Electrochromic polymer, electrochromic film, preparation method and application thereof

Abstract

The present invention relates to an electrochromic polymer, an electrochromic film, a preparation method, and applications thereof, belonging to the technical field of electrochromic materials. The electrochromic polymer is obtained by polymerizing a first thiophene derivative and a second thiophene derivative; the first thiophene derivative has a structural formula as shown in Formula (1): The second thiophene derivative is a thiophene derivative containing multiple benzene ring structures. The electrochromic polymer provided by the present invention exhibits significant electrochromic behavior, can achieve reversible changes between colored and transparent colors, and the color change process has a low driving potential, a fast response rate, high coloring efficiency, and good stability.

Description

Technical Field

[0001] The present invention relates to the technical field of electrochromic materials, and in particular to an electrochromic polymer, an electrochromic film, and a preparation method and application thereof. Background Art

[0002] Electrochromic materials are materials whose optical properties change due to a charge transfer process under the action of an external electric field. They have broad application prospects in flexible displays, smart windows, anti-glare rearview mirrors, and military intelligent camouflage. Electrochromic materials include transition metal oxides, viologens, small molecules, and conductive polymers. Among them, conductive polymers have become a hot research and application topic in the field of electrochromism due to their advantages such as structural designability, rich color changes, high contrast, fast response rate, high coloring efficiency, and good stability. The development of new conductive polymers with excellent electrochromic properties, especially those that display red and purple, is of great significance to the research of polymer electrochromism. However, existing electrochromic materials that can achieve red and purple to transparent transformations still have the problem of insufficient stability. Summary of the Invention

[0003] In response to one or more technical problems existing in the prior art, the present invention provides an electrochromic polymer, an electrochromic film, and a preparation method and application thereof. The electrochromic polymer provided by the present invention exhibits obvious electrochromic behavior and can achieve reversible changes between colored and transparent colors. The color change process has a low driving potential, a fast response rate, high coloring efficiency, and good stability.

[0004] The present invention provides an electrochromic polymer, which is obtained by polymerizing a first thiophene derivative and a second thiophene derivative; the structural formula of the first thiophene derivative is as shown in formula (1):

[0005] ; The second thiophene derivative is a thiophene derivative including a plurality of benzene rings and a plurality of thiophene rings.

[0006] Preferably, the second thiophene derivative is selected from one or more of formulas (2)-(3);

[0007] .

[0008] Preferably, the structural formula of the electrochromic polymer is one of formulas (4)-(5);

[0009] , Where n is 8~100.

[0010] In a second aspect, the present invention provides a method for preparing the electrochromic polymer according to the first aspect, the preparation method comprising:

[0011] The first thiophene derivative, the second thiophene derivative, a solvent, potassium carbonate, palladium acetate and pivalic acid are mixed, and subjected to polymerization reaction and a first purification treatment to obtain an electrochromic polymer.

[0012] Preferably, the molar ratio of the first thiophene derivative to potassium carbonate is 1:2-4;

[0013] The molar ratio of the first thiophene derivative to palladium acetate is 1:0.02-0.2;

[0014] The molar ratio of the first thiophene derivative to pivalic acid is 1:0.1-0.25; and / or

[0015] The ratio of the first thiophene derivative to the solvent is 1 mmol:100-500 mL. Preferably, the solvent is an aprotic polar solvent.

[0016] Preferably, the polymerization reaction temperature is 100-120° C. and the time is 48-96 hours; and / or

[0017] The first purification treatment includes: mixing the reaction solution after the polymerization reaction with methanol, extracting the precipitate with methanol, n-hexane and chloroform in sequence, concentrating the solution after chloroform extraction, mixing it with methanol again, filtering and drying.

[0018] Preferably, the preparation method of the first thiophene derivative comprises: (i) subjecting 3,4-dimethoxythiophene and cyclopentylmethanol to a heating reflux reaction in the presence of a catalyst, followed by a second purification treatment to obtain an intermediate product; preferably, the catalyst is p-toluenesulfonic acid monohydrate; (ii) subjecting the intermediate product to a bromination reaction with N-bromosuccinimide, followed by a third purification treatment to obtain the first thiophene derivative.

[0019] Preferably, the second purification treatment comprises: separating the reaction solution after the heating reflux reaction to obtain a first aqueous phase and a first organic phase, then extracting the first aqueous phase, combining the obtained second organic phase with the first organic phase, drying, and then wet-loading the mixture on a silica gel column; and / or

[0020] The third purification treatment includes: separating the reaction liquid after the bromination reaction to obtain a second aqueous phase and a third organic phase, then extracting the second aqueous phase, and combining the obtained fourth organic phase with the third organic phase, drying, and then dry-loading the mixture onto a silica gel column.

