阅读说明：本技术 非手性侧甲基烷基三联苯类液晶化合物及制备方法、液晶组合物及应用 (Achiral side methyl alkyl terphenyl liquid crystal compound, preparation method, liquid crystal composition and application ) 是由 张智勇 卢金应 胡晨 洪磊 刘豪浩 关金涛 乔俊飞 陈红梅 汪洋 汪相如 余承勇 于 2019-10-31 设计创作，主要内容包括：本发明公开一种非手性侧甲基烷基三联苯类液晶化合物及其制备方法、液晶组合物及应用,所述非手性侧甲基烷基三联苯类液晶化合物具有式(Ⅰ)所示的分子结构。所述化合物(Ⅰ)的非手性构象支链端基使其具有较宽温的向列相态,支链端基还增加分子的柔性,使得所述化合物(Ⅰ)具有较低的熔点,较大介电和光学各向异性；因化合物(Ⅰ)的分子结构稳定,对微波吸收少,可降低微波器件的介电损耗；可与其它向列相液晶化合物混合组成大介电各向异性、较大光学各向异性的向列相液晶材料；将其应用到微波器件中有利于增大液晶微波器件的相位调制能力,提高液晶材料作为微波介质的品质因数。(The invention discloses an achiral side methyl alkyl terphenyl liquid crystal compound and a preparation method, a liquid crystal composition and application thereof. The achiral conformation branched end group of the compound (I) enables the compound (I) to have a wide-temperature nematic phase state, and the branched end group also increases the flexibility of molecules, so that the compound (I) has a lower melting point, larger dielectric and optical anisotropy; the compound (I) has stable molecular structure and less microwave absorption, so that the dielectric loss of a microwave device can be reduced; can be mixed with other nematic phase liquid crystal compounds to form nematic phase liquid crystal materials with large dielectric anisotropy and large optical anisotropy; the phase modulation material is applied to the microwave device, so that the phase modulation capability of the liquid crystal microwave device is increased, and the quality factor of the liquid crystal material as a microwave medium is improved.)

1. An achiral side methyl alkyl terphenyl liquid crystal compound is characterized by having a structure shown as a structural formula (I):

wherein, X₁And X₂Each independently selected from H atom, F atom, Cl atom or-CH₃，X₄And X₅Each independently selected fromH atom, F atom or Cl atom, and Y is F atom or-NCS.

2. The achiral pendant methylalkyl terphenyl liquid crystal compound according to claim 1, wherein the achiral pendant methylalkyl terphenyl liquid crystal compound is a compound having a structure represented by the following structural formula (I-1):

wherein X in the structural formula (I-1)₁And X₂Each independently selected from H atom, F atom, Cl atom or-CH₃，X₄And X₅Each independently selected from a H atom, a F atom or a Cl atom.

3. The achiral pendant methylalkyl terphenyl liquid crystal compound according to claim 1, wherein the achiral pendant methylalkyl terphenyl liquid crystal compound is a compound having a structure represented by the following structural formula (I-2):

wherein X in the structural formula (I-2)₁And X₂Each independently selected from H atom, F atom, Cl atom or-CH₃，X₄And X₅Each independently selected from a H atom, a F atom or a Cl atom.

4. A preparation method of an achiral side methyl alkyl terphenyl liquid crystal compound is characterized by comprising the following steps:

step S10: under the protection of nitrogen, dissolving a first reactant in tetrahydrofuran, then adding the first reactant into a mixed solution of magnesium powder, tetrahydrofuran and an iodine simple substance, fully reacting to obtain a Grignard reagent, adding the Grignard reagent into a mixture of copper chloride, DL-1-iodine-2-methylbutane and tetrahydrofuran, carrying out reflux reaction, adding diluted hydrochloric acid, stirring, and then carrying out separation, washing and purification treatment to obtain a first intermediate;

step S20: mixing and reacting the first intermediate, periodic acid, iodine simple substance, ethyl acetate, acetic acid, water and concentrated sulfuric acid, heating to 100-110 ℃, refluxing, cooling, adding sodium bisulfite solution, performing suction filtration, washing, extracting and purifying to obtain a second intermediate;

step S30: adding the second intermediate into tetrahydrofuran at the temperature of-80 to-75 ℃ under the protection of nitrogen, adding n-butyl lithium, stirring, adding a mixture of trimethyl borate and tetrahydrofuran, fully mixing, heating to 20-25 ℃, finally adding hydrochloric acid, and performing separation, washing and purification treatment to obtain a third intermediate;

step S40: under the protection of nitrogen, the third intermediate, the second reactant, the palladium catalyst and K are reacted₂CO₃Carrying out Suzuki coupling reaction on ethanol, toluene and water under the condition of heating and stirring, and then carrying out separation, washing, drying and purification treatment to obtain a target compound, wherein the target compound is an achiral side methyl alkyl terphenyl liquid crystal compound with a structural formula shown as (I-1);

wherein the first reactant in step S10 is a compound having a structure represented by the following structural formula (ii), and the second reactant in step S40 is a compound having a structure represented by the following structural formula (iii):

wherein X in the structural formulae (II) and (I-1)₁And X₂Each independently selected from H atom, F atom, Cl atom or-CH₃X in the structural formulae (III) and (I-1)₄And X₅Each independently selected from a H atom, a F atom or a Cl atom.

