CN112342032A

CN112342032A - Rod-like polar liquid crystal molecule, preparation method thereof and rod-like polar nematic liquid crystal

Info

Publication number: CN112342032A
Application number: CN202011169100.9A
Authority: CN
Inventors: 黄明俊; 谢晓晨; 李金星; 西川浩矢; 戴书琪; 向后润一; 周俊琛
Original assignee: South China University of Technology SCUT
Current assignee: South China University of Technology SCUT
Priority date: 2020-10-28
Filing date: 2020-10-28
Publication date: 2021-02-09

Abstract

The invention discloses a rodlike polar liquid crystal molecule, a preparation method thereof and a rodlike polar nematic liquid crystal. The rodlike polar liquid crystal molecules have ultrahigh dielectric constant (10^3-10^4) and nonlinear optical response. The invention has the following advantages and innovation points: the rod-shaped liquid crystal molecules generally have larger dipole moment (>8D), and can show a novel polar liquid crystal nematic phase in different temperature intervals; the polar nematic liquid crystal has ultrahigh dielectric constant and nonlinear optical response.

Description

Rod-like polar liquid crystal molecule, preparation method thereof and rod-like polar nematic liquid crystal

Technical Field

The invention relates to general design and preparation of a polar liquid crystal molecule, in particular to a rod-shaped polar liquid crystal molecule, a preparation method thereof and a rod-shaped polar nematic liquid crystal.

Background

In the present life, electricity based on dielectric materialsSub-application devices are ubiquitous. The proportion of the number of the dielectric elements in various electronic devices exceeds 30%. In order to further improve the performance and portability of high-end electronic devices, miniaturization and high integration of electronic materials are inevitable trends, and a challenge to be faced directly is how to develop a class of flexible ultrathin dielectric materials with ultrahigh dielectric properties. High- κ dielectric generally refers to a material having a dielectric constant ∈ greater than 7 (silicon nitride). High-k materials have been more widely understood and used in recent decades through research into barium titanate type and 2D crystalline materials, where epsilon reaches about 10³Thereby making it possible to realize applications such as small capacitors, broadband insulators, and high-density memories. The high dielectric of barium titanate type crystals results from a break in overall cubic symmetry, while two-dimensional crystals are mainly due to the large specific surface area of the ordered atoms on the surface. It is generally accepted that the high κ state is allowed to occur only when the material has a symmetry break and the thickness of the material is small, so that a high epsilon value can be achieved with polarization that maintains a high density. Amorphous materials are generally considered to be unable to achieve the high- κ state because both properties, symmetry-breaking and flowability, are hardly able to coexist in the same material.

A new class of liquid crystal molecules with large dipole moments was reported to have ultra-high dielectric constants in 2017 [ see Nishikawa, Hiroya et al, Advanced Materials 29.43:1702354(2017) ]; mandle, Richard J. et al, Physical Chemistry Chemical Physics 19.18:11429-11435(2017)]E.g. epsilon at 1kHz exceeds 10⁴. In addition, the novel liquid crystal is simultaneously found to have ultrahigh nonlinear optical response, and is expected to be applied to the flexible optical fields of high-efficiency adjustable wavelength conversion, nonlinear optical elements and the like. Compared with inorganic materials, organic materials have better properties of structure regulation and control, flexibility, processability and the like, and can realize fluid/flexible nonlinear optical materials which cannot be realized by inorganic materials. However, because of the high fluidity and low order of nematic liquid crystals, the structural arrangement of such polar nematic liquid crystals with large dipole moments from the molecular level to the nanoscale and finally to the microscale is still unknown, while the special dielectric and ferroelectric properties thereof cannot be explained, andthe general molecular design of such materials is also a great obstacle, and the chemical structure of the mesogen capable of presenting such novel polar liquid crystal molecules is very limited. The present invention has been made in view of this situation. The invention aims to solve the problem that a series of novel liquid crystal molecules with large dipole moment and ultrahigh dielectric constant are prepared from the perspective of molecular design, so that on one hand, the novel liquid crystal materials are greatly enriched, and on the other hand, the invention also provides the idea in the aspect of molecular structure hierarchy for the research on the special dielectric and ferroelectric properties of the molecules.

Disclosure of Invention

In order to solve the deficiencies and shortcomings of the existing polar mesogen, the primary object of the present invention is to provide a general design strategy for such polar mesogens, i.e. the dipole moment of the rod-like mesogen must be larger than 8D, and the mesogen has a larger cross-sectional area or a lower asymmetry ratio to suppress the crystallization process, which can be achieved by side-chain modification or introduction of oxa-hexatomic ring; another object of the present invention is to provide various designs and syntheses of rod-like mesogens with large dipole moments, by the cascade connection of various electron-withdrawing groups; the material can be used in the fields of flexible optical and electronic materials such as high-density micro capacitors, high-efficiency adjustable wavelength conversion, nonlinear optical elements and the like.

It is still another object of the present invention to provide the nonlinear optical response and dielectric constant properties of the above-mentioned liquid crystal with different polarity.

In order to achieve the purpose, the invention adopts the following technical scheme:

a rod-shaped polar liquid crystal molecule is disclosed, wherein the compound has a structure shown in a general formula I:

wherein m is 0 or 1;

R₁、R₂is a substituent; r₁、R₂Are selected from the group including but not limited to-OMe, -OEt, -OPr, -OC₄H₉、-OC₅H₁₁、-OC₆H₁₃、 -OCH(CH₃)₂、-OCH₂CH₂OCH₃、-OCH₂CH₂CH₂OCH₃、-NO₂-H, -Me, -Et, -Pr, -Bu, or R₁、R₂Chiral groups including, but not limited to;

L₁、L₂is a linking group, L₁、L₂Is ester bond, difluoromethyl ether bond, amide bond with hydrogen atom substituted by alkyl, diazaolyene bond, carbon-nitrogen double bond, ethylene bond, acetylene bond, ether bond or alkyl chain group; or L₁、L₂Is a chemical bond;

ring A, ring B and ring C are the same or different and each independently represents a 1, 4-phenylene group; wherein 0-4 hydrogen atoms in the 1, 4-phenylene group are replaced by F, CN, Cl, Br, NO₂、Me、C2H5、C(CH3)3、CH(CH3)2、OMe、OEt、OPr、COCH₃、 COC₂H₅、COOCH₃、OCH₂OCH₃、O(CH₂)₂OCH₃、O(CH₂)₃OCH₃、CF₃、OCF₃And (4) substitution.

Preferably, the compound of formula i has the following formula i-1 when m is 0, and has the following formula i-2 when m is 1:

in the formula: m₁、M₂、B₁、B₂The unit is substituted or unsubstituted 1-4 phenylene;

L₃is a linking group, L₃Is ester bond, difluoromethyl ether bond, amide bond with hydrogen atom substituted by alkyl, diazaolyene bond, carbon-nitrogen double bond, ethylene bond, acetylene bond, ether bond or alkyl chain group; or L₃Is a chemical bond.

Preferably, the rod-like polar liquid crystal molecules can present a thermodynamically stable polar nematic liquid crystal structure at a temperature range of 25-100 ℃; the rod-like polar liquid crystal molecules have an extremely high SHG signal at 30 times the intensity of quartz in the nematic phase.

A rod-like polar nematic liquid crystal comprising one or more of the above-mentioned rod-like polar liquid crystal molecules, which has a polar liquid crystal phase.

The preparation method of the rod-shaped polar liquid crystal molecule is characterized by comprising the following steps,

the method comprises the following steps: preparation method of I-1 liquid crystal molecules 1:

(A) synthesizing an S1 unit with a carboxyl functional group;

(B) the S1 unit with carboxyl functional group and M with the para-terminal group being phenolic hydroxyl and aldehyde group respectively₁The units are subjected to esterification reaction to obtain S1-M with an aldehyde group as a terminal group₁A unit; S1-M with terminal group as aldehyde group₁The unit is oxidized to obtain S1-M with a carboxyl end group₁A unit;

(C) S1-M with carboxyl as end group₁B with units and terminal groups being phenolic hydroxy groups₁The units are subjected to esterification reaction to obtain I-1 liquid crystal molecules; b with the end group of phenolic hydroxyl₁Unit and B₂The unit structural formula is the same as follows:

in the formula R₃、R₄、R₅、R₆、R₇Is a substituent, including but not limited to F, CN, Cl, Br, NO₂、Me、C₂H₅、 C(CH₃)3、CH(CH₃)2、OMe、OEt、OPr、COCH₃、COC₂H₅、COOCH₃、OCH₂OCH₃、O(CH₂)₂OCH₃、 O(CH₂)₃OCH₃、CF₃、OCF₃May be mono-or polysubstituted;

the second method comprises the following steps: preparation method 2 of I-1 liquid crystal molecules:

(a) synthesizing an S1 unit with a carboxyl functional group;

(b) synthesis of M having phenolic hydroxyl group at the end₁-L₁-B₁A unit;

(c) the S1 unit with the end group being carboxyl is reacted with M with the end group having phenolic hydroxyl₁-L₁-B₁The units are subjected to esterification reaction to obtain I-1 liquid crystal molecules;

the third method comprises the following steps: preparation method of I-2 liquid crystal molecules 1:

(1) synthesizing an S2 unit with a carboxyl end group;

(2) synthesis of M having phenolic hydroxyl group at the end₂-L₂-B₂A unit;

(3) the S2 unit with the end group being carboxyl is reacted with M with the end group having phenolic hydroxyl₂-L₂-B₂The unit is subjected to esterification reaction to obtain I-2 liquid crystal molecules;

the method four comprises the following steps: preparation method 2 of I-2 liquid crystal molecules:

(1) synthesis of end group of-CF₂S2 units of Br;

(2) the end group being-CF₂S2 unit of Br and M having phenolic hydroxyl group at terminal₂Etherifying to generate S2-M with terminal group containing aldehyde group₂Units, subsequent oxidation of the units to give S2-M terminated with a carboxyl group₂Unit, finally with B having a phenolic hydroxy group as end group₂Performing unit esterification reaction to obtain I-2 liquid crystal molecules; or end groups are-CF₂The S2 unit of Br directly reacts with M with a phenolic hydroxyl group at the end₂-L₂-B₂The units are subjected to etherification reaction to obtain I-2 liquid crystal molecules; said L₂Bridging linkages in this case include, but are not limited to, chemical linkages, azo double bonds, acetylenic linkages, and the like;

the esterification reaction is a general esterification method which comprises the following steps: under the protection of inert gas, 1-1.2eq of liquid crystal element with carboxyl functional group and 1eq of liquid crystal element with para-position end group as phenolic hydroxyl are dispersed and dissolved in anhydrous dichloromethane solution, then 0.01-0.1eq of 4-dimethylaminopyridine catalyst is added, after stirring for 10min under ice bath, 1.2-2eq of dichloromethane solution of 1- (3-dimethylaminopropyl) -3-ethylcarbodiimide hydrochloride is slowly dropped, ice bath is continued for 30min, room temperature is slowly recovered, reaction is continued for 12-20h, TLC detection reaction is carried out, and after the reaction is finished, the target product polar liquid crystal molecule is obtained after purification.

