Electrochromic material based on dithiophene, preparation method thereof and electrochromic film

Abstract

The present invention provides an electrochromic material based on dithiophene, a preparation method thereof and an electrochromic film, and relates to the technical field of organic optoelectronic materials. The present invention uses dithiophene as a matrix, and a long alkoxy chain containing a triple bond is externally connected to the side chain to synthesize an electrochromic material DTFDT-yne based on dithiophene. Benefiting from the advantages of low redox potential caused by dithiophene enhancing the conjugation of the molecule, and long alkoxy chains making the polymer stacking more loose and providing more ion migration channels, the present invention uses DTFDT-yne as a monomer and prepares a new electrochromic film by cyclic voltammetry. The new electrochromic film has electrochromic characteristics such as high contrast and fast response speed. In the wavelength range of 720nm, there is no obvious decrease in contrast after 50 cycles, and the cycle performance is excellent. It is a new high-performance electrochromic material with great potential.

Description

Technical Field

[0001] The invention relates to the technical field of organic photoelectric materials, and in particular to an electrochromic material based on dithiophene, a preparation method thereof and an electrochromic film. Background Art

[0002] As an important component of electrochromic materials, organic conductive polymers are considered to be the most promising electrochromic materials of the next generation. However, researchers have found that the long response time limits its further development and application. Professor Reynold increased the length of the alkoxy bridge bond in the structure of poly(3,4-ethylenedioxythiophene) (PEDOT) to make the stacking looser, providing more migration channels, and significantly shortening the electrochromic response time; Koyuncu's recent research also confirmed that the loose stacking obtained by introducing long alkyl side chains into pyrrole-thiophene-carbazole conductive polymers is conducive to the migration process of balanced ions, thereby shortening the response time. As a classic color-changing group, dithiophene is favored by scholars because its introduction into the molecule will greatly enhance the molecular conjugation, thereby giving the molecule the advantage of a lower redox potential.

[0003] However, to date, no electrochromic material based on dithiophene that can respond quickly has been obtained in the world. Therefore, how to provide an electrochromic material based on dithiophene with fast response speed and good cycle performance is a technical problem that needs to be solved urgently by those skilled in the art. Summary of the invention

[0004] The object of the present invention is to provide an electrochromic material based on dithiophene and a preparation method thereof and an electrochromic film, so as to fill the gap in the prior art.

[0005] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0006] The present invention provides an electrochromic material based on dithiophene, which has the following structure:

[0007]

[0008] The present invention also provides a method for preparing an electrochromic material based on dithiophene, comprising the following steps:

[0009] 1) iodination reaction of 1,4-dimethoxybenzene to generate 2,5-diiodo-1,4-dimethoxybenzene;

[0010] 2) causing 2,5-diiodo-1,4-dimethoxybenzene to undergo a reduction reaction to generate 2,5-diiodo-1,4-diphenol;

[0011] 3) reacting 6-chlorohexyne with triisopropylsilyl chloride to generate 6-chlorohexyne-triisopropylsilane;

[0012] 4) reacting 2,5-diiodo-1,4-diphenol with 6-chlorohexynyl-triisopropylsilane to generate 1,4-diiodo-2,5-bis-(6-triisopropylsilylhexynyl)-benzene;

[0013] 5) 1,4-diiodo-2,5-bis-(6-triisopropylsilylhexynyl)-benzene reacts with tin-bis-thiophene to generate 1,4-bis-thiophene-2,5-bis-(6-triisopropylsilylhexynyl)-benzene;

[0014] 6) 1,4-dithiophene-2,5-bis-(6-triisopropylsilylhexynyl)-benzene reacts with tetrabutylammonium fluoride to generate the dithiophene-based electrochromic material DTFDT-yne;

[0015] There is no restriction on the order of step 2) and step 3).

[0016] Preferably, the iodination reaction in step 1) is carried out as follows: potassium iodide, iodine, glacial acetic acid, concentrated sulfuric acid, water and 1,4-dimethoxybenzene are mixed, heated to reflux, and then naturally cooled to room temperature;

[0017] The molar ratio of potassium iodide, iodine and 1,4-dimethoxybenzene is 0.4-0.6:0.8-1.1:1; the addition ratio of glacial acetic acid, concentrated sulfuric acid, water and 1,4-dimethoxybenzene is 20-30mL:0.25-0.3mL:0.65-1mL:1g;

[0018] The heating reflux temperature is 110-125° C. and the time is 6-10 hours.

[0019] Preferably, the reduction reaction in step 2) is carried out as follows: dissolving 2,5-diiodo-1,4-dimethoxybenzene in dichloromethane, adding dropwise a dichloromethane solution of boron tribromide, and then naturally warming to room temperature to react;

[0020] The addition ratio of dichloromethane, dichloromethane solution of boron tribromide and 2,5-diiodo-1,4-dimethoxybenzene is 20-30 mL: 4.9-5.2 mL: 1 g; the system temperature is set to -75°C to -80°C when the reactants are mixed; the concentration of the dichloromethane solution of boron tribromide is 0.8 to 1.2 mol / L;

[0021] The reaction is carried out under stirring conditions, and the stirring time is 40 to 60 hours;

[0022] The reaction is carried out under a protective atmosphere, which includes a nitrogen atmosphere or an argon atmosphere.

[0023] Preferably, the reaction steps in step 3) are as follows: 6-chlorohexyne, tetrahydrofuran and an n-heptane solution of lithium diisopropylamide are mixed, the temperature is naturally raised under stirring conditions, stirring is continued, then the system temperature is lowered and triisopropylsilicon chloride is added dropwise, and the temperature is naturally raised to room temperature for reaction;

[0024] The addition ratio of tetrahydrofuran, heptane solution of lithium diisopropylamine and 6-chlorohexyne is 20-25 mL: 4-4.3 mL: 1 g; the molar ratio of triisopropylsilyl chloride to 6-chlorohexyne is 1:10-11; the concentration of the heptane solution of lithium diisopropylamine is 1.5-2.5 mol / L;

[0025] The temperature of 6-chlorohexyne, tetrahydrofuran and n-heptane solution of lithium diisopropylamine when mixed is -75°C to -80°C; the stirring time of natural heating under stirring condition is 10 to 20 minutes; the temperature of natural heating is -12°C to -8°C; the stirring time is continued for 25 to 35 minutes; the temperature of lowering the system temperature is -75°C to -80°C;

[0026] The reaction is carried out under stirring conditions for 20 to 30 hours; the reaction is carried out under a protective atmosphere, which includes a nitrogen atmosphere or an argon atmosphere.

[0027] Preferably, the reaction steps in step 4) are as follows: 2,5-diiodo-1,4-diphenol, potassium carbonate, 6-chlorohexyne-triisopropylsilane and N,N-dimethylformamide are mixed and reacted;

[0028] The molar ratio of potassium carbonate, 6-chlorohexyne-triisopropylsilane and 2,5-diiodo-1,4-diphenol is 9-11:4-5:1; the addition ratio of N,N-dimethylformamide and 2,5-diiodo-1,4-diphenol is 60-80mL:1g;

[0029] The reaction temperature is 110-130°C and the reaction time is 68-75h;

[0030] The reaction is carried out under a protective atmosphere, which includes a nitrogen atmosphere or an argon atmosphere.

