A conjugated polymer based on alkyl-substituted phenyl group and preparation method and application thereof

Abstract

The application discloses a kind of conjugated polymer based on alkyl-substituted phenyl and its preparation method and application, belong to polymer material technical field.The conjugated polymer provided in the application has structural formula as shown in formula (I):In formula (I), X1-X4 each independently is H or R, and at least one of X1-X4 is R.The alkyl-substituted phenyl is used as intermediate unit in the application, 3,4-ethylenedioxythiophene is used as electron-donating unit, by introducing benzene ring, so that rigid coplanar existence fusion ring structure in molecule, enhance charge flow, again combined with the alkyl of specific substitution quantity and substitution position, can adjust the electronic distribution and conjugated chain length of conjugated polymer, obtain the conjugated polymer with good electrochromic performance such as low bandwidth, wide absorption range, fast response time, good optical transmittance, good stability, the conjugated polymer has wide application in the preparation of electrochromic material or electrochromic device.

Description

Technical Field

[0001] This invention belongs to the field of polymer materials technology, and particularly relates to a conjugated polymer based on alkyl-substituted phenyl groups, its preparation method, and its applications. Background Technology

[0002] Electrochromism refers to the phenomenon where a material's color, absorbance, and transmittance undergo reversible changes under the application of voltage. Materials exhibiting this color-changing property are called electrochromic materials. Compared to other electrochromic materials, electrochromic conjugated polymers possess a broad absorption spectrum (from ultraviolet to visible light, as well as the infrared region), high optical contrast, and fast switching speed, making them promising candidates for applications in smart windows, information encryption, electronic paper, spacecraft thermal control, and military camouflage.

[0003] Conventional electrochromic materials are inorganic, mostly transition metal oxides. Due to the scarcity of metal resources, the production cost of these metal oxides is often very high. Compared to metal oxide materials, conductive polymers offer many unique advantages as electrochromic materials, such as better flexibility, ease of achieving bandgap and color transitions through structural modifications, and lower cost. However, with ongoing research, conductive polymer electrochromic materials also have their limitations, such as poor stability and susceptibility to oxidation in some polymers, which significantly restricts their development.

[0004] Electrochromism in conjugated polymers is a redox process involving the removal or injection of electrons (p-doping or n-doping, respectively) from the electrochromic conjugated polymer, leading to the formation of polarons and bipolarons and resulting in structural changes in the polymer backbone. Currently, many materials can serve as electrochromic intermediates, such as benzo[c][1,2,5]thiadiazole (BT), thiadiazole[3,4-c]pyridine, benzotriazole, thiophenepyrazine, and quinoline. However, the preparation processes of these materials are relatively complex, and there is room for further improvement in their stability and electrochromic properties. Summary of the Invention

[0005] In order to overcome at least one of the problems existing in the prior art, one of the objectives of the present invention is to provide a conjugated polymer based on alkyl-substituted phenyl groups, which has the characteristics of low bandwidth, fast response time and high coloring efficiency.

[0006] A second objective of this invention is to provide a method for preparing the above-mentioned conjugated polymer.

[0007] A third objective of this invention is to provide an application of the aforementioned conjugated polymer.

[0008] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0009] A first aspect of the present invention provides a conjugated polymer based on alkyl-substituted phenyl groups, the conjugated polymer having the structural formula shown in formula (I):

[0010]

[0011] In formula (I), X1 to X4 are each independently H or R, and at least one of X1 to X4 is R; when any two of X1 to X4 are R, X1 and X3 are not R at the same time, and X2 and X4 are not R at the same time; R is C1 to C5 alkyl; n is 3 to 200.

[0012] The conjugated polymer of this invention uses alkyl-substituted phenyl groups as intermediate units and 3,4-ethylenedioxythiophene (EDOT) as electron-donating units. The addition of the benzene ring in the intermediate unit results in a rigid, coplanar fused ring structure in the molecule, which enhances charge mobility. This allows the conjugated polymer of this invention to exhibit a lower band gap, a wider redox peak, good optical contrast, fast response time, high coloring efficiency, and good stability as an electrochromic material. The alkyl group is an electron-donating group; by controlling the length of the alkyl group in the intermediate unit, as well as the number and position of alkyl substitutions, the electron distribution and conjugated chain length of the conjugated polymer can be adjusted, thereby regulating the polymer's absorption spectrum and changing its color. This also helps improve the polymer's response speed, coloring efficiency, optical stability, and other electrochromic properties. Furthermore, the alkyl groups of this invention have suitable substitution positions, which avoids excessive steric hindrance that would hinder polymerization.

[0013] Preferably, in formula (I), R is methyl, ethyl, or propyl; more preferably, in formula (I), R is methyl.

[0014] In the intermediate unit of this invention, alkyl groups are used to replace phenyl groups. As electron-donating groups, the introduction of alkyl groups can reduce the band gap of the conjugated polymer, thereby enabling the regulation of the optical properties of the polymer and enhancing the electrochromic properties and solubility of the polymer. As the alkyl chain length increases, the electron-donating properties of the alkyl group are enhanced. This invention uses alkyl groups with shorter chain lengths, such as methyl, ethyl, or propyl, which can appropriately control the electron distribution and conjugated chain length of the conjugated polymer to obtain materials with good electrochromic properties.

[0015] Preferably, in formula (I), at least two of X1 to X4 are R.