5. The method for preparing achiral pendant methyl alkyl terphenyl liquid crystal compounds according to claim 4, wherein in step S40, the palladium catalyst is palladium tetrakistriphenylphosphine; and/or the presence of a gas in the gas,

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

6. A preparation method of an achiral side methyl alkyl terphenyl liquid crystal compound is characterized by comprising the following steps:

step S10: under the protection of nitrogen, dissolving a first reactant in tetrahydrofuran, then adding the first reactant into a mixed solution of magnesium powder, tetrahydrofuran and an iodine simple substance, fully reacting to obtain a Grignard reagent, adding the Grignard reagent into a mixture of copper chloride, DL-1-iodine-2-methylbutane and tetrahydrofuran, carrying out reflux reaction, adding diluted hydrochloric acid, stirring, and then carrying out separation, washing and purification treatment to obtain a first intermediate;

step S20: mixing and reacting the first intermediate, periodic acid, iodine simple substance, ethyl acetate, acetic acid, water and concentrated sulfuric acid, heating to 100-110 ℃, refluxing, cooling, adding sodium bisulfite solution, performing suction filtration, washing, extracting and purifying to obtain a second intermediate;

step S30: adding the second intermediate into tetrahydrofuran at the temperature of-80 to-75 ℃ under the protection of nitrogen, adding n-butyl lithium, stirring, adding a mixture of trimethyl borate and tetrahydrofuran, fully mixing, heating to 20-25 ℃, finally adding hydrochloric acid, and performing separation, washing and purification treatment to obtain a third intermediate;

step S50: under the protection of nitrogen, the third intermediate, the third reactant, the palladium catalyst and K are reacted₂CO₃Carrying out Suzuki coupling reaction on ethanol, toluene and water under the condition of heating and stirring, and then carrying out separation, washing, drying and purification treatment to obtain a fourth intermediate;

step S60: uniformly mixing the fourth intermediate, calcium carbonate, water and dichloromethane, cooling to 0-5 ℃, adding a mixed solution of dichloromethane and dichlorocarbon sulfide for reaction, heating to 20-25 ℃, fully reacting, heating to 45-50 ℃, adding ethanol, performing suction filtration, washing and purifying to obtain a target compound, wherein the target compound is the achiral side methyl alkyl terphenyl liquid crystal compound shown in (I-2);

wherein the first reactant in step S10 is a compound having a structure represented by the following structural formula (ii), and the third reactant in step S50 is a compound having a structure represented by the following structural formula (vi):

wherein X in the structural formulae (II) and (I-2)₁And X₂Each independently selected from H atom, F atom, Cl atom or-CH₃X in the structural formulae (VI) and (I-2)₄And X₅Each independently selected from a H atom, a F atom or a Cl atom.

7. A liquid crystal composition, wherein the liquid crystal composition comprises a first compound, and the first compound is the achiral side methyl alkyl terphenyl liquid crystal compound according to any one of claims 1 to 3.

8. The liquid crystal composition of claim 7, further comprising a second class of compounds, a third class of compounds, a fourth class of compounds, and a fifth class of compounds, wherein the second class of compounds comprises at least one compound having a structure represented by the following structural formula (vii), the third class of compounds comprises at least one compound having a structure represented by the following structural formula (viii), the fourth class of compounds comprises at least one compound having a structure represented by the following structural formula (ix), and the fifth class of compounds comprises at least one of compounds having structures represented by the following structural formulae (X-1), (X-2), (X-3), and (X-4):

wherein m and n in the structural formula (VII) are independently selected from 2,3, 4, 5 or 6, n in the structural formula (VIII) is 2,3, 4 or 5, m is 0 or 1, n in the structural formula (IX) is 2,3 or 4, and n in the structural formulae (X-1), (X-2), (X-3) and (X-4) is 4 or 5.

9. The liquid crystal composition of claim 8, further comprising at least one sixth compound having a structure represented by formula (XI):

wherein n in the formula (XI) is 2,3, 4 or 5.

10. A microwave communication device comprising the liquid crystal composition according to any one of claims 7 to 9.

Technical Field

The invention relates to the technical field of organic synthesis, and particularly relates to an achiral side methyl alkyl terphenyl liquid crystal compound, a preparation method thereof, a liquid crystal composition and application thereof.

Background

At present, liquid crystal has been widely applied in the display field, with the development of science and technology, the application range of liquid crystal is gradually increased, the research of liquid crystal for microwave devices starts at the end of the 20 th century, the liquid crystal rapidly develops in the beginning of the century, especially in recent years, the liquid crystal has gained wide attention all over the world, the development is rapid, and the research finds that the liquid crystal can be used in important fields such as tunable filters, reconfigurable antennas, tunable frequency selectors, tunable phase shifters and the like. However, there are fundamental problems to be solved in many aspects of related key technologies, such as liquid crystal materials, alignment, packaging, wiring, device design and functional characterization, and especially there are few research reports in the liquid crystal materials.