Preferably, said method one step (a) and said method two step (a) preparation of S1 units with a carboxyl function: the precursor alkoxybenzaldehyde or alkoxymethyl benzoate derivative is shown as follows:

the preparation of the unit is:

1)N₂refluxing 1eq of hydroxybenzaldehyde derivative and 1.2-2.5eq of alkyl bromide (iodine) or alkoxy bromide (iodine) in the presence of potassium carbonate in an N, N-dimethylformamide/acetone solution to carry out etherification reaction to generate mono-substituted or di-substituted alkoxybenzaldehyde derivative or mono-substituted or di-substituted alkoxymethyl benzoate derivative;

2) further, 1eq of S1 units having an aldehyde group as a terminal group was reacted with 3.5eq of NaClO₂And 4eq of NaH₂PO₄At a solvent volume ratio of V_DMSO/V_H2OThe mixed solution with the concentration of 4/3 is subjected to ice bath for 20min, then stirred at room temperature for 6-18h, after the reaction is finished, water with the volume 2-4 times that of the mixed solution is poured, then solid sodium bicarbonate is added, the pH value is adjusted to 8, then 1M hydrochloric acid solution is added, the pH value is adjusted to about 4, the mixture is extracted with ethyl acetate for three times, and the solvent is dried in a spinning mode to obtain the alkoxy benzoic acid derivative;

3) further, 1eq of S1 units containing methyl formate as an end group and 4-8eq of KOH in a solvent volume ratio of V_THF/V_MeOH/V_H2OHeating and refluxing the mixed solvent of 1/1/1 overnight, cooling to room temperature after the reaction is finished, pouring water with 2-4 times of the volume of the mixed solution, adding 1M hydrochloric acid solution, adjusting the pH to about 1, directly filtering if solid is precipitated to obtain a solid filtrate which is the obtained alkoxy benzoic acid derivative, extracting with ethyl acetate if no solid is precipitated, and spin-drying the solvent to obtain the alkoxy benzoic acid derivativeA compound (I) is provided.

Preferably, the terminal group of step (B) of the method is carboxyl S1-M₁The synthesis method of the unit comprises the following steps:

1) under the protection of inert gas, 1-1.2eq of S1 unit with carboxyl functional group and 1eq of M with phenolic hydroxyl and aldehyde group as the para-terminal group₁The unit is dissolved in an anhydrous dichloromethane solution, then 0.01-0.1eq of 4-dimethylaminopyridine catalyst is added, after stirring for 10min in ice bath, 1.2-2eq of 1- (3-dimethylaminopropyl) -3-ethylcarbodiimide hydrochloride dichloromethane solution is slowly added dropwise, ice bath is continued for 30min, the temperature is slowly recovered to room temperature, reaction is continued for 12-20h, TLC detection reaction is carried out, and after the reaction is finished, the target product is obtained after purification. M₁The structure of the unit is shown in the following structural formula

2) Further, S1-M having 1eq as an aldehyde group as a terminal group₁Unit with 3.5eq NaClO₂And 4eq of NaH₂PO₄At a solvent volume ratio of V_DMSO/V_H2OThe mixed solution is iced for 20min firstly and then stirred for 6-18h at room temperature, after the reaction is finished, water with 2-4 times of the volume of the mixed solution is poured, then solid sodium bicarbonate is added, the pH value is adjusted to 8, then 1M hydrochloric acid solution is added, the pH value is adjusted to about 4, extraction is carried out for three times by ethyl acetate, and the S1-M with the end group as carboxyl is obtained after the solvent is dried by spinning₁And (4) units.

Preferably, the method comprises two steps (b) synthesizing M with a phenolic hydroxyl group at the end group₁-L₁-B₁Unit and the method three-step (2) synthesis of M with phenolic hydroxyl at end group₂-L₂-B₂Methods for the units include but are not limited to the following categories,

the first intermediate bridging bond is a specific synthetic process of an ester bond:

1) under the protection of nitrogen, 1eq of p-hydroxybenzoic acid derivative, 0.2-0.5eq of p-toluenesulfonic acid and a proper volume of diethyl ether are added into a single-mouth bottle to form a suspension; dropwise adding 1.2-1.5eq of 3, 4-dihydro-2H-pyran by using an injector at the temperature of ice bath 0 ℃, gradually returning the mixed solution to the room temperature, and stirring for 5-6H; at the moment, the solution generates a large amount of precipitates, is filtered, is washed by diethyl ether as little as possible for many times, and is dried in vacuum to obtain a THP-M unit with a carboxyl end group, wherein the structural formula is shown as the following formula;

2) carrying out the esterification reaction on the THP-M unit and the phenol derivative B unit to obtain a THP-M-L-B unit;

3) deprotecting the THP-M-L-B unit to obtain an M-L-B unit with a phenolic hydroxyl end group, specifically, 1eq of THP-M-L-B unit and 1.2-1.5eq of pyridinium 4-methylbenzenesulfonate are added in a solution volume ratio of V_MeOH/V_THFStirring the mixed solution of 1/1 at 60 ℃ for 6-24 h; after the reaction is finished, purifying to obtain an M-L-B unit with the end group of phenolic hydroxyl, wherein the M-L-B unit is shown as the following structural formula;

the second intermediate bridging bond is a specific synthetic process of azo double bonds: is shown in the following structural formula

Adding 1eq of 4-nitroaniline derivative into 1 volume equivalent of aqueous hydrochloric acid solution, wherein the volume fraction of the aqueous hydrochloric acid solution is 10%; stirring until dissolved. Dissolving 1.28eq of sodium nitrite in 1 volume equivalent of water and adding dropwise to the solution over 1 hour, then stirring for another 30 minutes, keeping the temperature below 2 ℃; 1.28eq of phenol and 1.28eq of sodium hydroxide are dissolved in 1 volume equivalent of water, and the mixture is then added dropwise to the above diazonium salt solution over 1 hour, maintaining the temperature below 2 ℃; stirring for 1 hour and then finishing the reaction; stirring at 2 deg.C for 3 hr; held overnight at room temperature, precipitated as an orange precipitate and was collected by filtration; the product was sufficiently pure without further purification, with yields approaching 100%;

the third intermediate bridging bond is a chemical bond: based on the Suzuki coupling reaction, the structural formula is shown as follows:

under the atmosphere of nitrogen, 1eq of p-bromophenol derivative, 1.2-1.5eq of phenylboronic acid derivative and 2-4eq of potassium carbonate are put into a mixed solution with the volume ratio of toluene/isopropanol/water being 7/7/3, then 0.01-0.1eq of tetratriphenylphosphine palladium/bis-triphenylphosphine palladium dichloride is added as a catalyst, reflux reaction is carried out for 14-20h, and after the reaction is finished, the product is obtained by purification;

or under the nitrogen atmosphere, 1eq of bromobenzene derivative, 1.2-1.5eq of pinacol ester diboron borate and 2-4eq of potassium carbonate are put into 1, 4-dioxane, then 0.01-0.1eq of tetratriphenylphosphine palladium/bis-triphenylphosphine palladium dichloride is added as a catalyst, reflux reaction is carried out for 14-20h, the pinacol ester benzene derivative borate is obtained by purification after the reaction is finished, and the subsequent reaction is the same as the previous reaction conditions, thus obtaining the final product.

Preferably, the synthetic route of the S2 unit obtained in the third step (1) and the fourth step (1) of the method is as follows:

1) refluxing (1.2eq) 2-propyl-1, 3-diol derivative, (1eq)3, 5-difluorobenzaldehyde, (0.01-0.05eq)2, 6-di-tert-butyl-4-methylphenol (BHT), (0.4-0.6eq) p-toluenesulfonic acid (p-TsOH) in a toluene solution for 18-24h to obtain the following unit D;

2) 1eq of the D units are placed under a nitrogen atmosphere at-78 ℃ in tetrahydrofuranSlowly dripping 4-6eq of n-hexane solution of butyl lithium into the solution, continuing to react for 3 hours after dripping is finished, and then adding excessive dry ice or introducing CO₂The gas is continuously reacted for 1h, and finally the pH value is adjusted to 1-4 to obtain an S2 unit with the following end group as carboxyl;

or slowly dripping 4-6eq of n-hexane solution of butyl lithium into 1eq of D unit at-78 ℃ in tetrahydrofuran solution in nitrogen atmosphere, continuing to react for 3h after dripping is finished, and then slowly injecting 2-6eq of CF₂Br₂The reaction was continued for 1h with THF and finally adjusted to pH 1-4 to give the following end group-CF₂S2 units of Br;

preferably, the etherification reaction in the fourth step (2) of the method is as follows:

1 to 1.2eq of terminal groups are-CF₂S2 unit of Br, 1eq of M having phenolic hydroxyl group and aldehyde group₂Or M having a phenolic hydroxyl group₂-L₂-B₂Unit, 2-4eq potassium carbonate, adding into DMF or acetone solution, refluxing for 14-18h, purifying to obtain S₂-M₂Cell or class I-2 liquid crystal molecules.