[0016] The substitution sites and number of alkyl groups on the phenyl group also affect the electron distribution and conjugated chain length of the conjugated polymer. Introducing two or more alkyl groups for regulation can improve the electrochromic properties of the conjugated polymer. The introduction of alkyl groups makes the polymer more porous and enhances charge mobility. Therefore, introducing more alkyl groups can make the polymer response time faster, and the introduction of alkyl groups is beneficial to increasing the polymer solubility. However, the introduction of too many alkyl groups will affect its coloring efficiency, resulting in a slight decrease in the electrochromic properties of the polymer. Therefore, by controlling the length and number of alkyl groups within the range of this invention, a conjugated polymer with good overall electrochromic properties can be obtained.

[0017] In some specific embodiments of the present invention, the conjugated polymer includes at least one of the compounds shown in formulas (1) to (3):

[0018]

[0019] In equations (1) to (3), n ranges from 3 to 200.

[0020] A second aspect of the present invention provides a method for preparing the conjugated polymer described in the first aspect of the present invention, comprising the following steps: subjecting an active precursor to an electrochemical polymerization reaction to obtain the conjugated polymer; the active precursor has the structural formula shown in formula (i):

[0021]

[0022] Preferably, the active precursor is prepared by a method comprising the following steps: subjecting a donor compound (ii) and an intermediate compound (iii) to a cross-coupling reaction in a catalyst and a solvent to obtain the active precursor;

[0023]

[0024] In equation (iii), Y1 to Y2 are each independently selected from halogens.

[0025] Preferably, in formula (iii), Y1 to Y2 are each independently selected from F, Cl, Br or I; more preferably, in formula (iii), Y1 to Y2 are each independently selected from Cl or Br; in some specific embodiments of the present invention, in formula (iii), Y1 to Y2 are all selected from Br.

[0026] In some specific embodiments of the present invention, intermediate compound (iii) is...

[0027] Preferably, in the method for preparing the active precursor, the solvent includes at least one of benzene, toluene, or N,N-dimethylformamide (DMF); more preferably, the solvent includes toluene and N,N-dimethylformamide; even more preferably, the volume ratio of toluene to N,N-dimethylformamide in the solvent is (3-5):1.

[0028] Preferably, in the method for preparing the active precursor, the catalyst is selected from palladium catalysts; more preferably, the palladium catalyst includes tetratetraphenylphosphine palladium (Pd(PPh3)4), bis(triphenylphosphine) palladium dichloride (Pd(PPh3)2Cl2) or a combination thereof.

[0029] Preferably, the temperature of the cross-coupling reaction is 100–140°C; more preferably, it is 110–130°C.

[0030] Preferably, the cross-coupling reaction takes 24 to 72 hours; more preferably 36 to 60 hours.

[0031] Preferably, in the method for preparing the active precursor, the molar ratio of the intermediate compound (iii) to the donor compound (ii) is 1:(2-3).

[0032] Preferably, in the method for preparing the active precursor, the molar ratio of the intermediate compound (iii) to the catalyst is 1:(0.01-0.1); more preferably 1:(0.03-0.05).

[0033] Preferably, in the method for preparing the active precursor, the ratio of the intermediate compound (iii) to the solvent is 1 mmol: (50-200) mL.

[0034] Preferably, the method for preparing the active precursor further includes a purification step after the cross-coupling reaction; more preferably, the purification method is chromatographic separation and purification.

[0035] Preferably, the chromatographic column used for chromatographic separation and purification is selected from silica gel columns.

[0036] Preferably, the eluent used for chromatographic separation and purification includes dichloromethane (DCM) and petroleum ether (PE); more preferably, the volume ratio of dichloromethane to petroleum ether is 1:(1-3).

[0037] In the preparation method of the active precursor of the present invention, the cross-coupling reaction is a Stille / Suzuki palladium-catalyzed cross-coupling reaction, and the active precursor shown in formula (i) can be obtained through this cross-coupling reaction.

[0038] Preferably, in the method for preparing the active precursor, the cross-coupling reaction is carried out in a protective gas atmosphere. In some specific embodiments of the present invention, the protective gas in the cross-coupling reaction includes at least one of nitrogen, argon, or helium; in some more specific embodiments of the present invention, the protective gas in the cross-coupling reaction is selected from nitrogen.

[0039] Preferably, in the method for preparing the conjugated polymer, the electrochemical polymerization reaction specifically involves: using a solution containing the active precursor as an electrolyte solution, performing electrodeposition to obtain the polymer.

[0040] Preferably, in the electrochemical polymerization reaction, the concentration of the active precursor in the electrolyte solution is 0.001–0.01 mmol·L⁻¹. -1 .

[0041] Preferably, in the electrochemical polymerization reaction, the electrolyte solution further contains a supporting electrolyte.

[0042] Preferably, in the electrolyte solution, the supporting electrolyte includes at least one of tetrabutylammonium hexafluoride phosphate (PF6), tetrabutylammonium tetrafluoroborate (BF4), or lithium perchlorate.

[0043] Preferably, the concentration of the supporting electrolyte in the electrolyte solution is 0.01–0.2 mmol·L⁻¹. -1 .

[0044] Preferably, in the electrochemical polymerization reaction, the solvent of the electrolyte solution includes at least one of dichloromethane (CH2Cl2), chloroform (CHCl3), or acetonitrile (MeCN).

[0045] Furthermore, the electrochemical polymerization reaction is more specifically described as follows: using a solution containing the active precursor as an electrolyte solution, electrodeposition is performed in a three-electrode system consisting of a reference electrode, a counter electrode, and a working electrode to obtain the polymer on the working electrode.

[0046] Preferably, in the electrochemical polymerization reaction, the reference electrode is selected from an Ag / AgCl electrode; the counter electrode is selected from a platinum wire electrode; and the working electrode is selected from a Pt / ITO conductive glass electrode.