For the sake of understanding, the relevant performance parameters for the liquid crystal material are described as follows, Deltaε represents the dielectric anisotropy, △ n represents the optical anisotropy, i.e. the birefringence (589nm, 20 ℃), Iso. is the clearing point temperature (DEG C) of the phase state of the liquid crystal composition, and the dielectric anisotropy in the microwave range is defined as △ ε_r≡(εr||-εr_⊥) The tunability (tau) is defined as tau [ identical to ] (delta [ epsilon ] r/epsilon r |), the material quality (η) is defined as η [ identical to ] (tau/tan [ delta ] epsilon r max.), the maximum dielectric loss is tan [ delta ] epsilon r ⊥, tan [ delta ] epsilon r | }, wherein the dielectric loss refers to the microwave wave frequency loss caused by the wave frequency absorption generated when microwaves (4-40 GHz) irradiate or pass through the liquid crystal material, generally called microwave insertion loss, and the liquid crystal material has good liquid crystal quality (LC) and can be used for manufacturing the liquid crystal display panelExhibited in the material as a dielectric constant of_r", the dielectric constant is divided into a component" ε which is parallel to the long axis of the liquid crystal_r/' and vertical component ∈_r⊥' and has a dielectric constant value of Deltaε_r＝ε_r∥-ε_r⊥, the quantitative expression of the microwave dielectric loss is the tangent value (tan delta epsilon)_r⊥, or tan delta epsilon_{r max}) Is a main performance index parameter reflecting the liquid crystal material in a microwave field and generally requires tan delta epsilon_r⊥(or tan. delta. epsilon.)_{r max}) A value of less than or equal to about 0.03 and tan delta epsilon_r/value is about 0.006 or less. The birefringence is an expression method of optical anisotropy of liquid crystal compound and mixed liquid crystal material, and refers to that light passes through the liquid crystal material and is refracted and scattered by liquid crystal to form ordinary light and extraordinary light, the ordinary light refractive index represents ' no ', and the extraordinary light refractive index represents ' n_e", the birefringence is represented by" Δ n ", and" Δ n ═ n_e-n_o", the microwave high frequency device requires the delta n value to be more than or equal to 0.35, and the higher the delta n value is, the more beneficial the microwave phase shift quantity is to be improved. The liquid crystal material with high dielectric anisotropy, high optical anisotropy and low dielectric loss is used as the liquid crystal material with high dielectric anisotropy, high optical anisotropy and low dielectric loss; the microwave has small dielectric loss and tan delta epsilon after being irradiated by the liquid crystal material_r⊥(or tan. delta. epsilon.)_{r max}) A value lower than about 0.008 and tan delta epsilon_r/value is less than 0.004. the "phase modulation coefficient" of the microwave liquid crystal phase shifter is expressed as "tau", which reflects the parameter of the phase modulation capability of the liquid crystal material to the microwave frequency, 0.15. ltoreq. tau. ltoreq.0.6. the "quality factor" (η, or FOM) of the liquid crystal means the comprehensive evaluation result of the performance after the microwave passes through the liquid crystal, which reflects the performance and quality of the liquid crystal material, and generally requires η. gtoreq.20.

In the existing large amount of research processes, the following problems mainly exist in the practical application of the current liquid crystal material for microwave: firstly, the value of optical anisotropy delta n is smaller than 0.22, so that the phase shift quantity is insufficient; secondly, the dielectric loss of the liquid crystal material is large due to the wave absorption and polarizability of the structural groups in the liquid crystal molecules; finally, the absence of high Δ n values, low melting point liquid crystal solvents and nematic liquid crystal components results in affecting the low temperature performance of the liquid crystal material. The above problems make the liquid crystal material for microwave unable to meet the requirements of microwave devices, and therefore, it is highly desirable to provide a novel nematic liquid crystal compound with high stability, Δ n not less than 0.35, low melting point, high dielectric constant and low consumption.

Disclosure of Invention

The invention mainly aims to provide an achiral side methyl alkyl terphenyl liquid crystal compound, a preparation method thereof, a liquid crystal composition and application, and aims to reduce dielectric loss of a liquid crystal microwave device.

In order to achieve the purpose, the invention provides an achiral side methyl alkyl terphenyl liquid crystal compound, which is characterized in that the liquid crystal compound has a structure shown in the following structural formula (I):

wherein, X₁And X₂Each independently selected from H atom, F atom, Cl atom or-CH₃，X₄And X₅Each independently selected from a H atom, a F atom or a Cl atom, and Y is a F atom or-NCS.

Optionally, the achiral side methyl alkyl terphenyl liquid crystal compound is a compound with a structure shown in the following structural formula (I-1):

wherein X in the structural formula (I-1)₁And X₂Each independently selected from H atom, F atom, Cl atom or-CH₃，X₄And X₅Each independently selected from a H atom, a F atom or a Cl atom.