[0031] Preferably, the reaction steps in step 5) are as follows: 1,4-diiodo-2,5-bis-(6-triisopropylsilylhexynyl)-benzene, tin-bis-dithiophene, Pd(PPh3)4 and dioxane are mixed and reacted;

[0032] The molar ratio of tin-bis-dithiophene to 1,4-diiodo-2,5-bis-(6-triisopropylsilylhexynyl)-benzene is 3-5:1; the addition ratio of dioxane, Pd(PPh3)4 and 1,4-diiodo-2,5-bis-(6-triisopropylsilylhexynyl)-benzene is 30-40mL:15-25mg:1g;

[0033] The reaction temperature is 120-140°C and the reaction time is 15-20h;

[0034] The reaction is carried out under a protective atmosphere, which includes a nitrogen atmosphere or an argon atmosphere.

[0035] Preferably, the steps of the reaction in step 6) are as follows: The steps of the reaction in step 6) are as follows: 1,4-dithiophene-2,5-bis-(6-triisopropylsilylhexynyl)-benzene and tetrahydrofuran are mixed, and then a tetrahydrofuran solution of tetrabutylammonium fluoride is added dropwise to react;

[0036] The addition ratio of tetrahydrofuran, tetrabutylammonium fluoride tetrahydrofuran solution and 1,4-dithiophene-2,5-bis-(6-triisopropylsilylhexynyl)-benzene is 30-35 mL: 0.75-0.85 mL: 1 g; the concentration of tetrabutylammonium fluoride tetrahydrofuran solution is 0.8-1.2 mol / L;

[0037] The reaction is carried out under stirring conditions, the stirring time is 10 to 14 hours, and the reaction temperature is room temperature.

[0038] Another object of the present invention is to provide a method for preparing an electrochromic film using the electrochromic material based on dithiophene, comprising the following steps:

[0039] The electrochromic material DTFDT-yne based on dithiophene was dissolved in a mixed solvent of dichloromethane and acetonitrile, tetrabutylammonium hexafluorophosphate was added, and electrochemical polymerization was performed to form a film by cyclic voltammetry.

[0040] Among them, the scanning speed is 90-110mV / s, the voltage range is 0-1.2V, and the number of cycles is 8-12;

[0041] The addition ratio of dichloromethane, acetonitrile and DTFDT-yne is 500-600 mL: 300-400 mL: 1 g; the concentration of tetrabutylammonium hexafluorophosphate in the mixed solvent is 0.08-0.15 mol / L.

[0042] Another object of the present invention is to provide an electrochromic film based on dithiophene prepared by the method.

[0043] The present invention has at least the following beneficial effects:

[0044] The present invention uses dithiophene as a matrix, and a long alkoxy chain containing a triple bond is connected to the side chain to synthesize an electrochromic material DTFDT-yne based on dithiophene. Benefiting from the advantages of low redox potential caused by the enhanced conjugation of the molecule by dithiophene, and the long alkoxy chain makes the polymer stacking more loose and provides more ion migration channels, the present invention uses DTFDT-yne as a monomer and prepares a new electrochromic film by cyclic voltammetry. The new electrochromic film has electrochromic characteristics such as high contrast and fast response speed. The prepared film can change color at a voltage of 0-1.2V, and the optical contrast in the wavelength range of 720nm is 38%, the coloring time is 1.72s, and the fading time is 1.37s; the optical contrast in the wavelength range of 1100nm is about 50%, the coloring time is 2.29s, and the fading time is 0.63s. After 50 cycles, the contrast does not decrease significantly. It is a new high-performance electrochromic material with great potential. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 This is the synthesis route for preparing the electrochromic material DTFDT-yne based on bithiophene in Example 1 of the present invention.

[0046] Figure 2 It is a cyclic voltammetry polymerization curve of the electrochromic film prepared in Example 1 of the present invention.

[0047] Figure 3 It is a graph of the ultraviolet-visible absorption spectra of the electrochromic film prepared in Example 1 of the present invention at different voltages.

[0048] Figure 4 It is the response time of the electrochromic film prepared in Example 1 of the present invention at 720nm.

[0049] Figure 5 It is the response time of the electrochromic film prepared in Example 1 of the present invention at 1100nm.

[0050] Figure 6 This is a kinetic test of the electrochromic film prepared in Example 1 of the present invention at 720 nm. DETAILED DESCRIPTION

[0051] The present invention provides an electrochromic material based on dithiophene, which has the following structure:

[0052]

[0053] The present invention also provides a method for preparing an electrochromic material based on dithiophene, comprising the following steps:

[0054] 1) iodination reaction of 1,4-dimethoxybenzene to generate 2,5-diiodo-1,4-dimethoxybenzene;

[0055] 2) causing 2,5-diiodo-1,4-dimethoxybenzene to undergo a reduction reaction to generate 2,5-diiodo-1,4-diphenol;

[0056] 3) reacting 6-chlorohexyne with triisopropylsilyl chloride to generate 6-chlorohexyne-triisopropylsilane;

[0057] 4) reacting 2,5-diiodo-1,4-diphenol with 6-chlorohexynyl-triisopropylsilane to generate 1,4-diiodo-2,5-bis-(6-triisopropylsilylhexynyl)-benzene;

[0058] 5) 1,4-diiodo-2,5-bis-(6-triisopropylsilylhexynyl)-benzene reacts with tin-bis-thiophene to generate 1,4-bis-thiophene-2,5-bis-(6-triisopropylsilylhexynyl)-benzene;

[0059] 6) 1,4-dithiophene-2,5-bis-(6-triisopropylsilylhexynyl)-benzene reacts with tetrabutylammonium fluoride to generate the dithiophene-based electrochromic material DTFDT-yne;

[0060] There is no restriction on the order of step 2) and step 3).

[0061] In the present invention, the steps of the iodination reaction in step 1) are as follows: potassium iodide, iodine, glacial acetic acid, concentrated sulfuric acid, water and 1,4-dimethoxybenzene are mixed, heated to reflux, and then naturally cooled to room temperature;

[0062] The molar ratio of potassium iodide, iodine and 1,4-dimethoxybenzene is preferably 0.4-0.6:0.8-1.1:1, more preferably 0.45-0.55:0.9-1.1:1, and more preferably 0.5:1:1; the addition ratio of glacial acetic acid, concentrated sulfuric acid, water and 1,4-dimethoxybenzene is preferably 20-30 mL:0.25-0.3 mL:0.65-1 mL:1 g, more preferably 22-28 mL:0.26-0.29 mL:0.7-0.95 mL:1 g, and more preferably 24-26 mL:0.27-0.28 mL:0.8-0.9 mL:1 g;

[0063] The heating reflux temperature is preferably 110-125° C., more preferably 112-122° C., more preferably 115-120° C.; the heating reflux time is preferably 6-10 h, more preferably 7-9 h, more preferably 8 h.

