A kind of triphenylamine monomer based on benzodithiophene-4,8-dione, polymer and its preparation method and application

Abstract

The application discloses a triphenylamine monomer based on benzodithiophene-4,8-dione, a polymer and a preparation method and application thereof, and relates to the field of electrochromic materials. The triphenylamine monomer based on benzodithiophene-4,8-dione has a structure shown in formula (I); wherein R is selected from C1-C18 alkyl, aryl or substituted aryl; D is a triphenylamine group; and pi is selected from the following structures. The triphenylamine monomer based on benzodithiophene-4,8-dione has a unique 'donor-conjugated bridge-acceptor-conjugated bridge-donor' (D-pi-A-pi-D) molecular structure.

Description

Technical Field

[0001] This invention relates to the field of electrochromic materials technology, and in particular to a triphenylamine monomer, polymer, preparation method and application based on benzodithiophene-4,8-dione. Background Technology

[0002] Electrochromism refers to the phenomenon where a material's optical properties, such as color, absorbance, and transmittance, undergo reversible changes when an external voltage is applied. Materials possessing this property are called electrochromic materials, and their color-changing process originates from changes in the material's electronic structure caused by electrochemical redox reactions. This technology, due to its unique advantages in controllable optical modulation, shows great application potential in many cutting-edge fields, such as dynamically dimming windows in smart energy-saving buildings, anti-glare rearview mirrors and displays, low-power information display devices, and emerging flexible wearable electronic devices. Among the many electrochromic material systems, conjugated polymers have become a research hotspot in this field due to their advantages such as strong molecular structure designability, excellent optical properties, relatively fast response speed, and the ability to be processed using solution methods.

[0003] The electrochromic behavior of conjugated polymers is essentially a redox process of doping and dedoping. When a voltage is applied, the polymer backbone undergoes p-type doping (loss of electrons) or n-type doping (gain of electrons), leading to the generation of charge carriers such as polarons or bipolarons. This, in turn, causes changes in the geometry and electronic band structure of the polymer's conjugated backbone, ultimately manifesting as a significant shift or alteration in the absorption spectrum in the visible and near-infrared regions, achieving reversible color switching. Compared to inorganic electrochromic materials, conjugated polymers typically possess a wider color tuning range, higher optical contrast, faster response speed, and better processing compatibility, making them one of the ideal candidate materials for realizing next-generation high-performance, low-cost, flexible electrochromic devices.

[0004] Currently, conjugated polymers used in electrochromic applications are mainly based on several classic aromatic heterocyclic or aromatic amine structural units. Among them, polythiophene and its derivatives are one of the earliest and most widely studied systems. By adjusting the alkyl side chains on the thiophene ring, their solubility and film-forming properties can be improved to some extent, and their redox potential and color change range can be controlled. However, traditional polythiophene materials usually suffer from poor intrinsic solubility. Even with the introduction of side chains, their solution processability is still not ideal, limiting the process window for preparing large-area uniform films. In addition, their driving voltage is relatively high, limiting the potential for improving optical contrast. Furthermore, during long-term cyclic redox processes, irreversible structural changes or side reactions may occur in the polymer chains, leading to optical performance degradation and insufficient cycle stability. Polyaniline is another important class of conductive polymers with a rich variety of color-changing states. However, its fully reduced and fully oxidized states are usually colorless or pale yellow. High-contrast color changes mostly occur in intermediate oxidation states, and materials in these states often have poor chemical stability in conventional electrolyte environments, are prone to hydrolysis or degradation, and have long response times for color switching. Polypyrrole materials face similar challenges. The density of their films often affects the kinetics of ion implantation / extraction, leading to slower response rates. Furthermore, their coloring efficiency and long-term cycling stability need further improvement. Polymers with triphenylamine as the core unit are electrochromic material systems that have attracted considerable attention in recent years. Due to the excellent hole transport capability and stable free radical cation characteristics of the triphenylamine group, polymers using it as a building block typically exhibit low oxidation potential, high coloring efficiency, and good oxidation-state stability. These materials readily produce strong color-developing effects upon oxidation, especially in dark states (such as blue and green). However, traditional triphenylamine homopolymers or simple copolymers also have some inherent limitations. For example, the planarity and rigidity of their molecular skeleton can lead to strong inter-chain stacking, affecting their solubility in common organic solvents and making solution processing difficult. During electrochemical cycling, although the triphenylamine free radical cation is relatively stable, the overall structural stability of the polymer, especially its adhesion to the electrode substrate after multiple volume expansion / contractions and its oxidation tolerance at high potentials, still needs further improvement. Furthermore, how to precisely control its conjugation length, energy level structure, and ion transport channels through molecular design to simultaneously achieve low driving voltage, high optical contrast, fast switching speed, excellent cycling stability, and rich color control remains a common challenge for existing triphenylamine electrochromic polymers.