Compared with the prior art, the invention has the following advantages and innovation points:

(1) the invention discloses a general design strategy of liquid crystal elements of the special polar liquid crystal material;

(2) the invention provides a synthesis path of various polar liquid crystal elements, and polar liquid crystal structures can be obtained in different temperature ranges; the invention discloses that the polar liquid crystal has larger dipole moment, ultrahigh dielectric constant and nonlinear optical response.

Drawings

FIG. 1 is a DSC of 4- ((4-nitrophenoxy) carbonyl) phenyl 2, 4-dimethoxybenzoate of example 1;

FIG. 2 is a polarizing microscope (POM) photograph of 4- ((4-nitrophenoxy) carbonyl) phenyl 2, 4-dimethoxybenzoate from the liquid phase into the nematic phase in example 1;

FIG. 3 is a diagram of a polarizing microscope (POM) of 4- ((4-nitrophenoxy) carbonyl) phenyl 2, 4-dimethoxybenzoate from a nematic phase into a polar nematic phase (different director directions in domains) in example 1;

FIG. 4 is a three-dimensional graph of the dielectric strength as a function of temperature and frequency for the 4- ((4-nitrophenoxy) carbonyl) phenyl 2, 4-dimethoxybenzoate of example 1; the coordinate scale corresponding to the frequency (HZ) in the figure is respectively 10 from the left lower part to the right upper part⁶、10⁵、 10⁴、10³、10²、10¹The coordinate scales corresponding to the temperature (DEG C) are respectively 100, 120, 140, 160, 180 and 200;

FIG. 5 is a graph showing the ratio of SHG signal intensity to quartz intensity at different temperatures for 4- ((4-nitrophenoxy) carbonyl) phenyl 2, 4-dimethoxybenzoate in example 1;

FIG. 6 is a DSC of a liquid crystal molecule prepared in example 22;

FIG. 7 POM diagram of liquid crystal molecules prepared in example 22 when they enter a nematic phase;

FIG. 8 POM diagram of the liquid crystal molecules prepared in example 22 entering a polar nematic phase;

FIG. 9 is a three-dimensional graph showing the dielectric strength of liquid crystal molecules prepared in example 22 as a function of temperature and frequency; in the figure, the coordinate scales corresponding to the frequency (HZ) are respectively 100, 1000, 10000, 100000 and 1000000, and the coordinate scales corresponding to the temperature (DEG C) are respectively 111, 101, 90.9, 81, 71, 61.1 and 51;

FIG. 10 SHG signal intensities of liquid crystal molecules prepared in example 22 in different temperature regions.

Detailed Description

The present invention will be described in further detail with reference to examples, but the embodiments and the scope of the present invention are not limited thereto.

Table 1 shows the chemical structures and corresponding dipole moments of the polar liquid crystal molecules prepared in examples 1 to 25

TABLE 1

Example 1

Preparation of 4- ((4-nitrophenoxy) carbonyl) phenyl 2, 4-dimethoxybenzoate

(1)4- ((tetrahydro-2H-pyran-2-yl) oxy) benzoic acid:

parahydroxybenzoic acid (2.76g, 0.02mol), p-toluenesulfonic acid (1.96g, 0.0103mol) and 20mL of ether were added to a 50mL single-necked flask under nitrogen to form a suspension. 3, 4-dihydro-2H-pyran (2.8mL, 0.0307mol) was added dropwise with a syringe at 0 ℃ in an ice bath, and the mixture was gradually returned to room temperature and stirred for 5-6H. The solution produced a large amount of precipitate at this point, was filtered, washed several times with 20mL of ether, and dried under vacuum to give 2.89g of white powder in 69.3% yield;¹H NMR(400MHz, Chloroform-d)δ8.06(d,J＝8.7Hz,2H,ArH),7.10(d,J＝8.6Hz,2H,ArH),5.53(q,J＝2.8Hz, 1H,CH),3.86(d,J＝21.0Hz,1H,CH2),3.63(d,J＝11.2Hz,1H,CH2),2.07–1.50(m,6H, CH2).

(2) 4-nitrophenyl 4- ((tetrahydro-2H-pyran-2-yl) oxy) benzoate:

under the protection of nitrogen, compound 3(10g, 45mmol), 1- (3)-dimethylaminopropyl) -3-ethylcarbodiimide hydrochloride (10.35g, 54mmol), N, N-dimethylaminopyridine (0.71g, 0.54mmol) was added to 100mL of dichloromethane. The solution was stirred for 1h in an ice bath, after which time it was gradually returned to room temperature for 14-24h with monitoring of the reaction by TLC. After completion of the reaction, the reaction mixture was washed three times with saturated brine and extracted with ethyl acetate. The organic phase was dried over anhydrous magnesium sulfate, filtered, spin dried and the crude product was purified by column chromatography using petroleum ether/ethyl acetate 3/1 as eluent to give 12g of product as a white solid in 76.8% yield.¹H NMR(500MHz,Chloroform-d)δ8.31(d,J＝9.1Hz,2H,ArH),8.12(dd,J＝17.7,8.9Hz,2H, ArH),7.40(d,J＝9.2Hz,2H,ArH),7.05(dd,J＝114.9,8.9Hz,2H,ArH),5.57(s,1H,CH),4.06 –3.82(m,1H,CH2),3.61(d,J＝55.9Hz,1H,CH2),2.03-1.64(s,6H,CH2).

(3) 4-Nitrophenyl 4-hydroxybenzoates:

compound 4(1g, 2.9mmol), pyridinium p-toluenesulfonate (72.8mg, 0.29mmol), 20mL of tetrahydrofuran, and 20mL of methanol were added to a 100mL one-necked flask, and the mixture was heated to 60 ℃ and stirred for 6-24h until TLC detection was complete. Stopping the reaction, cooling to room temperature, removing more solvent by rotary evaporation, dissolving the solvent by ethyl acetate, washing the solvent by deionized water, washing an organic phase by saturated saline solution, drying the organic phase by anhydrous magnesium sulfate, filtering, and carrying out rotary drying, and purifying a crude product by using petroleum ether/ethyl acetate 2/1 as eluent column chromatography to obtain 0.72g of a white solid product, wherein the yield is 95.1%.¹H NMR(400MHz, DMSO-d6)δ10.64(s,1H,OH),8.34(d,J＝9.1Hz,2H,ArH),8.02(d,J＝8.8Hz,2H,ArH),7.58 (d,J＝9.1Hz,2H,ArH),6.95(d,J＝8.8Hz,2H,ArH).

(4)4- ((4-nitrophenoxy) carbonyl) phenyl 2, 4-dimethoxybenzoate:

under a nitrogen atmosphere, compound 3(2.35g, 9.07mmol), commercially available 2, 4-dimethoxybenzoic acid (1.73g, 9.52mmol), 1- (3-dimethylaminopropyl) -3-ethylcarbodiimide hydrochloride (2.6g, 13.6mmol), N, N-dimethylaminopyridine (110mg, 0.91mmol) were added to 50mL of anhydrous dichloromethane and the solution was stirred for 1h with ice bath, after which time it was gradually returned to room temperature and stirring was continued for 14-24h, and the reaction was monitored by TLC. After the reaction is completed, useThe mixture was washed three times with saturated brine and extracted with ethyl acetate. The organic phase was dried over anhydrous magnesium sulfate, filtered, spin dried and the crude product was purified by column chromatography using petroleum ether/dichloromethane 1/1 as eluent to give 2.86g of product as a white solid in 74.51% yield.¹H NMR(500MHz, Chloroform-d)δ8.33(d,J＝9.1Hz,2H),8.25(d,J＝8.7Hz,2H),8.10(d,J＝8.7Hz,1H),7.41 (dd,J＝19.6,8.9Hz,4H),6.62–6.52(m,2H),3.92(d,J＝18.6Hz,6H).

As shown in the DSC of FIG. 1, the temperature drop curve of the liquid crystal molecule of example 1 has two protrusions at about 120 ℃ and about 80 ℃, indicating that the molecule undergoes two phase transitions during the temperature drop. When observed in an aligned cell with a cross-polarization microscope (POM), the liquid crystal molecules begin to decrease in temperature at around 120 ℃ with a change in the liquid crystal micro-alignment from black to bright, and begin to enter the nematic phase (as shown in fig. 2). When the temperature is reduced to about 80 ℃, the refractive index can be obviously changed, the visual field is obviously lightened from a dark background under the POM, the micro orientation of the liquid crystal is changed, and the liquid crystal enters a polar nematic phase (as shown in figure 3). The liquid crystal molecules can present a thermodynamically stable polar nematic liquid crystal structure in a wide temperature range.

By testing the dielectric coefficient of the liquid crystal molecules in the whole phase transition temperature range, the liquid crystal molecules are found to have 10 after entering into the polar phase⁴An extremely high dielectric strength of the order of magnitude (as shown in fig. 4), while the polar liquid crystal phase of the molecule has a very good SHG response in this temperature range (as shown in fig. 5).

Example 2

Preparation of 4- ((4-nitrophenoxy) carbonyl) phenyl 4-methoxy-2-propoxybenzoate (3)

(1) Methyl 4-methoxy-2-propoxybenzoate:

under nitrogen protection, the commercially available reactant methyl 2-hydroxy-4-methoxybenzoate (2g, 10.98mmol) and potassium carbonate (3.03g, 21.96mmol) were added to 30mL of DMF, 6-bromopropane (1.62g,13.17mmol) was injected dropwise, and after reflux reaction overnight under heating, the crude product was washed with saturated aqueous sodium chloride solution 3 times, then extracted with ethyl acetate, and after drying the solvent of the organic layer, the crude product was purified by column chromatography using petroleum ether/ethyl acetate 5/1 as an eluent to give 2.03g of a white powdery product in 82.46% yield.

