Thiophene-based derivatives of benzo[2,1-d]thiophene-4,8-dione monomers, polymers, and methods of preparation and use

Abstract

The application belongs to the technical field of electrochromic materials, and discloses a thienyl derivative monomer of benzo[2,1-d]thiophene-4,8-dione, a polymer, and a preparation method and application thereof.The thienyl derivative monomer of benzo[2,1-d]thiophene-4,8-dione has a structure shown in formula (I) or formula (II). The polymer is obtained by electrochemical polymerization of the thienyl derivative monomer of benzo[2,1-d]thiophene-4,8-dione, and has the advantages of low driving voltage, high contrast, fast switching time, and good stability.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of electrochromic materials, and particularly relates to a thienyl derivative monomer of benzo[2,1-d]thiophene-4,8-dione, a polymer, and a preparation method and application thereof. BACKGROUND

[0002] Electrochromism (EC) refers to the reversible change of color, absorbance and transmittance of a material under the action of an applied voltage. The material with such a color change performance is called an electrochromic material. Compared with other electrochromic materials, electrochromic conjugated polymers have a wide absorption spectrum (from ultraviolet to visible light, and an absorption range in the infrared region), high optical contrast and fast switching speed, making them excellent candidates for green building intelligent windows, anti-glare mirrors, electronic displays, smart glasses and wearable clothing.

[0003] The electrochromism of the conjugated polymer is a redox process, which involves the removal or injection of electrons from the electrochromic conjugated polymer (p-doping or n-doping, respectively), leading to the formation of polarons and bipolarons, and causing structural changes in the polymer main chain.

[0004] Traditional polythiophenes usually have poor solubility, which is too tricky for further processing.

[0005] Existing electrochromic polymers have high driving voltage, low contrast, slow switching time, and poor stability.

[0006] Therefore, there is an urgent need to provide an electrochromic polymer with low driving voltage, high contrast, fast switching time and good stability. SUMMARY

[0007] The present application aims to at least solve one of the technical problems existing in the prior art. To this end, the present application proposes a thienyl derivative monomer of benzo[2,1-d]thiophene-4,8-dione, a polymer, and a preparation method and application thereof. The polymer is obtained by electrochemical polymerization of the thienyl derivative monomer of benzo[2,1-d]thiophene-4,8-dione, and the polymer has the advantages of low driving voltage, high contrast, fast switching time and good stability.

[0008] The first aspect of the present application provides a thienyl derivative monomer of benzo[2,1-d]thiophene-4,8-dione.

[0009] Specifically, the thienyl derivative monomer of benzo[2,1-d]thiophene-4,8-dione has the structure shown in formula (I) or formula (II):

[0010]

[0011] wherein R is selected from C1-C18 alkyl, aryl or substituted aryl;

[0012] Ar is selected from thiophene or 3,4-ethylenedioxythiophene.

[0013] Preferably, R is selected from C4-C15 alkyl, aryl and or substituted aryl.

[0014] Preferably, the substituted aryl refers to aryl substituted by halogen, nitro, amino, hydroxyl or carboxyl.

[0015] Preferably, Ar is 3,4-ethylenedioxythiophene.

[0016] The second aspect of the present application provides a method for preparing a thiophene derivative monomer of benzo[2,1-d]thiophene-4,8-dione.

[0017] Specifically, the method for preparing a thiophene derivative monomer of benzo[2,1-d]thiophene-4,8-dione comprises the following steps:

[0018] After mixing the acceptor with tributyl(2,3-dihydro[3,4-b][1,4]dioxin-5-yl)stannane under a protective gas atmosphere, a solvent and a catalyst are added to perform a Stille coupling reaction (i.e. Stille reaction) to obtain the thiophene derivative monomer of benzo[2,1-d]thiophene-4,8-dione.

[0019] The acceptor has the structural formula R is selected from C1-C18 alkyl, aryl or substituted aryl.