[0005] In summary, existing electrochromic polymer materials, whether classic polythiophene, polyaniline, and polypyrrole, or improved triphenylamine polymers, generally face a series of key technological bottlenecks on their path to practical application. Solubility and processability issues restrict low-cost, large-scale, and high-quality thin-film fabrication processes. Excessively high driving voltages increase device power consumption, hindering low-power applications. Insufficient optical contrast limits the clarity of visual differences, slow switching times affect the real-time dynamic response, and poor cycle stability directly impacts device lifespan and reliability. These defects are interconnected, often stemming from the material's molecular structure. For example, poor solubility often arises from strong intermolecular forces caused by an overly rigid and planar conjugated framework; high driving voltages are related to a mismatch in the material's redox energy levels; slow switching speeds may be related to limited ion diffusion rates in polymer films; and stability issues involve the chemical stability of redox intermediates or final products, as well as the mechanical stability of the polymer film during repeated doping / dedoping processes.

[0006] Therefore, the development of novel electrochromic polymer materials urgently requires designing and synthesizing conjugated monomers with novel donor-acceptor structures or specific functional groups from a molecular engineering perspective, and constructing polymers with excellent comprehensive performance through reasonable copolymerization strategies. Summary of the Invention

[0007] The purpose of this invention is to develop an electrochromic polymer with low driving voltage, high contrast, fast switching time, and good stability.

[0008] A triphenylamine monomer based on benzodithiophene-4,8-dione has the structure shown in formula (I): ; Wherein, R is selected from C1-C18 alkyl, aryl, or substituted aryl groups; D is a triphenylamine group; π is selected from the following structures: .

[0009] According to embodiments of the present invention, one of the technical solutions has at least one of the following advantages or beneficial effects: This invention is based on the triphenylamine monomer of benzodithiophene-4,8-dione, which has a unique “donor-conjugated bridge-acceptor-conjugated bridge-donor” (D-π-A-π-D) molecular structure. This structure uses the strongly electron-withdrawing benzodithiophene-4,8-dione as the acceptor core (A), the strongly electron-withdrawing triphenylamine as the terminal donor (D), and the connection is made through a thiophene conjugated bridge (π).

[0010] This architecture generates a significant intramolecular push-pull electronic effect, greatly enhancing the intramolecular charge transfer intensity and effectively modulating and narrowing the molecule's optical band gap. The reduced band gap means optimized molecular frontier orbital energy levels, enabling the conjugated polymer obtained through electrochemical polymerization to undergo effective redox reactions at lower driving voltages, providing a molecular basis for low-voltage driving. Simultaneously, this strong charge transfer characteristic and narrow band gap result in distinctly different electronic structures and light absorption behaviors between the neutral and oxidized states, exhibiting high-contrast color changes in the visible to near-infrared region. Furthermore, the rigidity and stability of the triphenylamine donor, combined with the charge transport-promoting effect of the conjugated thiophene bridge, contribute to the material's rapid electrochemical response and excellent cycling stability.

[0011] The optional alkyl or aryl side chains (R) provide structural flexibility for adjusting monomer solubility and optimizing the morphology and processing properties of subsequent polymer films.

[0012] Therefore, the monomer of this invention is the key structural unit of the entire invention of high-performance electrochromic polymer, and its D-π-A-π-D structure is the core of solving existing technical problems such as high driving voltage and low contrast.

[0013] According to one embodiment of the present invention, R is selected from C4-C15 alkyl, aryl, and / or substituted aryl groups; preferably, R is selected from C4-C15 alkyl groups. The C4-C15 alkyl chain provides sufficient hydrophobicity and steric volume to improve solubility in organic solvents without excessively disrupting the π-π stacking in the solid state.

[0014] According to one embodiment of the present invention, the substituent on the substituted aryl group is selected from halogen, nitro, amino, hydroxyl, or carboxyl groups. Different substituents can adjust the polarity, solubility, and redox potential of the monomer, providing a means for fine-tuning the material properties. 。

[0015] A method for preparing the triphenylamine monomer based on benzodithiophene-4,8-dione includes the following steps: Under a protective gas atmosphere, the acceptor, triphenylamine-4-boronic acid, base, palladium catalyst and solvent are mixed and subjected to a Suzuki coupling reaction to obtain the thiophene derivative monomer of the benzodithiophene-4,8-dione. The structural formula of the receptor is: ; The definitions of R and π are consistent with those of the triphenylamine monomers based on benzodithiophene-4,8-dione.

