMPLE 9 1-isothiocyanate-2, 5-dimethyl-4- ((4- (4-n-pentylcyclohexyl) phenyl) ethynyl) benzene

Is abbreviated as 5CPTP (M-2, 5) S;

the same procedures used in example 1 were repeated except for using 4- (4-n-pentylcyclohexyl) phenylacetylene instead of 4-n-pentylphenylalcetylene and 2, 5-dimethyl-4-iodoaniline instead of 2, 3-dimethyl-4-iodoaniline in example 1 to give 1-isothiocyanate-2, 5-dimethyl-4- ((4- (4-n-pentylcyclohexyl) phenyl) ethynyl) benzene.

The structural identification data are as follows:

¹H NMR(500MHz,CDCl₃)δ(ppm):0.90(t,J＝7.5Hz,3H),1.06–1.31(m,11H),1.50–1.53(m,2H),1.87(m,4H),2.34(m,3H),2.46(s,3H),2.62(t,1H),7.04–7.05(d,J＝7Hz,1H),7.17–7.20(m,2H),7.24–7.27(m,1H),7.41–7.43(m,2H).

¹³C NMR(125MHz,CDCl₃)δ(ppm):14.2,17.7,20.1,22.8,26.7,32.3,33.6,34.2,37.4,37.4,44.7,86.9,95.3,120.5,122.6,126.7,128.0,129.7,131.5,132.1,133.7,136.2,139.0,148.6.

MS m/z(RI,%):415.4(M⁺,100),302.2(4),276.1(11),229.1(9),215.1(4).

DSC:C 77.44N 157.95 Iso。

EXAMPLE 10 4-isothiocyanate-2, 5-dimethyl-4 '-n-pentyl-1, 1':4', 1' -terphenyl

Abbreviated as 5PPP (M-2, 5) S;

In the synthesis step 1, under the protection of nitrogen, 24.7g of 2, 5-dimethyl-4-iodoaniline, 26.8g of 4' -amyl diphenyl boric acid, 1.2g of tetra (triphenylphosphine) palladium, 27.6g of potassium carbonate, 100ml of toluene, 100ml of ethanol and 100ml of water are added into a three-necked flask, stirred, heated to reflux and reacted for 8 hours. Cooled to room temperature, 100mL of toluene was added, and the organic layer was separated. The organic layer was washed with water to neutrality and concentrated to remove solvent. The resulting product was recrystallized from petroleum ether to give 27.8g of brown solid.

And 2, adding 27.8g of the brown solid obtained in the previous step into a three-necked flask, adding 200mL of chloroform and 50mL of water, cooling to below 5 ℃, and slowly dropwise adding 14.0g of thiophosgene. After the completion of the dropwise addition, the temperature was raised to reflux for 2 hours. Cooling to room temperature, separating, washing the organic layer with sodium bicarbonate aqueous solution, and washing with water to neutrality. The solvent was distilled off under reduced pressure, and the obtained product was subjected to a silica gel column and eluted with n-heptane. The product was recrystallized from n-heptane to give 23.7g of white solid with a gas chromatography purity of 99.9%.

The structural identification data are as follows:

¹HNMR：0.91(t,J＝7Hz,3H),1.35–1.39(m,4H),1.64–1.70(m,2H),2.25(s,3H),2.38(s,3H),2.66(t,J＝8Hz,2H),7.12(d,J＝3Hz,2H),7.27(d,J＝8.5Hz,2H),7.33(q,J＝8.5Hz,2H),7.55(d,J＝8.5Hz,2H),7.63(d,J＝8.5Hz,2H).

¹³CNMR：14.2,18.0,20.1,22.7,31.3,31.7,35.8,110.2,126.9,127.1,127.7,129.1,129.3,129.5,132.2,132.3,134.5,138.1,139.5,140.3,141.1,142.5.

MS m/z(RI,%):385.3(M⁺,100),328.2(91),296.2(24),255.1(4),164.1(5).

DSC:C 76.79 Iso。

EXAMPLE 11 4- (4-butylcyclohexyl) -4'- ((4-isothiocyanato-2, 5-dimethylphenyl) ethynyl) -1,1' -biphenyl

Is abbreviated as 4CPPTP (M-2, 5) S;

The same procedures used in example 1 were repeated except for using 4' - (4-n-butylcyclohexyl) -4-ethynylbiphenyl instead of 4-n-pentylphenylalkylene and 2, 5-dimethyl-4-iodoaniline instead of 2, 3-dimethyl-4-iodoaniline in example 1 to give 4- (4-butylcyclohexyl) -4' - ((4-isothiocyanato-2, 5-dimethylphenyl) ethynyl) -1,1' -biphenyl.

The structural identification data are as follows:

¹HNMR：0.90(t,3H),1.31～1.61(m,15H),2.34(s,3H),2.48(s,3H),2.72(m,1H),7.03(s,1H),7.36(d,2H),7.37(d,2H),7.62(d,2H),7.65(d,2H),7.78(s,1H)..

¹³CNMR：14.4,17.0,19.6,23.0,29.5,29.6,30.9(2C),31.2(2C),43.7,88.3,95.2,121.6,122.5,127.1,127.6(2C),128.5(2C),129.2(2C),130.9,132.8(2C),138.0,140.5(2C),145.9.

DSC:C121.15 N>300 Iso。

EXAMPLE 12 4- (4- ((4-isothiocyanato-2, 5-dimethylphenyl) ethynyl) phenyl) -4 '-propyl-1, 1' -bicyclohexane

Is abbreviated as 3CCPTP (M-2, 5) S;

The same procedures used in example 1 were repeated except for using 4- (4-ethynylphenyl) -4 '-propyl-1, 1' -bicyclohexane instead of 4-n-pentylphenylaletylene and 2, 5-dimethyl-4-iodoaniline instead of 2, 3-dimethyl-4-iodoaniline used in example 1 to give 4- (4- ((4-isothiocyanato-2, 5-dimethylphenyl) ethynyl) phenyl) -4 '-propyl-1, 1' -bicyclohexane.

The structural identification data are as follows:

¹HNMR：0.90(t,3H),1.25～1.61(m,23H),2.34(s,3H),2.48(s,3H),2.72(m,1H),7.03(s,1H),7.26(d,2H),7.51(d,2H),7.78(s,1H).

¹³CNMR:14.4,17.0,19.6,20.5,23.5(2C),26.8(2C),29.3,30.9(2C),31.4(2C),37.1,41.6(2C),43.1,88.3,95.3,119.9,122.5,126.1(2C),127.1,129.0,130.9,132.0(2C),134.5,140.5,146.7.

DSC:C 118.92N 288.88 Iso。

example 13:

The liquid crystal composition M0 was composed of the monomer liquid crystal compound shown in Table 6.

TABLE 6 composition of liquid crystal composition M0

Monomer liquid crystal	Mass ratio/%
		2CPUS	25
3CPUS	25
		5CPUS	25
3CCV	25

To evaluate the properties of the newly synthesized liquid crystal compounds, the liquid crystal compounds prepared in examples 7 to 9 and 11 were uniformly mixed with M0 in a mass ratio of 15:85, respectively, to obtain test compositions M1 to M4, as shown in Table 7.

TABLE 7 mass ratios of liquid Crystal compositions

Composition and method for producing the same	Compounds of formula (I)	Mass ratio (Compound: M0)
			M1 (example 7)	5CPTP(M-2,3)S	15:85
M2 (example 8)	5CPTP(M-2,6)S	15:85
			M3 (example 9)	5CPTP(M-2,5)S	15:85
M4 (example 11)	4CPPTP(M-2,5)S	15:85

Liquid crystal compositions M0 to M4 were poured into polytetrafluoroethylene tubes, respectively, and dielectric constant and loss tangent at 19GHz were measured by cavity perturbation at 25℃and quality factors were calculated, and the results are shown in Table 8 below.

Table 8M 0 to M4 microwave performance

From the test data in the table, it can be found that after the compound of the present invention is added into M0, the obtained liquid crystal compositions M1 to M4 have significantly reduced tan delta _⊥, increased delta epsilon and significantly increased eta compared with M0.

Example 14:

the property data of the liquid crystal composition in mass ratio are shown in Table 9.

TABLE 9 example 14 liquid crystal compositions and Properties

Example 15:

the property data of the liquid crystal composition in mass ratio are shown in Table 10.

TABLE 10 example 15 liquid crystal compositions and Properties

Example 16:

The property data of the liquid crystal composition in mass ratio are shown in Table 11.

TABLE 11 example 16 liquid crystal compositions and Properties

Example 17:

the property data of the liquid crystal composition in mass ratio are shown in Table 12.

TABLE 12 example 17 liquid crystal compositions and Properties

Comparative example 1:

Patent CN107955630a discloses a compound 5CPTUS having 2 lateral fluorine atoms at the molecular terminal, the structural formula is shown below:

this monomer liquid crystal was uniformly mixed with M0 in a mass ratio of 15:85 to obtain a liquid crystal composition M5.

Chinese patent application 202010288457.2 discloses isothiocyanato liquid crystals having a molecule with three ring structures, the structures being shown in the following figures:

this monomer liquid crystal was uniformly mixed with M0 in a mass ratio of 15:85 to obtain a liquid crystal composition M6.

The physical properties of the liquid crystal compositions M5, M6 at 19GHz were tested at 25℃and the data are shown in Table 12.

Table 12 test data for comparative example 1 liquid crystal composition

Liquid crystal composition	ε⊥	ε∥	△ε	tanδ⊥	tanδ∥	τ	η
								M5	2.365	3.080	0.715	0.0112	0.0050	0.232	20.74
M6	2.402	3.106	0.704	0.0096	0.0042	0.227	23.65

Comparison of the liquid crystal compositions M5 to M6 of comparative example 1 with the liquid crystal compositions M1 to M4 of example 12 shows that the liquid crystal compounds of the present invention have significantly reduced dielectric loss at high frequencies and a larger quality factor eta.

Comparative example 2:

liquid crystal compositions for high frequency components, the components of which are selected from fluorine-substituted isothiocyanato liquid crystal compounds, are disclosed in CN107955630 a. In its example 1, the following compositions and performance parameters are disclosed, see in particular table 13:

TABLE 13 comparative example 2 Mass ratio and Properties of liquid Crystal composition

The liquid crystal composition of examples 14 to 17 of the present invention showed a significantly reduced dielectric loss and a double increase in quality factor as compared with comparative example 2.

Comparative example 3:

example N52 of patent CN110499163A discloses compositions comprising fluorine-substituted isothiocyanato liquid crystal compounds and their properties such as high frequency dielectric constants, see in particular Table 14:

TABLE 14 comparative example 3 liquid crystal composition Performance data

The liquid crystal composition of examples 14 to 17 of the present invention showed a significantly reduced dielectric loss and a double increase in quality factor as compared with comparative example 3.

The preferred embodiments of the present disclosure have been described in detail above, but the present disclosure is not limited to the specific details of the above embodiments, and various simple modifications may be made to the technical solutions of the present disclosure within the scope of the technical concept of the present disclosure, and all the simple modifications belong to the protection scope of the present disclosure.

In addition, the specific features described in the foregoing embodiments may be combined in any suitable manner, and in order to avoid unnecessary repetition, the present disclosure does not further describe various possible combinations.

Moreover, any combination between the various embodiments of the present disclosure is possible as long as it does not depart from the spirit of the present disclosure, which should also be construed as the disclosure of the present disclosure.

Claims (9)

1. A liquid crystal compound with ultra-low dielectric loss, characterized in that the specific compounds are shown in the following table:

Wherein R is selected from alkyl with 1-10 carbon atoms, X ₁～X₈ is methyl or hydrogen, and at least two substituents in X ₁～X₈ are methyl.

2. The liquid crystal compound with ultralow dielectric loss according to claim 1, wherein the structural formula of the compound is shown in the following table:

。

3. A liquid crystal composition having an ultralow dielectric loss, comprising one or more liquid crystal compounds having an ultralow dielectric loss selected from any one of claims 1 to 2.

4. The liquid crystal composition with ultralow dielectric loss according to claim 3, wherein the content of the liquid crystal compound with ultralow dielectric loss is 1% -100% by mass.

5. The liquid crystal composition with ultra-low dielectric loss according to claim 3 or 4, comprising one or more compounds selected from the group consisting of structural formula II as a second component:

;

Wherein R ₂ and R ₃ are each an alkyl group having 1 to 10 carbon atoms, an alkenyl group having 2 to 10 carbon atoms, a fluorinated alkyl group, a fluorinated alkenyl group, a cycloalkyl group, a halogen or NCS, and the ring A and the ring B are each a benzene ring, cyclohexane, cyclohexene or a benzene ring in which a hydrogen atom is substituted with a fluorine atom;

The content of the compound shown in the structural general formula II is 0% -40% by mass.

6. The liquid crystal composition with ultra-low dielectric loss according to claim 5, comprising one or more compounds selected from the group consisting of structural formula III as a third component:

;

Wherein R ₁ is alkyl with 1-10 carbon atoms, alkenyl with 2-10 carbon atoms, fluorinated alkyl, fluorinated alkenyl or cycloalkyl, X ₉～X₁₃ is selected from H, F, methyl and ethyl, one of X ₉～X₁₃ is methyl or ethyl, k, m and n are 0 or 1, and ring A is benzene ring, cyclohexane or cyclohexene;

the content of the compound shown in the structural general formula III is 0% -90% by mass.

7. The liquid crystal composition with ultra-low dielectric loss according to claim 6, comprising one or more compounds selected from the group consisting of structural formula IV as a fourth component:

;

Wherein R ₁ is alkyl with 1-10 carbon atoms, alkenyl with 2-10 carbon atoms, fluorinated alkyl and fluorinated alkenyl, X ₁₄～X₁₇ is H, methyl and ethyl, one of X ₁₄～X₁₇ is methyl or ethyl, and the rest is H;

the content of the compound shown in the structural general formula IV is 0% -50% by mass.

8. The liquid crystal composition with ultra-low dielectric loss according to claim 3 or 4, wherein said liquid crystal composition has:

The tuning rate tau is more than or equal to 0.25, the dielectric loss tan delta _⊥ in the vertical direction is less than or equal to 0.006, the material quality factor eta is more than or equal to 50, the temperature interval range of the nematic phase is 0-90 ℃, and the dielectric constant of low-frequency 1KHz is more than or equal to 6.0.

9. A high frequency device comprising the liquid crystal compound of any one of claims 1 to 2 or the liquid crystal composition of any one of claims 3 to 8 having an ultra-low dielectric loss.