High birefringence liquid crystal compounds, synthesis methods, liquid crystal compositions and applications

Abstract

This invention discloses a liquid crystal compound with high birefringence, a synthesis method, a liquid crystal composition, and its applications. The disclosed liquid crystal compound has the general structural formula shown in Formula I. The disclosed liquid crystal composition includes one or more compounds shown in Formula I. The liquid crystal compound and its composition of this invention not only have ultra-high birefringence but also have the advantages of low viscosity and a wide nematic phase temperature range, and can be used to prepare optoelectronic devices and microwave devices.

Description

Technical Field

[0001] This invention belongs to the field of liquid crystal material technology, specifically relating to a liquid crystal compound having a wide liquid crystal phase temperature range, high birefringence, and low viscosity, as well as its synthesis method, compositions containing the liquid crystal compound, and related applications. Background Technology

[0002] Liquid crystal materials have been widely used in optoelectronic display devices, such as various LCD TVs, desktop LCD monitors, and mobile display terminals.

[0003] Beyond displays, liquid crystals are also gaining significant attention for applications. Utilizing the birefringence of liquid crystals, optical phase modulation devices based on them can be fabricated. Taking advantage of the dielectric constant differences of liquid crystals at high frequencies, microwave and terahertz phase shifters, metamaterial holographic phased array antennas, and other technologies based on liquid crystal materials have been developed. Furthermore, liquid crystal materials have shown great application potential in laser communication; for example, wavelength selective switches based on liquid crystals are already used in 5G / 6G optical communication.

[0004] The development of these new components requires liquid crystal materials with high birefringence, low viscosity, and a wide liquid crystal temperature range. Higher birefringence in the liquid crystal material is beneficial for increasing phase modulation and reducing the cell thickness of the liquid crystal device, thereby improving the liquid crystal response speed. Lower viscosity of the liquid crystal is beneficial for shortening the response time and improving the response speed.

[0005] Therefore, for novel component applications, there is a need for novel liquid crystal materials with a birefringence (589 nm) greater than 0.4, or even greater than 0.5. Liquid crystals with isothiocyanate (NCS) groups at the molecular ends have a large birefringence due to their large conjugated groups. The literature (Xianyu, H., Gauza, S. et al. High birefringence and large negativedielectric anisotropy phenyl-tolane liquid crystals. Liquid Crystals, 2007, 34(12): 1473-1478) reported NCS liquid crystals containing a phenyldiphenylacetylene skeleton. Although the birefringence is close to 0.5, the rotational viscosity of this type of compound is relatively large.

[0006] The literature (Catanescu, CO, S.-T. Wu, et al. Tailoring the physical properties of some high birefringence isothiocyanato-based liquid crystals. Liquid Crystals, 2004, 31(4): 541-555) reported NCS liquid crystal compounds containing olefin-terminated groups conjugated with benzene rings. These compounds have high birefringence, but the nematic liquid crystal phase temperature range is relatively narrow. Furthermore, when applied to the microwave frequency band, it was found that the dielectric loss of this type of liquid crystal structure is relatively large, which needs further improvement. Summary of the Invention

[0007] In view of the defects or deficiencies of the prior art, the present invention provides a liquid crystal compound with high birefringence.

[0008] Therefore, the structure of the liquid crystal compound provided by the present invention is shown in general formula I:

[0009]

[0010] Wherein: R is selected from hydrogen, fluorine, chlorine or alkyl groups having 1 to 10 carbon atoms;

[0011] X1 to X4 are independently fluorine, chlorine, hydrogen or methyl; and when X1 = hydrogen and X3 = hydrogen, one or both of X2 and X4 are not fluorine atoms.

[0012] Optionally, the structure of the liquid crystal compound is shown in any one of general formulas I-1 to I-5:

[0013]

[0014] The present invention also provides a method for synthesizing the above-mentioned liquid crystal compound. The provided synthesis method includes:

[0015] (1) 4-Bromophenyl ketone derivatives are reduced to 4-bromophenyl alcohol derivatives in the presence of reducing agents sodium borohydride or potassium borohydride.

[0016] (2) 4-Bromophenyl alcohol derivatives react with hydrochloric acid or hydrobromic acid to be converted into halogenated derivatives;

[0017] (3) The halogenated product reacts with a base to eliminate a molecule of hydrogen halide and give a 4-bromobenzene-substituted alkene;

[0018] (4) 4-Bromobenzene-substituted alkenes are reacted with an acetylation reagent under palladium catalysis to obtain phenylacetylene derivatives; the acetylation reagent is selected from trimethylsilylacetylene or 2-methylbutynol.