[0047] Preferably, in the electrochemical polymerization reaction, the electrodeposition method is a constant potential method; more preferably, the constant potential method is a constant current method or a cyclic voltammetry method.

[0048] Preferably, the electrochemical polymerization reaction is carried out under a protective gas atmosphere. In some specific embodiments of the present invention, the protective gas in the electrochemical polymerization reaction includes at least one of nitrogen, argon, or helium; in some more specific embodiments of the present invention, the protective gas in the electrochemical polymerization reaction is selected from argon.

[0049] A third aspect of the present invention provides the use of the conjugated polymer described in the first aspect of the present invention in the preparation of electrochromic materials or electrochromic devices.

[0050] In some specific embodiments of the present invention, the electrochromic device includes one or both of a display device and a light-transmitting device; in some more specific embodiments of the present invention, the electrochromic device includes at least one of a display, electrochromic glass, a smart window, or a rearview mirror.

[0051] The beneficial effects of this invention are as follows: This invention uses alkyl-substituted phenyl as an intermediate unit and ethylenedioxythiophene as an electron-donating unit. By introducing a benzene ring, a rigid coplanar fused ring structure exists in the molecule, enhancing charge mobility. Combined with alkyl groups having specific substitution numbers and positions, the electron distribution and conjugated chain length of the conjugated polymer can be adjusted, resulting in a conjugated polymer with good electrochromic properties such as low bandwidth, wide absorption range, fast response time, good optical transmittance, and good stability. This conjugated polymer has wide applications in the preparation of electrochromic materials or electrochromic devices.

[0052] Specifically, compared with the prior art, the present invention has the following advantages:

[0053] 1. This invention uses phenyl groups as the base intermediate, which possesses excellent electrochromic properties, ease of preparation, and good stability. Furthermore, the substitution of the phenyl unit plays a crucial role in finely adjusting the photoelectric and electronic properties of the polymer (band gap, molecular weight, inter- and intra-chain interactions, charge transport, etc.). Alkyl groups, as electron-donating groups, can reduce the polymer's band gap, thereby enabling the regulation of the polymer's optical properties and enhancing its electrochromic performance.

[0054] 2. The introduction of alkyl groups makes the polymer more porous and enhances charge flow. Therefore, the introduction of more alkyl groups can make the polymer response time faster. The introduction of alkyl groups is also beneficial to increase the solubility of the polymer. However, the introduction of too many alkyl groups will affect its coloring efficiency and cause a slight decrease in the electrochromic properties of the polymer. Therefore, by controlling the length and substitution amount of alkyl groups within the scope of this invention, a conjugated polymer with good overall electrochromic properties can be obtained.

[0055] 3. Under the influence of an applied voltage, the conjugated polymer of the present invention exhibits stable and reversible color changes from brown to dark gray to black, light brown to gray, and dark gray to transparent gray, and possesses excellent electrochromic properties, including fast response time, high coloring efficiency, and good optical transmittance. Furthermore, the conjugated polymer of the present invention is easy to prepare and has low raw material costs, making it suitable for large-scale production and processing. Attached Figure Description

[0056] Figure 1 NMR of the precursor p2MPh-EDOT in Example 1 1 H NMR spectrum.

[0057] Figure 2 The conjugated polymer P(p2MPh-EDOT) of Example 1 was used in MeCN-Bu4NPF6 (0.1 mol·L⁻¹). -1 ) spectroelectrochemical diagrams of the system.

[0058] Figure 3 The transmittance-time curves of the conjugated polymer P(p2MPh-EDOT) in Example 1 at 397 nm, 669 nm, and 1100 nm are shown.

[0059] Figure 4 NMR of the precursor o2MPh-EDOT in Example 2 1 H NMR spectrum.

[0060] Figure 5 The conjugated polymer P(o2MPh-EDOT) of Example 2 was used in MeCN-Bu4NPF6 (0.1 mol·L⁻¹). -1 ) spectroelectrochemical diagrams of the system.

[0061] Figure 6 The transmittance-time curves of the conjugated polymer P(o2MPh-EDOT) in Example 2 at 464 nm, 743 nm, and 1100 nm are shown.

[0062] Figure 7 NMR of the precursor 4MPh-EDOT in Example 3 1 H NMR spectrum.

[0063] Figure 8 The conjugated polymer P(4MPh-EDOT) of Example 3 was used in MeCN-Bu4NPF6 (0.1 mol·L⁻¹). -1 ) spectroelectrochemical diagrams of the system.

[0064] Figure 9The transmittance-time curves of the conjugated polymer P(4MPh-EDOT) in Example 3 at 535 nm, 776 nm, and 1100 nm are shown.

[0065] Figure 10 NMR of the precursor m2MPh-EDOT for Comparative Example 1 1 H NMR spectrum.

[0066] Figure 11 NMR of Ph-EDOT precursor for Comparative Example 2 1 H NMR spectrum.

[0067] Figure 12 The conjugated polymer P(Ph-EDOT) of Comparative Example 2 was used in MeCN-Bu4NPF6 (0.1 mol·L⁻¹). -1 ) spectroelectrochemical diagrams of the system.