[0021] In a third aspect, the present invention provides an electrochromic polymer film, which is made using the electrochromic polymer described in the first aspect; preferably, the electrochromic polymer film has a thickness of 200-800 nm.

[0022] In a fourth aspect, the present invention provides an application of the electrochromic polymer film described in the third aspect, which is applied to an electrochromic device.

[0023] Compared with the prior art, the present invention has at least the following beneficial effects:

[0024] The present invention polymerizes a first thiophene derivative containing a cyclopentylmethoxy group and bromine with a second thiophene derivative containing multiple benzene rings and multiple thiophene rings within the molecule. The structural units of the second thiophene derivative are introduced into the main chain of the first thiophene derivative. The different planar properties of the second thiophene derivative are utilized to adjust the polymer band gap, resulting in an electrochromic polymer exhibiting distinct electrochromic behavior and reversible color transitions between colored and transparent colors. The color change process exhibits a low driving potential, a fast response rate, high coloring efficiency, and excellent stability. The electrochromic polymer film produced using the present invention exhibits excellent electrochemical stability, thermal stability, and cyclic stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0026] Figure 1 This is the H NMR spectrum of the intermediate product in the preparation process of the first thiophene derivative provided by the present invention;

[0027] Figure 2 is the H NMR spectrum of the first thiophene derivative provided by the present invention;

[0028] Figure 3 is the H NMR spectrum of the electrochromic polymer provided in Example 1 of the present invention;

[0029] Figure 4 is the H NMR spectrum of the electrochromic polymer provided in Example 2 of the present invention;

[0030] Figure 5 spectral absorption curves and color comparison diagrams of the electrochromic polymer solutions provided in Examples 1-2 of the present invention;

[0031] Figure 6 is the thermal stability curve of the electrochromic polymer provided in Examples 1-2 of the present invention;

[0032] Figure 7 3 is a comparison diagram of the ultraviolet-visible absorption spectra and color changes of the electrochromic polymer film provided in Example 3 of the present invention at different potentials;

[0033] Figure 8 1 is a comparison diagram of the UV-visible absorption spectra and color changes of the electrochromic polymer film provided in Example 4 of the present invention at different potentials;

[0034] Figure 9 cyclic voltammetry curves of the electrochromic polymer film provided in Example 3 of the present invention at different scan rates;

[0035] Figure 10 cyclic voltammetry curves of the electrochromic polymer film provided in Example 4 of the present invention at different scan rates;

[0036] Figure 11 This is the timed transmittance response and stability curve of the electrochromic polymer film provided in Example 3 of the present invention;

[0037] Figure 12 This is the timed transmittance response and stability curve of the electrochromic polymer film provided in Example 4 of the present invention. DETAILED DESCRIPTION

[0038] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are part of the embodiments of the present invention, not all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0039] The present invention provides an electrochromic polymer, which is obtained by polymerizing a first thiophene derivative and a second thiophene derivative; the structural formula of the first thiophene derivative is as shown in formula (1): ; The second thiophene derivative is a thiophene derivative comprising multiple benzene rings and multiple thiophene rings.

[0040] The present invention polymerizes a first thiophene derivative containing a cyclopentylmethoxy group and bromine with a second thiophene derivative containing multiple benzene rings and multiple thiophene rings within the molecule. The structural units of the second thiophene derivative are introduced into the main chain of the first thiophene derivative. The different planar properties of the second thiophene derivative are utilized to adjust the polymer band gap, resulting in an electrochromic polymer exhibiting distinct electrochromic behavior and reversible color transitions between colored and transparent colors. The color change process exhibits a low driving potential, a fast response rate, high coloring efficiency, and excellent stability. The electrochromic polymer film produced using the present invention exhibits excellent electrochemical stability, thermal stability, and cyclic stability.

[0041] According to some preferred embodiments, the second thiophene derivative is selected from one or more of formulas (2)-(3);

[0042] .

[0043] According to some preferred embodiments, the electrochromic polymer has a structural formula of one of formulas (4)-(5);

[0044] , Where n is 8~100.