[0064] In the present invention, after the reaction in step 1) is completed, a post-treatment step is further included: deionized water is added to the reaction system, and the resulting mixture is cooled in an ice water bath to obtain a black crystalline precipitate. The precipitate is collected by suction filtration, rinsed with deionized water and dried. The black crystals are redissolved in chloroform, and activated carbon is added thereto for reflux. The mixture is filtered while hot, and the filtrate is cooled to obtain a light brown needle-shaped crystal product, which is suction filtered, filtered and dried, and recrystallized in ethanol to obtain the target product 2,5-diiodo-1,4-dimethoxybenzene;

[0065] The structural formula of 2,5-diiodo-1,4-dimethoxybenzene is as follows

[0066]

[0067] In the present invention, the reduction reaction in step 2) is as follows: dissolving 2,5-diiodo-1,4-dimethoxybenzene in dichloromethane, adding a dichloromethane solution of boron tribromide dropwise, and then naturally warming to room temperature to react;

[0068] The addition ratio of dichloromethane, dichloromethane solution of boron tribromide and 2,5-diiodo-1,4-dimethoxybenzene is preferably 20-30 mL: 4.9-5.2 mL: 1 g, more preferably 22-28 mL: 5-5.1 mL: 1 g, and more preferably 24-26 mL: 5 mL: 1 g; preferably, the system temperature is set to -75°C to -80°C when the reactants are mixed, more preferably -76°C to -79°C, and more preferably -78°C; the concentration of the dichloromethane solution of boron tribromide is preferably 0.8-1.2 mol / L, more preferably 0.9-1.1 mol / L, and more preferably 1 mol / L;

[0069] The reaction is carried out under stirring conditions, and the stirring time is preferably 40 to 60 hours, more preferably 45 to 55 hours, and more preferably 48 to 52 hours;

[0070] The reaction is carried out under a protective atmosphere, which includes a nitrogen atmosphere or an argon atmosphere.

[0071] In the present invention, after the reaction in step 2) is completed, a post-treatment step is also included: after the reaction is completed, deionized water is added for hydrolysis, and the aqueous phase is extracted with ether after separation. The organic phases are combined, extracted with NaOH solution, and the extract is neutralized with dilute hydrochloric acid in an ice water bath. A pink precipitate appears in the solution, which is filtered and the filter cake is dried. The target product 2,5-diiodo-1,4-diphenol is obtained by recrystallization in benzene;

[0072] The concentration of the NaOH solution is preferably 1.5 to 2.5 mol / L, more preferably 1.6 to 2.4 mol / L, and more preferably 1.8 to 2.2 mol / L; the concentration of the dilute hydrochloric acid is preferably 0.1 mol / L;

[0073] The structure of 2,5-diiodo-1,4-diphenol is as follows:

[0074]

[0075] In the present invention, the reaction steps in step 3) are as follows: 6-chlorohexyne, tetrahydrofuran and an n-heptane solution of lithium diisopropylamide are mixed, the temperature is naturally raised under stirring, stirring is continued, then the system temperature is lowered and triisopropylsilicon chloride is added dropwise, and the temperature is naturally raised to room temperature for reaction;

[0076] The addition ratio of tetrahydrofuran, the heptane solution of lithium diisopropylamine and 6-chlorohexyne is preferably 20-25 mL: 4-4.3 mL: 1 g, more preferably 21-24 mL: 4.1-4.2 mL: 1 g, and more preferably 22-23 mL: 4.1 mL: 1 g; the molar ratio of triisopropylsilyl chloride to 6-chlorohexyne is preferably 1: 10-11, and more preferably 1: 10.5; the concentration of the heptane solution of lithium diisopropylamine is preferably 1.5-2.5 mol / L, and more preferably 1.6-2.4 mol / L, and more preferably 1.8-2.2 mol / L;

[0077] The temperature when 6-chlorohexyne, tetrahydrofuran and n-heptane solution of lithium diisopropylamine are mixed is preferably -75°C to -80°C, more preferably -76°C to -79°C, and more preferably -78°C; the stirring time of natural temperature rise under stirring conditions is preferably 10 to 20 minutes, more preferably 12 to 18 minutes, and more preferably 14 to 16 minutes; the temperature of natural temperature rise is preferably -12°C to -8°C, more preferably -11°C to -9°C, and more preferably 10°C; the time of continued stirring is preferably 25 to 35 minutes, more preferably 26 to 34 minutes, and more preferably 28 to 32 minutes; the temperature for reducing the temperature of the system is preferably -75°C to -80°C, more preferably -76°C to -79°C, and more preferably -78°C;

[0078] The reaction is carried out under stirring conditions, and the stirring time is preferably 20 to 30 hours, more preferably 22 to 28 hours, and more preferably 24 to 26 hours; the reaction is carried out under a protective atmosphere, and the protective atmosphere includes a nitrogen atmosphere or an argon atmosphere.

[0079] In the present invention, after the reaction in step 3) is completed, a post-treatment step is further included: the mixed solution is slowly poured into deionized water and extracted with chloroform. The organic phase is then extracted with HCl solution, dried with anhydrous MgSO4, and then the solvent is removed by rotary evaporation. The residual oil obtained after evaporation of the solvent is distilled to obtain the target product 6-chlorohexyne-triisopropylsilane;

[0080] The concentration of the HCl solution is preferably 0.4-0.6 mol / L, more preferably 0.5 mol / L;

[0081] The structure of 6-chlorohexyne-triisopropylsilane is as follows:

[0082]

[0083] In the present invention, the steps of the reaction in step 4) are as follows: 2,5-diiodo-1,4-diphenol, potassium carbonate, 6-chlorohexyne-triisopropylsilane and N,N-dimethylformamide are mixed and reacted;

[0084] The molar ratio of potassium carbonate, 6-chlorohexyne-triisopropylsilane and 2,5-diiodo-1,4-diphenol is preferably 9-11:4-5:1, and more preferably 10:4.5:1; the addition ratio of N,N-dimethylformamide and 2,5-diiodo-1,4-diphenol is preferably 60-80 mL:1 g, and more preferably 65-75 mL:1 g, and more preferably 68-72 mL:1 g;

[0085] The reaction temperature is preferably 110-130°C, more preferably 115-125°C, and more preferably 118-122°C; the reaction time is preferably 68-75h, more preferably 70-74h, and more preferably 72h;

[0086] The reaction is carried out under a protective atmosphere, which includes a nitrogen atmosphere or an argon atmosphere.