(2) 4-methoxy-2-propoxybenzoic acid:

reaction 1(1.5g, 6.69mmol) was dissolved in 60mL THF/MeOH/H₂To a mixed solution of O ═ 1/1/1, KOH (1.5g, 26.76mmol) was added, the mixture was heated under reflux overnight, the reaction was gradually returned to room temperature after completion, 200mL of water was added, pH was adjusted to ≈ 1 with 1M hydrochloric acid solution, and extraction was performed with ethyl acetate. The organic phase was dried over anhydrous magnesium sulfate, filtered, spin-dried and the crude product was purified by column chromatography using petroleum ether/ethyl acetate 2/1 as eluent to give 1.35g of product as a white solid in 96.01% yield.

(3)4- ((4-nitrophenoxy) carbonyl) phenyl 4-methoxy-2-propoxybenzoate:

compound 2(2g, 9.51mmol), 4-nitrophenyl 4-hydroxybenzoate (2.35g, 9.06mmol), 1- (3-dimethylaminopropyl) -3-ethylcarbodiimide hydrochloride (2.6g, 13.6mmol), N, N-dimethylaminopyridine (110mg, 0.91mmol) were added to 50mL of anhydrous dichloromethane under a nitrogen atmosphere, the solution was stirred for 1h with an ice bath, after which time it was gradually returned to room temperature and stirring was continued for 14-24h, and the reaction was monitored by TLC. After completion of the reaction, the reaction mixture was washed three times with saturated brine and extracted with ethyl acetate. The organic phase was dried over anhydrous magnesium sulfate, filtered, spin-dried and the crude product was purified by column chromatography using petroleum ether/dichloromethane 1/1 as eluent to give the product as a white solid 3.06g in 74.81% yield.¹H NMR(500MHz,Chloroform-d)δ8.38–8.31(m,2H), 8.26(d,J＝8.7Hz,2H),8.06(d,J＝8.8Hz,1H),7.46–7.41(m,2H),7.39(d,J＝8.7Hz,2H), 6.57(dd,J＝8.8,2.3Hz,1H),6.53(d,J＝2.2Hz,1H),4.03(t,J＝6.4Hz,2H),3.89(s,3H),1.88 (h,J＝7.2Hz,2H),1.07(t,J＝7.4Hz,3H).

Example 3

4- ((4-Nitrophenoxy) carbonyl) phenyl 4-methoxy-2- (pentyloxy) benzoate was prepared by methods analogous to those described in example 2.¹H NMR(400MHz,Chloroform-d)δ8.33(d,J＝9.1Hz,2H),8.26(d,J＝ 8.7Hz,2H),8.06(d,J＝8.7Hz,1H),7.41(dd,J＝17.2,8.9Hz,4H),6.59–6.54(m,1H),6.52(d, J＝2.2Hz,1H),4.06(t,J＝6.5Hz,2H),3.89(s,3H),1.86(dt,J＝14.5,6.6Hz,2H),1.49(dt,J＝ 14.7,7.1Hz,2H),1.37(dt,J＝14.9,7.2Hz,2H),0.89(t,J＝7.3Hz,3H).

Example 4

4- ((4-Nitrophenoxy) carbonyl) phenyl 4-methoxy-2- (2-methoxyethoxy) benzoate was prepared by methods analogous to those described in example 2.¹H NMR(400MHz,Chloroform-d)δ8.31–8.23(m,2H),8.23–8.16 (m,2H),8.00(d,J＝8.8Hz,1H),7.42–7.29(m,4H),6.53(dd,J＝8.8,2.3Hz,1H),6.49(d,J＝ 2.3Hz,1H),4.21–4.11(m,2H),3.82(s,3H),3.79–3.70(m,2H),3.37(s,3H).

Example 5

4- ((4-Nitrophenoxy) carbonyl) phenyl 4-methoxy-2- (3-methoxypropoxy) benzoate was prepared by methods analogous to those described for example 2.¹H NMR(400MHz,Chloroform-d)δ8.32–8.23(m,2H),8.23–8.16 (m,2H),8.00(d,J＝8.6Hz,1H),7.41–7.26(m,4H),6.54–6.45(m,2H),4.10(t,J＝6.2Hz,2H), 3.82(s,3H),3.53(t,J＝6.1Hz,2H),3.25(s,3H),2.04(p,J＝6.1Hz,2H).

Example 6

4- ((4-Nitrophenoxy) carbonyl) phenyl 2, 4-bis (2-methoxyethoxy) benzoate was prepared by methods analogous to those described in example 2.¹H NMR(400MHz,Chloroform-d)δ8.29–8.23(m,2H),8.21–8.16(m, 2H),7.98(dd,J＝8.6,1.9Hz,1H),7.37–7.29(m,4H),6.53(d,J＝8.7Hz,2H),4.22–4.04(m, 4H),3.73(dt,J＝9.7,4.6Hz,4H),3.38(d,J＝14.2Hz,6H).

Particularly the synthesis of the 2, 4-bis (2-methoxyethoxy) methyl benzoate (1) compound.

(1) Methyl 2, 4-bis (2-methoxyethoxy) benzoate:

under nitrogen protection, the commercially available reaction product, methyl 2, 4-dihydroxy-benzoate (2g, 11.89mmol) and potassium carbonate (9.86g, 71.37mmol), were added to 50mL of DMF, 1-bromo-2-methoxyethane (3.64g,26.17mmol) was added dropwise, and after reflux reaction overnight under heating, the crude product was washed with saturated aqueous sodium chloride solution 3 times, then extracted with ethyl acetate, and after drying the solvent of the organic layer, the crude product was purified by column chromatography using petroleum ether/ethyl acetate 5/1 as eluent, to give 3.21g of a white powdery product with a yield of 94.9%.

Example 7

Preparation of 4-nitrophenyl 2-methoxy-4- ((4-methoxybenzoyl) oxy) benzoate (3)

(1) 4-methoxy-3-methoxyphenyl 4-methoxybenzoate:

under a nitrogen atmosphere, commercially available 4-methoxybenzoic acid (1g, 6.57mmol), 4-hydroxy-2-methoxybenzaldehyde (0.95g, 6.26mmol), 1- (3-dimethylaminopropyl) -3-ethylcarbodiimide hydrochloride (1.80g, 9.39mmol), N, N-dimethylaminopyridine (76mg, 0.626mmol) were added to 50mL of anhydrous dichloromethane, the solution was stirred in an ice bath for 1h, after which time it was gradually returned to room temperature and stirring was continued for 14-24h, and the reaction was monitored by TLC. After completion of the reaction, the reaction mixture was washed three times with saturated brine and extracted with ethyl acetate. The organic phase was dried over anhydrous magnesium sulfate, filtered, spin-dried, and the crude product was purified by column chromatography using petroleum ether/ethyl acetate 4/1 as eluent to give 1.58g of colorless crystals in 88.17% yield.

(2) 2-methoxy-4- ((4-methoxybenzoyl) oxy) benzoic acid:

compound 1(1g,3.49mmol) was dissolved in DMSO (20mL) while cooling on ice, disodium hydrogen phosphate (1.68g, 13.97mmol), sodium hypochlorite (1.11g,12.23mmol), and water (15mL) were added, and the mixture was stirred for 30min, gradually returned to room temperature, and stirring was continued for 6 h. After the reaction, the solution was diluted with 100mL of deionized water, sodium bicarbonate was added to adjust the pH to 8, 100mL of ethyl acetate was extracted, the aqueous phase was adjusted to pH 4 with 1mol/L hydrochloric acid solution, (3 × 50mL) of ethyl acetate was extracted, all the organic phases were dried over anhydrous magnesium sulfate, filtered, ethyl acetate was removed by a rotary evaporator, the crude product was purified by column chromatography using silica gel as the stationary phase and petroleum ether/ethyl acetate as the mobile phase to obtain 1.02g of a white solid with a yield of 96.6%.

(3) 4-nitrophenyl 2-methoxy-4- ((4-methoxybenzoyl) oxy) benzoate:

compound 2(1g, 3.31mmol), p-nitrophenol (0.438g, 3.15mmol), 1- (3-dimethylaminopropyl) -3-ethylcarbodiimide hydrochloride (0.906g, 4.73mmol), N, N-dimethylaminopyridine (39mg, 0.331mmol) were added to 50mL of anhydrous dichloromethane under a nitrogen atmosphere, the solution was stirred for 1h under an ice bath, after which time stirring was continued for 14-24h gradually returning to room temperature, and the reaction was monitored by TLC. After completion of the reaction, the reaction mixture was washed three times with saturated brine and extracted with ethyl acetate. The organic phase was dried over anhydrous magnesium sulfate, filtered, spin-dried, and the crude product was purified by column chromatography using petroleum ether/ethyl acetate 4/1 as eluent to give 1.05g of colorless crystals in 78.2% yield.¹H NMR(500MHz,Chloroform-d)δ8.40–8.31(m,2H), 8.24–8.10(m,3H),7.49–7.38(m,2H),7.11–6.93(m,4H),3.97(d,J＝23.7Hz,6H).

