Yellow-transparent electrochromic polymer and preparation method and application thereof

Abstract

The present invention provides a yellow-transparent electrochromic polymer, its preparation method, and its application, belonging to the technical field of electrochromic materials. The present invention incorporates an electrochromic polymer represented by formula (I) into an electrochromic polymer film. The resulting electrochromic polymer film can reversibly switch from yellow to transparent under different voltage windows, with an optical contrast ratio of 5.82% at a wavelength of 640nm. In its neutral state, the film exhibits a pure yellow color with almost no residual absorption. The film maintains high transmittance throughout the color change process, and is expected to find application in display fields such as electronic paper and electronic tags.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of electrochromic materials, and particularly relates to a yellow-transparent display electrochromic polymer and a preparation method and application thereof. BACKGROUND

[0002] Electrochromic materials can be divided into inorganic electrochromic materials and organic electrochromic materials. Conducting polymer electrochromic materials (ECPs) have developed rapidly due to their numerous advantages over inorganic or organic small molecule materials, including simple structural design, diverse coloring, high coloring efficiency, great potential for manufacturing large-area or flexible devices, etc. Thienyl derivative 3,3-bis(((2-ethylhexyl)oxy)methyl)-3,4-dihydro-2H-thieno[3,4-B][1,4]dioxepine (ProDOT) allows the introduction of bulky substituents in the structure, which is conducive to the formation of a more 'open' surface morphology and thus promotes the transport of counterions, ultimately resulting in higher optical contrast, faster response speed and better coloring efficiency, which helps the polymer material to realize 'color-transparent' and is of great significance for display applications. In addition, the introduction of long alkyl chains improves the solubility of the polymer as a whole, which helps to realize solution processing of the polymer into a film by spraying or spin coating.

[0003] Yellow is a basic component color of the subtractive three primary colors (cyan, magenta, and yellow), and plays a very important role in color regulation and display effect. The yellow polymer in the neutral state needs to have a high band gap value, and the absorption band needs to be located in the range of 380-550 nm. In the oxidized state, the absorption band needs to shift to the near-infrared region across the entire visible light region to achieve high transmittance. The existing yellow-transparent display conducting polymer electrochromic material often has a lot of absorption residues in the neutral state, making the material appear orange-yellow or orange-red, and it is difficult to achieve pure yellow. Therefore, it is of great significance to study a yellow-transparent display electrochromic polymer and a preparation method and application thereof, so that it can exhibit pure yellow in the neutral state. SUMMARY

[0004] The present application aims to provide a yellow-transparent display electrochromic polymer and a preparation method and application thereof, so as to solve the problem that the existing yellow-transparent display conducting polymer electrochromic material has a lot of absorption residues in the neutral state, making the material appear orange-yellow or orange-red, and it is difficult to achieve pure yellow.

[0005] In order to achieve the above-mentioned application purposes, the present application provides the following technical solutions:

[0006] The present application provides a yellow-transparent display electrochromic polymer, and the structure of the electrochromic polymer is shown in formula (I):

[0007]

[0008] wherein n represents an average polymerization degree, and n is an integer of 100-2,000.

[0009] The present application provides a preparation method of the yellow-transparent display electrochromic polymer as described above, comprising the following steps:

[0010] (1) dissolving 3,6-dibromo-1,2-phenylenediamine, benzaldehyde and zirconium chloride in chloroform to perform a cyclization reaction, to obtain 4,7-dibromo-2-phenyl-1H-benzimidazole;

[0011] (2) dissolving 4,7-dibromo-2-phenyl-1H-benzimidazole, potassium tert-butoxide and iodomethane in tetrahydrofuran to perform a substitution reaction, to obtain 4,7-dibromo-1-methyl-2-phenyl-1H-benzimidazole;

[0012] (3) mixing 4,7-dibromo-1-methyl-2-phenyl-1H-benzimidazole, 3,3-bis(((2-ethylhexyl)oxy)methyl)-3,4-dihydro-2H-thieno[3,4-B][1,4]dioxepine, potassium carbonate, pivalic acid and a palladium catalyst in dimethylacetamide to perform an aryl coupling reaction, to obtain the electrochromic polymer as shown in formula (I).

[0013] Preferably, in the step (1), the molar ratio of 3,6-dibromo-1,2-phenylenediamine, benzaldehyde and zirconium chloride is 1:0.8-1.2:0.08-0.12; and the addition amount of chloroform is 10-20 mL / g based on the mass of benzaldehyde.