[0020] Preferably, the mass ratio of the acceptor to tributyl(2,3-dihydro[3,4-b][1,4]dioxin-5-yl)stannane is 0.1:(0.1-0.5), and further preferably 0.1:(0.14-0.4).

[0021] Preferably, the mass ratio of the acceptor to the catalyst is 0.1:(0.003-0.00625).

[0022] Preferably, the catalyst comprises Pd(PPh3)4 (i.e. palladium tetraphenylphosphine).

[0023] Preferably, the solvent comprises any one of N,N-dimethylformamide, benzene, acetone and ethanol.

[0024] Preferably, the protective gas atmosphere comprises nitrogen or a noble gas.

[0025] Preferably, the Stille coupling reaction is carried out at a temperature of 70-130℃ for 8-24 hours; further preferably, the Stille coupling reaction is carried out at a temperature of 90-120℃ for 12-24 hours.

[0026] Preferably, after the Stille coupling reaction, a washing step is further carried out; the washing reagent is preferably a sodium chloride solution; after the washing, a chromatographic separation and purification step is further carried out; the chromatographic separation and purification is preferably carried out by using a silica gel column.

[0027] The third aspect of the present application provides a polymer.

[0028] Specifically, the polymer has a general structure as shown in formula (III) or formula (IV)

[0029]

[0030] wherein R is selected from C1-C18 alkyl, aryl or substituted aryl;

[0031] Ar is selected from thiophene or 3,4-ethylenedioxythiophene;

[0032] n is greater than 0.

[0033] Preferably, n represents the average degree of polymerization, and n is 10-5000.

[0034] Further preferably, n is 10-3000.

[0035] Preferably, R is selected from C4-C15 alkyl, aryl or substituted aryl.

[0036] Preferably, the substituted aryl refers to aryl substituted by halogen, nitro, amino, hydroxyl or carboxyl.

[0037] Preferably, Ar is 3,4-ethylenedioxythiophene.

[0038] The above polymer is a polythiophene conductive polymer.

[0039] The fourth aspect of the present application provides a preparation method of the above polymer.

[0040] Specifically, the preparation method of the polymer comprises the following steps:

[0041] (1) dissolving a thiophene derivative monomer of benzodithiophene-4,8-dione and a supporting electrolyte in a solvent, and then adding into an electrolytic cell of a three-electrode system;

[0042] (2) The polymer is obtained by depositing through electrochemical polymerization reaction on the working electrode of a three-electrode system.

[0043] The polymer is a conjugated polymer electrochromic thin film material.

[0044] The electrochemical polymerization (referred to as "electropolymerization" hereinafter) is performed in a one-chamber three-electrode system.

[0045] Preferably, the constant potential method includes constant current method or cyclic voltammetry.

[0046] Preferably, the concentration of the thienyl derivative monomer of benzodithiophene-4,8-dione in the solvent is 1-12 mmol·L -1 , and more preferably 1-10 mmol·L -1 .

[0047] Preferably, the concentration of the supporting electrolyte is 0.05-0.3 mol·L -1 , and more preferably 0.06-0.1 mol·L -1 .

[0048] The process of the electrochemical polymerization reaction in step (2) is shown in the following reaction formula:

[0049]

[0050] Preferably, in the three-electrode system, Ag / AgCl electrode is used as the reference electrode, platinum wire is used as the counter electrode, and Pt / ITO conductive glass is used as the working electrode.

[0051] Preferably, the solvent is at least one of dichloromethane (CH2Cl2), trichloromethane (CHCl3) or acetonitrile (MeCN).

[0052] Preferably, the supporting electrolyte is at least one of tetrabutylammonium hexafluorophosphate, tetrabutylammonium tetrafluoroborate or lithium perchlorate.

[0053] The fifth aspect of the present application provides the use of the above polymer.

[0054] An electrochromic material comprises the above polymer.