[0019] (5) Under the action of alkali, the trimethylsilyl group or acetone of the phenylacetylene derivative is eliminated to obtain the phenylacetylene intermediate;

[0020] (6) The phenylacetylene intermediate is coupled with an iodinated or brominated aniline under palladium catalysis to obtain a diphenylacetylene intermediate;

[0021] (7) The diphenylacetylene intermediate is reacted with sulfur phosgene to obtain the liquid crystal compound of claim 1.

[0022] The synthesis reaction equation is shown below:

[0023]

[0024] The synthesis method described in this invention has the advantages of inexpensive and readily available raw materials, mild reaction conditions, and good selectivity.

[0025] The present invention also provides a liquid crystal composition. Accordingly, the provided liquid crystal composition includes a first component comprising one or more liquid crystal compounds selected from those described in Formula I.

[0026] Optionally, the first component comprises one or more liquid crystal compounds selected from any structure of general formulas I-1 to I-5.

[0027] Furthermore, the liquid crystal composition further includes a second component, the second component comprising one or more liquid crystal compounds of general formula II:

[0028]

[0029] Wherein: R2 is selected from alkyl groups having 1 to 10 carbon atoms; X8 and X9 are independently fluorine or hydrogen.

[0030] Furthermore, the liquid crystal composition further includes a third component, which comprises one or more liquid crystal compounds of general formula II:

[0031]

[0032] in:

[0033] R1 is an alkyl group having 1 to 10 carbon atoms, or an alkenyl group having 2 to 10 carbon atoms, a fluorinated alkyl group having 2 to 10 carbon atoms, a fluorinated alkenyl group having 2 to 10 carbon atoms, or a cycloalkyl group having 2 to 10 carbon atoms; X5, X6, and X7 are independently fluorine, chlorine, hydrogen, methyl, or ethyl.

[0034] k, m, n, and p are independently 0 or 1;

[0035] Ring A is a benzene ring, cyclohexane, or cyclohexene; when R1 is an alkenyl or fluorinated alkenyl group and ring A is a benzene ring, the alkenyl bond is separated from the benzene ring by at least one ethylene (-CH2-).

[0036] Optionally, the mass ratio of the first component is 1 to 100%, the mass ratio of the second component is 0 to 90%, and the mass ratio of the third component is 0 to 90%.

[0037] Preferably, the liquid crystal composition has a birefringence greater than 0.40 at 25°C and 589 nm.

[0038] Preferably, the liquid crystal composition has a rotational viscosity of less than 500 mPa·s at 25°C.

[0039] Preferably, the liquid crystal composition has a dielectric anisotropy Δε ≥ 1.4 at a high frequency of 19 GHz and a tunability ≥ 0.34.

[0040] The liquid crystal composition of this invention simultaneously possesses extremely high birefringence, a wide nematic liquid crystal temperature range, low rotational viscosity, high dielectric tuning efficiency, and low dielectric loss at high frequencies. The liquid crystal composition of this invention can be used to fabricate optical components, and is particularly suitable for fabricating microwave assemblies. It is mainly applicable to fields such as optical devices, microwave phase shifters, microwave phased array antennas, laser phase modulation, laser phased arrays, and laser communication. Detailed Implementation

[0041] Unless otherwise specified, the scientific and technical terms used in this article are intended for understanding by those skilled in the art.

[0042] In a preferred embodiment of the invention, the liquid crystal composition comprises one or more compounds selected from general formula I and one or more compounds selected from general formula II. In another preferred embodiment of the invention, the liquid crystal composition comprises one or more compounds of general formula (I), one or more compounds of general formula (II), and one or more compounds of general formula (III).

[0043] The liquid crystal composition according to the present invention comprises 1% to 100%, preferably 10% to 90%, more preferably 20% to 80% of a compound of formula I based on the total amount of the mixture. The liquid crystal composition according to the present invention comprises 0% to 90%, preferably 10% to 70%, particularly preferably 20% to 60% of a compound of general formula II based on the total amount of the mixture. The liquid crystal composition according to the present invention further comprises 0% to 90%, preferably 10% to 70%, particularly preferably 20% to 60% of a compound of general formula III based on the total amount of the mixture. Those skilled in the art can optimize the specific combinations and proportions within the scope of this invention.