[0045] In the second thiophene derivative having the structure of the above formula (2), sp 3 The availability of hybridized carbon atoms allows functional side chains to be easily attached to its structural units to increase its solubility in organic solvents. In addition, the inherent coplanar "ladder" structure of its structural units enhances the degree of π electron delocalization, making it highly electron-rich. Copolymerization with the first thiophene derivative having the structure of formula (1) above can produce an electrochromic polymer having the structure of formula (4) above, which can achieve reversible electrochromic behavior between red and transparent colors.

[0046] Compared with the second thiophene derivative having the structure of formula (2), the second thiophene derivative having the structure of formula (3) has better planarity and regularity while maintaining a good conjugated structure. When cycloalkoxythiophene is copolymerized with the second thiophene derivative having the structure of formula (3), it has a lower band gap, so that the absorption spectrum of the polymer is red-shifted to show purple. When copolymerized with the first thiophene derivative having the structure of formula (1), an electrochromic polymer having the structure of formula (5) is obtained. The electrochromic polymer can achieve reversible electrochromic behavior between purple and transparent colors.

[0047] In a second aspect, the present invention provides a method for preparing the electrochromic polymer according to the first aspect, the preparation method comprising:

[0048] The first thiophene derivative, the second thiophene derivative, a solvent, potassium carbonate, palladium acetate and pivalic acid are mixed, and subjected to polymerization reaction and a first purification treatment to obtain an electrochromic polymer.

[0049] According to some preferred embodiments, the molar ratio of the first thiophene derivative to potassium carbonate is 1:2-4;

[0050] The molar ratio of the first thiophene derivative to palladium acetate is 1:0.02-0.2;

[0051] The molar ratio of the first thiophene derivative to pivalic acid is 1:0.1-0.25; and / or

[0052] The ratio of the first thiophene derivative to the solvent is 1 mmol:100-500 mL. Preferably, the solvent is an aprotic polar solvent.

[0053] According to some preferred embodiments, the polymerization reaction temperature is 100-120° C. and the time is 48-96 hours. The polymerization reaction of the present invention is an arylation coupling polymerization reaction and is carried out under a protective atmosphere.

[0054] According to some preferred embodiments, the first purification treatment includes: mixing the reaction solution after the polymerization reaction with methanol, extracting the precipitate with methanol, n-hexane and chloroform in sequence, concentrating the solution after chloroform extraction and mixing it with methanol again, filtering and drying.

[0055] According to some preferred embodiments, the preparation method of the first thiophene derivative comprises: (i) subjecting 3,4-dimethoxythiophene and cyclopentylmethanol to a heating reflux reaction in the presence of a catalyst, followed by a second purification process to obtain an intermediate product; preferably, the catalyst is p-toluenesulfonic acid monohydrate; and (ii) subjecting the intermediate product to a bromination reaction with N-bromosuccinimide, followed by a third purification process to obtain the first thiophene derivative. It should be noted that in addition to the aforementioned raw materials, the preparation process of the first thiophene derivative also includes a solvent for dissolving and dispersing the reactants.

[0056] According to some preferred embodiments, the second purification treatment includes: separating the reaction liquid after the heating reflux reaction to obtain a first aqueous phase and a first organic phase, then extracting the first aqueous phase, and combining the obtained second organic phase with the first organic phase, and then wet-loading the obtained phase onto a silica gel column after drying.

[0057] According to some preferred embodiments, the third purification treatment includes: separating the reaction liquid after the bromination reaction to obtain a second aqueous phase and a third organic phase, then extracting the second aqueous phase, and combining the obtained fourth organic phase with the third organic phase, and then drying and dry-loading the mixture onto a silica gel column.

[0058] In some preferred embodiments of the present invention, during the second purification treatment and the third purification treatment, the solvent used for extraction is dichloromethane.

[0059] In some preferred embodiments of the present invention, during the second purification treatment and the third purification treatment, the desiccant used for drying is anhydrous magnesium sulfate.

[0060] In some preferred embodiments of the present invention, in the second purification process, the eluent used in the wet loading of the sample through the silica gel column is a mixture of petroleum ether and dichloromethane.

[0061] In some preferred embodiments of the present invention, in the third purification process, the eluent used for dry loading the sample through the silica gel column is a mixture of petroleum ether and dichloromethane.

[0062] In a third aspect, the present invention provides an electrochromic polymer film, which is prepared using the electrochromic polymer described in the first aspect.

[0063] The polymer provided by the present invention is soluble in organic solvents such as chloroform, tetrahydrofuran, toluene, etc., and can form an electrochromic polymer film on the surface of a conductive material through a spraying or scraping process.