Optionally, the achiral side methyl alkyl terphenyl liquid crystal compound is a compound with a structure shown in the following structural formula (I-2):

wherein X in the structural formula (I-2)₁And X₂Each independently selected from H atom, F atom, Cl atom or-CH₃，X₄And X₅Each independently selected from a H atom, a F atom or a Cl atom.

In order to achieve the above object, the present invention further provides a method for preparing the above achiral side methyl alkyl terphenyl liquid crystal compound, comprising the following steps:

step S10: under the protection of nitrogen, dissolving a first reactant in tetrahydrofuran, then adding the first reactant into a mixed solution of magnesium powder, tetrahydrofuran and an iodine simple substance, fully reacting to obtain a Grignard reagent, adding the Grignard reagent into a mixture of copper chloride, DL-1-iodine-2-methylbutane and tetrahydrofuran, carrying out reflux reaction, adding diluted hydrochloric acid, stirring, and then carrying out separation, washing and purification treatment to obtain a first intermediate;

step S20: mixing and reacting the first intermediate, periodic acid, iodine simple substance, ethyl acetate, acetic acid, water and concentrated sulfuric acid, heating to 100-110 ℃, refluxing, cooling, adding sodium bisulfite solution, performing suction filtration, washing, extracting and purifying to obtain a second intermediate;

step S30: adding the second intermediate into tetrahydrofuran at the temperature of-80 to-75 ℃ under the protection of nitrogen, adding n-butyl lithium, stirring, adding a mixture of trimethyl borate and tetrahydrofuran, fully mixing, heating to 20-25 ℃, finally adding hydrochloric acid, and performing separation, washing and purification treatment to obtain a third intermediate;

step S40: under the protection of nitrogen, the third intermediate, the second reactant, the palladium catalyst and K are reacted₂CO₃Carrying out Suzuki coupling reaction on ethanol, toluene and water under the condition of heating and stirring, and then carrying out separation, washing, drying and purification treatment to obtain a target compound, wherein the target compound is an achiral side methyl alkyl terphenyl liquid crystal compound with a structural formula shown as (I-1);

wherein the first reactant in step S10 is a compound having a structure represented by the following structural formula (ii), and the second reactant in step S40 is a compound having a structure represented by the following structural formula (iii):

wherein X in the structural formulae (II) and (I-1)₁And X₂Each independently selected from H atom, F atom, Cl atom or-CH₃X in the structural formulae (III) and (I-1)₄And X₅Each independently selected from a H atom, a F atom or a Cl atom.

Alternatively, in step S40, the palladium catalyst is tetrakistriphenylphosphine palladium; and/or the presence of a gas in the gas,

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

In order to achieve the above object, the present invention further provides another method for preparing the achiral side methyl alkyl terphenyl liquid crystal compound (I-2), comprising the following steps:

step S10: under the protection of nitrogen, dissolving a first reactant in tetrahydrofuran, then adding the first reactant into a mixed solution of magnesium powder, tetrahydrofuran and an iodine simple substance, fully reacting to obtain a Grignard reagent, adding the Grignard reagent into a mixture of copper chloride, DL-1-iodine-2-methylbutane and tetrahydrofuran, carrying out reflux reaction, adding diluted hydrochloric acid, stirring, and then carrying out separation, washing and purification treatment to obtain a first intermediate;

step S20: mixing and reacting the first intermediate, periodic acid, iodine simple substance, ethyl acetate, acetic acid, water and concentrated sulfuric acid, heating to 100-110 ℃, refluxing, cooling, adding sodium bisulfite solution, performing suction filtration, washing, extracting and purifying to obtain a second intermediate;

step S30: adding the second intermediate into tetrahydrofuran at the temperature of-80 to-75 ℃ under the protection of nitrogen, adding n-butyl lithium, stirring, adding a mixture of trimethyl borate and tetrahydrofuran, fully mixing, heating to 20-25 ℃, finally adding hydrochloric acid, and performing separation, washing and purification treatment to obtain a third intermediate;

step (ii) ofS50: under the protection of nitrogen, the third intermediate, the third reactant, the palladium catalyst and K are reacted₂CO₃Carrying out Suzuki coupling reaction on ethanol, toluene and water under the condition of heating and stirring, and then carrying out separation, washing, drying and purification treatment to obtain a fourth intermediate;

step S60: uniformly mixing the fourth intermediate, calcium carbonate, water and dichloromethane, cooling to 0-5 ℃, adding a mixed solution of dichloromethane and dichlorocarbon sulfide for reaction, heating to 20-25 ℃, fully reacting, heating to 45-50 ℃, adding ethanol, performing suction filtration, washing and purifying to obtain a target compound, wherein the target compound is the achiral side methyl alkyl terphenyl liquid crystal compound shown in (I-2);

wherein the first reactant in step S10 is a compound having a structure represented by the following structural formula (ii), and the third reactant in step S50 is a compound having a structure represented by the following structural formula (vi):

wherein X in the structural formulae (II) and (I-2)₁And X₂Each independently selected from H atom, F atom, Cl atom or-CH₃X in the structural formulae (VI) and (I-2)₄And X₅Each independently selected from a H atom, a F atom or a Cl atom.