Example 8

Preparation of 4-nitrophenyl 2-ethoxy-4- ((4-methoxybenzoyl) oxy) benzoate (6)

(1) 2-hydroxy-4- ((tetrahydro-2H-pyran-2-yl) oxy) benzaldehyde:

under nitrogen atmosphere, to CHCl₃To (100mL) was added 2, 4-dihydroxybenzaldehyde (3.55g, 25.7mmol) and 3, 4-dihydro-2H-pyran (2.82mL, 30.85mmol), pyridinium p-toluenesulfonate (0.645g, 2.57mmol), and the reaction mixture was stirred at room temperature for 1.5H. After the reaction is finished, NaHCO₃The solution was added to the reaction mixture, followed by CHCl₃And (4) extracting. The organic phase is concentrated, the residue is purified by chromatography on silica gel (n-hexane: ethyl acetate 95: 5 to 70: 30),2-hydroxy-4- ((tetrahydro-2H-pyran-2-yl) oxy) benzaldehyde (1) was obtained as a colorless oily liquid (5.5g, 22.55mmol, 88% yield).

(2) 2-ethoxy-4- ((tetrahydro-2H-pyran-2-yl) oxy) benzaldehyde:

compound (1) (2g, 9mmol) and potassium carbonate (3.73g, 27mmol) were added to 50mL of acetone under nitrogen protection, ethyl bromide (1.18g,10.8mmol) was added dropwise, the mixture was refluxed overnight, washed with saturated aqueous sodium chloride solution 3 times, extracted with ethyl acetate, and after drying the solvent of the organic layer, the crude product was purified by column chromatography using petroleum ether/ethyl acetate 5/1 as eluent to give 2.0g of an oily liquid in 91.46% yield.

(3) 2-ethoxy-4-hydroxybenzaldehyde:

compound 2(2g, 7.99mmol), pyridinium p-toluenesulfonate (0.2g, 0.799mmol), 30mL tetrahydrofuran, 30mL methanol were added to a 100mL single-necked flask and the mixture heated to 60 deg.C and stirring continued for 6-24h until TLC detection was complete. Stopping the reaction, cooling to room temperature, removing more solvent by rotary evaporation, dissolving the solvent by ethyl acetate, washing the solvent by deionized water, washing an organic phase by saturated saline solution, drying the organic phase by anhydrous magnesium sulfate, filtering, and carrying out rotary drying, and purifying a crude product by using petroleum ether/ethyl acetate 2/1 as eluent column chromatography to obtain 1.28g of a white solid product, wherein the yield is 96.4%.

(4) 3-ethoxy-4-formylphenyl 4-methoxybenzoate:

compound 2(1g, 3.31mmol), p-nitrophenol (0.438g, 3.15mmol), 1- (3-dimethylaminopropyl) -3-ethylcarbodiimide hydrochloride (0.906g, 4.73mmol), N, N-dimethylaminopyridine (39mg, 0.331mmol) were added to 50mL of anhydrous dichloromethane under a nitrogen atmosphere, the solution was stirred for 1h under an ice bath, after which time stirring was continued for 14-24h gradually returning to room temperature, and the reaction was monitored by TLC. After completion of the reaction, the reaction mixture was washed three times with saturated brine and extracted with ethyl acetate. The organic phase was dried over anhydrous magnesium sulfate, filtered, spin-dried, and the crude product was purified by column chromatography using petroleum ether/ethyl acetate 4/1 as eluent to give 1.05g of colorless crystals in 78.2% yield.

(5) 2-ethoxy-4- ((4-methoxybenzoyl) oxy) benzoic acid:

compound 4(2g,6.66mmol) was dissolved in DMSO (40mL) while cooling on ice, disodium hydrogen phosphate (3.2g, 26.64mmol), sodium hypochlorite (2.11g,23.31mmol), and water (30mL) were added, and the mixture was stirred for 30min, gradually returned to room temperature, and stirring was continued for 6 h. After the reaction, the solution was diluted with 200mL of deionized water, sodium bicarbonate was added to adjust the pH to 8, 200mL of ethyl acetate was extracted, the aqueous phase was adjusted to pH 4 with 1mol/L hydrochloric acid solution, (3 × 80mL) of ethyl acetate was extracted, all the organic phases were dried over anhydrous magnesium sulfate, filtered, ethyl acetate was removed by a rotary evaporator, the crude product was purified by column chromatography using silica gel as the stationary phase and petroleum ether/ethyl acetate as the mobile phase to give 2.01g of a white solid with a yield of 95.42%.

(6) 4-nitrophenyl 2-ethoxy-4- ((4-methoxybenzoyl) oxy) benzoate:

compound 5(2g, 6.32mmol), p-nitrophenol (0.838g, 6.02mmol), 1- (3-dimethylaminopropyl) -3-ethylcarbodiimide hydrochloride (1.73g, 9.03mmol), N, N-dimethylaminopyridine (74mg, 0.602mmol) were added to 100mL of anhydrous dichloromethane under a nitrogen atmosphere, the solution was stirred for 1h under an ice bath, after which time stirring was continued for 14-24h gradually returning to room temperature and the reaction was monitored by TLC. After completion of the reaction, the reaction mixture was washed three times with saturated brine and extracted with ethyl acetate. The organic phase was dried over anhydrous magnesium sulfate, filtered, dried by spinning, and the crude product was purified by column chromatography using dichloromethane/petroleum ether (3/2) as eluent to give 2.06g of a white powdery solid in 78.2% yield.¹H NMR(500MHz,Chloroform-d)δ8.35–8.29 (m,2H),8.19–8.14(m,2H),8.12–8.08(m,1H),7.45–7.39(m,2H),7.01(dd,J＝9.4,2.4Hz, 2H),6.93(d,J＝7.4Hz,2H),4.17(q,J＝7.0Hz,2H),3.92(s,3H),1.49(t,J＝7.0Hz,3H).

Example 9

Nitrophenyl 4- (4- ((4-methoxybenzoyl) oxy) -2-propoxybenzoate was prepared by methods analogous to those described in example 4.¹H NMR(500MHz,Chloroform-d)δ8.36–8.29(m,2H),8.19–8.14(m, 2H),8.10(d,J＝8.3Hz,1H),7.45–7.37(m,2H),7.04–6.97(m,2H),6.97–6.89(m,2H),4.06(t, J＝6.4Hz,2H),3.92(s,3H),1.88(h,J＝7.2Hz,2H),1.06(t,J＝7.4Hz,3H).

Example 10

Preparation of 4- ((3-methoxy-4-nitrophenoxy) carbonyl) phenyl 4-methoxybenzoate

(1) 4-methoxyphenyl 4-methoxybenzoate:

the compound (1) was prepared in the same manner as in the esterification method described in example 8 above to give 4-methoxyphenyl 4-methoxybenzoate (1) as a colorless crystal as a final product in 92% yield.

(2)4- ((4-methoxybenzoyl) oxy) benzoic acid:

this compound was prepared in the same manner as described for the oxidation of an aldehyde group to a carboxyl group in example 8 above to give the final product 4- ((4-methoxybenzoyl) oxy) benzoic acid (2) as colorless crystals in 98% yield.

(3)4- ((3-methoxy-4-nitrophenoxy) carbonyl) phenyl 4-methoxybenzoate:

this compound was prepared in the same manner as the esterification method in example 8 above, and finally obtained as a white solid powder with a yield of 72%.¹H NMR(500MHz,Chloroform-d)δ8.32–8.23(m,2H),8.22–8.12(m,2H),8.01(d,J＝8.9Hz, 1H),7.44–7.36(m,2H),7.08–6.97(m,3H),6.94(dd,J＝8.9,2.3Hz,1H),3.95(d,J＝36.8Hz, 6H).

Example 11

Preparation of 4- ((3,4, 5-trifluorophenoxy) carbonyl) phenyl (4)2, 4-dimethoxybenzoate

(1) The preparation of 4- ((tetrahydro-2H-pyran-2-yl) oxy) benzoic acid is described in example 1 and is not described in further detail herein.

(2)3,4, 5-trifluorophenyl 4- ((tetrahydro-2H-pyran-2-yl) oxy) benzoate:

compound 1(5g, 22.5mmol), 3,4, 5-trifluorophenol (3.17g, 21.43mmol), 1- (3-dimethylaminopropyl) -3-ethylcarbodiimide hydrochloride (6.47g, 33.75mmol), N, N-dimethylaminopyridine (0.282g, 2.14mmol) were added to 100mL of dichloromethane under a nitrogen blanket. The solution was stirred for 1h in an ice bath, after which time it was gradually returned to room temperature for 14-24h with monitoring of the reaction by TLC. After completion of the reaction, the reaction mixture was washed three times with saturated brine and extracted with ethyl acetate. The organic phase was dried over anhydrous magnesium sulfate, filtered, spin-dried, and the crude product was purified by column chromatography using petroleum ether/ethyl acetate 3/1 as eluent to give 7.15g of the product as white crystals in 94.7% yield.

(3)3,4, 5-trifluorophenyl 4-hydroxybenzoate:

compound 2(7g, 19.87mmol), pyridinium p-toluenesulfonate (0.5g, 1.99mmol), 50mL tetrahydrofuran, 50mL methanol were added to a 150mL single-necked flask and the mixture heated to 60 deg.C and stirring continued for 6-24h until TLC detection was complete. Stopping the reaction, cooling to room temperature, performing rotary evaporation to remove more solvent, dissolving with ethyl acetate, washing with deionized water, washing an organic phase with saturated saline solution, drying the organic phase with anhydrous magnesium sulfate, filtering, performing rotary drying, and purifying a crude product by using petroleum ether/ethyl acetate 2/1 as an eluent column chromatography to obtain a white solid product 5.06g, wherein the yield is 95%.