[0016] According to embodiments of the present invention, one of the technical solutions has at least one of the following advantages or beneficial effects: The method of this invention employs the Suzuki coupling reaction as a key step. Under palladium catalysis, a pre-designed "acceptor-π" module with a bromine leaving group undergoes cross-coupling with the borate group of triphenylamine-4-boronic acid. This reaction exhibits high chemoselectivity and position selectivity, enabling the precise formation of new carbon-carbon bonds at specific positions on the thiophene ring, thereby covalently linking the strong electron-donating unit (triphenylamine) with the strong electron-withdrawing core (benzodithiophene dione) via a conjugated bridge.

[0017] The method of this invention has relatively mild conditions and good tolerance to functional groups. It can obtain D-π-A-π-D target molecules with well-defined structures in feasible yields, laying a solid process foundation for the subsequent large-scale preparation of monomer materials with consistent performance.

[0018] According to one embodiment of the present invention, the molar ratio of the receptor compound to triphenylamine-4-boronic acid is 1:(2.5-3.5).

[0019] According to one embodiment of the present invention, the molar ratio of the receptor to triphenylamine-4-boronic acid is 1:3.

[0020] According to one embodiment of the invention, the base is potassium carbonate, and / or the molar ratio of the acceptor compound to the base is 1:(8-12). Sufficient potassium carbonate provides the necessary alkaline environment, promoting the transmetallization step of the borate ester and accelerating the coupling reaction process.

[0021] According to one embodiment of the present invention, the molar ratio of the receptor compound to the base is 1:(10-12). Preferably, the molar ratio of the receptor compound to the base is 1:10.

[0022] According to one embodiment of the present invention, the palladium catalyst is tetrakis(triphenylphosphine)palladium, and / or the molar ratio of the acceptor compound to the palladium catalyst is 1:(0.05-0.15). Tetrakis(triphenylphosphine)palladium exhibits high catalytic activity for Suzuki coupling.

[0023] Preferably, the molar ratio of the acceptor compound to the palladium catalyst is 1:(0.1-0.15); more preferably, the molar ratio of the acceptor compound to the palladium catalyst is 1:0.1.

[0024] According to one embodiment of the present invention, the temperature of the Suzuki coupling reaction is 70-130°C.

[0025] According to one embodiment of the present invention, the reaction time of the Suzuki coupling reaction is 8-48 hours. More preferably, the temperature of the Suzuki coupling reaction is 90-120°C; and the reaction time is 12-24 hours.

[0026] According to one embodiment of the present invention, the solvent includes at least one selected from N,N-dimethylformamide, benzene, acetone, water, and ethanol.

[0027] According to one embodiment of the present invention, the solvent is a mixture of toluene, water and ethanol.

[0028] According to one embodiment of the present invention, the protective gas atmosphere includes nitrogen or a rare gas.

[0029] According to one embodiment of the present invention, a washing step is performed after the Suzuki coupling reaction is completed; the washing reagent is preferably a sodium chloride solution.

[0030] According to one embodiment of the present invention, a chromatographic separation and purification step is performed after washing.

[0031] According to one embodiment of the present invention, the chromatographic separation and purification uses a silica gel column.

[0032] An electrochromic polymer, prepared by electrochemical polymerization of a triphenylamine monomer based on benzodithiophene-4,8-dione, has the general structural formula shown in formula (II): ; Wherein, the definition of R is the same as that of the triphenylamine monomer based on benzodithiophene-4,8-dione; n is a positive integer representing the degree of aggregation.

[0033] According to embodiments of the present invention, one of the technical solutions has at least one of the following advantages or beneficial effects: The polymer of this invention uses benzodithiophene-4,8-dione as the acceptor, thiophene as the π-bridge, and triphenylamine as the donor, forming a D-π-A-π-D structure. Benzodithiophene-4,8-dione has a strong electron-withdrawing ability, which can enhance the intramolecular charge transfer of the DAD conjugated polymer. EDOT, as a strong electron-donating group, can reduce the initial oxidation potential of the monomer, decrease the optical band gap of the conjugated polymer, and improve the electrochromic properties.

[0034] The polymer of the present invention exhibits a stable and reversible color change from yellow to dark green under an applied voltage, and has excellent electrochromic properties such as high contrast, high coloring efficiency, and fast switching time.

[0035] Therefore, the polymer of this invention is itself a direct material carrier for solving technical problems such as low driving voltage, high contrast, and fast response.

[0036] According to one embodiment of the present invention, n is 10-5000. Polymers with a degree of polymerization within this range can form thin films with sufficient mechanical strength and continuous conductive networks, ensuring the stability and repeatability of electrochromic properties.

[0037] According to one embodiment of the present invention, n is 10-3000.

[0038] A method for preparing an electrochromic polymer includes the following steps: S1 dissolves the thiophene derivative monomer of benzodithiophene-4,8-dione and the electrolyte in a solvent to prepare an electrolyte solution; S2 The electrolyte is placed in an electrochemical electrolytic cell, and an electrochemical polymerization reaction is carried out on the working electrode using a constant potential method to deposit the electrochromic polymer on the surface of the working electrode.