[0014] Preferably, in the step (1), the cyclization reaction time is 44-52 h.

[0015] Preferably, in the step (2), the molar ratio of 4,7-dibromo-2-phenyl-1H-benzimidazole, potassium tert-butoxide and iodomethane is 1:1.0-1.2:1.1-1.3; and the addition amount of tetrahydrofuran is 10-30 mL / g based on the mass of 4,7-dibromo-2-phenyl-1H-benzimidazole.

[0016] Preferably, in the step (2), the substitution reaction time is 22-26 h.

[0017] As preferred, in the step (3), the molar ratio of 4,7-dibromo-1-methyl-2-phenyl-1H-benzimidazole, 3,3-bis(((2-ethylhexyl)oxy)methyl)-3,4-dihydro-2H-thieno[3,4-B][1,4]dioxepine, potassium carbonate, pivalic acid and palladium catalyst is 1:1:2.3-2.7:0.2-0.4:0.03-0.05; the addition amount of dimethylacetamide is 30-60 mL / g based on the mass of 4,7-dibromo-1-methyl-2-phenyl-1H-benzimidazole.

[0018] As preferred, in the step (3), the temperature of the aryl coupling reaction is 130-150℃, and the time is 34-38h.

[0019] The application provides an application of the yellow-transparent display electrochromic polymer to an electrochromic polymer film, and the electrochromic polymer shown in the formula (I) is dissolved in a solvent, and then sprayed to form a film.

[0020] As preferred, the concentration of the electrochromic polymer shown in the formula (I) is 3-10 mg / mL; and the solvent is one or more of trichloromethane, dichloromethane, tetrahydrofuran and toluene.

[0021] The application has the following beneficial effects:

[0022] (1) The application uses benzimidazole derivatives as conjugated nuclei, and aryl coupling reaction is performed with thienyl derivatives 3,3-bis(((2-ethylhexyl)oxy)methyl)-3,4-dihydro-2H-thieno[3,4-B][1,4]dioxepine (ProDOT), and the obtained electrochromic polymer shown in the formula (I) is a D-π type conductive polymer.

[0023] (2) The electrochromic polymer shown in the formula (I) is dissolved in a solvent, and then sprayed to form a film, and the electrochromic polymer film can realize reversible switching from yellow to transparent under different voltage windows, the optical contrast under a wavelength range of 640 nm is 5.82%, and the film presents pure yellow in a neutral state, almost no absorption residue, and the film always maintains high transmittance in the color changing process, and is expected to be applied in the display field such as electronic paper and electronic tags. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 It is a cyclic voltammogram of the electrochromic polymer film in application example 1 under different current sweep speeds;

[0025] Figure 2 It is an ultraviolet-visible absorption spectrum of the electrochromic polymer film in application example 1 under different voltages;

[0026] Figure 3 A spectrum dynamic stability graph of the electrochromic polymer thin film of application example 1 under 640 nm wave band;

[0027] Figure 4 A chroma curve graph of the electrochromic polymer thin film of application example 1;

[0028] Figure 5 A brightness curve graph of the electrochromic polymer thin film of application example 1. DETAILED DESCRIPTION

[0029] The present application provides a yellow-transparent display electrochromic polymer, the structure of which is shown as formula (I):

[0030]

[0031] In the formula, n represents an average polymerization degree, and n is an integer of 100-2000.

[0032] The present application provides a preparation method of the yellow-transparent display electrochromic polymer described above, comprising the following steps:

[0033] (1) 3,6-dibromo-1,2-phenylenediamine, benzaldehyde and zirconium chloride are dissolved in chloroform to perform a cyclization reaction, to obtain 4,7-dibromo-2-phenyl-1H-benzimidazole;

[0034] (2) 4,7-dibromo-2-phenyl-1H-benzimidazole, potassium tert-butoxide and iodomethane are dissolved in tetrahydrofuran to perform a substitution reaction, to obtain 4,7-dibromo-1-methyl-2-phenyl-1H-benzimidazole;

[0035] (3) 4,7-dibromo-1-methyl-2-phenyl-1H-benzimidazole, 3,3-bis(((2-ethylhexyl)oxy) methyl)-3,4-dihydro-2H-thieno[3,4-B][1,4]dioxepine, potassium carbonate, pivalic acid and a palladium catalyst are mixed in dimethylacetamide to perform an aryl coupling reaction, to obtain the electrochromic polymer shown as formula (I).

