Relaxation ferroelectric / anti-ferroelectric liquid crystal material as well as preparation method and application thereof

Abstract

The invention relates to the technical field of ferroelectric liquid crystals, in particular to a relaxor ferroelectric / anti-ferroelectric liquid crystal material and a preparation method and application thereof. The relaxor ferroelectric / anti-ferroelectric liquid crystal material provided by the invention retains the ferroelectricity of ferroelectric nematic phase liquid crystal, generates isotropic-ferroelectric phase transition at 43.3 DEG C, and shows the specific ferroelectric hysteresis loop and dielectric relaxation behavior of the relaxor ferroelectric.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of ferroelectric liquid crystals, in particular to a relaxor ferroelectric / anti-ferroelectric liquid crystal material and a preparation method and application thereof. BACKGROUND

[0002] Liquid crystal materials, with their unique molecular order arrangement characteristics, have become the core materials of modern display technology and optoelectronic devices, and are widely used in liquid crystal displays, microwave tuning devices and other fields. Traditional nematic liquid crystals can realize the rapid reorientation of the director under the action of an electric field through the synergistic effect of their anisotropy and fluidity, and then control the optical birefringence. This characteristic makes them an ideal choice for optical display devices. However, due to their low dielectric anisotropy (Δε) (for example, Δε<10), the device driving voltage is high; at the same time, the limitation of high rotational viscosity or elastic constant may further prolong the response time. These factors restrict the development of low-power and miniaturization of flexible electronic devices. The recently discovered ferroelectric liquid crystals can achieve microsecond-level response under weak fields, providing a key material basis for the development of higher-performance optical and electrical devices.

[0003] As early as 1916, the physicist Born proposed a theoretical concept of a ferroelectric fluid. It was not until 1974 that researchers first discovered the existence of ferroelectricity in chiral smectic C phase liquid crystals. However, this ferroelectric liquid crystal has weak polarity and poor fluidity, making it difficult to meet the engineering needs of flexible devices. The Nishikawa team and the Goodby team independently reported the non-chiral polar liquid crystal molecules DIO and RM734, respectively, and their ferroelectric nematic phase characteristics were later confirmed by the Clark team. Taking RM734 as an example, this material exhibits an ultra-high dielectric constant (ε≈1×10 4 ) at 1 kHz, which is two orders of magnitude higher than that of traditional smectic phase liquid crystals; its polarization density reaches 6μC / cm 2 , and it can achieve microsecond-level response under a weak field of 100V / m, marking the beginning of a new stage of development of soft ferroelectric materials.

[0004] Ferroelectric nematic liquid crystals have large dielectric tunability and fast polarization response rate near the ferroelectric phase transition, which makes them have great application potential in variable capacitance, phase change refrigeration and other fields. However, the commonly reported liquid crystals have a high temperature range of ferroelectric nematic phase, and usually crystallize at room temperature, making it difficult to exist stably in the form of ferroelectric nematic phase, especially after crystallization, losing its fluidity and ferroelectricity. The phase transition temperature range is narrow, and a sharp phase transition occurs near the Curie temperature (Tc), causing various electrical performance indicators such as dielectric response and polarization to change abruptly. These problems seriously hinder the practical application of ferroelectric nematic liquid crystals in variable capacitance, phase change refrigeration and other fields near room temperature. In addition, the high residual polarization affects the energy storage density and charging and discharging speed, limiting its application in high-energy-density energy storage capacitors.

[0005] Relaxor ferroelectric has the characteristic of diffuse phase transition, and its dielectric response, piezoelectric response, polarization response and other electrical properties can remain relatively stable in the phase transition temperature range, which makes the relaxor ferroelectric material have a great advantage in the application of phase transition characteristics (such as variable capacitance, phase transition refrigeration, etc.) compared with normal ferroelectric materials. Due to the anti-parallel coupling characteristics of its dipole, the remanent polarization of anti-ferroelectric material is extremely low, and the loss is extremely low under subcritical electric field, so its application in high energy density energy storage capacitor is more advantageous than ferroelectric material. However, so far, there is no officially published literature on how to convert normal ferroelectric liquid crystal into relaxor ferroelectric liquid crystal or anti-ferroelectric liquid crystal molecules. SUMMARY

[0006] The purpose of the present application is to provide a relaxor ferroelectric / anti-ferroelectric liquid crystal material and its preparation method and application.