[0068] Figure 13 The transmittance-time curves of the conjugated polymer P (Ph-EDOT) in Comparative Example 2 at 460 nm, 700 nm, and 1100 nm are shown. Detailed Implementation

[0069] The following specific embodiments further illustrate the content of the present invention in detail. It should also be understood that the following embodiments are only for further explanation of the present invention and should not be construed as limiting the scope of protection of the present invention. Non-essential improvements and adjustments made by those skilled in the art based on the principles described herein are all within the scope of protection of the present invention. The specific process parameters, etc., in the following examples are merely examples within a suitable range; that is, those skilled in the art can make selections within a suitable range based on the description herein, and are not intended to be limited to the specific data in the examples below. Unless otherwise specified, the raw materials, reagents, or apparatus used in the following embodiments and comparative examples can be obtained from conventional commercial sources or by existing known methods.

[0070] It should be noted that, in the embodiments of the present invention, coloring efficiency refers to the ratio of the change in absorbance of the electrochromic material at a given wavelength to the total number of electrons injected or extracted that cause the change; for an electrochromic material, coloring efficiency is an important parameter for evaluating material performance. The study of the coloring efficiency of conductive polymers should be combined with the electrochemical and spectral changes of the electrochromic film. The formula for calculating coloring efficiency (CE) is as follows:

[0071] CE=ΔOD / Q d

[0072] Among them, Q d It refers to the amount of charge migrating in / out per unit area; ΔOD refers to the change in light contrast, specifically at a specific wavelength λ.max The logarithm of the ratio of the corresponding transmittance during electrochemical oxidation and reduction of the polymer film, i.e., the transmittance T of the polymer film in the doped state. ox Transmittance T in neutral state red The logarithm of the ratio is calculated using the following formula:

[0073]

[0074] The change in transmittance refers to the change in the optical properties of a material under an applied voltage, which is quantitatively detected in an ultraviolet spectrometer. It is denoted by ΔT, where ΔT = T. red -T ox .

[0075] Response time refers to the time required for a material to achieve a 95% change in transmittance when a square wave voltage changes its potential under an applied voltage. A shorter response time indicates a faster conversion time, which better meets the requirements of practical applications. However, this value is related to many factors, including the conductivity of the substrate, the inherent properties of the material, the conductivity of the system, the concentration of free ions in the system, and the ion migration rate. Furthermore, different working environments in applications require different conversion times.

[0076] In some embodiments of the present invention, the conjugated polymer includes at least one of the compounds shown in formulas (1) to (3):

[0077]

[0078] In equations (1) to (3), n ranges from 3 to 200.

[0079] In some embodiments of the present invention, the compounds represented by formulas (1) to (3) are prepared by a method comprising the following steps:

[0080] (1) Preparation of active precursors (a) to (c): The electron-donating unit and intermediates (a') to (c') are cross-coupled in a catalyst and a solvent to obtain the active precursors (a) to (c) respectively;

[0081] The electron-donating unit is:

[0082] The intermediates (a') to (c') are:

[0083] The active precursors (a) to (c) are:

[0084] (2) Electrochemical polymerization: The active precursors (a) to (c) are subjected to electrochemical polymerization to obtain the compounds shown in formulas (1) to (3).

[0085] The present invention will be further described below with reference to specific embodiments and comparative examples.

[0086] Example 1

[0087] Electrochemical synthesis of conjugated polymer P(p2MPh-EDOT):

[0088] Based on the polymerization precursor structure (a) of 5,5'-(2,5-dimethyl-1,4-phenylene)bis(3,4-ethylenedioxythiophene), the chemical reaction process for the preparation of p2MPh-EDOT is shown below, with specific reaction steps and conditions as follows:

[0089]

[0090] (1) Preparation of compound (a)

[0091] 1,4-Dibromo-2,5-dimethylbenzene (0.5 g, 1.89 mmol), tributyl(2,3-dihydrothiopheno[3,4-ethylenedioxythiophene])stanane (2.04 g, 4.73 mmol), and tetrakis(triphenylphosphine)palladium (0.053 g, 0.0756 mmol) were placed in a 250 mL flask. After rinsing the apparatus with argon, a mixture of 80 mL toluene and 20 mL N,N-dimethylformamide was added to the flask under negative pressure. The mixture was then heated to 120 °C and stirred under reflux for 48 hours. The mixture was cooled to room temperature, toluene was removed by rotary evaporation, and the product was extracted with dichloromethane and washed with saturated sodium chloride solution. Dichloromethane was removed by rotary evaporation to give the crude product. Column chromatography yielded a pure white solid (0.23 g) in 31.5%. NMR of the product was analyzed. 1 H NMR spectrum as shown Figure 1 As shown.

[0092] (2) Synthesis of polymer P(p2MPh-EDOT):

[0093] The 5,5'-(2,5-dimethyl-1,4-phenylene)bis(3,4-ethylenedioxythiophene) conjugated polymer precursor was electrochemically polymerized into the corresponding polymer. The chemical reaction flow is shown below, and the specific reaction steps and conditions are as follows:

[0094]

[0095] Under nitrogen protection, compound (a) 5,5'-(2,5-dimethyl-1,4-phenylene)bis(3,4-ethylenedioxythiophene) prepared in step (1) was dissolved in 10 mL of purified dichloromethane as electrolyte to prepare a polymerization precursor with a concentration of 0.01 mol / L and 0.1 mol / L tetrabutylammonium hexafluorophosphate as electrolyte. After stirring evenly and continuously purging with argon for 20 minutes, the solution was kept under argon atmosphere and deposited on ITO conductive glass as working electrode, platinum sheet as counter electrode, and Ag / AgCl as reference electrode at a constant potential of 1.3 V to obtain 5,5'-(2,5-dimethyl-1,4-phenylene)bis(3,4-ethylenedioxythiophene) conjugated polymer P(p2MPh-EDOT).

[0096] Electrochromic performance study:

[0097] (1) Testing polymer P (p2MPh-EDOT) in MeCN-Bu4NPF6 (0.1 mol·L⁻¹) -1 ) spectroelectrochemical plots in the system, such as Figure 2 As shown, and combined with visual observation of the color change of the polymer material, it can be seen that as the potential increases, the color of the polymer material changes from light brown to dark black (light brown in the completely dedoped state). This is because the neutral polymer material has an absorption peak at around 397 nm, and the neutral polymer material appears light brown. After the polymer material is oxidized, the absorption peak at 397 nm gradually weakens and eventually disappears completely, while a new absorption peak appears at 600 nm to 1100 nm. This is due to the formation of polarons and bipolarons. Therefore, the polymer material appears light brown in the completely dedoped state and dark black in the doped state.

[0098] (2) The optical transmittance of P(p2MPh-EDOT) at wavelengths of 397 nm, 669 nm, and 1100 nm was studied using time-of-time absorption spectroscopy. During the experiment, the time interval between potential step changes was 5 s. The transmittance-time curves of polymer P(p2MPh-EDOT) at 397 nm, 669 nm, and 1100 nm were obtained, as shown below. Figure 3 As shown, the polymer material exhibits a certain degree of optical contrast at all three wavelengths. Furthermore, optical transmittance has a significant impact on the color change of the polymer material. The conjugated polymer material in Example 1 can change from light brown in the completely dedoped state to dark black in the doped state.

[0099] Furthermore, the transmittance change value ΔT, response time, and coloring efficiency can be obtained from the time-transmittance curve, as detailed in Table 1. Table 1 shows that polymer P(p2MPh-EDOT) exhibits high coloring efficiency.

[0100] Table 1 Electrochromic parameters of polymer P (p2MPh-EDOT)

[0101]

[0102] Example 2

[0103] Electrochemical synthesis of conjugated polymer P(o2MPh-EDOT):

[0104] Based on the polymerization precursor structure (a) of 5,5'-(2,3-dimethyl-1,4-phenylene)bis(3,4-ethylenedioxythiophene), the chemical reaction process for the preparation of p2MPh-EDOT is shown below, with specific reaction steps and conditions as follows:

[0105]

[0106] (1) Preparation of compound (b)

[0107] 1,4-Dibromo-2,3-dimethylbenzene (0.5 g, 1.89 mmol), tributyl(2,3-dihydrothiopheno[3,4-ethylenedioxythiophene])stanane (2.04 g, 4.73 mmol), and tetrakis(triphenylphosphine)palladium (0.053 g, 0.0756 mmol) were placed in a 250 mL flask. After rinsing the apparatus with argon, a mixture of 80 mL toluene and 20 mL N,N-dimethylformamide was added to the flask under negative pressure. The mixture was then heated to 120 °C and stirred under reflux for 48 hours. The mixture was cooled to room temperature, toluene was removed by rotary evaporation, and the product was extracted with dichloromethane and washed with saturated sodium chloride solution. Dichloromethane was removed by rotary evaporation to obtain the crude product. Column chromatography yielded a pure white solid (0.26 g) in 35.6%. NMR of the product was analyzed. 1 H NMR spectrum as shown Figure 4 As shown.

[0108] (2) Synthesis of polymer P(o2MPh-EDOT):

[0109] The 5,5'-(2,3-dimethyl-1,4-phenylene)bis(3,4-ethylenedioxythiophene) conjugated polymer precursor was electrochemically polymerized into the corresponding polymer. The chemical reaction flow is shown below, and the specific reaction steps and conditions are as follows:

[0110]

[0111] Under nitrogen protection, compound (b) 5,5'-(2,3-dimethyl-1,4-phenylene)bis(3,4-ethylenedioxythiophene) prepared in step (1) was dissolved in 10 mL of purified dichloromethane as electrolyte to prepare a polymerization precursor with a concentration of 0.01 mol / L and 0.1 mol / L tetrabutylammonium hexafluorophosphate as electrolyte. After stirring evenly and continuously purging with argon for 20 minutes, the solution was kept under argon atmosphere and deposited on ITO conductive glass as working electrode, platinum sheet as counter electrode, and Ag / AgCl as reference electrode at a constant potential of 1.3 V to obtain 5,5'-(2,3-dimethyl-1,4-phenylene)bis(3,4-ethylenedioxythiophene) conjugated polymer P(o2MPh-EDOT).

[0112] Electrochromic performance study:

[0113] (1) Testing of polymer P(o2MPh-EDOT) in MeCN-Bu4NPF6 (0.1 mol·L⁻¹) -1 ) spectroelectrochemical plots in the system, such as Figure 5 As shown, and combined with visual observation of the color change of the polymer material, it can be seen that as the potential increases, the color of the polymer material changes from dark brown to gray (dark brown in the completely dedoped state). This is because the neutral polymer material has an absorption peak at around 464 nm, and the neutral polymer material appears dark brown. After the polymer material is oxidized, the absorption peak at 464 nm gradually weakens and eventually disappears completely. Therefore, the polymer material appears dark brown in the completely dedoped state and gray in the doped state.

[0114] (2) The optical transmittance of P(o2MPh-EDOT) at wavelengths of 464 nm, 743 nm, and 1100 nm was studied using time-of-time absorption spectroscopy. During the experiment, the time interval between potential step changes was 5 s. The transmittance-time curves of the polymer P(o2MPh-EDOT) at 464 nm, 743 nm, and 1100 nm were obtained, as shown below. Figure 6 As shown, the polymer material exhibits good optical contrast and good optical stability at all three wavelengths. Furthermore, the optical transmittance has a significant impact on the color change of the polymer material, which can transform from a completely dedoped dark brown state to a doped gray state.

[0115] Furthermore, the transmittance change value ΔT, response time, and coloring efficiency can be obtained from the time-transmittance curve, as detailed in Table 2. Table 2 shows that the polymer P(o2MPh-EDOT) exhibits a relatively fast response time and a relatively ideal coloring efficiency.

[0116] Table 2 Electrochromic parameters of polymer P(o2MPh-EDOT)

[0117]

[0118] Example 3

[0119] Electrochemical synthesis of conjugated polymer P(4MPh-EDOT):

[0120] The chemical reaction process for preparing the polymerization precursor based on 5,5'-(2,3,5,6-tetramethyl-1,4-phenylene)bis((3,4-ethylenedioxythiophene)) is shown below, with specific reaction steps and conditions as follows:

[0121]

[0122] (1) Preparation of compound (4MPh-EDOT)

[0123] 1,4-Dibromo-2,3,5,6-tetramethylbenzene (0.5 g, 1.71 mmol), tributyl(2,3-dihydrothiopheno[3,4-ethylenedioxythiophene])stanane (1.85 g, 4.28 mmol), and tetra(triphenylphosphine)palladium (0.048 g, 0.0684 mmol) were placed in a 250 mL flask. After rinsing the apparatus with argon, a mixture of 80 mL toluene and 20 mL N,N-dimethylformamide was added to the flask under negative pressure. The mixture was then heated to 120 °C and stirred under reflux for 48 hours. The mixture was cooled to room temperature, toluene was removed by rotary evaporation, and the product was extracted with dichloromethane and washed with saturated sodium chloride solution. Dichloromethane was removed by rotary evaporation to obtain the crude product. Column chromatography yielded a pure white solid (0.32 g) in 45.7% of the product. NMR of the product was analyzed. 1 HNMR spectrum as follows Figure 7 As shown.

[0124] (2) Synthesis of polymer P(4MPh-EDOT):

[0125] The 5,5'-(2,3,5,6-tetramethyl-1,4-phenylene)bis(3,4-ethylenedioxythiophene) conjugated polymer precursor was electrochemically polymerized into the corresponding polymer. The chemical reaction flow is shown below, and the specific reaction steps and conditions are as follows:

[0126]

[0127] Under nitrogen protection, the compound 5,5'-(2,3,5,6-tetramethyl-1,4-phenylene)bis(3,4-ethylenedioxythiophene) prepared in step (1) was dissolved in 10 mL of purified dichloromethane as an electrolyte to prepare a polymerization precursor with a concentration of 0.01 mol / L and 0.1 mol / L tetrabutylammonium hexafluorophosphate as an electrolyte. After stirring evenly and continuously purging with argon for 20 minutes, the solution was kept under an argon atmosphere. Using ITO conductive glass as the working electrode, a platinum sheet as the counter electrode, and Ag / AgCl as the reference electrode, the 5,5'-(2,3,5,6-tetramethyl-1,4-phenylene)bis(3,4-ethylenedioxythiophene) conjugated polymer P(4MPh-EDOT) was deposited on ITO conductive glass at a constant potential to obtain the 5,5'-(2,3,5,6-tetramethyl-1,4-phenylene)bis(3,4-ethylenedioxythiophene) conjugated polymer P(4MPh-EDOT).

[0128] Electrochromic performance study:

[0129] (1) Testing polymer P (4MPh-EDOT) in MeCN-Bu4NPF6 (0.1mol·L⁻¹) -1 ) spectroelectrochemical plots in the system, such as Figure 8 As shown, and combined with visual observation of the color change of the polymer material, it can be seen that as the potential increases, the color of the polymer material changes from dark gray to transparent light gray (dark gray in the completely dedoped state). This is because the neutral polymer material has an absorption peak at around 535 nm, which is caused by the π-π* transition. The neutral polymer material appears dark gray. After the polymer material is oxidized, the absorption peak at 535 nm gradually weakens and eventually disappears completely. A new absorption band appears at 700 nm to 1100 nm, which is due to the formation of polarons and bipolarons. Therefore, the polymer material appears dark gray in the completely dedoped state and light gray in the doped state.

[0130] (2) The optical transmittance of P(4MPh-EDOT) at wavelengths of 535 nm, 776 nm, and 1100 nm was studied using time-of-flight absorption spectroscopy. During the experiment, the time interval between potential step changes was 5 s. The transmittance-time curves of polymer P(4MPh-EDOT) at 535 nm, 776 nm, and 1100 nm were obtained, as shown below. Figure 9 As shown, the polymer material exhibits fast response time and good optical stability at all three wavelengths. Furthermore, optical transmittance has a significant impact on the color change of the polymer material, which can transform from a completely dedoped dark gray to a more transparent light gray in a doped state.

[0131] Furthermore, the transmittance change value ΔT, response time, and coloring efficiency can be obtained from the time-transmittance curve, as shown in Table 3. Table 3 shows that polymer P(4MPh-EDOT) has a fast response time and also possesses relatively ideal coloring efficiency.

[0132] Table 3 Electrochromic parameters of polymer P (4MPh-EDOT)

[0133]

[0134] Comparative Example 1

[0135] Electrochemical synthesis of conjugated polymer P(m2MPh-EDOT):

[0136] The chemical reaction process for preparing the polymerization precursor based on 5,5'-(2,6-dimethyl-1,4-phenylene)bis(3,4-ethylenedioxythiophene) is shown below, with specific reaction steps and conditions as follows:

[0137]

[0138] (1) Preparation of compound (m2MPh-EDOT)

[0139] 2,5-Dibromo-1,3-dimethylbenzene (0.5 g, 1.89 mmol), tributyl(2,3-dihydrothiopheno[3,4-ethylenedioxythiophene])stanane (2.04 g, 4.73 mmol), and tetrakis(triphenylphosphine)palladium (0.053 g, 0.0756 mmol) were placed in a 250 mL flask. After rinsing the apparatus with argon, a mixture of 80 mL toluene and 20 mL N,N-dimethylformamide was added to the flask under negative pressure. The mixture was then heated to 120 °C and stirred under reflux for 48 hours. The mixture was cooled to room temperature, toluene was removed by rotary evaporation, and the product was extracted with dichloromethane and washed with saturated sodium chloride solution. Dichloromethane was removed by rotary evaporation to give the crude product. Column chromatography yielded an orange solid (0.21 g) in 28.8% of the product. NMR of the product was analyzed. 1 H NMR spectrum as shown Figure 10 As shown.

[0140] (3) Synthesis of polymer P(m2MPh-EDOT):

[0141] The 5,5'-(2,6-dimethyl-1,4-phenylene)bis(3,4-ethylenedioxythiophene) conjugated polymer precursor was electrochemically polymerized into the corresponding polymer. The chemical reaction flow is shown below, and the specific reaction steps and conditions are as follows:

[0142]

[0143] Under nitrogen protection, the compound 5,5'-(2,6-dimethyl-1,4-phenylene)bis(3,4-ethylenedioxythiophene) prepared in step (1) was dissolved in 10 mL of purified dichloromethane as an electrolyte to prepare a polymerization precursor with a concentration of 0.01 mol / L and a tetrabutylammonium hexafluorophosphate with a concentration of 0.1 mol / L as an electrolyte. After stirring evenly and continuously purging with argon gas for 20 minutes, the solution was kept under an argon atmosphere and deposited at a constant potential using ITO conductive glass as the working electrode, a platinum sheet as the counter electrode, and Ag / AgCl as the reference electrode.

[0144] However, tests failed to yield a polymer of this substance, possibly because the methyl group's position on the phenyl group resulted in excessive steric hindrance, preventing electropolymerization.

[0145] Comparative Example 2

[0146] Electrochemical synthesis of conjugated polymer P (Ph-EDOT):

[0147] The chemical reaction process for preparing the polymerization precursor based on 1,4-bis(3,4-ethylenedioxythiophene)benzene is shown below, with specific reaction steps and conditions as follows:

[0148]

[0149] (1) Preparation of compound (Ph-EDOT)

[0150] 1,4-Dibromobenzene (0.5 g, 2.12 mmol), tributyl(2,3-dihydrothiopheno[3,4-ethylenedioxythiophene])stanane (2.29 g, 5.3 mmol), and tetrakis(triphenylphosphine)palladium (0.059 g, 0.0848 mmol) were placed in a 250 mL flask. After rinsing the apparatus with argon, a mixture of 80 mL toluene and 20 mL N,N-dimethylformamide was added to the flask under negative pressure. The mixture was then heated to 120 °C and stirred under reflux for 48 hours. The mixture was cooled to room temperature, toluene was removed by rotary evaporation, and the product was extracted with dichloromethane and washed with saturated sodium chloride solution. Dichloromethane was removed by rotary evaporation to give the crude product. Column chromatography yielded an orange solid (0.32 g) in 42.1% of the product. NMR of the product was... 1 H NMR spectrum as shown Figure 11 As shown.

[0151] (4) Synthesis of polymer P (Ph-EDOT):

[0152] The 1,4-bis(3,4-ethylenedioxythiophene)benzene conjugated polymer precursor was electrochemically polymerized into the corresponding polymer. The chemical reaction flow is shown below, and the specific reaction steps and conditions are as follows:

[0153]

[0154] Under nitrogen protection, the compound 1,4-bis(3,4-ethylenedioxythiophene)benzene prepared in step (1) was dissolved in 10 mL of purified dichloromethane as an electrolyte to prepare a polymerization precursor with a concentration of 0.01 mol / L and 0.1 mol / L tetrabutylammonium hexafluorophosphate as an electrolyte. After stirring evenly and continuously purging with argon for 20 minutes, the solution was kept under an argon atmosphere. Using ITO conductive glass as the working electrode, a platinum sheet as the counter electrode, and Ag / AgCl as the reference electrode, the conjugated polymer P (Ph-EDOT) was deposited on the ITO conductive glass under constant potential to obtain the conjugated polymer.

[0155] Electrochromic performance study:

[0156] (1) Testing polymer P (Ph-EDOT) in MeCN-Bu4NPF6 (0.1 mol·L⁻¹) -1 ) spectroelectrochemical plots in the system, such as Figure 12 As shown, and combined with visual observation of the color change of the polymer material, it can be seen that as the potential increases, the color of the polymer material changes from reddish-brown to grayish-green (reddish-brown in the completely dedoped state). This is because the neutral polymer material has an absorption peak at 460 nm, which is caused by the π-π* transition, and the neutral polymer material appears reddish-brown. After the polymer material is oxidized, the absorption peak at 460 nm gradually weakens and eventually disappears completely, and a new absorption band appears at 700 nm to 1100 nm. This is due to the formation of polarons and bipolarons. Therefore, the polymer material appears reddish-brown in the completely dedoped state and grayish-green in the doped state.

[0157] (2) The optical transmittance of P(Ph-EDOT) at wavelengths of 460 nm, 700 nm, and 1100 nm was studied using time-of-flight absorption spectroscopy. During the experiment, the time interval between potential step changes was 5 s. The transmittance-time curves of polymer P(Ph-EDOT) at 460 nm, 700 nm, and 1100 nm were obtained, as shown below. Figure 13 As shown, the polymer material exhibits a relatively slow response time and fairly average optical stability at all three wavelengths. Furthermore, the optical transmittance has a significant impact on the color change of the polymer material, which can change from a completely dedoped reddish-brown state to a doped grayish-green state.

[0158] Furthermore, the transmittance change ΔT, response time, and coloring efficiency can be obtained from the time-transmittance curve, as detailed in Table 4. Table 4 shows that the polymer P (Ph-EDOT) has a relatively slow response time.

[0159] Table 4 Electrochromic parameters of polymer P (Ph-EDOT)

[0160]

[0161]

[0162] As can be seen from the above embodiments and comparative examples, the polymers of the present invention use a series of benzene units with different methyl substitution sites as intermediates, and 3,4-ethylenedioxythiophene (EDOT) as electron-donating units. By changing the methyl substitution sites and the number of methyl groups, the length of the conjugated chain can be controlled, thereby adjusting the absorption spectrum of the polymer and thus changing the color of the polymer. Methyl groups are electron-donating groups, and the introduction of methyl groups can reduce the band gap of the polymer, thereby achieving the regulation of the optical properties of the polymer and enhancing the electrochromic properties and solubility of the polymer. At the same time, the addition of benzene rings results in a rigid coplanar fused ring structure in the molecule, which is beneficial to enhance charge flow. This makes the polymers, as electrochromic materials, have a lower band gap, a wider redox peak, good optical contrast, fast response time, high coloring efficiency, and good stability.

[0163] Furthermore, the introduction of methyl groups makes the polymer more porous and enhances charge flow. Therefore, introducing more methyl groups can make the polymer response time faster, and the introduction of methyl groups is beneficial to increasing the polymer solubility. However, the introduction of too many methyl groups will affect its coloring efficiency, resulting in a slight decrease in the electrochromic properties of the polymer. Therefore, by controlling the length and substitution amount of methyl groups within the range of the embodiments of the present invention, a conjugated polymer with good overall electrochromic properties can be obtained.

[0164] This invention uses phenyl groups as the base intermediate unit, which exhibits excellent electrochromic properties, ease of preparation, and good stability. Furthermore, the substitution of the phenyl unit plays a crucial role in finely adjusting the photoelectric and electronic properties of the polymer (band gap, molecular weight, inter- and intra-chain interactions, charge transport, etc.). Alkyl groups, as electron-donating groups, can reduce the polymer's band gap, thereby enabling the regulation of the polymer's optical properties and enhancing its electrochromic performance. Under an applied voltage, the conjugated polymers of this invention exhibit stable and reversible color changes from brown to dark gray to black, light brown to gray, and dark gray to transparent gray, and possess excellent electrochromic properties, including fast response time, high coloring efficiency, and good optical transmittance. Moreover, the conjugated polymers of this invention are easy to prepare and have low raw material costs, making them suitable for large-scale production and processing.

[0165] In summary, this invention uses alkyl-substituted phenyl groups as intermediate units and ethylenedioxythiophene as electron-donating units. By introducing a benzene ring, a rigid coplanar fused ring structure is formed in the molecule, enhancing charge mobility. Furthermore, by combining alkyl groups with specific substitution numbers and positions, the electron distribution and conjugated chain length of the conjugated polymer can be adjusted, resulting in a conjugated polymer with excellent electrochromic properties such as low bandwidth, wide absorption range, fast response time, good optical transmittance, and good stability. This conjugated polymer has wide applications in the preparation of electrochromic materials or electrochromic devices.

Claims

1. The application of a conjugated polymer based on alkyl-substituted phenyl groups in the preparation of electrochromic materials or electrochromic devices, characterized in that, The conjugated polymer includes at least one of the compounds shown in formulas (1) to (3): （1）； （2）； （3）； In equations (1) to (3), n is 3 to 200; The compounds shown in formulas (1) to (3) are prepared by a method comprising the following steps: (1) Preparation of active precursors (a) to (c): The electron-donating unit and the intermediates (a') to (c') are cross-coupled in a catalyst and a solvent to obtain the active precursors (a) to (c). The electron-donating unit is: ; The intermediates (a') to (c') are: (a'); (b'); (c'); The active precursors (a) to (c) are: (a); (b); (c); (2) Electrochemical polymerization: The active precursors (a) to (c) are subjected to electrochemical polymerization to obtain the compounds shown in formulas (1) to (3); The solvent includes at least one of benzene, toluene, or N,N-dimethylformamide; The catalyst is selected from palladium catalysts; the palladium catalyst includes tetratriphenylphosphine palladium, bistriphenylphosphine dichloride palladium, or a combination thereof; The temperature for the cross-coupling reaction is 100~140℃; The cross-coupling reaction takes 24-72 hours; The electrochemical polymerization reaction specifically involves electrodeposition using a solution containing the active precursor as an electrolyte solution to obtain the polymer. The concentration of the active precursor in the electrolyte solution is 0.001~0.01 mmol·L⁻¹. -1 ; The electrolyte solution also contains a supporting electrolyte; the supporting electrolyte includes at least one of tetrabutylammonium hexafluoride, tetrabutylammonium tetrafluoroborate, or lithium perchlorate; the concentration of the supporting electrolyte in the electrolyte solution is 0.01~0.2 mmol·L⁻¹. -1 .

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