(4)2, 4-Dimethoxybenzoic acid 4- ((3,4, 5-Trifluorophenoxy) carbonyl) phenyl

Under a nitrogen atmosphere, 2, 4-dimethoxybenzoic acid (1g, 5.49mmol), compound (3) (1.4g, 5.23mmol), 1- (3-dimethylaminopropyl) -3-ethylcarbodiimide hydrochloride (1.58g, 8.23mmol), N, N-dimethylaminopyridine (67mg, 0.549mmol) were added to 50mL of anhydrous dichloromethane, the solution was stirred for 1h under an ice bath, after which time it was gradually returned to room temperature and stirring was continued for 14-24h, and the reaction was monitored by TLC. After completion of the reaction, the reaction mixture was washed three times with saturated brine and extracted with ethyl acetate. The organic phase was dried over anhydrous magnesium sulfate, filtered, spin-dried, and the crude product was purified by column chromatography using dichloromethane/petroleum ether (3/2) as eluent to give 1.76g of a white powdery solid in 77.8% yield.¹H NMR(400MHz,Chloroform-d)δ8.21(d,J＝ 8.8Hz,2H),8.10(d,J＝8.7Hz,1H),7.42–7.34(m,2H),7.05–6.88(m,2H),6.65–6.51(m, 2H),3.93(d,J＝11.9Hz,6H)

Example 12

2-ethoxy-4-methoxybenzoic acid 4- (((3,4, 5-trifluorophenoxy) carbonyl) phenyl) was prepared by methods analogous to those described for example 11; wherein 2-ethoxy-4-methoxybenzoic acid was prepared with reference to the preparation of the substance (2) in example 2.¹H NMR(400MHz,Chloroform-d)δ8.26–8.17(m,2H),8.07(d,J＝8.8Hz,1H),7.42– 7.33(m,2H),7.00–6.89(m,2H),6.63–6.47(m,2H),4.14(q,J＝7.0Hz,2H),3.89(s,3H),1.49 (t,J＝7.0Hz,3H).

Example 13

4- ((3,4, 5-Trifluorophenoxy) carbonyl) phenyl 4-methoxy-2-propoxybenzoate was prepared by methods analogous to those described for example 11; wherein the preparation of 4-methoxy-2-propoxybenzoic acid refers to the preparation of the substance (2) in example 2.¹H NMR(400MHz,Chloroform-d)δ8.25–8.18(m,2H),8.06(d,J＝8.7Hz,1H),7.41–7.33 (m,2H),6.95(ddd,J＝9.1,4.4,3.0Hz,2H),6.62–6.48(m,2H),4.03(t,J＝6.4Hz,2H),3.89(s, 3H),1.88(dtd,J＝13.8,7.4,6.3Hz,2H),1.07(t,J＝7.4Hz,3H).

Example 14

Phenyl 4- ((3,4, 5-trifluorophenoxy) carbonyl) 2-butoxy-4-methoxybenzoate was prepared by methods analogous to those described for example 11; wherein 2-butoxy-4-methoxybenzoic acid was prepared with reference to the preparation of the substance (2) in example 2.¹H NMR(400MHz,Chloroform-d)δ8.21(d,J＝8.8Hz,2H),8.06(d,J＝8.7Hz,1H),7.37(d,J ＝8.8Hz,2H),7.04–6.85(m,2H),6.62–6.47(m,2H),4.07(t,J＝6.4Hz,2H),3.89(s,3H),1.92 –1.76(m,2H),1.52(dd,J＝14.8,7.4Hz,2H),0.95(t,J＝7.4Hz,3H).

Example 15

Phenyl 4- ((3,4, 5-trifluorophenoxy) carbonyl) 2-butoxy-4-methoxybenzoate was prepared by methods analogous to those described for example 11;¹H NMR(400MHz,Chloroform-d)δ8.21(d,J＝8.8Hz,2H),8.04(d,J＝8.7 Hz,1H),7.37(d,J＝8.8Hz,2H),7.06–6.83(m,2H),6.66–6.44(m,2H),4.12–3.94(m,4H), 1.95–1.78(m,4H),1.07(t,J＝7.4Hz,6H).

wherein the preparation process of the 2, 4-dipropoxybenzoic acid is as follows:

(1)2, 4-Dipropoxybenzoic acid methyl ester

Under nitrogen protection, the commercially available reaction product, methyl 2, 4-dihydroxy-benzoate (2g, 11.89mmol) and potassium carbonate (4.93g, 35.68mmol), was added dropwise to 50mL of DMF, and after heating and refluxing overnight, 1-bromopropane (3.22g,26.17mmol) was injected, and after reflux reaction, the crude product was washed with saturated aqueous sodium chloride solution 3 times, extracted with ethyl acetate, and after drying the solvent of the organic layer, the crude product was purified by column chromatography using petroleum ether/ethyl acetate 3/1 as eluent, to obtain 2.03g of colorless oily liquid, with a yield of 82.46%.

(2)2, 4-Dipropoxybenzoic acid

Reaction (1) (2g, 7.93mmol) was dissolved in 60mL THF/MeOH/H₂To a mixed solution of O ═ 1/1/1, KOH (3.56g, 63.41mmol) was added, the mixture was heated under reflux overnight, the reaction was gradually returned to room temperature after completion, 200mL of water was added, pH was adjusted to ≈ 1 with 1M hydrochloric acid solution, and extraction was performed with ethyl acetate. The organic phase was dried over anhydrous magnesium sulfate, filtered, spin-dried, and the crude product was purified by column chromatography using petroleum ether/ethyl acetate 2/1 as eluent to give 1.82g of the product as a white solid in 96.4% yield.

Example 16

Preparation of 4- ((4-Nitrophenoxy) carbonyl) phenyl (S) -2- (sec-butoxy) -4-methoxybenzoate (4)

(1) (S) sec-butyl 4-methylbenzenesulfonate:

to a solution of (R) -butan-2-ol (1g, 13.49mmol) and triethylamine (2.82mL, 20.24mmol), N, N-dimethylaminopyridine (164mg, 1.349mmol) in DCM (50mL) at 0 deg.C was added 4-methylbenzenesulfonylA solution of chlorine (p-TsOH) (3.86g, 20.24mmol) in dichloromethane was added dropwise over 20 min. After the mixture was stirred at room temperature overnight, the reaction mixture was concentrated in vacuo and the residue was dissolved in ethyl acetate. The resulting solution was washed with water and brine, MgSO₄Dried and concentrated. The oily residue was purified by column chromatography in 73% yield.

(2) (S) -methyl 2- (sec-butoxy) -4-methoxybenzoate:

a round-bottom flask was charged with (1) (1g, 4.38mmol), methyl 2-hydroxy-4-methoxybenzoate (0.96g, 5.26mmol), K under nitrogen atmosphere₂CO₃(1.82g, 13.14mmol), KI (70mg, 0.44mmol), 20mL DMF. And the solution was heated to reflux until the reaction was judged complete by TLC (6-48 hours) and cooled to room temperature. Water (80mL) was added to the solution and extracted with DCM (3X 100 mL). The organic phase was over anhydrous MgSO₄Drying, removal of the solvent and purification of the residue by chromatography and drying in a vacuum oven. The yield was 82%.

(3) Preparation of (S) -2- (sec-butoxy) -4-methoxybenzoic acid reference example 2 was made to the preparation of the substance (2).

(4) Preparation of 4- ((4-nitrophenoxy) carbonyl) phenyl (S) -2- (sec-butoxy) -4-methoxybenzoate the preparation of (4) in reference example 1 was made.¹H NMR(400MHz,Chloroform-d)δ8.37–8.30(m,2H),8.29–8.22 (m,2H),8.04(d,J＝8.7Hz,1H),7.47–7.35(m,4H),6.59–6.50(m,2H),4.42(h,J＝6.0Hz, 1H),3.89(s,3H),1.82(ddd,J＝13.8,7.5,6.2Hz,1H),1.71(dtd,J＝13.8,7.3,5.7Hz,1H),1.37 (d,J＝6.1Hz,3H),1.01(t,J＝7.4Hz,3H).

Example 17

Preparation of 4- ((4-nitrophenoxy) carbonyl) phenyl (R) -4- (sec-butoxy) -2-methoxybenzoate preparation reference example 16 was made.

Example 18

Preparation of 4- ((4-nitrophenoxy) carbonyl) phenyl (R) -4-methoxy-2- (2-methylbutoxy) benzoate preparation reference example 16 was made.¹H NMR(400MHz,Chloroform-d)δ8.37–8.30(m,2H),8.30–8.23(m, 2H),8.06(d,J＝8.7Hz,1H),7.47–7.35(m,4H),6.56(dd,J＝8.8,2.3Hz,1H),6.52(d,J＝2.3 Hz,1H),3.96–3.82(m,5H),1.99–1.88(m,1H),1.67–1.59(m,1H),1.36–1.28(m,1H),1.06 (d,J＝6.8Hz,3H),0.93(t,J＝7.5Hz,3H).

Example 19

Preparation of 4- ((4-nitrophenoxy) carbonyl) phenyl (S) -2-methoxy-4- (2-methylbutoxy) benzoate preparation reference example 16 was made.¹H NMR(400MHz,Chloroform-d)δ8.37–8.30(m,2H),8.28–8.22(m, 2H),8.08(d,J＝8.6Hz,1H),7.48–7.35(m,4H),6.62–6.50(m,2H),4.44(h,J＝6.1Hz,1H), 3.01-3.93(s,5H),1.86–1.74(m,1H),1.74–1.64(m,1H),1.36(d,J＝6.1Hz,3H),1.01(t,J＝ 7.5Hz,3H).

Example 20

Preparation of 4- ((4-nitrophenoxy) carbonyl) phenyl (S) -4-methoxy-2- (octane-2-yloxy) benzoate preparation reference example 16 was made.¹H NMR(500MHz,Chloroform-d)δ8.37–8.31(m,2H),8.29–8.23(m, 2H),8.08(d,J＝8.7Hz,1H),7.47–7.35(m,4H),6.58–6.49(m,2H),4.49(h,J＝6.1Hz,1H), 3.93(s,3H),1.82–1.73(m,1H),1.69–1.59(m,1H),1.51–1.37(m,2H),1.36(d,J＝6.0Hz, 5H),1.30(tdd,J＝8.8,5.2,2.5Hz,5H),0.94–0.85(m,3H).