[0007] To achieve the above purpose, the present application provides a relaxor ferroelectric / anti-ferroelectric liquid crystal material, which has the following structure:

[0008]

[0009] R1 includes -RCOOCH=CH2, -RCF3, -RNO2, -ROCH2CH2CH=CH2;

[0010] R2 includes -RCOOCH=CH2, -RCF3, -ROCH2CH2CN,

[0011] -ROCH2CH2CH=CH2;

[0012] R3 includes -RCH=CH2, -RCN, -RCOOCH=CH2, -OCH2CH2Br, -RNO2,

[0013] -ROCH2CH2CH=CH2;

[0014] R4 includes -NO2, -CN, -NCS or -CF3;

[0015] Wherein -R is a hydrocarbon group with C atom number of 2-20.

[0016] In some embodiments of the present application, the relaxor ferroelectric / anti-ferroelectric liquid crystal material comprises:

[0017]

[0018]

[0019]

[0020] The application further provides a preparation method of the above-mentioned relaxor ferroelectric / anti-ferroelectric liquid crystal material, comprising the following preparation steps:

[0021] S1, mixing an aldehyde compound, potassium carbonate, a halogenated alcohol and an organic solvent to obtain an intermediate product A1;

[0022] S2, mixing the intermediate product A1, triethylamine and dichloromethane, and then adding acryloyl chloride to obtain an intermediate product A2;

[0023] S3, dissolving the intermediate product A2, sodium dihydrogen phosphate and sodium chlorite in dimethyl sulfoxide solution to obtain an intermediate product A3;

[0024] S4, dissolving the intermediate product A3, 4-nitrophenyl 4-hydroxybenzoate, 1-ethyl-(3-dimethylaminopropyl) carbodiimide and 4-dimethylaminopyridine in dichloromethane to obtain the relaxor ferroelectric / anti-ferroelectric liquid crystal material.

[0025] In some embodiments of the application, the aldehyde compound in S1 comprises 2-hydroxy-4-methoxybenzaldehyde or 4-hydroxy-2-methoxybenzaldehyde.

[0026] The halogenated alcohol comprises 6-bromo-1-hexanol or 4-bromo-1-butanol.

[0027] In some embodiments of the application, the CAS number of the 6-bromo-1-hexanol is 4286-55-9, and the CAS number of the 4-bromo-1-butanol is 33036-62-3.

[0028] In some embodiments of the application, the molar volume ratio of the aldehyde compound, potassium carbonate, halogenated alcohol and organic solvent in S1 is 1.5-1.7 mol: 3-3.5 mol: 2 mol: 30 mL.

[0029] The organic solvent comprises N-N dimethylformamide.

[0030] The temperature of the mixing in S1 is 55-65°C, and the mixing time is 8-12 h.

[0031] In some embodiments of the application, the molar volume ratio of the intermediate product A1, triethylamine and dichloromethane in S2 is 1.5-2.5: 3: 20 mL.

[0032] The temperature of the mixing in S2 is 0-2°C, and the mixing time is 3-7 min; the molar volume ratio of the intermediate product A1 and acryloyl chloride is 1.5-2.5 mol: 2 mL.

[0033] In some embodiments of the present application, the molar ratio of the intermediate product A2, sodium dihydrogen phosphate and sodium chlorite in S3 is 1:4:3-4, the volume ratio of dimethyl sulfoxide to solvent in the dimethyl sulfoxide solution is 4:3, and the solvent comprises water.

[0034] In some embodiments of the present application, the temperature of the reaction in S3 is 0-25℃, and the reaction time is 5-8h.

[0035] In some embodiments of the present application, the specific reaction step in S3 is: dissolving the intermediate product A2, sodium dihydrogen phosphate and sodium chlorite in a dimethyl sulfoxide solution, stirring at a temperature of 0-2℃, then warming to 25℃, reacting for 5-8h, and then adjusting the pH to obtain the intermediate product A3.

[0036] In some embodiments of the present application, the molar ratio of the intermediate product A3, 4-nitrophenyl 4-hydroxybenzoate, 1-ethyl-(3-dimethylaminopropyl) carbonyldiimide and 4-dimethylaminopyridine in S4 is 1:1:1-2:0.05;

[0037] The reaction time in S4 is 14-16h.