[0087] In the present invention, after the reaction in step 4) is completed, a post-treatment step is further included: the reaction system is diluted with dichloromethane, and extracted with HCl solution, deionized water and saturated sodium chloride solution in sequence. The solvent is removed by rotary evaporation, and the crude product is purified by column chromatography to obtain the target product 1,4-diiodo-2,5-bis-(6-triisopropylsilylhexynyl)-benzene;

[0088] The concentration of the HCl solution is preferably 0.8 to 1.2 mol / L, more preferably 0.9 to 1.1 mol / L, and more preferably 1 mol / L; the mobile phase used in the column chromatography is preferably n-hexane and dichloromethane, and the volume ratio of n-hexane to dichloromethane is preferably 3 to 5:1, and more preferably 4:1;

[0089] The structure of 1,4-diiodo-2,5-bis-(6-triisopropylsilylhexynyl)-benzene is as follows:

[0090]

[0091] In the present invention, the steps of the reaction in step 5) are as follows: 1,4-diiodo-2,5-bis-(6-triisopropylsilylhexynyl)-benzene, tin-bis-dithiophene, Pd(PPh3)4 and dioxane are mixed and reacted;

[0092] The molar ratio of tin-bis-dithiophene to 1,4-diiodo-2,5-bis-(6-triisopropylsilylhexynyl)-benzene is preferably 3-5:1, and more preferably 4:1; the addition ratio of dioxane, Pd(PPh3)4, and 1,4-diiodo-2,5-bis-(6-triisopropylsilylhexynyl)-benzene is preferably 30-40 mL: 15-25 mg: 1 g, and more preferably 32-38 mL: 16-24 mg: 1 g, and more preferably 34-36 mL: 18-22 mg: 1 g;

[0093] The reaction temperature is preferably 120-140°C, more preferably 125-135°C, and more preferably 128-132°C; the reaction time is preferably 15-20h, more preferably 16-19h, and more preferably 17-18h;

[0094] The reaction is carried out under a protective atmosphere, which includes a nitrogen atmosphere or an argon atmosphere.

[0095] In the present invention, after the reaction in step 5) is completed, a post-treatment step is further included: after the reaction is completed, deionized water is added to the reaction system and extracted with dichloromethane, and purified by column chromatography to obtain the target product;

[0096] The mobile phase used in column chromatography is preferably dichloromethane and n-hexane, and the volume ratio of dichloromethane to n-hexane is preferably 1:1.5 to 2.5, and more preferably 1:2;

[0097] The structure of 1,4-dithiophene-2,5-bis-(6-triisopropylsilylhexynyl)-benzene is as follows:

[0098]

[0099] In the present invention, the steps of the reaction in step 6) are as follows: The steps of the reaction in step 6) are as follows: 1,4-dithiophene-2,5-bis-(6-triisopropylsilylhexynyl)-benzene and tetrahydrofuran are mixed, and then a tetrahydrofuran solution of tetrabutylammonium fluoride is added dropwise to react;

[0100] The addition ratio of tetrahydrofuran, tetrabutylammonium fluoride tetrahydrofuran solution and 1,4-dithiophene-2,5-bis-(6-triisopropylsilylhexynyl)-benzene is preferably 30-35 mL: 0.75-0.85 mL: 1 g, more preferably 31-34 mL: 0.76-0.84 mL: 1 g, and more preferably 32-33 mL: 0.78-0.82 mL: 1 g; the concentration of tetrabutylammonium fluoride tetrahydrofuran solution is 0.8-1.2 mol / L, more preferably 0.9-1.1 mol / L, and more preferably 1 mol / L;

[0101] The reaction is carried out under stirring conditions, and the stirring time is preferably 10 to 14 hours, more preferably 11 to 13 hours, and more preferably 12 hours; the reaction temperature is preferably room temperature.

[0102] In the present invention, after the reaction in step 6) is completed, a post-treatment step is further included: the reaction system is rotary evaporated to remove the solvent, the residue is redissolved in dichloromethane and extracted with HCl solution, NH4OH solution and deionized water in sequence. The organic phase is dried with anhydrous MgSO4, concentrated, and column chromatographed to obtain a yellow solid;

[0103] The concentration of the HCl solution is preferably 0.8 to 1.2 mol / L, more preferably 0.9 to 1.1 mol / L, and more preferably 1 mol / L; the concentration of the NH4OH solution is preferably 0.8 to 1.2 mol / L, more preferably 0.9 to 1.1 mol / L, and more preferably 1 mol / L;

[0104] The mobile phase used in column chromatography is preferably dichloromethane and n-hexane, and the volume ratio of dichloromethane to n-hexane is preferably 1:1.

[0105] Another object of the present invention is to provide a method for preparing an electrochromic film based on an electrochromic material of dithiophene, comprising the following steps:

[0106] The electrochromic material DTFDT-yne based on bithiophene was dissolved in a mixed solvent of dichloromethane and acetonitrile, tetrabutylammonium hexafluorophosphate was added, and electrochemical polymerization was performed to form a film by cyclic voltammetry.

[0107] Among them, the scanning speed is preferably 90 to 110 mV / s, more preferably 95 to 105 mV / s, and more preferably 98 to 102 mV / s; the voltage range is preferably 0 to 1.2 V, more preferably 0.5 to 1.0 V, and more preferably 0.6 to 0.8 V; the number of cycles is preferably 8 to 12, more preferably 9 to 11, and more preferably 10;

[0108] The addition ratio of dichloromethane, acetonitrile and DTFDT-yne is preferably 500-600mL:300-400mL:1g, more preferably 520-580mL:320-380mL:1g, and more preferably 540-560mL:340-360mL:1g; the concentration of tetrabutylammonium hexafluorophosphate in the mixed solvent is preferably 0.08-0.15mol / L, more preferably 0.1-0.14mol / L, and more preferably 0.12-0.13mol / L.

[0109] In the present invention, after the polymerization is completed, the following steps are further included: washing the film in a mixed solvent of dichloromethane and acetonitrile to remove the unpolymerized monomers or oligomers on the surface and the residual electrolyte;

[0110] The volume ratio of dichloromethane to acetonitrile is preferably 5-7:3-5; more preferably 6:4.

[0111] Another object of the present invention is to provide an electrochromic film based on dithiophene prepared by the method.

[0112] The technical solutions provided by the present invention are described in detail below in conjunction with the embodiments, but they should not be construed as limiting the protection scope of the present invention.

[0113] Example 1

[0114] 1) Synthesis of 2,5-diiodo-1,4-dimethoxybenzene

[0115] Potassium iodide (0.072 mol) and iodine (0.12 mol) were added to a reaction bottle containing 400 mL of glacial acetic acid, 5 mL of concentrated sulfuric acid and 15 mL of deionized water. Then 1,4-dimethoxybenzene (17.96 g, 0.130 mol) was added thereto, and the mixture was refluxed at 118 ° C for 6 hours and cooled to room temperature. Deionized water was then added to the above mixture, and the resulting mixture was cooled in an ice-water bath to obtain a black crystalline precipitate. Filter by suction, collect the precipitate, rinse the filter cake with water and dry it. Then the black crystals were redissolved in chloroform, and activated carbon was added thereto and refluxed for 10 minutes. Filter while hot, and the filtrate was cooled to obtain a light brown needle-shaped crystal product, which was filtered by suction, filtered and dried, and recrystallized in ethanol to obtain a white needle-shaped target product 2,5-diiodo-1,4-dimethoxybenzene.

[0116] 1 H NMR (400MHz, CDCl3): δ = 7.20 (s, 2H), 3.84 (s, 6H).

[0117] 2) Synthesis of 2,5-diiodo-1,4-diphenol

[0118] At -78 ° C, under nitrogen protection, 2,5-diiodo-1,4-dimethoxybenzene (8.40g, 21.54mmol) was added to a reaction bottle equipped with a reflux condenser, and then 200mL of ultra-dry dichloromethane was added to dissolve. 43mL of dichloromethane solution of boron tribromide (1mol / L) was slowly added dropwise. Then it was warmed to room temperature and stirred for 48h. After the reaction was completed, 250mL of deionized water was added for hydrolysis. After separation, the aqueous phase was extracted with ether three times, using 100mL each time. The organic phases were combined, 400mL of NaOH solution (2mol / L) was added for extraction, and the extract was neutralized with 0.1mol / L dilute hydrochloric acid in an ice-water bath. A pink precipitate appeared in the solution, which was filtered and dried. The target product was obtained by recrystallization in benzene.

[0119] 1 H NMR (400MHz, DMSO-d6): δ = 9.82 (s, 2H), 7.14 (s, 2H).

[0120] 3) Synthesis of 6-chlorohexyne-triisopropylsilane

[0121] At -78 ° C, under nitrogen protection, 6-chlorohexyne (5g, 42.9mmol) and 100mL ultra-dry tetrahydrofuran were added to the reaction bottle. 21mL of lithium diisopropylamine in heptane solution (2mol / L) was added dropwise. After stirring for 10min, the temperature was slowly raised to -10°C and continued to stir for 30min, then the temperature was lowered to -78°C again, and triisopropylsilicon chloride (751.92mg, 3.9mmol) was added dropwise, and then the temperature was slowly raised to room temperature and stirred for 24h. After the reaction was completed, the mixed solution was slowly poured into deionized water and extracted with chloroform. The organic phase was extracted with 0.5M HCl solution, dried with anhydrous MgSO4, and then the solvent was removed by rotary evaporation. The remaining oil was distilled to obtain the target product.

[0122] 1 H NMR (400MHz, CDCl3): δ = 3.59 (t, 2H), 2.32 (t, 2H), 1.97-1.90 (m, 2H), 1.73-1.66 (m, 2H), 1.09-0.99 (m, 21H).

[0123] 4) Synthesis of 1-2,5-bis-(6-triisopropylsilylhexynyl)-benzene

[0124] At -78 ° C, under nitrogen protection, 2,5-diiodo-1,4-diphenol (2.79 g, 7.71 mmol), potassium carbonate (77.10 mmol) and 6-chlorohexyne-triisopropylsilane (30.84 mmol) were dissolved in a reaction bottle containing 200 mL of ultra-dry DMF and reacted at 120 ° C for 72 h. The reaction mixture was diluted with dichloromethane, extracted twice with 150 mL of 1 mol / L HCl solution, and then extracted with deionized water and saturated sodium chloride solution. The solvent was removed by rotary evaporation, and the crude product was purified by column chromatography (n-hexane: dichloromethane = 4:1) to obtain the target product.

[0125] 1 H NMR (400MHz, CDCl3): δ = 7.18 (s, 2H), 3.98 (t, J = 6.4Hz, 4H), 2.37 (t, J = 6.8Hz, 4H), 1.99-1.92 (m, 4H), 1.82-1.74 (m, 4H), 1.08-1.04 (s, 42H).

[0126] 5) Synthesis of 1,4-dithiophene-2,5-bis-(6-triisopropylsilylhexynyl)-benzene

[0127] Under nitrogen protection, 1,4-diiodo-2,5-bis-(6-triisopropylsilylhexynyl)-benzene (834.82 mg, 1 mmol), tin dithiophene (4 mmol) and Pd(PPh3)4 (16.7 mg) were added to a reaction bottle containing 30 mL of ultra-dry dioxane, and reacted at 130°C for 16 hours. After the reaction, deionized water was added and extracted with dichloromethane, and purified by column chromatography, with the mobile phase being dichloromethane and n-hexane (the volume ratio of dichloromethane to n-hexane was 1:2), to obtain the target product.

[0128] 1 H NMR (500MHz, CDCl3) δ7.47(d,J=3.9Hz,2H),7.25(s,2H),7.24-7.21(m,4H),7.18(d,J=3.9Hz,2H),7.07-7.03( m,2H),3.98(t,J=6.4Hz,4H),2.37(t,J=6.8Hz,4H),1.99-1.92(m,4H),1.82-1.74(m,4H),1.08-1.04(s,42H).

[0129] 6) Synthesis of DTFDT-yne

[0130] 1,4-dithiophene-2,5-bis-(6-triisopropylsilylhexynyl)-benzene (911.5 mg, 1 mmol) was added to a reaction bottle containing 30 mL of tetrahydrofuran, and 0.74 mL of tetrabutylammonium fluoride in tetrahydrofuran solution (1 mol / L) was added dropwise to the above solution. Stir at room temperature for 12 h. The solvent was then removed by rotary evaporation, and the residue was redissolved in dichloromethane and extracted with 1 mol / L HCl solution, 1 mol / L NH4OH solution and deionized water in sequence. The organic phase was dried over anhydrous MgSO4, concentrated, and column chromatography to obtain a yellow solid, with the mobile phase being dichloromethane and n-hexane (volume ratio 1:1).

[0131] 1 H NMR (400MHz, CDCl3) δ7.47(d,J=3.9Hz,2H),7.25(s,2H),7.24-7.21(m,4H),7.18(d,J=3.9Hz,2H),7.07-7.03(m,2H),4.14(t ,J=6.2Hz,4H),2.33(td,J=7.0,2.6Hz,4H),2.06(dt,J=12.0,6.2Hz,4H),2.01(t,J=2.6Hz,2H),1.83(dt,J=9.7,7.0Hz,4H).

[0132] 7) Preparation of DTFDT-yne electrochromic thin film by cyclic voltammetry

[0133] DTFDT-yne (10.99 mg) and tetrabutylammonium hexafluorophosphate (1 mmol) were added to a 10 mL volumetric flask, and 6 mL of dichloromethane and 4 mL of acetonitrile were added. Ultrasonication was performed for 5 minutes. After complete dissolution, electrochemical polymerization was performed. Cyclic voltammetry was used to polymerize the film using ITO glass as the working electrode, platinum wire as the counter electrode, and Ag / AgCl electrode as the reference electrode. The scanning speed was 100 mV / s, the voltage range was 0-1.2 V, and the number of cycles was 10. After the polymerization was completed, a mixed solvent of 6 mL of dichloromethane and 4 mL of acetonitrile was used to wash away the electrolyte and oligomers on the surface of the film. Figure 2 This is the cyclic voltammetry polymerization curve of the electrochromic film. It can be seen from the figure that: as the number of polymerization cycles increases, the peak current also increases, indicating that the monomers are successfully polymerized and the generated film is well attached to the ITO glass surface.

[0134] Example 2

[0135] 1) Synthesis of 2,5-diiodo-1,4-dimethoxybenzene

[0136] Potassium iodide (0.4 mol) and iodine (0.8 mol) were added to a reaction bottle containing 20 mL of glacial acetic acid, 0.25 mL of concentrated sulfuric acid and 0.65 mL of deionized water. Then 1,4-dimethoxybenzene (1 g, 7.24 mmol) was added thereto, and the mixture was refluxed at 110 ° C for 10 h and cooled to room temperature. Deionized water was then added to the above mixture, and the resulting mixture was cooled in an ice-water bath to obtain a black crystalline precipitate. Filter by suction, collect the precipitate, rinse the filter cake with water and dry it. Then the black crystals were redissolved in chloroform, and activated carbon was added thereto and refluxed for 10 min. Filter while hot, and the filtrate was cooled to obtain a light brown needle-shaped crystal product, which was filtered by suction, filtered and dried, and recrystallized in ethanol to obtain a white needle-shaped target product 2,5-diiodo-1,4-dimethoxybenzene.

[0137] 2) Synthesis of 2,5-diiodo-1,4-diphenol

[0138] At -75℃, nitrogen protection, add 2,5-diiodo-1,4-dimethoxybenzene (1g, 2.57mmol) to a reaction bottle equipped with a reflux condenser, and then add 20mL of ultra-dry dichloromethane to dissolve. Slowly drop 4.9mL of dichloromethane solution of boron tribromide (1.2mol / L). Then warm to room temperature and stir for 40h. After the reaction is completed, add 30mL of deionized water for hydrolysis. After separation, the aqueous phase is extracted with ether 3 times, using 12mL each time. Combine the organic phases, add 50mL of NaOH solution (1.5mol / L) for extraction, and the extract is neutralized with 0.1mol / L dilute hydrochloric acid in an ice-water bath. A pink precipitate appears in the solution, which is filtered and dried. Recrystallize from benzene to obtain the target product.

[0139] 3) Synthesis of 6-chlorohexyne-triisopropylsilane

[0140] At -75 ° C, under nitrogen protection, 6-chlorohexyne (1g, 8.58mmol) and 20mL ultra-dry tetrahydrofuran were added to the reaction bottle. 4mL of lithium diisopropylamine in heptane solution (2.5mol / L) was added dropwise. After stirring for 10min, the temperature was slowly raised to -8°C and continued to stir for 30min, then the temperature was lowered to -75°C again, and triisopropylsilicon chloride (165.42mg, 0.858mmol) was added dropwise, and then the temperature was slowly raised to room temperature and stirred for 20h. After the reaction was completed, the mixed solution was slowly poured into deionized water and extracted with chloroform. The organic phase was extracted with 0.4M HCl solution, dried with anhydrous MgSO4, and then the solvent was removed by rotary evaporation. The remaining oil was distilled to obtain the target product.

[0141] 4) Synthesis of 1-2,5-bis-(6-triisopropylsilylhexynyl)-benzene

[0142] At -75°C, under nitrogen protection, 2,5-diiodo-1,4-diphenol (1g, 2.76mmol), potassium carbonate (24.84mmol) and 6-chlorohexyne-triisopropylsilane (11.04mmol) were dissolved in a reaction bottle containing 60mL of ultra-dry DMF and reacted at 110°C for 75h. The reaction mixture was diluted with dichloromethane, extracted twice with 55mL of 0.8mol / L HCl solution, and then extracted with deionized water and saturated sodium chloride solution. The solvent was removed by rotary evaporation, and the crude product was purified by column chromatography (n-hexane: dichloromethane = 3:1) to obtain the target product.

[0143] 5) Synthesis of 1,4-dithiophene-2,5-bis-(6-triisopropylsilylhexynyl)-benzene

[0144] Under nitrogen protection, 1,4-diiodo-2,5-bis-(6-triisopropylsilylhexynyl)-benzene (1g, 1.2mmol), tin dithiophene (3.6mmol) and Pd(PPh3)4 (15mg) were added to a reaction bottle containing 30mL of ultra-dry dioxane, and reacted at 120°C for 20h. After the reaction, deionized water was added and extracted with dichloromethane, and purified by column chromatography, with the mobile phase being dichloromethane and n-hexane (the volume ratio of dichloromethane to n-hexane was 1:1.5), to obtain the target product.

[0145] 6) Synthesis of DTFDT-yne

[0146] 1,4-dithiophene-2,5-bis-(6-triisopropylsilylhexynyl)-benzene (1 g, 1.1 mmol) was added to a reaction bottle containing 30 mL of tetrahydrofuran, and 0.75 mL of tetrabutylammonium fluoride in tetrahydrofuran solution (1.2 mol / L) was added dropwise to the above solution. Stir at room temperature for 10 h. The solvent was then removed by rotary evaporation, and the residue was redissolved in dichloromethane and extracted with 0.8 mol / L HCl solution, 1.2 mol / L NH4OH solution and deionized water in sequence. The organic phase was dried over anhydrous MgSO4, concentrated, and column chromatography to obtain a yellow solid, with the mobile phase being dichloromethane and n-hexane (volume ratio 1:1).

[0147] 7) Preparation of DTFDT-yne electrochromic thin film by cyclic voltammetry

[0148] DTFDT-yne (10 mg) and tetrabutylammonium hexafluorophosphate (0.8 mmol) were added to a 10 mL volumetric flask, and 6 mL of dichloromethane and 4 mL of acetonitrile were added. After complete dissolution, electrochemical polymerization was performed. ITO glass was used as the working electrode, platinum wire as the counter electrode, and Ag / AgCl electrode as the reference electrode. Cyclic voltammetry was used to polymerize the film. The scanning speed was 90 mV / s, the voltage range was 0-1.2 V, and the number of cycles was 8. After the polymerization was completed, the electrolyte and oligomers on the surface of the film were washed away with a mixed solvent of 6 mL of dichloromethane and 4 mL of acetonitrile.

[0149] Example 3

[0150] 1) Synthesis of 2,5-diiodo-1,4-dimethoxybenzene

[0151] Potassium iodide (0.6 mol) and iodine (1.1 mol) were added to a reaction bottle containing 30 mL of glacial acetic acid, 0.3 mL of concentrated sulfuric acid and 1 mL of deionized water. Then 1,4-dimethoxybenzene (1 g, 7.24 mmol) was added thereto, and the mixture was refluxed at 125 ° C for 8 h and cooled to room temperature. Deionized water was then added to the above mixture, and the resulting mixture was cooled in an ice-water bath to obtain a black crystalline precipitate. Filter by suction, collect the precipitate, rinse the filter cake with water and dry it. Then the black crystals were redissolved in chloroform, and activated carbon was added thereto and refluxed for 10 min. Filter while hot, and the filtrate was cooled to obtain a light brown needle-shaped crystal product, which was filtered by suction, filtered and dried, and recrystallized in ethanol to obtain a white needle-shaped target product 2,5-diiodo-1,4-dimethoxybenzene.

[0152] 2) Synthesis of 2,5-diiodo-1,4-diphenol

[0153] At -80℃, under nitrogen protection, 2,5-diiodo-1,4-dimethoxybenzene (1g, 2.57mmol) was added to a reaction bottle equipped with a reflux condenser, and then 30mL of ultra-dry dichloromethane was added to dissolve. 5.2mL of dichloromethane solution of boron tribromide (0.8mol / L) was slowly added dropwise. Then it was warmed to room temperature and stirred for 60h. After the reaction was completed, 30mL of deionized water was added for hydrolysis. After separation, the aqueous phase was extracted with ether three times, using 12mL each time. The organic phases were combined, 50mL of NaOH solution (2.5mol / L) was added for extraction, and the extract was neutralized with 0.1mol / L of dilute hydrochloric acid in an ice-water bath. A pink precipitate appeared in the solution, which was filtered and dried. The target product was obtained by recrystallization in benzene.

[0154] 3) Synthesis of 6-chlorohexyne-triisopropylsilane

[0155] At -80 ° C, under nitrogen protection, 6-chlorohexyne (1g, 8.58mmol) and 25mL ultra-dry tetrahydrofuran were added to the reaction bottle. 4.3mL of lithium diisopropylamine in heptane solution (1.5mol / L) was added dropwise. After stirring for 10min, the temperature was slowly raised to -12°C and continued to stir for 30min, then the temperature was lowered to -80°C again, and triisopropylsilicon chloride (181.96mg, 0.944mmol) was added dropwise, and then the temperature was slowly raised to room temperature and stirred for 30h. After the reaction was completed, the mixed solution was slowly poured into deionized water and extracted with chloroform. The organic phase was extracted with 0.6M HCl solution, dried with anhydrous MgSO4, and then the solvent was removed by rotary evaporation. The remaining oil was distilled to obtain the target product.

[0156] 4) Synthesis of 1-2,5-bis-(6-triisopropylsilylhexynyl)-benzene

[0157] At -80°C, under nitrogen protection, 2,5-diiodo-1,4-diphenol (1g, 2.76mmol), potassium carbonate (30.36mmol) and 6-chlorohexyne-triisopropylsilane (13.8mmol) were dissolved in a reaction bottle containing 80mL of ultra-dry DMF and reacted at 130°C for 68h. The reaction mixture was diluted with dichloromethane, extracted twice with 55mL of 1.2mol / L HCl solution, and then extracted with deionized water and saturated sodium chloride solution. The solvent was removed by rotary evaporation, and the crude product was purified by column chromatography (n-hexane: dichloromethane = 5:1) to obtain the target product.

[0158] 5) Synthesis of 1,4-dithiophene-2,5-bis-(6-triisopropylsilylhexynyl)-benzene

[0159] Under nitrogen protection, 1,4-diiodo-2,5-bis-(6-triisopropylsilylhexynyl)-benzene (1g, 1.2mmol), tin dithiophene (6mmol) and Pd(PPh3)4 (25mg) were added to a reaction bottle containing 40mL of ultra-dry dioxane, and reacted at 140°C for 15h. After the reaction, deionized water was added and extracted with dichloromethane, and purified by column chromatography with the mobile phase of dichloromethane and n-hexane (the volume ratio of dichloromethane to n-hexane was 1:2.5) to obtain the target product.

[0160] 6) Synthesis of DTFDT-yne

[0161] 1,4-dithiophene-2,5-bis-(6-triisopropylsilylhexynyl)-benzene (1 g, 1.1 mmol) was added to a reaction bottle containing 35 mL of tetrahydrofuran, and 0.85 mL of tetrabutylammonium fluoride in tetrahydrofuran solution (0.8 mol / L) was added dropwise to the above solution. Stir at room temperature for 14 h. The solvent was then removed by rotary evaporation, and the residue was redissolved in dichloromethane and extracted with 1.2 mol / L HCl solution, 0.8 mol / L NH4OH solution and deionized water in sequence. The organic phase was dried over anhydrous MgSO4, concentrated, and column chromatography to obtain a yellow solid, with the mobile phase being dichloromethane and n-hexane (volume ratio 1:1).

[0162] 7) Preparation of DTFDT-yne electrochromic thin film by cyclic voltammetry

[0163] DTFDT-yne (10 mg) and tetrabutylammonium hexafluorophosphate (1.2 mmol) were added to a 10 mL volumetric flask, and 6 mL of dichloromethane and 4 mL of acetonitrile were added. After complete dissolution, electrochemical polymerization was performed. ITO glass was used as the working electrode, platinum wire as the counter electrode, and Ag / AgCl electrode as the reference electrode. Cyclic voltammetry was used to polymerize the film. The scanning speed was 110 mV / s, the voltage range was 0-1.2 V, and the number of cycles was 12. After the polymerization was completed, the electrolyte and oligomers on the surface of the film were washed away with a mixed solvent of 6 mL of dichloromethane and 4 mL of acetonitrile.

[0164] Performance test of DTFDT-yne electrochromic film:

[0165] 0.387 g of tetrabutylammonium hexafluorophosphate was added to a 10 mL volumetric flask, and the volume was fixed with 6 mL of dichloromethane and 4 mL of acetonitrile. This was used as a blank solution. ITO glass with a polymer film on the surface was used as the working electrode, platinum wire was used as the counter electrode, and Ag / AgCl electrode was used as the reference electrode. The electrochromic performance was tested in conjunction with a UV-visible spectrophotometer.

[0166] Figure 3 It is a graph of the ultraviolet-visible absorption spectra of the electrochromic film prepared in Example 1 of the present invention under different voltages. It can be seen from the figure that when a voltage of 0V is applied to the film material, the highest absorption peak appears at 500-550nm, and the film appears red at this time; and when a voltage of 1.2V is applied, the absorption of visible light is transferred to 720nm, and the film appears blue at this time.

[0167] Figure 4 and Figure 5The response times of the electrochromic film prepared in Example 1 of the present invention at 720nm and 110nm are respectively. Thanks to the low redox potential caused by the enhanced conjugation of the molecule by dithiophene, and the advantages of the long alkoxy chain making the polymer stack more loose and providing more ion migration channels, the prepared film can change color at a voltage of 0-1.2V. It can be seen from the figure: the optical contrast at a wavelength range of 720nm is 38%, the coloring time is 1.72s, and the fading time is 1.37s; the optical contrast at a wavelength range of 1100nm is about 50%, the coloring time is 2.29s, and the fading time is 0.63s. At a wavelength range of 720nm, there is no obvious decrease in contrast after 50 cycles. It is a new type of high-performance electrochromic material with great potential.

[0168] Figure 6 This is a kinetic test of the electrochromic film prepared in Example 1 of the present invention at 720nm. It can be seen from the figure that the contrast of the film at 720nm is as high as 40%, and after a cycle of 1000s, it can still maintain a contrast of 75% relative to the initial film.

[0169] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. An electrochromic material based on dithiophene, characterized in that: Has the following structure:

2. The method for preparing an electrochromic material based on dithiophene according to claim 1, characterized in that: The following steps are involved: 1) iodination reaction of 1,4-dimethoxybenzene to generate 2,5-diiodo-1,4-dimethoxybenzene; 2) causing 2,5-diiodo-1,4-dimethoxybenzene to undergo a reduction reaction to generate 2,5-diiodo-1,4-diphenol; 3) reacting 6-chlorohexyne with triisopropylsilyl chloride to generate 6-chlorohexyne-triisopropylsilane; 4) reacting 2,5-diiodo-1,4-diphenol with 6-chlorohexynyl-triisopropylsilane to generate 1,4-diiodo-2,5-bis-(6-triisopropylsilylhexynyl)-benzene; 5) 1,4-diiodo-2,5-bis-(6-triisopropylsilylhexynyl)-benzene reacts with tin-bis-thiophene to generate 1,4-bis-thiophene-2,5-bis-(6-triisopropylsilylhexynyl)-benzene; 6) 1,4-dithiophene-2,5-bis-(6-triisopropylsilylhexynyl)-benzene reacts with tetrabutylammonium fluoride to produce dithiophene-based electrochromic materials; There is no restriction on the order of step 2) and step 3).

3. The method for preparing an electrochromic material based on dithiophene according to claim 2, characterized in that: The steps of the iodination reaction in step 1) are as follows: potassium iodide, iodine, glacial acetic acid, concentrated sulfuric acid, water and 1,4-dimethoxybenzene are mixed, heated to reflux, and then naturally cooled to room temperature; The molar ratio of potassium iodide, iodine and 1,4-dimethoxybenzene is 0.4-0.6:0.8-1.1:1; the addition ratio of glacial acetic acid, concentrated sulfuric acid, water and 1,4-dimethoxybenzene is 20-30mL:0.25-0.3mL:0.65-1mL:1g; The heating reflux temperature is 110-125° C. and the time is 6-10 hours.

4. The method for preparing an electrochromic material based on dithiophene according to claim 2 or 3, characterized in that: The reduction reaction in step 2) is as follows: dissolving 2,5-diiodo-1,4-dimethoxybenzene in dichloromethane, adding a dichloromethane solution of boron tribromide dropwise, and then naturally warming to room temperature to react; The addition ratio of dichloromethane, dichloromethane solution of boron tribromide and 2,5-diiodo-1,4-dimethoxybenzene is 20-30 mL: 4.9-5.2 mL: 1 g; the system temperature is set to -75°C to -80°C when the reactants are mixed; the concentration of the dichloromethane solution of boron tribromide is 0.8 to 1.2 mol / L; The reaction is carried out under stirring conditions, and the stirring time is 40 to 60 hours; The reaction is carried out under a protective atmosphere, which is a nitrogen atmosphere or an argon atmosphere.

5. The method for preparing an electrochromic material based on dithiophene according to claim 4, characterized in that: The reaction steps in step 3) are as follows: 6-chlorohexyne, tetrahydrofuran and an n-heptane solution of lithium diisopropylamide are mixed, the temperature is naturally raised under stirring, stirring is continued, then the system temperature is lowered and triisopropylsilicon chloride is added dropwise, and the temperature is naturally raised to room temperature for reaction; The addition ratio of tetrahydrofuran, heptane solution of lithium diisopropylamine and 6-chlorohexyne is 20-25 mL: 4-4.3 mL: 1 g; the molar ratio of triisopropylsilyl chloride to 6-chlorohexyne is 1: 10-11; the concentration of the heptane solution of lithium diisopropylamine is 1.5-2.5 mol / L; The temperature of 6-chlorohexyne, tetrahydrofuran and n-heptane solution of lithium diisopropylamine when mixed is -75°C to -80°C; the stirring time of natural heating under stirring condition is 10 to 20 minutes; the temperature of natural heating is -12°C to -8°C; the stirring time is continued for 25 to 35 minutes; the temperature of lowering the system temperature is -75°C to -80°C; The reaction is carried out under stirring conditions for 20 to 30 hours; the reaction is carried out under a protective atmosphere, which is a nitrogen atmosphere or an argon atmosphere.

6. A method for preparing an electrochromic material based on dithiophene according to claim 2, 3 or 5, characterized in that: The steps of the reaction in step 4) are as follows: 2,5-diiodo-1,4-diphenol, potassium carbonate, 6-chlorohexyne-triisopropylsilane and N,N-dimethylformamide are mixed and reacted; The molar ratio of potassium carbonate, 6-chlorohexyne-triisopropylsilane and 2,5-diiodo-1,4-diphenol is 9-11:4-5:1; the addition ratio of N,N-dimethylformamide and 2,5-diiodo-1,4-diphenol is 60-80mL:1g; The reaction temperature is 110-130°C and the reaction time is 68-75h; The reaction is carried out under a protective atmosphere, which is a nitrogen atmosphere or an argon atmosphere.

7. The method for preparing an electrochromic material based on dithiophene according to claim 6, characterized in that: The steps of the reaction in step 5) are as follows: 1,4-diiodo-2,5-bis-(6-triisopropylsilylhexynyl)-benzene, tin-bis-dithiophene, Pd(PPh3)4 and dioxane are mixed and reacted; The molar ratio of tin-bis-dithiophene to 1,4-diiodo-2,5-bis-(6-triisopropylsilylhexynyl)-benzene is 3-5:1; the addition ratio of dioxane, Pd(PPh3)4 and 1,4-diiodo-2,5-bis-(6-triisopropylsilylhexynyl)-benzene is 30-40mL:15-25mg:1g; The reaction temperature is 120-140°C and the reaction time is 15-20h; The reaction is carried out under a protective atmosphere, which is a nitrogen atmosphere or an argon atmosphere.

8. A method for preparing an electrochromic material based on dithiophene according to claim 2, 3, 5 or 7, characterized in that: The reaction steps in step 6) are as follows: 1,4-dithiophene-2,5-bis-(6-triisopropylsilylhexynyl)-benzene and tetrahydrofuran are mixed, and then a tetrahydrofuran solution of tetrabutylammonium fluoride is added dropwise to react; The addition ratio of tetrahydrofuran, tetrabutylammonium fluoride tetrahydrofuran solution and 1,4-dithiophene-2,5-bis-(6-triisopropylsilylhexynyl)-benzene is 30-35 mL: 0.75-0.85 mL: 1 g; the concentration of tetrabutylammonium fluoride tetrahydrofuran solution is 0.8-1.2 mol / L; The reaction is carried out under stirring conditions, the stirring time is 10 to 14 hours, and the reaction temperature is room temperature.

9. A method for preparing an electrochromic film from the electrochromic material based on bithiophene according to claim 1, characterized in that: The following steps are included: The electrochromic material based on dithiophene is dissolved in a mixed solvent of dichloromethane and acetonitrile, tetrabutylammonium hexafluorophosphate is added, and electrochemical polymerization is performed to form a film by cyclic voltammetry; Among them, the scanning speed is 90-110mV / s, the voltage range is 0-1.2V, and the number of cycles is 8-12; The addition ratio of dichloromethane, acetonitrile and dithiophene-based electrochromic material is 500-600mL: 300-400mL: 1g; the concentration of tetrabutylammonium hexafluorophosphate in the mixed solvent is 0.08-0.15mol / L.

10. The electrochromic film based on dithiophene prepared by the method of claim 9.

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