Example 21

(E) Preparation of (3) -3-fluoro-4- ((4-nitrophenyl) diazenyl) phenyl 4-methoxy-2-propoxybenzoate

(1) (E) -3-fluoro-4- ((4-nitrophenyl) diazenyl) phenol:

4-nitroaniline (5g, 36.20mmol) was added to aqueous hydrochloric acid (10%, 100mL) and stirred until dissolved. Sodium nitrite (3.2g, 46.33mmol) was dissolved in 100mL of water and added dropwise to the solution over 1 hour, followed by stirring for a further 30 minutes, keeping the temperature below 2 ℃. (5.19g, 46.33mmol) 3-fluorophenol and (1.85g, 46.33mmol) sodium hydroxide were dissolved in 100mL water, and the mixture was added dropwise to the above diazonium salt solution over 1 hour, maintaining the temperature below 2 ℃. The reaction was complete after stirring for 1 hour. Stirring was maintained at 2 ℃ for a further 3 hours. It was kept overnight at room temperature and precipitated as an orange precipitate and was collected by filtration. The product was sufficiently pure without further purification, with yields approaching 100%.

(2) The preparation of 4-methoxy-2-propoxybenzoic acid was exactly the same as that of the compound (2) in example 2.

(3) (E) -3-fluoro-4- ((4-nitrophenyl) diazenyl) phenyl 4-methoxy-2-propoxybenzoate:

under a nitrogen atmosphere, 4-methoxy-2-propoxybenzoic acid (2g, 9.51mmol), compound (1) (2.37g, 9.06mmol), 1- (3-dimethylaminopropyl) -3-ethylcarbodiimide hydrochloride (2.61g, 13.59mmol), N, N-dimethylaminopyridine (115mg, 0.9mmol) were added to 50mL of anhydrous dichloromethane, the solution was stirred for 1h with ice bath, after which time it was gradually returned to room temperature and stirring was continued for 14-24h, and the reaction was monitored by TLC. After completion of the reaction, the reaction mixture was washed three times with saturated brine and extracted with ethyl acetate. The organic phase was dried over anhydrous magnesium sulfate, filtered, spin-dried, and the crude product was purified by column chromatography using ethyl acetate/petroleum ether (1/2) as eluent to give 3.86g of a red solid in 94% yield.¹H NMR(400MHz,Chloroform-d)δ8.48–8.36(m,2H),8.14 –8.01(m,3H),7.90(dd,J＝8.9,8.2Hz,1H),7.29(dd,J＝11.0,2.3Hz,1H),7.16(ddd,J＝8.9, 2.3,1.2Hz,1H),6.67–6.48(m,2H),4.06(t,J＝6.4Hz,2H),3.92(s,3H),1.92(dtd,J＝13.7,7.4, 6.4Hz,2H),1.11(t,J＝7.4Hz,3H).

Example 22

Preparation of 3', 4', 5 '-trifluoro-2-methoxy- [1,1' -biphenyl ] -4-yl 2, 6-difluoro-4- (5-propyl-1, 3-dioxan-2-yl) benzoate (4)

(1)2- (3, 5-difluorophenyl) -5-propyl-1, 3-dioxane:

2-Propylpropane-1, 3-diol (5g, 42.31mmol), 3, 5-difluorobenzaldehyde (5.01g, 35.26mmol), 2, 6-di-tert-butyl-4-methylphenol (BHT) (116.5mg, 0.53mmol) and p-toluenesulfonic acid (p-TsOH) (3.34g, 19.39mmol) were refluxed in a toluene solution for 18 to 24 hours under a nitrogen atmosphere, cooled, washed with saturated brine, extracted with ethyl acetate, and the solvent was dried by spinning to give 9.86g of a colorless oily liquid, with a yield of 96.2%.

(2)2, 6-difluoro-4- (5-propyl-1, 3-dioxan-2-yl) benzoic acid:

adding (10g, 41.28mmol)2- (3, 5-difluorophenyl) -5-propyl-1, 3-dioxane (1) into a tetrahydrofuran solution in a nitrogen atmosphere, placing the tetrahydrofuran solution at-78 ℃, stirring for 15min, then slowly dropwise adding 20.64mL 2M butyl lithium n-hexane solution, completing dropwise adding within half an hour, continuing to react for 3h, then adding excessive dry ice or introducing CO in a nitrogen environment₂And (3) continuously reacting for 1h by bubbling gas, finally adjusting the pH to be approximately equal to 1 by using 1M hydrochloric acid solution, precipitating a large amount of white solid in the solution, filtering, washing with a large amount of water, and drying to obtain 10.68g of a product with the yield of 90.38%.

(3)3', 4', 5 '-trifluoro-2-methoxy- [1,1' -biphenyl ] -4-ol:

under a nitrogen atmosphere, (1g, 4.93mmol) 4-bromo-3-methoxyphenol, (1.04g, 5.91mmol) (3,4, 5-trifluorophenyl) boronic acid, (2.04g, 14.78mmol) potassium carbonate was put into a mixed solution of toluene/isopropanol/water in a volume ratio of 7/7/3, followed by addition of (57mg, 0.05mmol) tetrakistriphenylphosphine palladium (Pd (PPh)₃)₄) The reaction is performed for 14 to 20 hours under reflux by using the catalyst, after the reaction is finished, 200mL of water is added for washing, the solvent is dried after extraction by ethyl acetate, and the colorless crystals are obtained by chromatographic column purification, wherein the yield is 83.8 percent.

(4)3', 4', 5 '-trifluoro-2-methoxy- [1,1' -biphenyl ] -4-yl 2, 6-difluoro-4- (5-propyl-1, 3-dioxan-2-yl) benzoate:

under nitrogen atmosphere, 4-methoxy-2-propoxybenzoic acid (2g, 6.99mmol), compound (1) (1.69g, 6.65mmol), 1- (3-dimethylaminopropyl) -3-ethylcarbodiimide hydrochloride (1.9g, 9.98mmol), N, N-dimethylaminopyridine (85mg, 0.66mmol) were added to 50mL of anhydrous dichloromethane, the solution was stirred for 1h with ice bath, after which time it was gradually returned to room temperature and stirring was continued for 14-24h, and the reaction was monitored by TLC. After completion of the reaction, the reaction mixture was washed three times with saturated brine and extracted with ethyl acetate. The organic phase is dried over anhydrous magnesium sulfate, filtered, dried by spinning, and the crude product is usedPurification by column chromatography using dichloromethane/petroleum ether 2/2 as eluent gave 3.09g of a white solid in 88.9% yield.¹H NMR(400MHz,Chloroform-d)δ7.30(d,J＝8.3Hz,1H, ArH),7.22–7.10(m,4H,ArH),6.94(dd,J＝8.3,2.2Hz,1H,ArH),6.88(d,J＝2.1Hz,1H,ArH), 5.40(s,1H,CH),4.26(dd,J＝11.8,4.6Hz,2H,CH₂),3.85(s,3H),3.54(t,J＝11.5Hz,2H,CH₂), 2.23–2.02(m,1H,CH),1.53(s,1H,CH),1.39–1.29(m,3H,CH₃),1.14–1.09(m,2H,CH₂), 0.94(t,J＝7.4Hz,3H,CH₃).

In the DSC shown in FIG. 6, the temperature decrease curves of the liquid crystal molecules of example 22 have two protrusions at around 140 ℃ and around 60 ℃, which indicates that the molecules undergo two phase transitions during the temperature decrease process. When observed in well-aligned cells with a cross-polarization microscope (POM), the liquid crystal molecules exhibited isotropy at a high temperature of about 200 ℃. The field of view brightens from black with a gradual decrease in temperature, beginning to enter the nematic phase at 140 ℃ (as shown in figure 7). When the temperature is reduced to about 60 ℃, the refractive index can be obviously changed, the visual field is obviously lightened from a dark background under the POM, the micro orientation of the liquid crystal is changed, and the liquid crystal enters a polar nematic phase (as shown in figure 8). The I-1 mode of the I-2 mode liquid crystal molecular ratio can present a thermodynamically stable polar nematic liquid crystal structure in a wide temperature range.

By testing the dielectric coefficient of the liquid crystal molecules in the whole phase transition temperature range, the liquid crystal molecules are found to have 10 after entering into the polar phase⁴An extremely high dielectric strength of the order of magnitude (as shown in fig. 9), while the polar liquid crystal phase of the molecule has a very good SHG response in this temperature range (as shown in fig. 10).

Example 23

2,3', 4', 5', 6-pentafluoro- [1,1' -biphenyl]-4-yl 2, 6-difluoro-4- (5-propyl-1, 3-dioxan-2-yl) benzoate was prepared by methods analogous to those described in example 22.¹H NMR(400MHz,Chloroform-d)δ7.17–7.10(m, 2H),7.05(ddt,J＝8.5,7.4,1.2Hz,2H),6.99–6.89(m,2H),5.33(s,1H),4.28–4.13(m,2H), 3.57–3.39(m,2H),2.07(tddd,J＝11.4,9.2,6.9,4.6Hz,1H),1.35–1.22(m,2H),1.10–0.98(m, 2H),0.87(t,J＝7.3Hz,3H).