[0038] In some embodiments of the present application, after the reaction in S4 is completed, the reaction product is recrystallized to remove impurities to obtain the relaxor ferroelectric / anti-ferroelectric liquid crystal material.

[0039] The present application also provides the use of the above-mentioned relaxor ferroelectric / anti-ferroelectric liquid crystal material or the relaxor ferroelectric / anti-ferroelectric liquid crystal material prepared by the above-mentioned preparation method of the relaxor ferroelectric / anti-ferroelectric liquid crystal material in the field of variable capacitance and phase change refrigeration.

[0040] The technical solutions of the present application are described in further detail below with reference to the accompanying drawings and examples. BRIEF DESCRIPTION OF DRAWINGS

[0041] Figure 1 is the nuclear magnetic analysis spectrum of the relaxor ferroelectric / anti-ferroelectric liquid crystal material prepared in Example 1 of the present application;

[0042] Figure 2 is the microstructure response test graph of the relaxor ferroelectric / anti-ferroelectric liquid crystal material prepared in Example 3 of the present application;

[0043] wherein, Figure 2 (a) is the texture graph under a polarizing microscope when the relaxor ferroelectric / anti-ferroelectric liquid crystal is isotropic, Figure 2 (b) is the texture change graph when the ferroelectric nematic phase transition occurs; Figure 2 (c) is the texture change graph when the ferroelectric nematic phase transition occurs; Figure 2 (d) is the texture change graph when the ferroelectric nematic phase transition occurs;

[0044] Figure 3 is a DSC spectrum of the relaxor ferroelectric / anti-ferroelectric liquid crystal material prepared in Example 2 of the present application;

[0045] Figure 4 is a P-E hysteresis loop of ferroelectric nematic liquid crystal RM734;

[0046] Figure 5 is a P-E hysteresis loop of the relaxor ferroelectric / anti-ferroelectric liquid crystal material prepared in Example 1 of the present application at 37℃;

[0047] Figure 6 is a P-E hysteresis loop of the relaxor ferroelectric / anti-ferroelectric liquid crystal material prepared in Example 1 of the present application at 50℃;

[0048] Figure 7 is a dielectric temperature spectrum of the relaxor ferroelectric / anti-ferroelectric liquid crystal material prepared in Example 1 of the present application. DETAILED DESCRIPTION

[0049] The present application will be further described with reference to the following figures and examples. Unless otherwise defined, the technical or scientific terms used in the present application shall be understood as having the ordinary meaning as would be understood by one of ordinary skill in the art to which this application belongs. The features or characteristics mentioned in the present application or the features or characteristics mentioned in the specific examples can be combined in any manner, and these specific examples are only used to illustrate the present application and are not used to limit the scope of the present application.

[0050] Example 1

[0051] The structural formula of 4-((4-nitrophenoxy)carbonyl)phenyl-2-((6- (acryloyloxy)hexyl)oxy)-4-methoxybenzoate is as follows:

[0052] The preparation method of the relaxor ferroelectric / anti-ferroelectric liquid crystal material is as follows:

[0053] S1, the molar ratio of 2-hydroxy-4-methoxybenzaldehyde, potassium carbonate and 6-bromo-1-hexanol is 1.65:3.3:2, after being dissolved in 30 mL of N,N-dimethylformamide, the mixed solution is heated to 60℃ and stirred vigorously for 12 h to obtain intermediate product A1.

[0054] S2, the molar ratio of intermediate product A1 and triethylamine is 2:3, after being dissolved in 20 mL of anhydrous dichloromethane, the mixture is mixed and stirred at a temperature of 0℃ for 5 min, and 2 mL of acryloyl chloride is added dropwise to obtain intermediate product A2.

[0055] S3, the molar ratio of sodium dihydrogen phosphate, sodium chlorite and intermediate product A2 is 4:3.5:1, which is dissolved in dimethyl sulfoxide solution (the volume ratio of dimethyl sulfoxide and water is 4:3) and stirred at 0°C. Then, the temperature is raised to 25°C and stirred for 6h. After adjusting the pH, intermediate product A3 is obtained.

[0056] S4, the molar ratio of intermediate product A3, 4-nitrophenyl 4-hydroxybenzoate, 1-ethyl-(3-dimethylaminopropyl) carbodiimide and 4-dimethylaminopyridine is 1:1:1.5:0.05, which is dissolved in dichloromethane and reacted for 15h to obtain the final target product. The target final product is purified by recrystallization to obtain the required relaxor ferroelectric / antiferroelectric liquid crystal material.