[0055] Compared with the prior art, the present application has the following advantages:

[0056] (1) The polymer of the present application takes benzo[2,1-d:6,5-d']bithiophene-4,8-dione as an acceptor, thiophene as a π bridge, and 3,4-ethylenedioxythiophene (EDOT) as a donor to form a D-π-A-π-D structure. Benzo[2,1-d:6,5-d']bithiophene-4,8-dione has strong electron-withdrawing ability, which can enhance the intramolecular charge transfer of the D-A-D conjugated polymer. EDOT as a strong electron-donating group can reduce the starting oxidation potential of the monomer, reduce the optical band gap of the conjugated polymer, and improve the electrochromic performance.

[0057] (2) The polymer of the present application can observe stable reversible color changes from deep blue to blue-gray or blue-black to gray in appearance under the action of an applied voltage, and has good electrochromic performance such as high contrast, high coloring efficiency, and fast switching time. BRIEF DESCRIPTION OF DRAWINGS

[0058] Figure 1 The spectroelectrochemical diagram of the polymer of Example 1-2 in MeCN-Bu4NPF6 (0.1 mol / L) system;

[0059] Figure 2 The transmittance-time curve of the polymer of Example 1-2 in MeCN-Bu4NPF6 (0.1 mol / L) system;

[0060] Figure 3 The short-term memory effect of the polymer of Example 1-2 in MeCN-Bu4NPF6 (0.1 mol / L) system. DETAILED DESCRIPTION

[0061] In order to make the skilled in the art more clearly understand the technical solutions described in the present application, the following examples are listed for illustration. There are many data parameters of electrochromic materials in the laboratory stage to evaluate their performance, such as ultraviolet absorbance, transmittance, coloring efficiency, response time and open circuit memory effect, which are important parameters for evaluating whether the material is suitable for application in actual life.

[0062] Ultraviolet absorbance refers to the change in the performance of the polymer during the doping and dedoping process, which macroscopically manifests as a change in the absorbance in the ultraviolet-visible spectrum. Different applied voltages result in different degrees of polymer doping, and the film color and brightness also change accordingly. However, this performance can only qualitatively analyze the test material to have electrochromic performance, and cannot subjectively judge and quantitatively analyze the good or bad of the material electrochromic performance.

[0063] Transmittance refers to the change in optical performance of the material under the condition of applied voltage, which is quantitatively detected in the ultraviolet spectrometer to determine the specific change in the light transmittance of the material, represented by ΔT.

[0064] Coloration efficiency is the quantitative analysis of the amount of charge flowing through the polymer under the condition of applied voltage when the color change and transmittance change occur, that is, the energy loss of the material in application. The higher the coloration efficiency, the higher the energy utilization rate of the material, and the more energy saving. The coloration efficiency, that is, the CE value, is calculated by the ratio of the change in optical density (ΔOD) of the material during doping and dedoping and the amount of charge Qd flowing through the potential area of the material, and the calculation formula is as follows:

[0065] CE = ΔOD / Qd;

[0066] Wherein, ΔOD is the logarithm of the ratio of the transmittance of the material in different states at a specified wavelength, and the calculation formula is as follows:

[0067] ΔOD = log (Tox / Tred);

[0068] Tox and Tred are the transmittance values of the material in oxidized and reduced states, respectively.

[0069] Response time refers to the time required for the transmittance to change by 95% in the transmittance-time curve when the potential of the square wave voltage changes under the condition of applied voltage. The shorter the time, the faster the conversion time of the material, which is more in line with the requirements of practical application. However, this value is related to many factors, such as the conductivity of the substrate, the performance of the material itself, the conductivity of the system, the concentration of free ions in the system, and the movement speed of the ions, which have a great influence on the conversion time. In application, different working environments have different requirements for the conversion time.

[0070] Memory effect refers to the performance of the material that can maintain the degree of doping or dedoping state under the condition of open circuit applied voltage. After a completely doped voltage or a completely dedoped voltage is applied to the material, the time-transmittance curve of the material in the UV spectrometer is observed under the condition of open circuit. Under normal circumstances, since the doped ions in the material are not bound under the condition of open circuit, they will automatically diffuse into the solution in the system, resulting in changes in the color and transmittance of the material, thereby indicating the degree of change of the memory effect of the material.