[0044] The liquid crystal composition according to the present invention may further contain 0.001% to 1% additives, such as hindered phenolic antioxidants, amine-based light stabilizers, etc. The hindered phenolic antioxidants are preferably derived from the following structures:

[0045]

[0046] Wherein: R3 is an alkyl group having 1 to 9 carbon atoms or an alkoxy group having 1 to 9 carbon atoms.

[0047] The hindered amine light stabilizer is preferably derived from the following structure:

[0048]

[0049] The preferred amount of hindered phenolic antioxidant and amine light stabilizer added is 0.01% to 0.5%, more preferably 0.02% to 0.2%.

[0050] The liquid crystal composition of the present invention may further contain one or more chiral additives in a content of 0.01% to 1%; preferably 0.1% to 0.5%. The chiral additives are preferably derived from the following structures:

[0051]

[0052] R4 is an alkyl group having 1 to 9 carbon atoms or an alkoxy group having 1 to 9 carbon atoms.

[0053] The liquid crystal composition according to the present invention comprises a variety of compounds, preferably 3 to 20 compounds, more preferably 5 to 18 compounds. These compounds can be mixed in a conventional manner: the various compounds are weighed according to a predetermined mass ratio, heated, and homogenized by stirring with magnetic force or ultrasound until all components are completely dissolved; then filtered to obtain the final product. The liquid crystal composition can also be prepared by other conventional methods, such as using so-called premixes or so-called "multi-bottle" systems, in which the components are themselves ready-to-use mixtures.

[0054] The performance of liquid crystals at high frequencies was tested using the method reported in the literature: Penirschke, A. (2004). Cavityperturbation method for characterization of liquid crystals up to 35 GHz. Microwave Conference,2004.34th European .

[0055] Liquid crystal is filled into a polytetrafluoroethylene (PTFE) or fused silica capillary, and the liquid crystal-filled capillary is inserted into the center of a resonant cavity. An input signal source is then applied, and the output signal is recorded using a vector network analyzer. The changes in the resonant frequency and Q-factor between the liquid crystal-filled capillary and the blank capillary are measured, and the dielectric constant and loss tangent are calculated. The dielectric constant components perpendicular to and parallel to the liquid crystal director are obtained by the orientation of the liquid crystal in a magnetic field; the direction of the magnetic field is set accordingly, and then rotated by 90°.

[0056] The preferred liquid crystal composition of the present invention preferably has a dielectric anisotropy Δε ≥ 1.4 at high frequencies and a tunability ≥ 0.35. The liquid crystal composition of the present invention has a dielectric constant ≥ 10.0 at low frequencies (1 kHz), more preferably ≥ 12.0.

[0057] The liquid crystal composition according to the present invention is well-suited for fabricating microwave components, capable of operating in the 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 up to 1 THz. The construction of the metamaterial phased array antenna according to this application is known to those skilled in the art.

[0058] Optical elements according to this application, such as laser phase modulation elements operating at 1550nm, wavelength selective switches, etc.

[0059] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0060] The present invention will be further described in detail below with reference to specific embodiments.

[0061] The mixed liquid crystal was then subjected to physical and photoelectric performance tests. The detailed testing methods for the physical and photoelectric performance involved in this invention are as follows:

[0062] (1) Clear the bright spots (Tni):

[0063] Polarizing hot stage method: The liquid crystal sample is coated on a glass slide and placed in an orthogonal polarizing microscopic hot stage, with a heating rate of 2℃ / min. The point at which the liquid crystal sample begins to turn from a bright state to a dark state is observed under a polarizing microscope; this point is the clearing point.

[0064] Alternatively, differential scanning calorimetry can be used: under a nitrogen atmosphere, the heating rate is set to 2℃ / min.

[0065] (2) Low Temperature Storage (LTS): Approximately 1 mL of the mixed liquid crystal is placed in a transparent glass bottle ("in bottle") or in a 5 μm antiparallel cell ("in cell"), and then placed in a low-temperature freezer. Temperatures are set to -20℃, -30℃, and -40℃, and stored for 120h, 500h, and 1000h respectively, observing for crystal precipitation or smectic phase formation. If no crystals precipitate at -30℃, the LTS is ≤ -30℃.

[0066] (3) Birefringence (Δn): Using an Abbe refractometer, under constant temperature conditions of 25℃ and a light source of 589nm, the birefringence (Δn) of the ordinary ray was measured. o ) and unusual light (n e The refractive index of ) and the birefringence Δn = n e -n o .

[0067] (4) Dielectric constant (Δε): Tested using an LCR meter under constant temperature conditions of 25℃. Δε=ε ∥ -ε ⊥ That is, the dielectric constant along the long axis of the molecule (ε) ∥ ) and the dielectric constant along the short axis of the molecule (ε) ⊥ The difference between ).