[0057] Example 2

[0058] The structural formula of 4-((4-nitrophenoxy)carbonyl)phenyl-2-((4-(acryloyloxy)butyl)oxy)-4-methoxybenzoate is as follows:

[0059] The preparation method and synthesis route of the relaxor ferroelectric / antiferroelectric liquid crystal material are as follows:

[0060] S1, the molar ratio of 2-hydroxy-4-methoxybenzaldehyde, potassium carbonate and 4-bromo-1-butanol is 1.65:3.3:2, which is dissolved in 30mL N,N-dimethylformamide, and then the mixed solution is heated to 60°C and stirred vigorously for 12h to obtain intermediate product A1.

[0061] S2, the molar ratio of intermediate product A1 and triethylamine is 2:3, which is dissolved in 20mL anhydrous dichloromethane, and then the mixture is mixed and stirred at 0°C for 5min. 2mL of acryloyl chloride is added dropwise to obtain intermediate product A2.

[0062] S3, the molar ratio of sodium dihydrogen phosphate, sodium chlorite and intermediate product A2 is 4:3.5:1, which is dissolved in dimethyl sulfoxide solution (the volume ratio of dimethyl sulfoxide and water is 4:3) and stirred at 0°C. Then, the temperature is raised to 25°C and stirred for 6h. After adjusting the pH, intermediate product A3 is obtained.

[0063] S4, the molar ratio of intermediate product A3, 4-nitrophenyl 4-hydroxybenzoate, 1-ethyl-(3-dimethylaminopropyl) carbodiimide and 4-dimethylaminopyridine is 1:1:1.5:0.05, which is dissolved in dichloromethane and reacted for 15h to obtain the final target product. The target final product is purified by recrystallization to obtain the required relaxor ferroelectric / antiferroelectric liquid crystal material.

[0064] Example 3

[0065] 4-((4-nitrophenoxy)carbonyl)phenyl-4-((6-(acryloyloxy)hexyl)oxy)-2- methoxybenzoate has the structural formula:

[0066] The preparation method and synthetic route of the relaxor ferroelectric / anti-ferroelectric liquid crystal material are as follows:

[0067] S1, the molar ratio of 4-hydroxy-2-methoxybenzaldehyde, potassium carbonate, and 6-bromo-1-hexanol is 1.65:3.3:2, the mixture is dissolved in 30 mL of N,N-dimethylformamide, the mixed solution is heated to 60°C and stirred vigorously for 12 hours to obtain an intermediate product A1.

[0068] S2, the molar ratio of the intermediate product A1 and triethylamine is 2:3, the mixture is dissolved in 20 mL of anhydrous dichloromethane, and the mixture is stirred at 0°C for 5 minutes, and 2 mL of acryloyl chloride is added dropwise to obtain an intermediate product A2.

[0069] S3, the molar ratio of sodium dihydrogen phosphate, sodium chlorite, and the intermediate product A2 is 4:3.5:1, and the mixture is dissolved in a dimethyl sulfoxide solution (the volume ratio of dimethyl sulfoxide and water is 4:3) and stirred at 0°C. Then, the temperature is increased to 25°C and stirred for 6 hours, and the intermediate product A3 is obtained after adjusting the pH.

[0070] S4, the molar ratio of the intermediate product A3, 4-nitrophenyl 4-hydroxybenzoate, 1-ethyl-(3-dimethylaminopropyl)carbonyldiimide, and 4-dimethylaminopyridine is 1:1:1.5:0.05, and the mixture is dissolved in dichloromethane and reacted for 15 hours to obtain the final target product. The target final product is recrystallized to remove impurities to obtain the required relaxor ferroelectric / anti-ferroelectric liquid crystal material.

[0071] Example 4

[0072] 4-((4-nitrophenoxy)carbonyl)phenyl-4-((4-(acryloyloxy)butyl)oxy)-2- methoxybenzoate has the structural formula:

[0073] The preparation method and synthetic route of the relaxor ferroelectric / anti-ferroelectric liquid crystal material are as follows:

[0074] S1, the molar ratio of 4-hydroxy-2-methoxybenzaldehyde, potassium carbonate, and 6-bromo-1-hexanol is 1.65:3.3:2, the mixture is dissolved in 30 mL of N,N-dimethylformamide, the mixed solution is heated to 60°C and stirred vigorously for 12 hours to obtain an intermediate product A1.