The invention further provides a liquid crystal composition which comprises a first compound, wherein the first compound is the achiral side methyl alkyl terphenyl liquid crystal compound (I).

Optionally, the liquid crystal composition further comprises a second kind of compound, a third kind of compound, a fourth kind of compound and a fifth kind of compound, wherein the second kind of compound comprises at least one compound having a structure shown in the following structural formula (VII), the third kind of compound comprises at least one compound having a structure shown in the following structural formula (VIII), the fourth kind of compound comprises at least one compound having a structure shown in the following structural formula (IX), and the fifth kind of compound comprises at least one compound having a structure shown in structural formulas (X-1), (X-2), (X-3) and (X-4):

wherein m and n in the structural formula (VII) are independently selected from 2,3, 4, 5 or 6, n in the structural formula (VIII) is 2,3, 4 or 5, m is 0 or 1, n in the structural formula (IX) is 2,3 or 4, and n in the structural formulae (X-1), (X-2), (X-3) and (X-4) is 4 or 5.

Optionally, the liquid crystal composition further comprises at least one sixth compound having a structure represented by formula (XI) below:

wherein n in the formula (XI) is 2,3, 4 or 5.

The invention also provides application of the liquid crystal composition, which can be used for microwave communication devices, wherein the microwave communication devices comprise the liquid crystal composition.

In the technical scheme provided by the invention, the achiral side methyl alkyl terphenyl liquid crystal compound has a terphenyl structure and an achiral branched chain end group in the structure, the achiral branched chain end group can increase the flexibility of liquid crystal molecules and reduce the melting point of the compound, so that the achiral side methyl alkyl terphenyl liquid crystal compound has the advantage of lower melting point, the terphenyl structure enables the molecular structure to be stable, the resonance absorption effect of microwaves on molecules can be reduced, and in addition, the F atom and the polar end group-NCS group in the molecules can increase the dielectric constant of the terphenyl liquid crystal compound; the-NCS group prolongs the length of a pi-electron conjugated system of the terphenyl molecule, and can increase the optical anisotropy (namely the birefringence delta n value) of the terphenyl liquid crystal compound. When the material is applied to a high dielectric anisotropy liquid crystal material, the dielectric loss of a liquid crystal microwave device is reduced, the microwave phase modulation capability is improved, and the quality factor of the liquid crystal microwave dielectric material can be improved.

Drawings

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

FIG. 1 is a schematic flow chart of an embodiment of a method for preparing an achiral pendant methyl alkyl terphenyl liquid crystal compound according to the present invention;

fig. 2 is a schematic flow chart of another embodiment of the method for preparing the achiral side methyl alkyl terphenyl liquid crystal compound provided by the invention.

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

Detailed Description

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

The invention aims to develop a liquid crystal material with a molecular structure with small microwave absorption coefficient and small polarizability by researching the influence of the liquid crystal molecular structure on the dielectric property of a microwave K frequency band, particularly the dielectric loss effect, design and synthesize novel nematic phase liquid crystal molecules with high delta n value, low melting point, low dielectric loss and high stable structure, and mix the liquid crystal compounds to prepare the nematic phase liquid crystal material with high dielectric loss, low consumption and stable low temperature performance meeting the requirements of microwave devices.

The invention provides an achiral side methyl alkyl terphenyl liquid crystal compound, which has a structure shown in the following structural formula (I):

wherein, X₁And X₂Each independently selected from H atom, F atom, Cl atom or-CH₃，X₄And X₅Each independently selected from a H atom, a F atom or a Cl atom, and Y is a F atom or-NCS.

In the technical scheme provided by the invention, the achiral side methyl alkyl terphenyl liquid crystal molecular structure simultaneously has a terphenyl structure and an achiral branched chain end group; the achiral branched chain end group can increase the flexibility of liquid crystal molecules and reduce the melting point of the compound, so that the achiral side methyl alkyl terphenyl liquid crystal compound has the advantage of low melting point; the terphenyl structure enables the molecular structure of the terphenyl structure to be stable, and can reduce the resonance absorption effect of microwaves on molecules; in addition, F atoms and polar end groups-NCS in the molecules can increase the dielectric constant of the terphenyl liquid crystal compound; the-NCS group prolongs the length of a pi-electron conjugated system of a terphenyl molecule, and can increase the optical anisotropy (namely the birefringence delta n value) of the terphenyl liquid crystal compound. Therefore, when the dielectric loss reducing and phase modulating materials are applied to high dielectric anisotropy liquid crystal materials, the dielectric loss of liquid crystal microwave devices is reduced, the microwave phase modulating capacity is improved, and the quality factor of the liquid crystal microwave dielectric materials can be improved.

The achiral side methyl alkyl terphenyl liquid crystal compound has a low melting point, for example, the melting point of the 2-methylbutyl fluorine-containing terphenyl liquid crystal compound reaches 34 ℃, and when the liquid crystal compound is added into a liquid crystal composition as a component, the eutectic point of the liquid crystal composition can be effectively reduced.