[0064] According to some preferred embodiments, the thickness of the electrochromic polymer film is 200-800 nm.

[0065] In a fourth aspect, the present invention provides an application of the electrochromic polymer film described in the third aspect, which is applied to an electrochromic device.

[0066] In order to more clearly illustrate the technical solutions and advantages of the present invention, the present invention is further described below in conjunction with the examples. The present invention does not specifically limit the sources of the reagents used in the examples and comparative examples, and they can be directly purchased or synthesized. Example 1

[0067] Preparation of the first thiophene derivative:

[0068] (i) 0.1 mol of 3,4-dimethoxythiophene, 0.25 mol of cyclopentylmethanol, and 0.001 mol of p-toluenesulfonic acid monohydrate were dissolved in 200 mL of toluene and placed in a 500 mL single-necked flask. A Soxhlet extractor with molecular sieves and a condenser were connected and the mixture was stirred under reflux for 24 h. The mixture was then cooled to room temperature and poured into water. The organic phase was separated and collected. The aqueous phase was extracted twice with 20 mL of dichloromethane. The organic phases were combined, dried over anhydrous magnesium sulfate, and wet-applied to a silica gel column using a mixture of petroleum ether and dichloromethane in a volume ratio of 4:1 as the eluent to obtain a white solid, which was recorded as an intermediate product with a yield of 46%. The H NMR spectrum of the intermediate product was as follows: Figure 1 , it can be seen that δ6.16 (s, 1H), δ3.85 (s, 2H), δ2.40 (s, 1H), δ1.59 (s, 8H), proving that the intermediate product with the molecular structure in the following reaction formula was obtained.

[0069]

[0070] (ii) 0.1 mmol of the white solid (intermediate product) was dissolved in 20 mL of chloroform and placed in a 100 mL two-necked flask. The two-necked flask was protected by argon and covered with tin foil to avoid light. 0.3 mmol of NBS (N-bromosuccinimide) was dissolved in 10 mL of N,N-dimethylformamide (DMF) and slowly injected into the two-necked flask via a syringe. The reaction was stirred for 36 hours. The reaction solution was poured into water, and the organic phase was separated and collected. The aqueous phase was extracted twice with 20 mL of dichloromethane. The organic phases were combined and dried over anhydrous magnesium sulfate. The sample was dry-applied to a silica gel column using a mixture of petroleum ether and dichloromethane in a volume ratio of 4:1 as the eluent to obtain a colorless oily liquid, which was recorded as the first thiophene derivative with a yield of 80%. The nuclear magnetic hydrogen spectrum of the first thiophene derivative was as follows: 1H NMR (400 MHz, Chloroform-d): Figure 2 It can be seen that δ 3.92 (s, 2H), δ 2.31 (s, 1H), δ 1.90 - 1.30 (m, 8H), which proves that the first thiophene derivative with the molecular structure in the following reaction formula was obtained.

[0071]

[0072] Preparation of electrochromic polymers:

[0073] 0.1 mmol of the first thiophene derivative, 0.1 mmol of the second thiophene derivative, 0.002 mmol of palladium acetate, 0.3 mmol of potassium carbonate and 0.025 mmol of pivalic acid were placed in a 25 mL two-necked flask, vented and injected with nitrogen, and 10 mL of anhydrous N, N-dimethylacetamide (DMAC) was injected. The flask was vented and filled with nitrogen again, heated to 120 ° C and refluxed for 72 h. After the reaction was completed, it was cooled to room temperature, and the reaction solution was dropped into cold methanol for precipitation. The precipitate was filtered and dried; then Soxhlet extraction was performed with methanol, n-hexane and chloroform respectively, each extraction time was 24 h, the chloroform extract was concentrated to 15 mL, and then dropped into cold methanol to precipitate to obtain a red solid, which was filtered and dried to obtain an electrochromic polymer, recorded as P1, with a yield of 56%. The nuclear magnetic hydrogen spectrum of the electrochromic polymer is as follows Figure 3 , proving that an electrochromic polymer with the molecular structure in the following reaction formula was prepared.

[0074] Example 2

[0075] Preparation of the first thiophene derivative: same as in Example 1.