[0071] The raw materials, reagents or devices used in the following examples, unless otherwise specified, can be obtained from conventional commercial channels or can be obtained by existing known methods.

[0072] The polymer is obtained by electropolymerization at different constant potentials, with 5,7-bis(5-(2,3-dihydrothiopheno[3,4-b][1,4]dioxin-5-yl)thiophen-2-yl)-2,3-bis(2-ethylhexyl)benzo[1,2-b:4,5-c']dithiophene-4,8-dione (ETTD) and 1,3-bis(5-(2,3-dihydrothiopheno[3,4-b][1,4]dioxin-5-yl)thiophen-2-yl)-5,7-bis(2-ethylhexyl)-4H,8H-benzo[1,2-c:4,5-c']dithiophene-4,8-dione (EBDD) as monomers, respectively. The benzo dithiophene-4,8-dione polymer film has good electrochromic performance, can realize reversible color switching and high contrast change under low driving voltage, and has great application prospect in the field of commercial electrochromic.

[0073] Example 1: Synthesis of monomer and polymer

[0074] (1) The synthesis process of the monomer (denoted as ETTD) is as follows:

[0075]

[0076] Under a nitrogen atmosphere, 5,7-bis(5-bromothiophen-2-yl)-2,3-bis(2-ethylhexyl)benzo[1,2-b:4,5-c']dithiophene-4,8-dione (0.1 g, 0.13 mmol), tributyl(2,3-dihydro[3,4-b][1,4]dioxin-5-yl)stannane (0.2 g), and a catalyst Pd(PPh3)4 (0.006 g, 0.0052 mmol) are placed in a 250 mL single-necked flask, TOL (methylbenzene, 32 mL) and DMF (N,N-dimethylacetamide, 8 mL, the volume ratio of TOL to DMF is 4:1) are added and stirred uniformly, heated to 120°C, and condensed to reflux for 48 hours. After the reaction system is cooled, the product is poured into saturated brine, extracted with dichloromethane 4 times, and then the organic layer is washed with water. After that, the solvent is removed by reduced pressure distillation and rotary evaporation, and the product is separated by a silica gel chromatographic column with dichloromethane and petroleum ether mixed at a volume ratio of 1:5 as the eluent. The black block product (monomer) is obtained by purification, with a yield of 45 mg and a yield of 38.9%.

[0077] The nuclear magnetic resonance hydrogen spectrum characterization result of the product (monomer) is as follows: 1H NMR (400 MHz, Chloroform-d) δ 7.79 (dd, J = 21.4, 4.1 Hz, 2H), 7.17 (t, J = 3.5 Hz, 2H), 6.24 (s, 2H), 4.35 - 4.19 (m, 8H), 2.86 (dq, J = 38.0, 6.6 Hz, 2H), 2.68 (d, J = 7.1 Hz, 2H), 1.59 (dd, J = 12.8, 6.1 Hz, 2H), 1.35 - 1.16 (m, 19H), 0.84 (ddd, J = 19.3, 12.2, 7.0 Hz, 13H).

[0078] (2) The synthesis process of the polymer P(ETTD) is as follows:

[0079]

[0080] The electrochemical polymerization was carried out in a three-electrode system, the working electrode was ITO conductive glass, the counter electrode was platinum sheet, and the reference electrode was Ag / AgCl electrode (Ag wire was electrolyzed on the surface to generate AgCl coating in 6 mol / L HCl solution with a constant potential of 1.5 V for 100 s).

[0081] The electrochemical polymerization was carried out by using constant potential method, with 10 mL dichloromethane as electrolyte, ETTD (0.01 mol / L) as monomer, and tetrabutylphosphonium hexafluorophosphate (0.1 mol / L) as supporting electrolyte, the polymerization potential was 0.85 V, the polymerization time was 40 s, and the polymer P(ETTD) film deposited on the surface of ITO conductive glass was washed with acetonitrile to remove the electrolyte solution and the generated oligomers in the polymer.