In addition, the side groups X in the formula (I)₁And X₂More preferably at least one of them is F atom or-CH₃，X₄And X₅More preferably, at least one of them is F atom, so that the side chain of the liquid crystal compound contains both an achiral branched terminal group, a fluorine atom and a group Y ═The NCS and the terphenyl structure make the optical anisotropy of the liquid crystal compound larger, the structural stability better, and are beneficial to further reducing the dielectric loss of the liquid crystal material and further increasing the quality factor of the liquid crystal material.

The achiral side methyl alkyl terphenyl liquid crystal compound can be a compound with a structure shown in the following structural formula (I-1):

wherein X in the structural formula (I-1)₁And X₂Each independently selected from H atom, F atom, Cl atom or-CH₃，X₄And X₅Each independently selected from a H atom, a F atom or a Cl atom. F atoms in molecules can increase the dielectric constant of the terphenyl liquid crystal compound, so that the delta n value of the achiral side methyl alkyl terphenyl liquid crystal compound is increased.

The achiral side methyl alkyl terphenyl liquid crystal compound can also be a compound with a structure shown in the following structural formula (I-2):

wherein X in the structural formula (I-2)₁And X₂Each independently selected from H atom, F atom, Cl atom or-CH₃，X₄And X₅Each independently selected from a H atom, a F atom or a Cl atom.

Due to the unsaturation of the-NCS group, a large pi-electron conjugated system is formed with the connected benzene ring; and the pi-electron cloud of the-NCS group is on 3 atoms, so that the length of a pi-electron conjugated system is prolonged, the delta n value of the achiral side methyl alkyl terphenyl liquid crystal compound is increased, and the dielectric loss is reduced.

Furthermore, the invention also provides a preparation method of the achiral side methyl alkyl terphenyl liquid crystal compound. For example, when Y is F atom, the liquid crystal compound has the following synthetic route:

fig. 1 is a schematic flow chart of an embodiment of a preparation method of an achiral side methyl alkyl terphenyl liquid crystal compound provided by the invention, which comprises the following steps:

step S10: under the protection of nitrogen, dissolving a first reactant in tetrahydrofuran, then adding the first reactant into a mixed solution of magnesium powder, tetrahydrofuran and an iodine simple substance, fully reacting to obtain a Grignard reagent, adding the Grignard reagent into a mixture of copper chloride, DL-1-iodine-2-methylbutane and tetrahydrofuran, carrying out reflux reaction, adding diluted hydrochloric acid, stirring, and then carrying out separation, washing and purification treatment to obtain a first intermediate;

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

wherein X in the structural formula (II)₁And X₂Each independently selected from H atom, F atom, Cl atom or-CH₃。

In this step, separation, washing and purification treatment may be carried out according to a conventional method in the field of organic synthesis, and for example, separation may be carried out by extraction and layering, washing with water until the product becomes neutral, recrystallization for purification, and the like. The following separation, washing and purification treatments are similar to those in this case and will not be described in detail.

In the present embodiment, a specific implementation manner of step S10 is provided: under the protection of nitrogen, adding magnesium powder, tetrahydrofuran and iodine into a reaction bottle, uniformly mixing, then dropwise adding a tetrahydrofuran solution of a first reactant into the reaction bottle, and fully reacting under a heating condition to obtain the Grignard reagent. And then adding copper chloride, DL-1-iodine-2-methylbutane and tetrahydrofuran into another reaction bottle under the protection of nitrogen, fully mixing to form a mixed solution, dropwise adding the prepared Grignard reagent into the mixed solution, heating and carrying out reflux reaction for 5-7 h, adding hydrochloric acid, stirring, carrying out suction filtration, separating the liquid, extracting a water layer with toluene, washing to be neutral, drying an organic layer with anhydrous sodium sulfate, and carrying out reduced pressure distillation to remove the solvent to obtain a first intermediate. The reaction bottle can be a conical flask, a three-neck flask or an organic synthesis reaction kettle and other containers, and is determined according to the dosage of reaction raw materials or the yield requirement of reaction products during specific operation. The following reaction flask is similar to that described here and will not be described in detail.

Further, in step S10, the molar ratio of the first reactant, magnesium, copper chloride and DL-1-iodo-2-methylbutane is (15 to 20): (20-25): 1: (20-25).

Step S20: mixing and reacting the first intermediate, periodic acid, iodine simple substance, ethyl acetate, acetic acid, water and concentrated sulfuric acid, heating to 100-110 ℃, refluxing, cooling, adding sodium bisulfite solution, performing suction filtration, washing, extracting and purifying to obtain a second intermediate;

in the present embodiment, a specific implementation manner of step S20 is provided: adding a first intermediate, periodic acid, an iodine simple substance, ethyl acetate, acetic acid, water and concentrated sulfuric acid into a reaction bottle in sequence, fully mixing and reacting, heating to 100-110 ℃, refluxing for 6-8 h, stopping heating and cooling, then adding a saturated sodium bisulfite solution to remove excessive iodine until the reaction solution is yellow, stopping stirring, carrying out suction filtration, washing a filter cake twice with ethyl acetate, washing the filtrate with water, extracting with dichloromethane to obtain a lower organic layer, and carrying out reduced pressure distillation to remove the solvent to obtain a second intermediate.