[0068] (5) Elastic constant (K) 11 K 33 K was obtained by fitting the capacitance-voltage (CV) curve of the liquid crystal under a constant temperature of 25℃. 11 and K 33 .

[0069] (6) Rotational viscosity (γ1): Under constant temperature of 25℃, the transient current value Ip of liquid crystal molecules deflected by electric field was measured by applying voltage to the liquid crystal test cell, and the rotational viscosity γ1 was calculated.

[0070] The code names and descriptions for this document are shown in Tables 1-3 below:

[0071] Table 1 Physical Parameters

[0072]

[0073]

[0074] Table 2 Structural Abbreviations

[0075]

[0076] Table 3 Examples of Abbreviations

[0077]

[0078]

[0079] Liquid crystal phase transition temperature: C represents melting point, S represents smectic phase, N represents nematic phase, and Iso represents liquid state.

[0080] Example 1:

[0081] This example describes the synthesis of 2-fluoro-4-isothiocyanate-1-((4-(E-1-n-pentenyl)phenyl)ethynyl)benzene.

[0082]

[0083] The synthesis route and method are as follows:

[0084]

[0085] Step 1:

[0086] 24.1 g of 4-pentanoyl-1-bromobenzene and 100 mL of ethanol were added to the reaction vessel. 1.51 g of sodium borohydride was slowly added in portions while stirring at 0–10 °C. The mixture was allowed to warm naturally to room temperature and reacted for 2 h. The ethanol was then removed by evaporation under reduced pressure.

[0087] Step Two:

[0088] Slowly add 100 mL of 10% hydrochloric acid to the product from step one, stir the reaction at room temperature for 2 h, separate the oil layer, wash with water until neutral, dry, and obtain an oily liquid.

[0089] Step 3:

[0090] The product obtained in step two, 100 mL of anhydrous ethanol, and 11.2 g of potassium hydroxide were added to a reaction vessel and heated under reflux for 2 h. The ethanol was removed by evaporation, and 200 mL of water and 100 mL of petroleum ether were slowly added to the product. The organic layer was separated, washed with water until neutral, dried, and the solvent was removed to obtain 20.2 g of E-4-pentenyl-1-bromobenzene, with a yield of 90%.

[0091] Step Four:

[0092] Under nitrogen protection, 11.3 g of E-4-pentenyl-1-bromobenzene, 100 mL of triethylamine, and catalysts (0.35 g of bis(triphenylphosphine)palladium chloride, 0.29 g of cuprous iodide, and 0.39 g of triphenylphosphine) were added to a reaction vessel. The temperature was raised to 50 °C, and 50 mL of triethylamine solution containing 9.8 g of trimethylsilylacetylene was added dropwise. After the addition was complete, the reaction was continued for 4 h. The temperature was lowered to room temperature, filtered, and the triethylamine was removed from the filtrate by vacuum distillation. The product was passed through a silica gel column and eluted with petroleum ether to obtain 10.9 g of an oily liquid.

[0093] Step 5:

[0094] Under nitrogen protection, 10.9 g of the product obtained in the previous step, 50 mL of ethanol, and 1.4 g of potassium carbonate were added to a reaction vessel and stirred at room temperature for 4 h. The ethanol was removed by vacuum distillation, and 50 mL of petroleum ether and 50 mL of water were added. The organic layer was separated, washed with water until neutral, and concentrated to obtain 7.6 g of (E)-4-pentenylphenylacetylene.

[0095] Step Six:

[0096] Under nitrogen protection, 7.1 g of 3-fluoro-4-iodoaniline, 100 mL of triethylamine (reaction solvent), 0.21 g of palladium chloride bis(triphenylphosphine)chloride, 0.17 g of cuprous iodide, and 0.24 g of triphenylphosphine were added to a reaction vessel. The temperature was raised to 40-50 °C, and 50 mL of triethylamine solution containing 5.1 g of (E)-4-pentenylphenylacetylene was added dropwise. After the addition was complete, the reaction was continued for 4 h. The temperature was lowered to room temperature, filtered, and the triethylamine was removed from the filtrate under reduced pressure. 100 mL of toluene and 100 mL of saturated ammonium chloride aqueous solution were added, and the mixture was washed with water. The organic layer was separated, and the toluene was removed by concentration. The product was recrystallized from petroleum ether to obtain 6.7 g of brown solid.