[0082] Study on electrochromic performance

[0083] (1) The prepared polymer film deposited on the surface of ITO conductive glass was placed in a three-electrode electrolytic cell, the electrolytic cell was 0.1 mol / L tetrabutylphosphonium hexafluorophosphate dichloromethane solution, the working electrode was ITO conductive glass with polymer film, the counter electrode was platinum sheet, and the reference electrode was Ag / AgCl electrode. The constant potential method was used, the voltage applied to the working electrode was adjusted by an electrochemical workstation, and the change trend of the absorption spectrum of the polymer film under different voltages was recorded by an ultraviolet visible spectrometer, so that the spectroelectrochemical spectrum of the polymer was obtained.

[0084] The spectroelectrochemical spectrum of the polymer P(ETTD) in MeCN-Bu4NPF6 (0.1 mol / L, i.e., tetrabutylphosphonium hexafluorophosphate acetonitrile solution) system was tested, as shown in Figure 1 ( Figure 1As shown in (a) of Fig. 1, and in combination with the naked eye observation of the color change of the polymer, it can be seen that as the potential increases, the color of the polymer changes from dark blue to blue-gray (dark blue in the fully dedoped state), which is due to the fact that the neutral state of the polymer has an absorption peak in the violet and red light regions, and the color of the neutral state of the polymer is dark blue; after the polymer is oxidized, the absorption peaks in the violet and red light regions gradually weaken and finally disappear, and the near-infrared region absorption peak appears and gradually rises, and the color also changes to blue-gray.

[0085] The UV-visible spectrophotometer is used to determine the transmittance of the polymer film at a specific wavelength under square wave potential in the doped state and the neutral state, so as to calculate the optical contrast, response time, etc.; the time-transmittance curve recorded by the UV-visible spectrophotometer and the time-current curve recorded by the electrochemical workstation can be used to calculate the coloring efficiency.

[0086] (2) The transmittance-time curves of the polymer P(ETTD) at 1100 nm, 900 nm, 678 nm and 420 nm were tested. The response time and coloring efficiency calculated from the time-transmittance curve are shown in Table 1.

[0087] As shown in Table 1, the polymer P(ETTD) has a fast response time and a general coloring efficiency.

[0088] Table 1: Electrochromic parameters of the polymer P(ETTD)

[0089]

[0090] The optical transmittance of the polymer P(ETTD) at 1100 nm, 900 nm, 678 nm and 420 nm was studied by chronabsorptometry, and during the experiment, the time interval of the potential step change was 5 s, as shown in Fig. 2. Figure 2 ( Figure 2 As shown in (a) of Fig. 1, and in combination with the naked eye observation of the color change of the polymer, it can be seen that as the potential increases, the color of the polymer changes from dark blue to blue-gray (dark blue in the fully dedoped state), which is due to the fact that the neutral state of the polymer has an absorption peak in the violet and red light regions, and the color of the neutral state of the polymer is dark blue; after the polymer is oxidized, the absorption peaks in the violet and red light regions gradually weaken and finally disappear, and the near-infrared region absorption peak appears and gradually rises, and the color also changes to blue-gray.

[0091] The short-term memory effect spectrum of the polymer is obtained by applying a 10 s voltage on the working electrode of the electrochemical workstation and applying a 2 s voltage every 100 s, and recording the change trend of the transmittance of the polymer at the maximum absorption peak in the oxidized state and the reduced state by the UV-visible spectrometer.

[0092] (3) The short-term memory effect of the polymer P(ETTD) was tested at a wavelength of 1100 nm, and a voltage of -0.3 V and 1.1 V was applied, respectively. The transmittance change of the polymer in the neutral state and the doped state was recorded, as shown in Table 1. Figure 3 ( Figure 3 As shown in (a) of Table 1, the transmittance change of the polymer in the neutral state was 1.5%, and the transmittance change of the polymer in the doped state was 5.2%, which indicated that the polymer had good short-term memory effect.