[0039] According to one embodiment of the present invention, the concentration of the thiophene derivative monomer of benzodithiophene-4,8-dione in the electrolyte is 1-12 mmol·L⁻¹. -1 Preferably, the thiophene derivative monomer of benzodithiophene-4,8-dione in the electrolyte is 1-10 mmol·L⁻¹. -1 .

[0040] According to one embodiment of the present invention, the electrolyte is selected from at least one of tetrabutylammonium hexafluorophosphate, tetrabutylammonium tetrafluoroborate, or lithium perchlorate.

[0041] According to one embodiment of the present invention, the concentration of the electrolyte in the electrolyte solution is 0.05-0.3 mol·L⁻¹. -1 Preferably, the concentration is 0.06-0.1 mol·L⁻¹. -1 .

[0042] The electropolymerization chemical reaction process in step (2) is shown in the following reaction equation:

[0043] According to one embodiment of the present invention, in the three-electrode system, the working electrode is Pt / ITO conductive glass.

[0044] According to one embodiment of the present invention, in the three-electrode system, the reference electrode is an Ag / AgCl electrode.

[0045] According to one embodiment of the present invention, in the three-electrode system, the counter electrode is a platinum wire.

[0046] According to one embodiment of the present invention, the solvent in step S1 is at least one of dichloromethane, trichloromethane and acetonitrile.

[0047] An electrochromic material comprising the aforementioned electrochromic polymer.

[0048] An electrochromic device comprising an electrochromic layer formed of the electrochromic polymer.

[0049] According to one embodiment of the present invention, the electrochromic device is a smart window, an anti-glare rearview mirror, an information display, or an electronic tag.

[0050] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0051] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which: Figure 1 The image shows the spectroelectrochemical spectrum of the electrochromic polymer prepared in Example 1.

[0052] Figure 2 The image shows the optical transmittance of the electrochromic polymer prepared in Example 1.

[0053] Figure 3 This is a test image of the short-term memory effect of the electrochromic polymer prepared in Example 1. Detailed Implementation

[0054] The terms "preferred," "more preferred," etc., used in this invention refer to embodiments of the invention that provide certain beneficial effects under certain circumstances. However, other embodiments may also be preferred under the same or other circumstances. Furthermore, the description of one or more preferred embodiments does not imply that other embodiments are unavailable, nor is it intended to exclude other embodiments from the scope of this invention.

[0055] When a numerical range is disclosed herein, the range is considered continuous and includes the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Furthermore, when the range refers to integers, it includes every integer between the minimum and maximum values ​​of the range. Additionally, when multiple ranges are provided to describe a feature or characteristic, the ranges may be combined. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all subranges to which they are incorporated.

[0056] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of the present invention.

[0057] Unless otherwise specified, the reagents, methods and equipment used in this invention are all conventional reagents, methods and equipment in this technical field.

[0058] The degree of polymerization n mentioned in this invention refers to the average number of repeating structural units in the conjugated polymer backbone, which ranges from 10 to 5000. The n value is a statistical average, and its specific value depends on the reaction conditions in the final electrochemical polymerization step, mainly including: the concentration of the precursor monomer, the applied deposition potential (voltage), the deposition time (charge), the type and concentration of the electrolyte, and the solvent system. Those skilled in the art know that in electrochemical polymerization, by precisely controlling the above parameters, the growth kinetics and termination process of the polymer chain can be directionally influenced, thereby obtaining polymer films with different n values ​​over a wide range. For example, increasing the monomer concentration, extending the deposition time, or optimizing the deposition potential generally tends to produce polymers with a higher degree of polymerization (larger n value); conversely, it is easier to obtain polymers with a lower degree of polymerization (smaller n value). Lower limit (n=10): corresponds to the oligomer or low-molecular-weight state. Such substances still possess the core star-shaped D-π-A structural unit of this invention, exhibiting basic electrochromic activity, and can be used in applications requiring extremely thin films or specific solubility. Upper limit (n=5000): corresponds to high molecular weight polymers. High molecular weight helps to form more continuous and stable solid films, improving mechanical strength and charge transport capabilities, which is crucial for the fabrication of high-performance, long-life electrochromic devices.

[0059] To enable those skilled in the art to more clearly understand the above-mentioned technical solutions of the present invention, the following embodiments are provided for illustration. Electrochromic materials have many data parameters that can be used to evaluate their performance in the laboratory stage, such as ultraviolet absorbance, transmittance, coloring efficiency, response time, and open-circuit memory effect, all of which are important parameters for evaluating whether a material is suitable for practical application.

[0060] Ultraviolet absorbance refers to the change in polymer properties during doping and dedoping processes. Macroscopically, this is manifested as a change in absorbance in the ultraviolet-visible spectrum. Different applied voltages and different degrees of polymer doping will result in corresponding changes in the color and brightness of the film. However, this property can only qualitatively analyze whether a material has electrochromic properties, and cannot subjectively judge or quantitatively analyze the quality of the material's electrochromic properties.

[0061] Transmittance refers to the change in the optical properties of a material under an applied voltage, which is quantitatively detected in an ultraviolet spectrometer and is represented by ΔT.

[0062] Coloring efficiency is a quantitative analysis of the amount of charge flowing through the polymer when a material undergoes color changes and transmittance alterations under an applied voltage. In other words, it reflects the energy loss during material application. Higher coloring efficiency indicates better energy utilization and greater energy savings. Coloring efficiency, or CE value, is calculated as the ratio of the change in optical density (ΔOD) during doping and dedoping to the amount of charge (Qd) flowing through the material's potential area. The formula is as follows: CE = ΔOD / Qd; Where ΔOD is the logarithm of the ratio of transmittance in different states of the material at a specified wavelength, and the calculation formula is as follows: ΔOD = log(Tox / Tred); Tox and Tred are the transmittance values ​​of the material in its oxidized and reduced states, respectively.

[0063] 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.

[0064] The memory effect refers to the property of a material to maintain its doped or dedoped state under open-circuit conditions with an applied voltage. When a fully doped or fully dedoped voltage is applied to a material, and then the applied voltage is disconnected, the time-transmittance curve of the material in a UV spectrometer is observed. Under normal circumstances, because the dopant ions in the material are not bound under open-circuit conditions, they will automatically dissociate into the solution, causing changes in the material's color and transmittance, thus indicating the degree of change in the material's memory effect.

[0065] Unless otherwise specified, the raw materials, reagents or devices used in the following examples are available from conventional commercial sources or can be obtained by existing known methods.

[0066] The polymer was obtained by electropolymerization using TPATBD as the monomer at different constant voltage potentials. The benzodithiophene-4,8-dione polymer film exhibits excellent electrochromic properties, enabling reversible color switching and high contrast changes at low driving voltages, and shows significant application potential in the commercial electrochromic field.

[0067] In the examples, 1,3-bis(5-bromothiophen-2-yl)-5,7-bis(2-ethylhexyl)-4H,8H-benzo[1,2-c:4,5-c']dithiophene-4,8-dione was prepared by the following method: Under a nitrogen atmosphere, 1,3-dibromo-5,7-bis(2-ethylhexyl)-4H,8H-benzo[1,2-c:4,5-c']dithiophene-4,8-dione (0.5 g, 0.83 mmol), tributyl(thiophene-2-yl)stanane (0.65 g, 1.743 mmol), and catalyst Pd(PPh3)4 (0.1 g, 0.083 mmol) were placed in a 250 mL single-necked flask, and TOL (toluene, 32...) was added. The product was stirred evenly with DMF (N,N-dimethylacetamide, 8 mL, TOL to DMF volume ratio of 4:1), heated to 120℃ and refluxed for 48 hours. After the reaction system was cooled, the product was poured into saturated brine, extracted 4 times with dichloromethane, and then the organic layer was washed with water. The solvent was then removed by vacuum distillation and rotary evaporation. Separation was performed using a silica gel column with dichloromethane and petroleum ether mixed in a volume ratio of 1:6 as the eluent. The purified product was a pale yellow powder (1) 476 mg, with a yield of 97%.

[0068] Under ice bath conditions, product (1) (0.3 g, 0.51 mmol) and 5 ml of tetrahydrofuran (THF) were placed in a 50 ml flask and stirred until fully dissolved. Then, 5 ml of THF solution containing N-bromosuccinimide (0.19 g, 1.07 mmol) was slowly added dropwise to the flask and stirred until well mixed. The reaction was carried out at room temperature for 12 hours. The reaction was stopped by adding pure water. Solid-liquid separation was performed through a filter funnel to obtain 220 mg of yellow powder product (2) (3-bis(5-bromothiophene-2-yl)-5,7-bis(2-ethylhexyl)-4H,8H-benzo[1,2-c:4,5-c']dithiophene-4,8-dione), with a yield of 56%.

[0069] Example 1 A triphenylamine monomer based on benzodithiophene-4,8-dione (named TPATBD) has the following structure: .

[0070] The synthesis process of the triphenylamine monomers based on benzodithiophene-4,8-dione is as follows: The above-mentioned method for preparing triphenylamine monomers based on benzodithiophene-4,8-dione includes the following steps: Under a nitrogen atmosphere, 1,3-bis(5-bromothiophene-2-yl)-5,7-bis(2-ethylhexyl)-4H,8H-benzo[1,2-c:4,5-c']dithiophene-4,8-dione (2) (0.22 g, 0.287 mmol), triphenylamine-4-boronic acid (0.249 g, 0.3 mmol), potassium carbonate (0.397 g, 2.87 mmol), and catalyst Pd(PPh3)4 (0.033 g, 0.0287 mmol) were placed in a 250 mL single-necked flask, and toluene (20 mL), water (10 mL), and ethanol (20 mL) were added. The mixture was stirred evenly (mL), heated to 70℃ and refluxed for 24 hours. After the reaction system cooled, the product was poured into saturated brine and extracted five times with dichloromethane. The organic layer was then washed with water. The solvent was removed by vacuum distillation and rotary evaporation. Separation was performed using a silica gel column with dichloromethane and petroleum ether as the eluent in a volume ratio of 1:4. The purified product (monomer TPATBD) was 80.2 mg red powder, with a yield of 25.5%.

[0071] The 1H NMR characterization results of the product (monomer TPATBD) are as follows: 1 H NMR (400 MHz, Chloroform- d δ 7.70 (s, 2H), 7.46 (d, J = 8.2 Hz, 4H), 7.30 – 7.15 (m, 10H), 7.06 (d, J =7.9 Hz, 8H), 6.98 (s, 8H), 3.25 (d, J = 7.0 Hz, 4H), 1.70 (s, 2H), 1.39 – 1.15(m, 18H), 0.83 (dt, J = 21.9, 7.2 Hz, 12H).

[0072] An electrochromic polymer (named P(TPATBD)) is synthesized as follows: .

[0073] The preparation method of the above-mentioned electrochromic polymer includes the following steps: Electrochemical polymerization was carried out in a one-chamber three-electrode system. The working electrode was ITO conductive glass, the counter electrode was a platinum sheet, and the reference electrode was an Ag / AgCl electrode (silver wire was electrolyzed at a constant potential of 1.5 V for 100 s in 6 mol / L HCl solution to generate an AgCl coating on the surface).

[0074] Using 10 mL of dichloromethane as the electrolyte, TPATBD (0.01 mol / L) as the monomer and tetrabutylammonium hexafluorophosphate (0.1 mol / L) as the electrolyte, polymerization was carried out using a potentiostatic method. The polymerization potential was 0.68 V, the polymerization time was 100 s, and the initial oxidation potential was +0.15 V. The polymer film obtained by electrodeposition was rinsed with acetonitrile to remove the electrolyte solution and oligomers generated in the polymer.

[0075] Comparative Example 1 The difference between Comparative Example 1 and Example 1 is that in Example 1, the π value in the triphenylamine monomer based on benzodithiophene-4,8-dione is... The π in Comparative Example 1 is: .

[0076] A triphenylamine monomer based on benzodithiophene-4,8-dione (named TPAEBD) has the following structure: .

[0077] The synthesis process of the triphenylamine monomers based on benzodithiophene-4,8-dione is as follows: .

[0078] The above method for preparing triphenylamine monomers based on benzodithiophene-4,8-dione includes the following steps: Under a nitrogen atmosphere, 1,3-bis(5-bromothiophene-2-yl)-5,7-bis(2-ethylhexyl)-4H,8H-benzo[1,2-c:4,5-c']dithiophene-4,8-dione (0.154 g, 0.174 mmol), triphenylamine-4-boronic acid (0.141 g, 0.522 mmol), potassium carbonate (0.241 g, 1.74 mmol), and catalyst Pd(PPh3)4 (0.02 g, 0.0174 mmol) were placed in a 250 mL single-necked flask, and toluene (20 mL), water (10 mL), and ethanol (20 mL) were added. The mixture was stirred thoroughly (mL), heated to 70°C, and refluxed for 24 hours. After cooling, the product was poured into saturated brine and extracted five times with dichloromethane. The organic layer was then washed with water. The solvent was removed by vacuum distillation and rotary evaporation. Separation was performed using a silica gel column with dichloromethane and petroleum ether as the eluent in a volume ratio of 1:3. The purified product (monomer TPAEBD) was 53.3 mg, yielding a dark red powder (53.3 mg) with a yield of 25.3%.

[0079] The 1H NMR characterization results of the product (monomer TPAEBD) are as follows: 1 H NMR (400 MHz, Chloroform- d ) δ 7.57 (s, 4H), 7.17 (t, J = 7.4 Hz, 8H), 7.10 – 6.80 (m, 16H), 4.25 (s, 8H), 1.71 (s, 2H), 1.44 – 1.06 (m, 20H), 0.81 (dt, J = 23.0, 7.1 Hz, 14H).

[0080] The above monomer (TPAEBD) was subjected to electropolymerization, and the steps are as follows: Electrochemical polymerization was carried out in a one-chamber three-electrode system. The working electrode was ITO conductive glass, the counter electrode was a platinum sheet, and the reference electrode was an Ag / AgCl electrode (silver wire was electrolyzed at a constant potential of 1.5 V for 100 s in 6 mol / L HCl solution to generate an AgCl coating on the surface).

[0081] Using 10 mL of dichloromethane as the electrolyte, TPAEBD (0.01 mol / L) as the monomer, and tetrabutylammonium hexafluorophosphate (0.1 mol / L) as the electrolyte, polymerization was carried out using a potentiostatic method. The polymerization potential was 0.68 V, the polymerization time was 100 s, and the initial oxidation potential was +0.45 V. It was found that the electrochromic polymer was not successfully obtained.

[0082] Comparative Example 2 The difference between Comparative Example 2 and Example 1 is that in Example 1, the π value in the triphenylamine monomer based on benzodithiophene-4,8-dione is... In Comparative Example 2, π is: .

[0083] A triphenylamine monomer based on benzodithiophene-4,8-dione (named TPATTBD) has the following structure: .

[0084] The synthesis process of the triphenylamine monomers based on benzodithiophene-4,8-dione is as follows: .

[0085] The above method for preparing triphenylamine monomers based on benzodithiophene-4,8-dione includes the following steps: Under a nitrogen atmosphere, 1,3-bis(5'-bromo-[2,2'-bithiophene]-5-yl)-5,7-bis(2-ethylhexyl)-4H,8H-benzo[1,2-c:4,5-c']dithiophene-4,8-dione (0.328 g, 0.352 mmol), triphenylamine-4-boronic acid (0.305 g, 1.056 mmol), potassium carbonate (0.486 g, 3.52 mmol), and catalyst Pd(PPh3)4 (0.041 g, 0.0352 mmol) were placed in a 250 mL single-necked flask, and toluene (20 mL), water (10 mL), and ethanol (20 mL) were added. The mixture was stirred thoroughly (mL), heated to 70°C, and refluxed for 48 hours. After cooling, the product was poured into saturated brine and extracted five times with dichloromethane. The organic layer was then washed with water. The solvent was removed by vacuum distillation and rotary evaporation. Separation was performed using a silica gel column with dichloromethane and petroleum ether as the eluent in a volume ratio of 1:4. The purified product was 62.7 mg of dark red powder (monomer TPATTBD), with a yield of 14.1%.

[0086] The 1H NMR characterization results of the product (monomer TPATTBD) are as follows: 1 H NMR (400 MHz, Chloroform- d ) δ 7.72 (d, J = 4.0 Hz, 2H), 7.49 (d, J = 8.7 Hz, 4H), 7.31 (d, J =8.5 Hz, 6H), 7.27 (d, J= 13.5 Hz, 4H), 7.20 – 7.13 (m, 12H), 7.08 (t, J = 8.8Hz, 8H), 3.34 (d, J = 7.0 Hz, 4H), 1.81 (s, 2H), 1.51 – 1.25 (m, 17H), 0.95(dt, J = 21.0, 7.3 Hz, 12H).

[0087] The above monomer (TPATTBD) was subjected to electropolymerization, and the steps are as follows: Electrochemical polymerization was carried out in a one-chamber three-electrode system. The working electrode was ITO conductive glass, the counter electrode was a platinum sheet, and the reference electrode was an Ag / AgCl electrode (silver wire was electrolyzed at a constant potential of 1.5 V for 100 s in 6 mol / L HCl solution to generate an AgCl coating on the surface).

[0088] Using 10 mL of dichloromethane as the electrolyte, TPATTBD (0.01 mol / L) as the monomer, and tetrabutylammonium hexafluorophosphate (0.1 mol / L) as the electrolyte, polymerization was carried out using a potentiostatic method. The polymerization potential was 0.68 V, the polymerization time was 100 s, and the initial oxidation potential was +0.15 V. It was found that the electrochromic polymer was not successfully obtained.

[0089] The reason why the electropolymerization of the monomer TPATTBD failed is that its bisthiophene structure increased the steric hindrance, which hindered the further electropolymerization of the monomer.

[0090] Performance testing: The electrochromic polymer (named P(TPATBD)) prepared in Example 1 was subjected to spectroelectrochemical testing in a MeCN-Bu4NPF6 (0.1 mol / L) system. The test results are as follows: Figure 1 As shown. Figure 1 In this context, Wavelength refers to the wavelength, and Absorbance refers to the absorbance.

[0091] from Figure 1 It is known that neutral polymers have absorption peaks at 370 nm and 500 nm. The absorption peak at 370 nm is attributed to π-π* transition, and the absorption peak at 500 nm is attributed to intramolecular charge transfer. The polymer appears yellow. As the voltage increases, these two absorption peaks gradually decrease and eventually disappear completely. Near-infrared absorption peaks appear and gradually increase, which may be attributed to the formation of polarons and bipolarons. The color also changes to dark green.

[0092] The electrochromic polymer (named P(TPATBD)) prepared in Example 1 was used, and the transmittance-time curves of polymer P(TPATBD) at 1100 nm, 715 nm, 500 nm, and 370 nm were measured using a UV-1900i spectrophotometer. The response time and coloring efficiency calculated from the time-transmittance curves are shown in Table 1.

[0093] Table 1: Electrochromic parameters of polymer P (TPATBD)

[0094] As shown in Table 1, polymer P (TPATBD) has high optical contrast and high coloring efficiency.

[0095] The optical transmittance of the electrochromic polymer (named P(TPATBD)) prepared in Example 1 was measured by chronoamperometry at wavelengths of 1100 nm, 715 nm, 500 nm, and 370 nm. During the experiment, the time interval between potential step changes was 5 s. The test results are as follows: Figure 2 . Figure 2 In this context, Time represents time and Transmittance represents the transmittance.

[0096] like Figure 2 As shown, polymer P (TPATBD) exhibits good optical contrast and good optical stability at four wavelengths, especially reaching an optical contrast of 45.48% at 715 nm. In addition, optical transmittance has a great influence on the color change of the polymer, and the polymer material can change from yellow in the completely dedoped state to dark green in the doped state.

[0097] like Figure 3 As shown, the short-term memory effect of the electrochromic polymer (named P(TPATBD)) prepared in Example 1 was tested at a wavelength of 715 nm. During the test, voltages of 0.3 V and 1.3 V were applied, and the transmittance changes of the polymer in the neutral and doped states were recorded. Figure 3 The study found that the transmittance of the polymer changed by 1% in the neutral state and by 10% in the doped state, indicating that the polymer P(TPATBD) has a good short-term memory effect.

[0098] The above are merely embodiments of the present invention and do not limit the patent scope of the present invention. Any equivalent modifications made based on the content of the present invention specification, or direct or indirect applications in related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A triphenylamine monomer based on benzodithiophene-4,8-dione, characterized in that: It has the structure shown in equation (I): ； Wherein, R is selected from C1-C18 alkyl, aryl, or substituted aryl groups; D is a triphenylamine group; π is selected from the following structures: 。 2. The triphenylamine monomer based on benzodithiophene-4,8-dione according to claim 1, characterized in that: The R is selected from C4-C15 alkyl, aryl, and / or substituted aryl groups; preferably, the R is selected from C4-C15 alkyl groups.

3. The triphenylamine monomer based on benzodithiophene-4,8-dione according to claim 1, characterized in that: The substituents on the substituted aryl group are selected from halogen, nitro, amino, hydroxyl or carboxyl groups.

4. A method for preparing a triphenylamine monomer based on benzodithiophene-4,8-dione as described in any one of claims 1 to 3, characterized in that: Includes the following steps: Under a protective gas atmosphere, the acceptor, triphenylamine-4-boronic acid, base, palladium catalyst and solvent are mixed and subjected to a Suzuki coupling reaction to obtain the thiophene derivative monomer of the benzodithiophene-4,8-dione. The structural formula of the receptor is: ; The definitions of R and π are consistent with any one of claims 1 to 3.

5. The method according to claim 4, characterized in that: The molar ratio of the receptor compound to triphenylamine-4-boronic acid is 1:(2.5-3.5).

6. The method according to claim 4, characterized in that: The base is potassium carbonate, and / or the molar ratio of the acceptor compound to the base is 1:(8-12).

7. The method according to claim 4, characterized in that: The temperature for the Suzuki coupling reaction is 70-130°C.

8. The method according to claim 4, characterized in that: The palladium catalyst is tetrakis(triphenylphosphine)palladium, and / or the molar ratio of the acceptor compound to the palladium catalyst is 1:(0.05-0.15).

9. An electrochromic polymer, characterized in that: The triphenylamine monomer based on benzodithiophene-4,8-dione as described in any one of claims 1 to 3 is prepared by electrochemical polymerization, and its general structural formula is shown in formula (II): ； Wherein, the definition of R is the same as that of the triphenylamine monomer based on benzodithiophene-4,8-dione; n is a positive integer representing the degree of aggregation.

10. A method for preparing the electrochromic polymer according to claim 9, characterized in that: Includes the following steps: S1 dissolves the triphenylamine monomer based on benzodithiophene-4,8-dione as described in any one of claims 1 to 3 and the electrolyte in a solvent to prepare an electrolyte solution; S2 The electrolyte is placed in an electrochemical electrolytic cell, and an electrochemical polymerization reaction is carried out on the working electrode using a constant potential method to deposit the electrochromic polymer on the surface of the working electrode.

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