[0097] Step Seven:

[0098] 6.7 g of the reaction product from the previous step, 100 mL of acetone, and 10 mL of water were added to a reaction vessel. 3.7 g of phosgene was slowly added dropwise at room temperature. After the addition, the mixture was stirred for 2 hours. The acetone was removed by evaporation, and 100 mL of toluene was added. The mixture was washed with water until neutral, and the toluene was removed by evaporation under reduced pressure. The product was passed through a silica gel column and eluted with petroleum ether. The crude product was recrystallized twice with n-heptane to give 5.8 g of a white solid with a liquid chromatography purity of 99.9%.

[0099] Structural assessment:

[0100] 1H NMR (500MHz, CDCl3) δ (ppm): 0.958 (t, J=7.5Hz, 3H), 1.467~1.540 (m, 2H), 2.203 (q, J=7.5Hz, 2H), 6.254~6.31 2(m,1H),6.371(d,J=16Hz,1H),6.974(dd,J1=16Hz,J2=8Hz,2H),7.323(d,J=8.5Hz,2H),7.443~7.474(m,3H).

[0101] 13 C NMR (125MHz, CDCl3) δ (ppm): 13.8, 22.5, 35.2, 82.1, 96.8, 111.6, 113.1, 113.3, 12 0.5,121.8,125.9,129.3,131.9,132.7,134.0,138.2,138.6,162.5(d,J=250Hz).

[0102] MS m / z (RI,%): 321.1 (M + ,100),292.1(20),234.1(61),233.1(80).

[0103] Its phase transition temperature was measured by DSC: C 82.4 N 141.7 Iso.

[0104] The monomeric liquid crystal was added to the basic formulation HOST at a ratio of 15%, and its birefringence Δn = 0.535 and rotational viscosity γ1 = 220 mPa·s were obtained by testing at 25°C.

[0105] Example 2:

[0106] This example describes the synthesis of 2-chloro-4-isothiocyanate-((4-E-(1-pentenyl)phenyl)ethynyl)benzene.

[0107]

[0108] Using the same method as in Example 1, the raw material 3-fluoro-4-iodoaniline in step five was replaced with 3-chloro-4-iodoaniline; 3VPTP(Cl-3)S was synthesized.

[0109] Structural assessment:

[0110] 1H NMR (500MHz, CDCl3) δ (ppm): 0.958 (t, J=7.5Hz, 3H), 1.467~1.537 (m, 2H), 2.202 (q, J=7.5Hz, 2H), 6.254~6.312 (m, 1H), 6 .371(d,J=16Hz,1H),7.071(dd,J1=8Hz,J2=2Hz,1H),7.278(d,J=2Hz,1H),7.324(d,J=8.5Hz,2H),7.426~7.449(m,3H).

[0111] 13 C NMR (125MHz, CDCl3) δ (ppm): 13.8, 22.5, 35.2, 85.7, 96.8, 120.5, 122.5, 12 4.0,125.9,126.4,129.3,131.6,132.0,132.7,133.7,136.7,138.3,138.7.

[0112] MS m / z(RI,%):339.2(38), 337.2(M + ,100.0),308.1(29),273.1(37),215.1(72). Its phase transition temperature was measured by DSC: C 47.6 N 113.5 Iso.

[0113] The monomeric liquid crystal was added to the basic formulation HOST at a ratio of 15%, and its birefringence Δn = 0.502 and rotational viscosity γ1 = 328 mPa·s were obtained by testing at 25°C.

[0114] Example 3:

[0115] This example describes the synthesis of 2-methyl-4-isothiocyanate-((4-E-(1-pentenyl)phenyl)ethynyl)benzene.

[0116] Using the same method as in Example 1, the raw material 3-fluoro-4-iodoaniline in step five was replaced with 3-methyl-4-iodoaniline; 3VPTP(M-3)S was synthesized.

[0117] Structural assessment:

[0118] 1H NMR (500MHz, CDCl3) δ (ppm): 0.957 (t, J=7.5Hz, 3H), 1.465~1.538 (m, 2H), 2.200 (q, J=7.5Hz, 2H), 2.469 (s, 3H), 6.240~6.299 (m, 1H), 6 .367(d,J=16Hz,1H),7.003(dd,J1=8Hz,J2=2Hz,1H),7.072(s,1H),7.314(d,J=8Hz,1H),7.324(d,J=8.5Hz,2H),7.418~7.441(m,3H).

[0119] 13 C NMR (125MHz, CDCl3) δ (ppm): 13.8, 22.5, 35.2, 82.1, 96.8, 111.6 (d, J = 15Hz), 113.2 (d, J = 24Hz), 120 .5,121.8,125.9,129.3,131.9,132.1(d,J=11Hz),132.7,134.0,138.2,138.6,162.5(d,J=250Hz).

[0120] MS m / z (RI,%): 317.2 (M + ,100.0),288.1(16),230.2(25),215.1(37).

[0121] Its phase transition temperature was measured by DSC: C 85.9 N 110.4 Iso.

[0122] The monomeric liquid crystal was added to the basic formulation HOST at a ratio of 15%, and its birefringence Δn = 0.518 and rotational viscosity γ1 = 345 mPa·s were obtained by testing at 25°C.

[0123] Example 4:

[0124] This example describes the synthesis of 2,5-difluoro-4-isothiocyanate-((4-E-(1-butenyl)phenyl)ethynyl)benzene.

[0125] Using the same method as in Example 1, 4-pentanoyl-1-bromobenzene in step 1 was replaced with 4-butanoyl-1-bromobenzene, and the raw material 3-fluoro-4-iodoaniline in step 5 was replaced with 2,5-difluoro-4-iodoaniline; 2VPTXS was synthesized.

[0126] Structural assessment:

[0127] 1H NMR (500MHz, CDCl3) δ (ppm): 1.002 (t, J = 7Hz, 3H), 2.119 ~ 2.173 (m, 2H), 6.189 ~ 6.274 (m, 2H), 6.672 (dd, J 1=8.5Hz,J2=6Hz,1H),7.122(dd,1H,J1=9.5Hz,J2=6.5Hz),7.210(d,J=8.5Hz,2H),7.339(d,J=8Hz,2H).

[0128] 13 C NMR (125MHz, CDCl3) δ (ppm): 13.5, 26.2, 81.4, 97.5, 111.8 (dd, J1=18.5Hz, J2=8.5Hz), 113.0 (d, J=26Hz), 119.3, 119.6 (dd, J1=22Hz, J2=2.4Hz), 120.1, 121.0 (dd, J1=16Hz, J2=11Hz), 126.0, 128.2, 132.0, 134.5, 138.9, 143.6, 154.6 (d, J=250Hz), 158.3 (d, J=250Hz).

[0129] MS m / z (RI,%): 325.1 (M + ,10.0),310.1(18),251.2(38),251.2(54).

[0130] Its phase transition temperature was measured using DSC: C 86.8 N 123.6 Iso.

[0131] The monomeric liquid crystal was added to the basic formulation HOST at a ratio of 15%, and its birefringence Δn = 0.528 and rotational viscosity γ1 = 192 mPa·s were obtained by testing at 25°C.

[0132] Example 5:

[0133] This example describes the synthesis of 2,5-difluoro-4-isothiocyanate-((4-E-(1-butenyl)phenyl)ethynyl)benzene.

[0134]

[0135] Using the same method as in Example 1, the raw material 3-fluoro-4-iodoaniline in step five was replaced with 2,5-difluoro-4-iodoaniline; 3VPTXS was synthesized.

[0136] Structural assessment:

[0137] 1H NMR (500MHz, CDCl3) δ (ppm): 0.945 (t, 3H, J = 7.5Hz), 1.363 ~ 1.425 (m, 2H), 1.617 ~ 1.663 (m, 2H), 2.652 (t, 2H, J = 8Hz), 6.189 ~ 6.2 74(m,2H),6.672(dd,J1=8.5Hz,J2=6Hz,1H),7.122(dd,1H,J1=9.5Hz,J2=6.5Hz),7.210(d,J=8.5Hz,2H),7.339(d,J=8Hz,2H).

[0138] 13 C NMR (125MHz, CDCl3) δ (ppm): 13.8, 22.4, 35.2, 81.3, 97.5, 111.8 (dd, J1=19Hz, J2=9Hz), 113.1 (d, J=26Hz), 119.6 (d, J=23H z), 120.1, 121.0 (dd, J1 = 19Hz, J2 = 9Hz), 126.0, 129.3, 132.0, 132.9, 138.9, 143.6, 154.7 (d, J = 250Hz), 158.3 (d, J = 250Hz).

[0139] MS m / z (RI,%): 339.1 (M + ,100),310.1(32),252.1(58),251.1(78).

[0140] Its phase transition temperature was measured using DSC: C 82.0 N 130.3 Iso.

[0141] The monomeric liquid crystal was added to the basic formulation HOST at a ratio of 15%, and its birefringence Δn = 0.520 and rotational viscosity γ1 = 214 mPa·s were obtained by testing at 25°C.

[0142] Example 6:

[0143] This example describes the synthesis of 2,6-difluoro-4-isothiocyanate-((4-E-(1-propenyl)phenyl)ethynyl)benzene.

[0144] Using the same method as in Example 1, 4-pentanoyl-1-bromobenzene in step 1 was replaced with 4-propanoyl-1-bromobenzene, and the raw material 3-fluoro-4-iodoaniline in step 5 was replaced with 3,5-difluoro-4-iodoaniline; 1VPTUiS was synthesized.

[0145] Structural assessment:

[0146] 1 H NMR (500MHz, CDCl3) δ (ppm): 1.898 (d, J = 3Hz, 3H), 6.262~6.332 (m, 1H), 6.388 ( d,J=16Hz,1H),6.800(d,J=7Hz,2H),7.307(d,J=8Hz,2H),7.476(d,J=8Hz,2H).

[0147] 13 C NMR (125MHz, CDCl3) δ (ppm): 18.6, 75.7, 101.1, 102.3 (t, J = 21Hz), 109.3, 109.5, 120. 2,125.8,127.6,130.5,132.0,132.2(t,J=14Hz),138.9,139.9,162.8,(d,J=254Hz).

[0148] MS m / z (RI,%): 311.2 (M + ,100),252.2(12),251.2(20).

[0149] Its phase transition temperature was measured using DSC: C 111.7 N 159.9 Iso.

[0150] The monomeric liquid crystal was added to the basic formulation HOST at a ratio of 10%, and its birefringence Δn = 0.569 and rotational viscosity γ1 = 152 mPa·s were obtained by testing at 25°C.

[0151] Example 7:

[0152] The mass ratio of each monomer in the liquid crystal composition of this embodiment and the performance data of the composition are shown in Table 4.

[0153] Table 4 Liquid Crystal Composition and Properties in Example 7

[0154]

[0155]

[0156] Example 8:

[0157] The mass ratio of each monomer in the liquid crystal composition of this embodiment and the performance data of the composition are shown in Table 5.

[0158] Table 5. Liquid Crystal Composition and Performance in Example 8

[0159]

[0160]

[0161] Example 9:

[0162] The mass ratio of each monomer in the liquid crystal composition of this embodiment and the performance data of the composition are shown in Table 6.

[0163] Table 6 Liquid Crystal Composition and Properties in Example 9

[0164]

[0165] Comparative Example 1:

[0166] An isothiocyanate-based liquid crystal compound containing a conjugated olefin chain with a benzene ring was reported in the publicly published journal Liquid Crystals, 2004, 31(4):541-555. A typical molecular structure is shown below:

[0167]

[0168] Compared with Example 1 of the present invention, each of these embodiments has a fluorine substituent on the benzene ring, the difference being the position of the fluorine substitution; the liquid crystal phase transition temperature and birefringence were tested, and the comparative data are shown in Table 7 below:

[0169] Table 7

[0170]

[0171]

[0172] As can be seen from the table, after the fluorine substitution positions of the liquid crystal compounds of the present invention are changed, the clearing point of the liquid crystal is significantly increased, the nematic phase temperature range is expanded, and the birefringence is also significantly improved.

[0173] Comparative Example 2:

[0174] An isothiocyanate-based liquid crystal compound containing a conjugated olefin chain with a benzene ring was reported in the publicly published journal Liquid Crystals, 2004, 31(4):541-555. A typical molecular structure is shown below:

[0175]

[0176] Compared with Example 5 of the present invention, both have two fluorine substituents on the benzene ring, the difference being the different positions of the fluorine substitution; the liquid crystal phase transition temperature and birefringence were tested, and the comparative data are shown in Table 8 below:

[0177] Table 8

[0178] project Monolithic liquid crystal Liquid crystal phase transition temperature (°C) Nematic phase temperature range (°C) Birefringence (Δn) Comparative Example 2 3VPTUS C63.3 N 108.0 Iso 44.7 0.501 Example 5 3VPTXS C82.0 N 130.3 Iso 48.3 0.520

[0179] As can be seen from the table, after the fluorine substitution positions of the liquid crystal compounds of the present invention are changed, the clearing point of the liquid crystal is significantly increased, the nematic phase temperature range is expanded, and the birefringence is significantly improved.

[0180] Liquid crystal compound 3VPTUS from Comparative Example 2 and liquid crystal compound 3VPTXS from Example 5 were mixed with M0 at a ratio of 15:85 to obtain liquid crystal compositions M1 and M2.

[0181] Liquid crystal composition M0: Composed of the monomeric liquid crystal compounds shown in Table 9 below.

[0182] Table 9

[0183] Monolithic liquid crystal mass percentage / % 2CPUS 25 3CPUS 25 5CPUS 25 3CCV 25

[0184] M0 to M2 were respectively filled into polytetrafluoroethylene tubes, and the dielectric constant and loss tangent were tested at 19 GHz using the cavity perturbation method at 25 ℃. The quality factor was calculated, and the results are shown in Table 10 below.

[0185] Table 10

[0186] Composition Liquid crystal compounds <![CDATA[ε ⊥ ]]> <![CDATA[ε ∥ ]]> Δε <![CDATA[tanδ ⊥ ]]> <![CDATA[tanδ ∥ ]]> η M0 - 2.361 2.989 0.628 0.0106 0.0049 19.82 M1 3VPTUS 2.515 3.294 0.779 0.0116 0.0052 20.38 M2 3VPTXS 2.513 3.295 0.782 0.0108 0.0051 21.97

[0187] As can be seen, the compound of Example 5 of the present invention has a lower dielectric loss value tanδ at 19 GHz compared with the compound of Comparative Example 2. ⊥ It also has a larger dielectric anisotropy value Δε, and a significantly increased quality factor η.

[0188] The preferred embodiments of this disclosure have been described in detail above. However, this disclosure is not limited to the specific details of the above embodiments. Within the scope of the technical concept of this disclosure, various simple modifications can be made to the technical solutions of this disclosure, and these simple modifications all fall within the protection scope of this disclosure.

[0189] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, this disclosure will not describe the various possible combinations separately.

[0190] Furthermore, various different embodiments of this disclosure can be combined in any way, as long as they do not violate the spirit of this disclosure, they should also be regarded as the content disclosed in this disclosure.

Claims

1. A liquid crystal compound with high birefringence, characterized in that, The structure of the liquid crystal compound is shown in any one of general formulas I-4 to I-5: Wherein: R is selected from hydrogen, chlorine or alkyl groups having 1 to 10 carbon atoms.

2. A liquid crystal composition, characterized in that, It includes a first component, which comprises one or more liquid crystal compounds selected from the liquid crystal compound of claim 1.

3. The liquid crystal composition according to claim 2, characterized in that, The liquid crystal composition further includes a second component, the second component comprising one or more liquid crystal compounds of general formula II: Wherein: R2 is selected from alkyl groups having 1 to 10 carbon atoms; X8 and X9 are independently fluorine or hydrogen.

4. The liquid crystal composition according to claim 3, characterized in that, The liquid crystal composition further includes a third component, the third component comprising one or more liquid crystal compounds of general formula III: in: R1 is an alkyl group having 1 to 10 carbon atoms, or an alkenyl group having 2 to 10 carbon atoms, a fluorinated alkyl group having 1 to 10 carbon atoms, a fluorinated alkenyl group having 2 to 10 carbon atoms, or a cycloalkyl group having 3 to 10 carbon atoms; X5, X6, and X7 are independently fluorine, chlorine, hydrogen, methyl, or ethyl. k, m, n, and p are independently 0 or 1; Ring A is a benzene ring, cyclohexane, or cyclohexene; when R1 is an alkenyl or fluorinated alkenyl group and ring A is a benzene ring, the alkenyl bond in R1 is separated from the benzene ring by at least one ethylene group.

5. The liquid crystal composition according to claim 2, 3 or 4, characterized in that, The first component has a mass ratio of 1 to 100%, the second component has a mass ratio of 0 to 90%, and the third component has a mass ratio of 0 to 90%.

6. The liquid crystal composition according to claim 2, 3 or 4, characterized in that, The liquid crystal composition has a birefringence greater than 0.40 at 25°C and 589 nm.

7. The liquid crystal composition according to claim 2, 3 or 4, characterized in that, The liquid crystal composition has a rotational viscosity of less than 500 mPa•s at 25°C.

8. The liquid crystal composition according to claim 2, 3 or 4, characterized in that, The liquid crystal composition exhibits dielectric anisotropy Δε ≥ 1.4 and tunability ≥ 0.34 at a high frequency of 19 GHz.

9. The use of the liquid crystal composition of claim 2, 3 or 4 in the preparation of optical elements.

10. The use of the liquid crystal composition of claim 2, 3 or 4 in the preparation of microwave components.

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