Example 24

Preparation of 3,4, 5-trifluorophenyl 4- (((2, 6-difluoro-4- (5-propyl-1, 3-dioxan-2-yl) phenyl) difluoromethoxy) benzoate (5)

(1)2- (3, 5-difluorophenyl) -5-methyl-1, 3-dioxane:

refluxing 2-methylpropane-1, 3-diol (5g, 55.48mmol), 3, 5-difluorobenzaldehyde (6.57g, 46.23mmol), 2, 6-di-tert-butyl-4-methylphenol (BHT) (122mg, 0.55mmol) and p-toluenesulfonic acid (p-TsOH) (5.2g, 30.5mmol) in a toluene solution for 18-24h under nitrogen atmosphere, cooling, washing with saturated brine, extracting with ethyl acetate, and spin-drying the solvent to obtain 9.06g of colorless oily liquid with a yield of 91.6%

(2)2- (4- (bromodifluoromethyl) -3, 5-difluorophenyl) -5-methyl-1, 3-dioxane:

adding 2- (3, 5-difluorophenyl) -5-methyl-1, 3-dioxane (8g, 37.35mmol) into 100mL of tetrahydrofuran solution in a nitrogen atmosphere, placing the mixture at-78 ℃, stirring for 15min, then slowly dropwise adding 93mL of 2M butyl lithium n-hexane solution, completing dropwise adding within half an hour, continuing to react for 3h, then slowly injecting 38mL of 2M difluorodibromomethane tetrahydrofuran solution in a nitrogen environment, continuing to react for 1h after completing injection, finally adjusting the pH to be approximately equal to 1 by using 1M hydrochloric acid solution, adding 200mL of water, extracting with ethyl acetate for three times, drying an organic layer with anhydrous magnesium sulfate, filtering, spin-drying filtrate, purifying a chromatographic column to obtain yellowish liquid, and obtaining 9.86g after vacuum drying, wherein the yield is 76.9%.

(3)4- ((2, 6-difluoro-4- (5-methyl-1, 3-dioxan-2-yl) phenyl) difluoromethoxy) benzaldehyde:

p-hydroxybenzaldehyde (0.748g, 6.12mmol), (2) (2g, 5.83mmol), potassium carbonate (2.42g, 17.49mmol) were added to 50mL DMF under nitrogen, heated under reflux overnight, washed with saturated aqueous sodium chloride solution 3 times, extracted with ethyl acetate, and after drying the solvent of the organic layer, the crude product was purified by column chromatography using petroleum ether/ethyl acetate 3/1 as eluent to give 2.01g of pale yellow solid in 89% yield.

(4) The specific synthesis of 4- ((2, 6-difluoro-4- (5-methyl-1, 3-dioxan-2-yl) phenyl) difluoromethoxy) benzoic acid was carried out in 98% yield as described in the previous examples.

(5) Specific synthetic procedures for 3,4, 5-trifluorophenyl 4- (((2, 6-difluoro-4- (5-propyl-1, 3-dioxan-2-yl) phenyl) difluoromethoxy) benzoate refer to the general esterification procedure described in the previous examples, with a yield of 86%.¹H NMR(400MHz, Chloroform-d)δ7.90(d,J＝8.6Hz,1H),7.07(d,J＝10.3Hz,2H),6.92–6.76(m,4H),5.30(s, 1H),4.17–4.02(m,2H),3.86(s,3H),3.53–3.25(m,2H),2.25–2.04(m,1H),0.71(d,J＝6.8 Hz,3H).

Example 25

4-Nitrophenyl 4- ((2, 6-difluoro-4- (5-methyl-1, 3-dioxan-2-yl) phenyl) difluoromethoxy) benzoate was prepared by methods analogous to those described for example 24.¹H NMR(400MHz,Chloroform-d)δ8.37–8.24(m, 2H),8.04(dd,J＝8.7,2.5Hz,1H),7.44–7.35(m,2H),7.14(d,J＝10.1Hz,2H),7.02–6.84(m, 2H),5.37(s,1H),4.19(dd,J＝11.8,4.7Hz,2H),3.94(s,3H),3.50(t,J＝11.5Hz,2H),2.21(td,J ＝11.2,6.6Hz,1H),0.79(d,J＝6.8Hz,3H)

The above embodiments are preferred embodiments of the present invention, but the present invention is not limited to the above embodiments, and any other changes, modifications, substitutions, combinations, and simplifications which do not depart from the spirit and principle of the present invention and are intended to be equivalent substitutions are included in the scope of the present invention.

Claims

1. A rod-shaped polar liquid crystal molecule is characterized in that the compound has a structure shown in a general formula I:

wherein m is 0 or 1;

R₁、R₂is a substituent; r₁、R₂Are selected from the group including but not limited to-OMe, -OEt, -OPr, -OC₄H₉、-OC₅H₁₁、-OC₆H₁₃、-OCH(CH₃)₂、-OCH₂CH₂OCH₃、-OCH₂CH₂CH₂OCH₃、-NO₂-H, -Me, -Et, -Pr, -Bu, or R₁、R₂Chiral groups including, but not limited to;

ring A, ring B and ring C are the same or different and each independently represents a 1, 4-phenylene group; wherein 0-4 hydrogen atoms in the 1, 4-phenylene group are replaced by F, CN, Cl, Br, NO₂、Me、C2H5、C(CH3)3、CH(CH3)2、OMe、OEt、OPr、COCH₃、COC₂H₅、COOCH₃、OCH₂OCH₃、O(CH₂)₂OCH₃、O(CH₂)₃OCH₃、CF₃、OCF₃And (4) substitution.

2. The polar liquid crystal molecule in rod form according to claim 1, wherein said compound of formula i has the following formula i-1 when m is 0, and has the following formula i-2 when m is 1:

3. The rod-like polar liquid crystal molecule according to claim 1, wherein said rod-like polar liquid crystal molecule is capable of exhibiting a thermodynamically stable polar nematic liquid crystal structure at a temperature range of 25 to 100 ℃; the rod-like polar liquid crystal molecules have an extremely high SHG signal at 30 times the intensity of quartz in the nematic phase.

4. A rod-like polar nematic liquid crystal comprising one or more rod-like polar liquid crystal molecules according to any one of claims 1 to 3, characterized by having a polar liquid crystal phase.

5. A method for producing a rod-like polar liquid crystal molecule according to any one of claims 1 to 3, comprising the steps of,

(A) synthesizing an S1 unit with a carboxyl functional group;

in the formula R₃、R₄、R₅、R₆、R₇Is a substituent, including but not limited to F, CN, Cl, Br, NO₂、Me、C₂H₅、C(CH₃)3、CH(CH₃)2、OMe、OEt、OPr、COCH₃、COC₂H₅、COOCH₃、OCH₂OCH₃、O(CH₂)₂OCH₃、O(CH₂)₃OCH₃、CF₃、OCF₃May be mono-or polysubstituted;

(a) synthesizing an S1 unit with a carboxyl functional group;

(1) synthesizing an S2 unit with a carboxyl end group;

(1) synthesis of end group of-CF₂S2 units of Br;

(2) the end group being-CF₂S2 unit of Br and M having phenolic hydroxyl group at terminal₂Etherifying to generate S2-M with terminal group containing aldehyde group₂Units, subsequent oxidation of the units to give S2-M terminated with a carboxyl group₂Unit, last and end group being phenolB of hydroxy groups₂Performing unit esterification reaction to obtain I-2 liquid crystal molecules; or end groups are-CF₂The S2 unit of Br directly reacts with M with a phenolic hydroxyl group at the end₂-L₂-B₂The units are subjected to etherification reaction to obtain I-2 liquid crystal molecules; said L₂Bridging linkages in this case include, but are not limited to, chemical linkages, azo double bonds, acetylenic linkages, and the like;

6. The method according to claim 5, characterized in that the method one step (A) and the method two step (a) are the preparation of the S1 unit with carboxyl function: the precursor alkoxybenzaldehyde or alkoxymethyl benzoate derivative is shown as follows:

the preparation of the unit is:

3) further, 1eq of S1 units containing methyl formate as an end group and 4-8eq of KOH in a solvent volume ratio of V_THF/V_MeOH/V_H2OHeating and refluxing the mixed solvent of 1/1/1 overnight, cooling to room temperature after the reaction is finished, pouring water with 2-4 times of the volume of the mixed solution, adding 1M hydrochloric acid solution, adjusting the pH to about 1, directly filtering if solid is precipitated to obtain a solid filtrate which is the obtained alkoxy benzoic acid derivative, extracting with ethyl acetate if no solid is precipitated, and then spin-drying the solvent to obtain the alkoxy benzoic acid derivative.

7. The method according to claim 5, wherein the terminal group in step (B) of the method is carboxyl group S1-M₁The synthesis method of the unit comprises the following steps:

2) Further, S1-M having 1eq as an aldehyde group as a terminal group₁Unit with 3.5eq NaClO₂And 4eq of NaH₂PO₄In the volume ratio of the solvent ofV_DMSO/V_H2OThe mixed solution is iced for 20min firstly and then stirred for 6-18h at room temperature, after the reaction is finished, water with 2-4 times of the volume of the mixed solution is poured, then solid sodium bicarbonate is added, the pH value is adjusted to 8, then 1M hydrochloric acid solution is added, the pH value is adjusted to about 4, extraction is carried out for three times by ethyl acetate, and the S1-M with the end group as carboxyl is obtained after the solvent is dried by spinning₁And (4) units.

8. The method according to claim 5, wherein the method comprises the step of (b) synthesizing M having a phenolic hydroxyl group at the end₁-L₁-B₁Unit and the method three-step (2) synthesis of M with phenolic hydroxyl at end group₂-L₂-B₂Methods for the units include but are not limited to the following categories,

9. The method according to claim 6, wherein the synthetic route of the S2 unit obtained in the third step (1) and the fourth step (1) is as follows:

1) refluxing 1.2eq of 2-propyl-1, 3-diol derivative, 1eq of 3, 5-difluorobenzaldehyde, 0.01-0.05eq of 2, 6-di-tert-butyl-4-methylphenol and 0.4-0.6eq of p-toluenesulfonic acid in a toluene solution for 18-24h to obtain the following unit D;

2) slowly dripping 4-6eq of n-hexane solution of butyl lithium into 1eq of D unit at-78 ℃ in a tetrahydrofuran solution in a nitrogen atmosphere, continuing to react for 3 hours after dripping is finished, and then adding excessive dry ice or introducing CO₂The gas is continuously reacted for 1h, and finally the pH value is adjusted to 1-4 to obtain an S2 unit with the following end group as carboxyl;

10. the process according to claim 6, wherein the etherification reaction in the fourth step (2) is: