Dimerization carbazole type electrochromic polymer as well as preparation method and application thereof

Abstract

The invention provides a dimerized carbazole type electrochromic polymer and a preparation method and application thereof, the structural formula of the dimerized carbazole type electrochromic polymer is as shown in formula I. In the formula I, R is a C6-C40 alkane chain or alkoxy hydrocarbon chain; n is the degree of polymerization, and n is 10-1000; the number-average molecular weight Mn of the dimerization carbazole type electrochromic polymer is 1000 to 5000 Da, and the polydispersity coefficient D of the dimerization carbazole type electrochromic polymer is 1.0 to 4.0. According to the preparation method, dimerized carbazole and trifluoroacetone are taken as monomers, and the dimerized carbazole type electrochromic polymer is prepared in one step through Friedel-Crafts hydroxyl alkylation condensation polymerization catalyzed by Lewis acid; the method is high in atom economy and mild in reaction condition, the carbazole monomer does not need to be pre-functionalized, and the synthesis steps are simplified.

Description

Technical Field

[0001] This invention relates to the field of functional small molecules and electrochromic materials, and in particular to a dicarbazole-type electrochromic polymer, its preparation method, and its applications. Background Technology

[0002] Electrochromic materials are smart materials that can undergo reversible and stable color changes under the influence of an applied electric field, and they have broad application prospects in fields such as smart windows, anti-glare rearview mirrors, smart glasses, and displays. An ideal electrochromic material not only needs to possess high optical contrast, fast response speed, and excellent cycling stability, but also needs to have a significant optical memory effect (i.e., bistable characteristics), enabling it to maintain its predetermined state for a long time after the external voltage is removed, thereby achieving ultra-low static power consumption of the device.

[0003] Among numerous electrochromic materials, carbazole and its derivatives have been extensively studied due to their excellent molecular designability. However, polymers based on traditional carbazole units often suffer from problems such as high oxidation potential, high driving energy consumption, and uncontrollable electropolymerization side reactions during electrochemical cycling. These issues reduce the predictability and limit the stability of their electrochromic behavior, making it difficult to meet the requirements of high-performance applications.

[0004] Therefore, existing carbazole-based polymers suffer from drawbacks such as high oxidation voltage, poor cycling stability (due to electropolymerization side reactions), intrinsic coloration in the neutral state, and weak memory effect, making it impossible to simultaneously achieve high transparency in the initial state and low power consumption driving performance. Solving this technical problem is of paramount importance for advancing the development of high-performance electrochromic devices. Summary of the Invention

[0005] In view of the shortcomings of the prior art described above, the purpose of this invention is to provide a dicarbazole-based electrochromic polymer, its preparation method, and its application, in order to solve the problems of limited color types and complex synthesis methods of existing carbazole-based polymers.

[0006] To achieve the above and other related objectives, the present invention provides a dicarbazole-type electrochromic polymer, the structural formula of which is shown in Formula I: .

[0007] In Formula I: R is a C6~C40 alkane chain or alkoxyalkane chain; n is the degree of polymerization, n is 10~1000, more preferably 10~200;

[0008] The number-average molecular weight M of the dicarbazole-type electrochromic polymer n The range is 1000~5000 Da, and the polydispersity index D is 1.0~4.0.

[0009] The dicarbazole-type electrochromic polymer of this application is characterized by the embedding of a trifluoroacetone unit as a "spacer group" within the polymer backbone with polycarbazole as the core color-changing unit. The key function of this trifluoroacetone spacer group is to break the continuous conjugation of the polymer backbone, giving it a wide optical band gap, thus laying the foundation for the material's neutral, colorless, and highly transparent properties. Based on this, by using dicarbazole, which has a larger conjugated system, as the electron donor unit, and copolymerizing it with the trifluoroacetone bridging unit to form a donor-acceptor (DA) type backbone, precise control of the polymer's band gap (Eg) and further optimization of its electrochromic performance are achieved. This invention also provides a method for preparing the dicarbazole-type electrochromic polymer, comprising:

[0010] (1) Carbazole is added to a first organic solvent containing an inorganic base, stirred and dissolved, and then a haloalkane is added to carry out a nucleophilic substitution reaction to obtain the monomer shown in Formula II. .

[0011] (2) The monomer shown in Formula II is added to a second organic solvent, and then an iron-based catalyst is added to react and obtain the monomer shown in Formula III; .

[0012] (3) Add the monomer shown in Formula III to the third organic solvent, and then add trifluoroacetone and Lewis acid catalyst to carry out the polymerization reaction to obtain the electrochromic polymer shown in Formula I.

[0013] In Formulas II and III, R is an alkane chain or alkoxycarbon chain of C6 to C40.

[0014] To improve the solubility of polymers, this application uses carbazole derivatives with alkane or alkoxy hydrocarbon chains introduced onto the dicarbazole ring as monomers, and prepares dicarbazole-type electrochromic polymers by blending with trifluoroacetone under Lewis acid catalysis via Friedel-Crafts hydroxyalkylation polycondensation reaction. This method has high atom economy, mild reaction conditions, and simplifies the synthesis steps by eliminating the need for prefunctionalization of the carbazole monomer.

[0015] Preferably, in step (1), the haloalkane is a haloalkane or a haloalkoxyalkane.

[0016] Preferably, in step (1), the inorganic base is one or both of potassium hydroxide and sodium hydroxide.

[0017] Preferably, in step (1), the first organic solvent is one or both of dimethyl sulfoxide and tetrahydrofuran.

[0018] Preferably, in step (1), the molar ratio of carbazole to haloalkanes is 1:(1.2~1.4).

[0019] Preferably, in step (1), the reaction temperature is 25~45℃ and the reaction time is 12~24 h.

[0020] Preferably, in step (1), after the nucleophilic substitution reaction, a post-processing step is also included, wherein the post-processing step is to extract the reaction solution with saturated brine and dichloromethane, combine the organic phases, dry them, and separate them by column chromatography to obtain the monomer shown in formula II.

[0021] Preferably, in step (2), the iron-based catalyst is ferric chloride or aluminum chloride.

[0022] Preferably, in step (2), the second organic solvent is chloroform or tetrahydrofuran.

[0023] Preferably, in step (2), the molar ratio of the monomer shown in Formula II to the iron-based catalyst is 1:(2~5).

[0024] Preferably, in step (2), the reaction temperature is 25~45 °C and the reaction time is 0.5~1 h.

[0025] Preferably, in step (2), after the reaction is completed, the mixture is precipitated in methanol and filtered, the filtrate is dried and concentrated to obtain a crude product, which is then separated by column chromatography to obtain the monomer shown in Formula II.

[0026] Preferably, in step (3), the Lewis acid catalyst is one or more of ferric chloride, aluminum chloride, sulfuric acid, p-toluenesulfonic acid and trifluoromethanesulfonic acid; most preferably p-toluenesulfonic acid or trifluoromethanesulfonic acid.

[0027] Preferably, in step (3), the third organic solvent is one or both of dichloromethane and 1,2-dichloroethane.

[0028] Preferably, in step (3), the Lewis acid catalyst is added at -10~0℃.

[0029] Preferably, in step (3), the reaction temperature of the polymerization reaction is 25~45℃; the reaction time of the polymerization reaction is 36~80 h.

[0030] Preferably, in step (3), the molar ratio of the monomer shown in Formula III to trifluoroacetone is 1:(1~1.5); the molar ratio of the monomer shown in Formula III to Lewis acid catalyst is 1:(5~20).

[0031] This invention also provides an application of the above-mentioned dicarbazole-type electrochromic polymer in the preparation of electrochromic polymer films. The prepared electrochromic polymer film exhibits high optical contrast, good cycling stability, and good film-forming properties.

[0032] Preferably, the electrochromic polymer film is obtained by solution processing of the electrochromic polymer.

[0033] More preferably, the solution is processed into a film by: dissolving the electrochromic polymer in a solvent to obtain a solution, then coating the solution onto a conductive substrate, and drying to obtain an electrochromic polymer film.

[0034] More preferably, the solvent is one or more of dichloromethane, trichloromethane, and tetrahydrofuran.

[0035] More preferably, the coating method is one of spraying, spin coating, or screen printing.

[0036] More preferably, the conductive substrate is one of ITO glass, FTO glass, ITO-PET substrate, and FTO-PET substrate.

[0037] As described above, the dicarbazole-type electrochromic polymer, its preparation method, and its application of the present invention have the following beneficial effects:

[0038] (1) Using dicarbazole and trifluoroacetone as monomers, a one-step Friedel-Crafts hydroxyalkylation polycondensation reaction catalyzed by Lewis acid was used to prepare a dicarbazole-type electrochromic polymer. This method has high atom economy, mild reaction conditions, and does not require prefunctionalization of the carbazole monomer, thus simplifying the synthesis steps.

[0039] (2) The electrochromic polymer film prepared using the dicarbazole type electrochromic polymer of this application has the characteristics of high transparency in the neutral state, green color in the oxidized state and excellent solution processability, and has broad application prospects in the fields of energy-saving display, static information display and dynamic information encryption, military camouflage, etc. Attached Figure Description

[0040] Figure 1 The figure shown is a cyclic voltammetry curve of the medium polymer PCC-F film prepared in Example 1.

[0041] Figure 2 The image shows the UV absorption spectra of the medium polymer PCC-F film prepared in Example 1 under different voltages.

[0042] Figure 3 The image shows the transmittance spectra of the medium polymer PCC-F film prepared in Example 1 in the neutral and oxidized states.

[0043] Figure 4 The image shows the chromaticity spectra of the medium polymer PCC-F film prepared in Example 1 at different voltages.

[0044] Figure 5The graph shown is a response time curve of the transmittance of the polymer PCC-F film prepared in Example 1 as a function of time under multiple potential steps from 0 to 1.1 V at a wavelength of 851 nm.

[0045] Figure 6 The graph shows the cyclic stability of the polymer PCC-F film prepared in Example 1 under multiple potential steps from 0 to 1.1 V at a wavelength of 851 nm, as a function of time.

[0046] Figure 7 The graph shown is a memory effect curve of the transmittance of the polymer PCC-F film prepared in Example 1 as a function of time under multiple potential steps from 0 to 1.1 V at a wavelength of 851 nm. Detailed Implementation

[0047] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

[0048] It should be noted that the process equipment or apparatus not specifically mentioned in the following embodiments are all conventional equipment or apparatus in the art.

[0049] Furthermore, it should be understood that the existence of other method steps before or after the combined steps, or the insertion of other method steps between these explicitly mentioned steps, does not preclude the existence of other method steps before or after the combined steps, or the insertion of other method steps between these explicitly mentioned steps, unless otherwise stated. It should also be understood that the combined connection relationship between one or more devices / apparatus mentioned in this invention does not preclude the existence of other devices / apparatus before or after the combined devices / apparatus, or the insertion of other devices / apparatus between these explicitly mentioned devices / apparatus, unless otherwise stated. Moreover, unless otherwise stated, the numbering of each method step is merely a convenient tool for identifying each method step, and not for limiting the order of the method steps or limiting the scope of the invention. Changes or adjustments to their relative relationships, without substantially altering the technical content, should also be considered within the scope of the invention.

[0050] Example 1

[0051] This embodiment provides a method for preparing a dicarbazole-type electrochromic polymer, referring to the following reaction route: .

[0052] (1) Carbazole (1.00 g, 5.98 mmol) and KOH (0.26 g, 4.78 mmol) were placed in a 50 mL double-necked round-bottom flask, and THF (20 mL) was added. The mixture was stirred to dissolve the mixture. Then 1-bromooctane (1.38 g, 7.17 mmol) was added to the mixture and stirred at room temperature for 12 h. Subsequently, the reaction mixture was extracted multiple times with saturated brine and dichloromethane. The organic layer was dried with Na2SO4 and concentrated to obtain the crude product. The crude product was purified by silica gel column chromatography using dichloromethane and petroleum ether (volume ratio 1:3) as eluent to obtain a yellow liquid monomer C (1.37 g, 64%).

[0053] The 1H NMR characterization data of monomer C are as follows: 1 H NMR (400 MHz, CDCl3) δ 8.24 (d, J=4.6 Hz, 2H), δ 7.58 (t, J=4.4 Hz, 2H), δ 7.52 (d, J=5.6 Hz, 2H), δ7.36 (t, J=4.8 Hz, 2H), δ 4.37 (t, J=4.6 Hz, 2H), δ 1.96 (m, J=2.8 Hz, 2 H), δ 1.49-1.37 (m, J=5.6 Hz, 10H), δ 1.02 (t, J=8.0 Hz, 3H).

[0054] (2) Compound C (0.40 g, 1.42 mmol), anhydrous ferric chloride (1.16 g, 7.17 mmol), and chloroform (10 mL) were added to a 50 mL round-bottom flask. The mixture was then stirred at room temperature for 30 minutes. After the reaction was complete, the mixture was precipitated in 100 mL of methanol and filtered. The filtrate was dried and concentrated to give the crude product. The crude product was purified by silica gel column chromatography using ethyl acetate and hexane (v / v 1:5) as eluents. The monomer CC (0.33 g, 84%) was separated as a yellow solid.

[0055] The 1H NMR characterization data of the monomer CC are as follows: 1H NMR (400 MHz, CDCl3) δ 8.43 (s, J=1.6 Hz, 2H), δ 8.21 (d, J=1.1 Hz, 2H), δ 8.13 (d, J=0.8 Hz, 2H), δ 7.86 (dd, J=0.8 Hz, 2H), δ 7.48 (m, J=1.6Hz, 4H), δ 7.26 (m, J=0.6 Hz, 2H), δ 4.36 (m, J=1.9 Hz, 4H), δ 1.94 (m, J=1.0Hz, 4H), δ 1.28 (m, J=3.6 Hz, 20H), δ 0.9 (m, J=3.8 Hz, 6H).

[0056] (3) Polymerization reaction: Monomer CC (300 mg, 0.54 mmol) and trifluoroacetone (0.072 g, 0.65 mmol) were added to a 35 mL reaction tube. The mixture was cooled in an ice bath, and then dichloromethane (1 mL) was added and stirred for 10 minutes. Then trifluoromethanesulfonic acid (3 mL) was added dropwise, the ice bath was removed, and the reaction mixture was stirred at room temperature for 72 h. After the reaction was completed, the system was poured into 100 mL of methanol to precipitate, the collected solid was filtered, dissolved in tetrahydrofuran, precipitated again in methanol and filtered. Subsequently, the solid product was purified by Soxhlet extraction with methanol, and finally a pale yellow solid polymer PC-F with n=15 (270 mg, 89%) was obtained, which is the dicarbazole type electrochromic polymer.

[0057] Polymer GPC test results (M n =2800 Da, PDI = 1.34).

[0058] The 1H NMR characterization data of polymer PCC-F are as follows: 1 H NMR (400 MHz, CDCl3) δ 8.24 (s, J =2.7 Hz, 2H), δ 8.33 (d, J =2.2Hz, 2H), δ 8.24 (d, J =0.8 Hz, 2H), δ 7.97 (d, J =1.9 Hz, 2H), δ 7.59 (m, J =2.7 Hz, 4H), δ 4.47 (m, J =2.0 Hz, 4H), δ 2.19 (s, J =3.9 Hz, 3H), δ 2.04 (m,J =2.1 Hz, 4H), δ 1.39 (m, J =4.7 Hz, 20H), δ 1.0 (m, J =4.9 Hz, 6H).

[0059] Preparation of polymer PCC-F thin films:

[0060] The polymer PCC-F obtained in Example 1 was dissolved in chloroform and sprayed onto an ITO substrate to obtain a polymer PCC-F film with a solution concentration of 10 mg / mL.

[0061] Electrochromic performance testing of polymer PCC-F films: Using an electrochemical workstation coupled with a UV-Vis spectrophotometer, the cyclic voltammetry curves and UV-Vis absorption at different voltages, transmittance spectra at specific wavelengths, and response time and stability of the films under step voltage were measured in 0.1 M lithium perchlorate / acetonitrile solution. The data processing results are shown below. Figure 1-7 As shown.

[0062] from Figure 1 It can be seen that the polymer PCC-F, based on its dicarbazole molecular structure, exhibits two continuous and highly reversible single-electron oxidation processes. The first oxidation process occurs at a relatively low voltage of 1.1 V. This stepwise, reversible redox characteristic results in excellent electrochemical performance.

[0063] like Figure 2-4 As shown, the film has extremely high transmittance in the visible light range at 0 V (neutral state) and appears colorless and transparent to the naked eye. When a voltage of 1.1 V (oxidized state) is applied, its transmission spectrum shows a significant increase in absorption in the red and blue light regions, and it turns green to the naked eye. Its chromaticity coordinates correspond to the green region in the CIE 1931 chromaticity diagram.

[0064] The optical properties of the polymer PCC-F film at different potentials were tested by applying a multi-potential step signal from 0 to 1.1 V and monitoring the change in optical transmittance of the film at 851 nm wavelength over time. The results were recorded in [the relevant documentation]. Figure 5-7 . Figure 5 It can be seen that the optical contrast of the thin film at 851 nm is 56%. For example... Figure 6 As shown, after 100 consecutive cycles of testing with a voltage step time of 12 seconds at a wavelength of 851 nm, its optical contrast retention rate reached 98.9%, indicating excellent fatigue resistance. Meanwhile, as... Figure 7 As shown, the optical state of the film can be maintained for a long time after the driving voltage is removed (in the open circuit state) in the colored or faded state, demonstrating excellent open circuit memory capability, which is crucial for reducing device power consumption.

[0065] Therefore, this invention, through a unique molecular engineering strategy, successfully synthesizes a colorless-green electrochromic polymer and its thin film based on the condensation reaction of a dicarbazole derivative and trifluoroacetone. This demonstrates that Friedel-Crafts hydroxyalkylation reaction holds promise as a novel method for constructing neutral, colorless, highly transparent, non-conjugated electrochromic polymer materials. Furthermore, it successfully provides a high-performance electrochromic material with low driving voltage, high stability, significant optical contrast, and low power consumption potential, effectively overcoming the shortcomings of existing technologies and showing broad industrial application prospects in fields such as smart windows, information displays, and anti-glare mirrors.

[0066] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A dicarbazole-type electrochromic polymer, characterized in that, Its structural formula is shown in Formula I: ， In Formula I: R is a C6~C40 alkane chain or alkoxyalkane chain; n is the degree of polymerization, n is 10~1000; The number-average molecular weight M of the dicarbazole-type electrochromic polymer n The range is 1000~5000 Da, and the polydispersity index D is 1.0~4.

0.

2. A method for preparing the dicarbazole-type electrochromic polymer as described in claim 1, characterized in that: include: (1) Carbazole is added to a first organic solvent containing an inorganic base, stirred and dissolved, and then a haloalkane is added to carry out a nucleophilic substitution reaction to obtain the monomer shown in Formula II. ； (2) The monomer shown in Formula II is added to a second organic solvent, and then an iron-based catalyst is added to react and obtain the monomer shown in Formula III; ， (3) Add the monomer shown in Formula III to the third organic solvent, and then add trifluoroacetone and Lewis acid catalyst to carry out the polymerization reaction to obtain the dicarbazole type electrochromic polymer shown in Formula I. In Formulas II and III, R is an alkane chain or alkoxycarbon chain of C6 to C40.

3. The preparation method according to claim 2, characterized in that: In step (1), the haloalkane is a haloalkane or a haloalkoxyalkane; the inorganic base is one or both of potassium hydroxide and sodium hydroxide; the first organic solvent is one or both of dimethyl sulfoxide and tetrahydrofuran; the molar ratio of carbazole to haloalkane is 1:(1.2~1.4); the reaction temperature is 25~45℃, and the reaction time is 12~24 h.

4. The preparation method according to claim 2, characterized in that: In step (1), after the nucleophilic substitution reaction, there is also a post-processing step, which involves extracting the reaction solution with saturated brine and dichloromethane, combining the organic phases, drying, and separating by column chromatography to obtain the monomer shown in Formula II.

5. The preparation method according to claim 2, characterized in that: In step (2), the iron-based catalyst is ferric chloride or aluminum chloride; the second organic solvent is chloroform or tetrahydrofuran; the molar ratio of the monomer shown in Formula II to the iron-based catalyst is 1:(2~5); the reaction temperature is 25~45 ℃, and the reaction time is 0.5~1 h.

6. The preparation method according to claim 2, characterized in that: In step (2), after the reaction is complete, the mixture is precipitated in methanol and filtered. The filtrate is dried and concentrated to obtain a crude product, which is then separated by column chromatography to obtain the monomer shown in Formula II.

7. The preparation method according to claim 2, characterized in that: In step (3), the Lewis acid catalyst is one or more of ferric chloride, aluminum chloride, sulfuric acid, p-toluenesulfonic acid and trifluoromethanesulfonic acid; the third organic solvent is one or two of dichloromethane and 1,2-dichloroethane; the Lewis acid catalyst is added at -10~0℃; the reaction temperature of the polymerization reaction is 25~45℃; and the reaction time of the polymerization reaction is 36~80 h.

8. The preparation method according to claim 7, characterized in that: The molar ratio of the monomer shown in Formula III to trifluoroacetone is 1:(1~1.5); the molar ratio of the monomer shown in Formula III to Lewis acid catalyst is 1:(5~20).

9. The use of the dicarbazole-type electrochromic polymer as described in claim 1 in the preparation of electrochromic polymer films.

10. The application according to claim 9, characterized in that: The electrochromic polymer film is obtained by solution processing of the electrochromic polymer.

Images