Further, in step S20, the molar ratio of the first intermediate, periodic acid and iodine is 1: (2-4): (2-4).

Step S30: adding the second intermediate into tetrahydrofuran at the temperature of-80 to-75 ℃ under the protection of nitrogen, adding n-butyl lithium, stirring, adding a mixture of trimethyl borate and tetrahydrofuran, fully mixing, heating to 20-25 ℃, finally adding hydrochloric acid, and performing separation, washing and purification treatment to obtain a third intermediate;

in this embodiment, step S30 can be implemented in the following manner: under the protection of nitrogen, tetrahydrofuran and a second intermediate are sequentially added into a reaction bottle at the temperature of-80 to-75 ℃, then n-butyllithium is slowly injected into the reaction bottle, after the mixture is stirred for a period of time, a mixture of trimethyl borate and tetrahydrofuran is slowly injected, the mixture is continuously stirred, then the temperature is increased to the room temperature of 20 to 25 ℃, finally, diluted hydrochloric acid is added, the mixture is stirred, the mixture is kept stand, liquid separation is carried out, ethyl acetate extraction is carried out, an organic phase is washed to be neutral, and a solvent is removed. Recrystallizing to obtain a third intermediate.

Further, in this embodiment, the molar ratio of the second intermediate, n-butyllithium, trimethyl borate, and hydrochloric acid in step S30 is 1: (1.2-1.4): (1.4-1.6).

Step S40: under the protection of nitrogen, the third intermediate, the second reactant, the palladium catalyst and K are reacted₂CO₃Carrying out Suzuki coupling reaction on ethanol, toluene and water under the condition of heating and stirring, and then carrying out separation, washing, drying and purification treatment to obtain a target compound, wherein the target compound is the achiral side methyl alkyl terphenyl liquid crystal compound with the structural formula shown as (I-1).

Wherein the second reactant in step S40 is a compound having a structure represented by the following structural formula (iii):

wherein X in the structural formula (III)₄And X₅Each independently selected from a H atom, a F atom or a Cl atom.

In the present embodiment, a specific implementation step of step S40 is provided: adding a third intermediate, a second reactant, a palladium catalyst and K into a reaction bottle under the protection of nitrogen₂CO₃Heating, stirring and refluxing for 3.5-4.5 h, stopping stirring, naturally cooling the reaction solution to room temperature, adding hydrochloric acid for neutralization, filtering to remove insoluble substances, adding toluene for extraction, separating, washing with water to neutrality, drying with anhydrous sodium sulfate, filtering, evaporating filtrate to dryness, and packagingEluting with petroleum ether in the chromatographic column, and removing the solvent in the eluent by rotary evaporation to obtain the achiral side methyl alkyl terphenyl liquid crystal compound (I-1).

In this embodiment, the palladium catalyst in step S40 is palladium tetrakistriphenylphosphine, the third intermediate, the second reactant, K₂CO₃And the molar ratio of the palladium catalyst is 1: (1-2): (2-5): (0.001-0.005) and the reaction temperature of the Suzuki coupling reaction is 40-80 ℃.

In addition, in this embodiment, in order to improve the purity of the obtained achiral side methyl alkyl terphenyl liquid crystal compound, the obtained achiral side methyl alkyl terphenyl liquid crystal compound is further refined by an electric field adsorption method, and the adsorption method and the external electric field method are combined together by using a high-activity adsorption material, so as to deeply purify and refine the liquid crystal material, reduce the content of trace impurity ions in the liquid crystal material, and achieve the purposes of improving the resistivity, the charge retention rate and the stability of the liquid crystal material.

By adopting the preparation method in the embodiment, a series of achiral side methyl alkyl terphenyl liquid crystal compounds with excellent performance are prepared, and the structural formula is as follows:

the invention further provides another preparation method of the achiral side methyl alkyl terphenyl liquid crystal compound, wherein Y is-NCS, and the synthetic route is as follows:

in the present synthetic route, due to the nature of the-NCS group, the-NCS needs to be generated in the last step, and the reactants, products and reaction process conditions of the steps S10-S30 are described above and will not be described herein again.

Step S50: under the protection of nitrogen, catalyzing the third intermediate, the third reactant and palladiumAgent, K₂CO₃Carrying out Suzuki coupling reaction on ethanol, toluene and water under the condition of heating and stirring, and then carrying out separation, washing, drying and purification treatment to obtain a fourth intermediate;

wherein the third reactant in step S50 is a compound having a structure represented by the following structural formula (vi):

wherein X in the structural formula (VI)₄And X₅Each independently selected from a H atom, a F atom or a Cl atom.

In this example, the palladium catalyst in step S50 is palladium tetrakistriphenylphosphine, a third intermediate, a third reactant, K₂CO₃And the molar ratio of the palladium catalyst is 1: (1-2): (2-5): (0.001-0.005) and the reaction temperature of the Suzuki coupling reaction is 40-80 ℃.

Step S60: uniformly mixing the fourth intermediate, calcium carbonate, water and dichloromethane, cooling to 0-5 ℃, adding a mixed solution of dichloromethane and dichlorocarbon sulfide for reaction, heating to 20-25 ℃, fully reacting, heating to 45-50 ℃, adding ethanol, performing suction filtration, washing and purifying to obtain a target compound, wherein the target compound is the achiral side methyl alkyl terphenyl liquid crystal compound shown in (I-2);

wherein X in the structural formula (V)₁And X₂Each independently selected from H atom, F atom, Cl atom or-CH₃，X₄And X₅Each independently selected from a H atom, a F atom or a Cl atom.

In the present embodiment, a specific implementation manner of step S60 is provided: and sequentially adding the fourth intermediate, calcium carbonate, water and dichloromethane into a reaction bottle, uniformly mixing, cooling to 0-5 ℃ in an ice bath, slowly dropwise adding a mixed solution of dichloromethane and dichlorosulfureted carbon, fully reacting, removing the ice bath, heating the reaction bottle to room temperature of 20-25 ℃, continuously reacting for a period of time, heating to 45-50 ℃, and adding ethanol to prevent a period of time so as to destroy incompletely reacted dichlorosulfureted carbon. And then carrying out suction filtration, washing with water, separating liquid, extracting a water layer by using dichloromethane, combining organic layers, and carrying out reduced pressure distillation to remove the dichloromethane to obtain the achiral side methyl alkyl terphenyl liquid crystal compound (I-2).

Further, in step S60, the molar ratio of the fourth intermediate, calcium carbonate and dichlorocarbon sulfide is 1: (2-3): (2-3).

Similarly, in this example, in order to improve the purity of the obtained achiral pendant methylalkyl terphenyl liquid crystal compound, the obtained achiral pendant methylalkyl terphenyl liquid crystal compound was further refined by an electric field adsorption method, and the liquid crystal material was further refined by combining the adsorption method and the external electric field method using a highly active adsorption material, thereby reducing the content of trace impurity ions in the liquid crystal material.

By adopting the preparation method in the embodiment, a series of achiral side methyl alkyl terphenyl liquid crystal compounds (I-2) with excellent performance are prepared, and the structural formula is as follows:

by adopting the preparation method of the achiral side methyl alkyl terphenyl liquid crystal compound provided by the invention, the achiral side methyl alkyl terphenyl liquid crystal compound can be stably prepared in batch through synthesis methods such as Grignard coupling reaction, halogen substitution, Suzuki coupling reaction and the like, has the advantages of large optical anisotropy and stable structure, can reduce the dielectric loss of the liquid crystal material and improve the tunability when applied to the liquid crystal material, and provides the liquid crystal material with better performance for developing microwave communication devices.

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

Optionally, the liquid crystal composition further comprises a second kind of compound, a third kind of compound, a fourth kind of compound and a fifth kind of compound, wherein the second kind of compound comprises at least one compound having a structure shown in the following structural formula (VII), the third kind of compound comprises at least one compound having a structure shown in the following structural formula (VIII), the fourth kind of compound comprises at least one compound having a structure shown in the following structural formula (IX), and the fifth kind of compound comprises at least one compound having a structure shown in structural formulas (X-1), (X-2), (X-3) and (X-4):

wherein m and n in the structural formula (VII) are independently selected from 2,3, 4, 5 or 6, n in the structural formula (VIII) is 2,3, 4 or 5, m is 0 or 1, n in the structural formula (IX) is 2,3 or 4, and n in the structural formulae (X-1), (X-2), (X-3) and (X-4) is 2,3, 4 or 5.

Preferably, the liquid crystal composition further comprises at least one sixth compound having a structure represented by the following formula (XI):

wherein n in the formula (XI) is 2,3, 4 or 5.

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

Furthermore, the invention also provides application of the liquid crystal composition, which can be applied to microwave communication devices, wherein the microwave communication devices comprise the liquid crystal composition. The microwave communication device can be a component or a device which can be tuned by applying a magnetic field and/or an electric field, such as a tunable filter, a reconfigurable antenna, a tunable frequency selector or a tunable phase shifter, and the like.

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

In order to distinguish the structures of the first compound (liquid crystal compound having a structure shown by a structural formula (I)), the second compound (compound having a structure shown by a structural formula (VII)), the third compound (compound having a structure shown by a structural formula (VIII)), the fourth compound (compound having a structure shown by a structural formula (IX)), the fifth compound (compounds having structures shown by structural formulas (X-1), (X-2), (X-3) and (X-4)) in the liquid crystal composition, the second compound is named as a compound nPTP (2) TPm, the third compound is named as a compound nPTUS, nPTGS, nPPTUS, the fourth compound is named as a compound n (1) PPTUS, and the fifth compound is named as a compound nPPI (1), nPPI (1) PUS, nPP (1) PUF, nPPI (1) PUS, the sixth class of compounds being named compound nPGUS.

The following is further described in conjunction with the abbreviations named above.

TABLE 1 element Classification