[0076] Preparation of electrochromic polymer: 0.1mmol of the first thiophene derivative, 0.1mmol of the second thiophene derivative, 0.002mmol of palladium acetate, 0.3mmol of potassium carbonate and 0.025mmol of pivalic acid were placed in a 25mL two-necked flask, ventilated and injected with nitrogen, and 10mL of anhydrous N,N-dimethylacetamide (DMAC) was injected. The ventilated and filled with nitrogen was then ventilated and filled with nitrogen. The reaction was heated to 120℃ and refluxed for 72h. After the reaction was completed, the reaction solution was cooled to room temperature and dropped into cold methanol for precipitation. The precipitate was filtered and dried. Soxhlet extraction was then performed with methanol, n-hexane and chloroform, respectively. Each extraction time was 24h. The chloroform extract was concentrated to 15mL, and then dropped into cold methanol to precipitate a purple solid. The target polymer P2 was obtained by filtration and drying with a yield of 50%. The nuclear magnetic hydrogen spectrum of the electrochromic polymer is shown as follows Figure 4 , proving that an electrochromic polymer with the molecular structure in the following reaction formula was prepared.

[0077]

[0078] The electrochromic polymers prepared in Example 1 and Example 2 were dissolved in chloroform to prepare a concentration of 2×10 -4 mg / mL solution, measure the absorption curve and color of the solution ( Figure 5(In the figure, the horizontal axis is wavelength and the vertical axis is absorbance). The electrochromic polymer P1 solution appears red, and the corresponding absorption peak of the solution is at 521nm when tested by a UV-visible spectrophotometer. The electrochromic polymer P2 solution appears purple, and the corresponding absorption peak of the solution is at 559nm when tested by a UV-visible spectrophotometer.

[0079] The present invention tests the thermal stability of the electrochromic polymers prepared in Example 1 and Example 2 ( Figure 6 , the horizontal axis is temperature and the vertical axis is mass fraction), the thermal decomposition temperature of the two electrochromic polymers is greater than 300 ° C, indicating that they can be used in working environments with higher temperatures. Example 3

[0080] An electrochromic polymer film is prepared using the electrochromic polymer P1 prepared in Example 1. The preparation method of the electrochromic polymer film comprises:

[0081] The electrochromic polymer P1 was dissolved in chloroform to prepare a 4 mg / mL solution. The insoluble matter was filtered out through a filter nozzle, and then placed in a spray gun with the air pressure controlled at 2 MPa. The solution was sprayed on a conductive glass. After spraying, the solution was placed in a vacuum drying oven at 40°C for vacuum drying to obtain an electrochromic polymer film (absorbance of 1.0). Example 4

[0082] An electrochromic polymer film is prepared using the electrochromic polymer P2 prepared in Example 2. The preparation method of the electrochromic polymer film comprises:

[0083] The electrochromic polymer P2 was dissolved in chloroform to prepare a 4 mg / mL solution. The insoluble matter was filtered out through a filter nozzle, and then placed in a spray gun with the air pressure controlled at 2 MPa. The solution was sprayed on conductive glass. After spraying, the solution was placed in a vacuum drying oven at 40°C for vacuum drying to obtain an electrochromic polymer film (absorbance of 1.0).

[0084] The present invention tested the spectroelectrochemical properties of the electrochromic polymer films prepared in Examples 3 and 4 at different voltages using a three-electrode system with a platinum wire as the counter electrode, a calibrated silver wire as the reference electrode, the polymer film as the working electrode, and a supporting electrolyte of 0.1 mol / L lithium perchlorate propylene carbonate solution. The spectroelectrochemical spectra and color-decolorized photographs of the two electrochromic polymer films at different applied voltages were obtained. Figure 7-8(In the figure, the horizontal axis is wavelength and the vertical axis is absorbance) It can be seen that both electrochromic polymer films have obvious electrochromic properties and can achieve reversible changes from purple to transparent at low voltages. Due to the accumulation of π-π* bonds, the obtained electrochromic polymer film has a certain red shift relative to the spectrum of the corresponding solution. The absorption peak of the film prepared using electrochromic polymer P1 in Example 3 is 524nm ( Figure 7 ), a reversible change from red to transparent can be achieved at a lower voltage. The absorption peak of the film made of electrochromic polymer P2 in Example 4 is 560nm ( Figure 8 ), and can achieve reversible changes from colored to transparent at lower voltages.