[0093] Example 2: Synthesis of monomer and polymer

[0094] (1) The synthesis process of the monomer (denoted as EBDD) is as follows:

[0095]

[0096] Under a nitrogen atmosphere, 1,3-bis(5-bromothiophene-2-yl)-5,7-bis(2-ethylhexyl)-4H,8H-benzo[1,2-c:4,5-c']dithiophene-4,8-dione (0.08 g, 0.105 mmol), tributyl(2,3-dihydro[3,4-b][1,4]dioxin-5-yl)stannane (0.114 g, excess), and catalyst Pd(PPh3)4 (0.005 g, 0.0042 mmol) were placed in a 250 mL single-necked flask, TOL (32 mL) and DMF (8 mL) were added and stirred uniformly, heated to 120°C and condensed to reflux for 48 hours. After the reaction system was cooled, the obtained product was poured into saturated brine, extracted with dichloromethane 5 times, and then the organic layer was washed with water. After that, the solvent was removed by reduced pressure distillation and rotary evaporation, and the product was separated by silica gel column chromatography, with dichloromethane and petroleum ether mixed at a volume ratio of 1:3 as the eluent. A brown-red block of product (monomer) was obtained by purification, with a yield of 37.9%.

[0097] The results of the nuclear magnetic resonance hydrogen spectrum characterization of the product (monomer) are as follows: 1 H NMR (400 MHz, Chloroform-d) δ 7.71 (d, J = 4.1 Hz, 2H), 7.16 (s, 2H), 6.23 (s, 2H), 4.26 (d, J = 46.6 Hz, 8H), 3.30 (dd, J = 15.5, 6.8 Hz, 2H), 3.22 (d, J = 6.5 Hz, 2H), 1.71 (s, 2H), 1.36 - 1.14 (m, 19H), 0.93 - 0.73 (m, 13H).

[0098] (2) The synthesis process of the polymer P(EBDD) is as follows:

[0099]

[0100] Electrochemical polymerization was carried out in a three-electrode system, the working electrode was ITO conductive glass, the counter electrode was platinum plate, and the reference electrode was Ag / AgCl electrode (Ag wire was electrolyzed on the surface to generate AgCl coating in 6 mol / L HCl solution with constant potential 1.5 V for 100 s).

[0101] The polymerization was carried out by constant potential method with 10 mL dichloromethane as electrolyte, monomer (EBDD) (0.01 mol / L) as polymerization monomer, and tetrabutylphosphonium hexafluorophosphate (0.1 mol / L) as supporting electrolyte, the polymerization potential was 0.95 V, and the polymerization time was 50 s. The polymer film obtained by electrodeposition was washed with acetonitrile to remove the electrolyte solution and the generated oligomers in the polymer.

[0102] Electrochromic performance research

[0103] (1) The spectroelectrochemical diagram of the polymer P(EBDD) in the MeCN-Bu4NPF6(0.1 mol / L) system was tested, as shown in (b) of FIG. 1, and the color change of the polymer was observed by naked eye. It can be seen that, with the increase of the potential, the color of the polymer changes from blue-black to gray (blue-black in the completely dedoped state), which is because the neutral state of the polymer has an absorption peak in the purple light region and the red light region, and the color of the neutral state of the polymer is blue-black; after the polymer is oxidized, the absorption peaks in the purple light region and the red light region gradually weaken and finally completely disappear, the absorption peak in the near-infrared region appears and gradually rises, and the color also changes to gray. Figure 1

[0104] (2) The transmittance-time curves of the polymer P(EBDD) at 1100 nm, 830 nm, 630 nm and 430 nm were tested. The response time and coloring efficiency calculated from the time-transmittance curve are shown in Table 2. It can be seen from Table 2 that the optical contrast of the polymer P(EBDD) is high, and the coloring efficiency is high.

[0105] Table 2: Electrochromic parameters of the polymer P(EBDD)

[0106]

[0107] The optical transmittance of the polymer P(EBDD) at 1100 nm, 830 nm, 630 nm and 430 nm was studied by chronosorption method, and the time interval of the potential step change was 5 s, as shown in FIG. 2. Figure 2 ​The optical contrast and optical stability of the polymer were good at four wavelengths, and the optical contrast reached 50.93% at 830 nm; in addition, the optical transmittance had a great influence on the color change of the polymer, and the polymer material could change from blue-black in the fully dedoped state to gray in the doped state.

[0108] (3) The short-term memory effect of the polymer P(EBDD) was tested at a wavelength of 830 nm, and the transmittance change of the polymer in the neutral state and the doped state was recorded by applying -0.3 V and 1.1 V voltages, respectively, as shown in Fig. 3. Figure 3 As shown in Fig. 3(b), it was found that the transmittance change of the polymer in the neutral state was 4.3%, and the transmittance change in the doped state was 3.7%, which indicated that the polymer had good short-term memory effect.

Claims

1. A thienyl derivative monomer of benzo[2,1- d]thiophene-4,8-dione, characterized in that, It has the structure shown in formula (I) or formula (II): Formula (I), Formula (II); Wherein, R is selected from C1-C18 alkyl; Ar is selected from 3,4-ethylenedioxythiophene.

2. The thienyl derivative monomer of benzo-dithiophene-4,8-dione according to claim 1, characterized by The R is selected from C4-C15 alkyl.

3. The method of producing a thienyl derivative monomer of benzo-dithiophene-4,8-dione according to claim 1 or 2, characterized by, The method comprises the following steps: After the acceptor is mixed with tributyl (2,3-dihydro[3,4-b][1,4] dioxin-5-yl) stannane under a protective gas atmosphere, a solvent and a catalyst are added to carry out a Stille coupling reaction to obtain the thiophene derivative monomer of the benzo-dithiophene-4,8-dione; The structural formula of the acceptor is or R is selected from C1-C18 alkyl.

4. The production method according to claim 3, characterized by, The mass ratio of the acceptor to tributyl (2,3-dihydro[3,4-b][1,4] dioxin-5-yl) stannane is 0.1: (0.1-0.5); and / or, the mass ratio of the acceptor to the catalyst is 0.1: (0.003-0.00625); and / or, the temperature of the Stille coupling reaction is 70-130℃; and / or, the time of the Stille coupling reaction is 8-24 hours.

5. The general structure of the polymer is shown in formula (III) or formula (IV): Formula (III), Formula (IV), wherein R is selected from C1-C18 alkyl; Ar is selected from 3,4-ethylenedioxythiophene; n is greater than 0.

6. The polymer of claim 5, wherein, The R is selected from C4-C15 alkyl.

7. The process for the preparation of a polymer according to claim 5 or 6, characterized in that, The method comprises the following steps: (1) Dissolving the thiophene derivative monomer of the benzo-dithiophene-4,8-dione and a supporting electrolyte in a solvent, and then adding into an electrolytic cell of a three-electrode system; (2) Depositing the polymer by an electrochemical polymerization reaction on a working electrode of the three-electrode system by using a constant potential method.

8. The preparation method according to claim 7, characterized in that The constant potential method comprises a constant current method or a cyclic voltammetry method; and / or, the concentration of the thiophene derivative monomer of the benzo[2,1-d]thiophene-4,8-dione in the solvent is 1-12 mmol·L -1 ; and / or, the concentration of the supporting electrolyte is 0.05-0.3 mol·L -1 ; and / or, the supporting electrolyte is at least one of tetrabutylammonium hexafluorophosphate, tetrabutylammonium tetrafluoroborate or lithium perchlorate.

9. An electrochromic material characterized in that, The polymer of claim 5 or 6.

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