[0075] S2, the molar ratio of intermediate product A1 and triethylamine is 2:3, the mixture is dissolved in 20 mL of anhydrous dichloromethane, and then stirred at 0°C for 5 min, 2 mL of acryloyl chloride is added dropwise to obtain intermediate product A2.

[0076] S3, the molar ratio of sodium phosphate, sodium chlorite and intermediate product A2 is 4:3.5:1, and the mixture is dissolved in dimethyl sulfoxide solution (volume ratio of dimethyl sulfoxide and water is 4:3) and stirred at 0°C. Then, the temperature is raised to 25°C and stirred for 6 h. After adjusting the pH, intermediate product A3 is obtained.

[0077] S4, the molar ratio of intermediate product A3, 4-nitrophenyl 4-hydroxybenzoate, 1-ethyl-(3-dimethylaminopropyl)carbodiimide and 4-dimethylaminopyridine is 1:1:1.5:0.05, and the mixture is dissolved in dichloromethane and reacted for 15 h to obtain the final target product. The target end product is recrystallized to remove impurities to obtain the desired relaxor ferroelectric / antiferroelectric liquid crystal material.

[0078] Characterization test

[0079] The relaxor ferroelectric / antiferroelectric liquid crystal material prepared in Example 1 is subjected to nuclear magnetic analysis, as shown in Figure 1 From Figure 1 it can be seen that the positions of all peaks match the molecular structure, proving the successful synthesis of the target molecule.

[0080] The relaxor ferroelectric / antiferroelectric liquid crystal material prepared in Example 3 is subjected to response test, as shown in Figure 2 From Figure 2 it can be seen that the relaxor ferroelectric / antiferroelectric liquid crystal material is filled in a parallel alignment liquid crystal cell, and the angle between the alignment direction and the polarization direction of the polarizer or analyzer is 45° when observed. The liquid crystal gradually changes from isotropic to ferroelectric nematic phase at 43.8°C.

[0081] The relaxor ferroelectric / antiferroelectric liquid crystal material prepared in Example 2 is subjected to differential scanning calorimetry analysis, as shown in Figure 3 From Figure 3 it can be seen that the clearing point is 45.1°C and the melting temperature of the liquid crystal is 85.5°C during the heating process; and the ferroelectric nematic phase enters at 43.3°C from the isotropic phase during the cooling process.

[0082] The ferroelectric nematic liquid crystal RM734 and the relaxor ferroelectric / antiferroelectric liquid crystal material prepared in Example 1 are subjected to P-E hysteresis loop analysis, respectively, as shown in Figure 4 , Figure 5 and Figure 6 From Figure 4 it can be seen that RM734 exhibits a typical hysteresis loop characteristic of ferroelectric materials, and the maximum polarization strength is as high as 6.4 μC / cm2 , the remanent polarization is 4.2 μC / cm 2 . From Figure 5 and Figure 6 , it can be seen that the relaxor ferroelectric / antiferroelectric liquid crystal material prepared in Example 1 exhibits an electric hysteresis loop characteristic of a typical relaxor ferroelectric at 37℃ and an electric hysteresis loop characteristic of a typical relaxor antiferroelectric at 50℃, and the remanent polarization of both is only 2.4 μC / cm 2 and 0.5 μC / cm 2 . Figures 4-6 By comparison, the remanent polarization of the ferroelectric nematic liquid crystal RM734 is much higher than that of the relaxor ferroelectric / antiferroelectric liquid crystal material prepared in Example 1.

[0083] The dielectric temperature spectrum analysis of the relaxor ferroelectric / antiferroelectric liquid crystal material prepared in Example 1 is shown in Figure 7 . From Figure 7 , it can be seen that the dielectric constant of the liquid crystal reaches 512 when the temperature is 37℃ and the frequency is 100 Hz. In addition, the dielectric constant peak temperature is frequency-dependent, i.e., the dielectric peak temperature increases with the increase of the frequency, showing a typical dielectric relaxation process characteristic of a relaxor ferroelectric.

[0084] Finally, it should be noted that the above examples are only used to illustrate the technical solutions of the present application but not to limit it. Although the present application has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present application can still be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present application.

Claims

1. A relaxor ferroelectric / antiferroelectric liquid crystal material, characterized in that: Has the following structure: R1 includes -RCOOCH=CH2, -RCF3, -RNO2, -ROCH2CH2CH=CH2; R2 includes -RCOOCH=CH2, -RCF3, -ROCH2CH2CN, -ROCH2CH2CH=CH2; R3 includes -RCH=CH2, -RCN, -RCOOCH=CH2, -OCH2CH2Br, -RNO2, -ROCH2CH2CH=CH2; R4 includes -NO2, -CN, -NCS or -CF3; Wherein -R is a hydrocarbon group having 2 to 20 carbon atoms.

2. A relaxor ferroelectric / antiferroelectric liquid crystal material according to claim 1, characterized in that: The relaxor ferroelectric / antiferroelectric liquid crystal material comprises:

3. A method for preparing the relaxor ferroelectric / antiferroelectric liquid crystal material according to claim 1 or 2, characterized in that: The method comprises the following preparation steps: S1: An aldehyde compound, potassium carbonate, a halohydrin and an organic solvent are mixed and reacted to obtain an intermediate product A1; S2: After mixing the intermediate product A1, triethylamine and dichloromethane, acryloyl chloride is added to obtain the intermediate product A2; S3: dissolving the intermediate product A2, sodium dihydrogen phosphate, and sodium chlorite in a dimethyl sulfoxide solution, and reacting to obtain the intermediate product A3; S4: dissolving the intermediate product A3, 4-nitrophenyl 4-hydroxybenzoate, 1-ethyl-(3-dimethylaminopropyl)carbodiimide and 4-dimethylaminopyridine in dichloromethane and reacting them to obtain the ferroelectric / antiferroelectric liquid crystal material.

4. The method for preparing the relaxor ferroelectric / antiferroelectric liquid crystal material according to claim 3, wherein: The aldehyde compound in S1 includes 2-hydroxy-4-methoxybenzaldehyde or 4-hydroxy-2-methoxybenzaldehyde; The halogenated alcohol includes 6-bromo-1-hexanol or 4-bromo-1-butanol.

5. The method for preparing the relaxor ferroelectric / antiferroelectric liquid crystal material according to claim 3, characterized in that: The molar volume ratio of the aldehyde compound, potassium carbonate, halohydrin and organic solvent in S1 is 1.5-1.7 mol: 3-3.5 mol: 2 mol: 30 mL; The organic solvent includes NN dimethylformamide; The mixing temperature in S1 is 55-65° C., and the mixing time is 8-12 h.

6. The method for preparing the relaxor ferroelectric / antiferroelectric liquid crystal material according to claim 3, characterized in that: The molar volume ratio of the intermediate product A1, triethylamine and dichloromethane in S2 is 1.5-2.5:3:20 mL; The mixing temperature in S2 is 0-2° C., and the mixing time is 3-7 min. The molar volume ratio of the intermediate product A1 to acryloyl chloride is 1.5-2.5 mol:2 mL.

7. The method for preparing the relaxor ferroelectric / antiferroelectric liquid crystal material according to claim 3, characterized in that: The molar ratio of the intermediate product A2, sodium dihydrogen phosphate, and sodium chlorite in S3 is 1:4:3-4, and the volume ratio of dimethyl sulfoxide to the solvent in the dimethyl sulfoxide solution is 4:

3.

8. The method for preparing the relaxor ferroelectric / antiferroelectric liquid crystal material according to claim 3, characterized in that: The reaction temperature in S3 is 0-25° C., and the reaction time is 5-8 h.

9. The method for preparing the relaxor ferroelectric / antiferroelectric liquid crystal material according to claim 3, characterized in that: The molar ratio of the intermediate product A3, 4-nitrophenyl 4-hydroxybenzoate, 1-ethyl-(3-dimethylaminopropyl)carbodiimide and 4-dimethylaminopyridine in S4 is 1:1:1-2:0.05; The reaction time in S4 is 14-16 hours.

10. Use of the relaxor ferroelectric / antiferroelectric liquid crystal material according to claim 1 or 2, or the relaxor ferroelectric / antiferroelectric liquid crystal material prepared by the preparation method of the relaxor ferroelectric / antiferroelectric liquid crystal material according to any one of claims 3 to 9 in the fields of variable capacitance and phase change refrigeration.

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