[0085] The present invention also uses cyclic voltammetry to test the electrochromic polymer films prepared in Example 3 and Example 4. The cyclic voltammetry curves at different scan rates are used to characterize the electrochemical stability of the two electrochromic polymers ( Figure 9-10 , the horizontal axis is voltage, and the vertical axis is current density). The peak current density of the anode and cathode of the two electrochromic polymers gradually increases with the increase of scanning speed, and both have low oxidation potentials. Among them, the initial oxidation potential of the electrochromic polymer P1 is 0.95V ( Figure 9 The initial oxidation potential of the electrochromic polymer P2 is 0.7 V ( Figure 10 ), the stability is maintained after multiple cyclic voltammetry scans.

[0086] The present invention uses a UV-visible spectrophotometer and an electrochemical workstation in combination, connects a three-electrode system to the electrochemical workstation, and places a quartz cuvette in the UV-visible spectrophotometer. While applying voltage to the electrochromic polymer film, the transmittance change at the wavelength of maximum transmittance is simultaneously measured to test the cyclic stability of the two polymers. The transmittance of the electrochromic polymer P1 at 520nm still maintains a contrast ratio of 40% after 300 cycles ( Figure 11 The horizontal axis in the figure is time, and the vertical axis is transmittance. The transmittance of the electrochromic polymer P2 at 560nm still maintains a contrast ratio of 49.1% after 600 cycles of switching. Figure 12 , in the figure, the horizontal axis is time and the vertical axis is transmittance), indicating that both polymers have long cycle life.

[0087] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. An electrochromic polymer, characterized in that The electrochromic polymer is obtained by polymerizing a first thiophene derivative and a second thiophene derivative; the structural formula of the first thiophene derivative is as shown in formula (1): ; The second thiophene derivative is a thiophene derivative comprising multiple benzene rings and multiple thiophene rings; The second thiophene derivative is selected from one or more of formulas (2) to (3); 。 2. The electrochromic polymer according to claim 1, characterized in that The structural formula of the electrochromic polymer is one of formulas (4)-(5); ， Where n is 8~100.

3. A method for preparing the electrochromic polymer according to claim 1 or 2, characterized in that: The preparation method comprises: The first thiophene derivative, the second thiophene derivative, a solvent, potassium carbonate, palladium acetate and pivalic acid are mixed, and subjected to polymerization reaction and a first purification treatment to obtain an electrochromic polymer.

4. The preparation method according to claim 3, characterized in that The molar ratio of the first thiophene derivative to potassium carbonate is 1:2-4; The molar ratio of the first thiophene derivative to palladium acetate is 1:0.02-0.2; The molar ratio of the first thiophene derivative to pivalic acid is 1:0.1-0.25; and / or The usage ratio of the first thiophene derivative to the solvent is 1 mmol:100-500 mL.

5. The preparation method according to claim 4, characterized in that The solvent is an aprotic polar solvent.

6. The preparation method according to claim 3, characterized in that The polymerization reaction temperature is 100-120° C. and the reaction time is 48-96 hours; and / or The first purification treatment includes: mixing the reaction solution after the polymerization reaction with methanol, extracting the precipitate with methanol, n-hexane and chloroform in sequence, concentrating the solution after chloroform extraction, mixing it with methanol again, filtering and drying.

7. The preparation method according to claim 3, characterized in that The preparation method of the first thiophene derivative comprises: (i) subjecting 3,4-dimethoxythiophene and cyclopentylmethanol to a heating reflux reaction under the action of a catalyst, and a second purification treatment to obtain an intermediate product; and (ii) subjecting the intermediate product to a bromination reaction with N-bromosuccinimide, and a third purification treatment to obtain the first thiophene derivative.

8. The preparation method according to claim 7, characterized in that In step (i), the catalyst is p-toluenesulfonic acid monohydrate.

9. The preparation method according to claim 7, characterized in that The second purification treatment comprises: separating the reaction liquid after the heating reflux reaction to obtain a first aqueous phase and a first organic phase, then extracting the first aqueous phase, combining the obtained second organic phase with the first organic phase, drying, and then wet-loading the mixture on a silica gel column; and / or The third purification treatment includes: separating the reaction liquid after the bromination reaction to obtain a second aqueous phase and a third organic phase, then extracting the second aqueous phase, and combining the obtained fourth organic phase with the third organic phase, drying, and then dry-loading the mixture onto a silica gel column.

10. An electrochromic polymer film, characterized in that: It is made from the electrochromic polymer according to claim 1 or 2.

11. The electrochromic polymer film according to claim 10, characterized in that: The thickness of the electrochromic polymer film is 200-800 nm.

12. Use of the electrochromic polymer film according to claim 10, characterized in that: Applied to electrochromic devices.

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