[0036] In the present application, the synthesis route of the electrochromic polymer shown as formula (I) is as follows:

[0037]

[0038] In the present application, in the step (1), the molar ratio of 3,6-dibromo-1,2-phenylenediamine, benzaldehyde and zirconium chloride is 1:0.8-1.2:0.08-0.12, preferably 1:0.9-1.1:0.09-0.11, further preferably 1:1:0.1; the amount of chloroform added is 10-20 mL / g, preferably 12-18 mL / g, further preferably 13-15 mL / g, based on the mass of benzaldehyde.

[0039] In the present application, in the step (1), the time of the cyclization reaction is 44-52 h, preferably 46-50 h, further preferably 48 h.

[0040] In the present application, in the step (2), the molar ratio of 4,7-dibromo-2-phenyl-1H-benzimidazole, potassium tert-butoxide and iodomethane is 1:1.0-1.2:1.1-1.3, preferably 1:1.1:1.2; the amount of tetrahydrofuran added is 10-30 mL / g, preferably 15-25 mL / g, further preferably 20 mL / g, based on the mass of 4,7-dibromo-2-phenyl-1H-benzimidazole.

[0041] In the present application, in the step (2), the time of the substitution reaction is 22-26 h, preferably 23-25 h, further preferably 24 h.

[0042] In the present application, in the step (3), the molar ratio of 4,7-dibromo-1-methyl-2-phenyl-1H-benzimidazole, 3,3-bis(((2-ethylhexyl)oxy)methyl)-3,4-dihydro-2H-thieno[3,4-B][1,4]dioxepine, potassium carbonate, pivalic acid and palladium catalyst is 1:1:2.3-2.7:0.2-0.4:0.03-0.05; preferably 1:1:2.4-2.6:0.3:0.035-0.045, further preferably 1:1:2.5:0.3:0.038-0.042; the amount of dimethylacetamide added is 30-60 mL / g, preferably 40-50 mL / g, further preferably 42-48 mL / g, based on the mass of 4,7-dibromo-1-methyl-2-phenyl-1H-benzimidazole.

[0043] In the present application, in the step (3), the temperature of the aryl coupling reaction is 130-150°C, preferably 135-145°C, further preferably 140°C, and the time is 34-38 h, preferably 35-37 h, further preferably 36 h.

[0044] The application provides application of the yellow-transparent display electrochromic polymer to an electrochromic polymer film.

[0045] In the application, the concentration of the electrochromic polymer as shown in the formula (I) is 3-10 mg / mL, preferably 5-8 mg / mL; and the solvent is one or more of chloroform, dichloromethane, tetrahydrofuran and toluene, preferably chloroform.

[0046] The technical solutions provided by the application are described in detail below in combination with examples, but they should not be understood as limitations to the protection scope of the application.

[0047] Example 1

[0048] Dissolve 3,6-dibromo-1,2-phenylenediamine (a) (4.5 g, 16.9 mmol), benzaldehyde (1.79 g, 16.9 mmol) and ZrCl4 (400 mg, 1.69 mmol) in 25 mL of chloroform, and stir at room temperature for 48 h to perform a cyclization reaction; after the reaction is completed, remove the solvent under reduced pressure, and recrystallize the crude compound from acetonitrile to obtain 5.05 g of 4,7-dibromo-2-phenyl-1H-benzimidazole (b) in the form of a light orange solid, with a yield of 85%.

[0049] Add potassium tert-butoxide (0.35 g, 3.125 mmol) and 4,7-dibromo-2-phenyl-1H-benzimidazole (b) (1 g, 2.84 mmol) into a two-necked tube, vacuumize and then fill with hydrogen, add 20 mL of anhydrous tetrahydrofuran, cool the temperature to -10℃, stir for half an hour to pull hydrogen, and then add iodomethane (0.484 g, 3.41 mmol); stir at room temperature for 24 h to perform a substitution reaction; after the reaction is completed, pour the obtained reaction solution into deionized water, collect the precipitate by filtration, and then extract the precipitate with saturated sodium chloride and dichloromethane, collect the organic phase and dry it with anhydrous sodium sulfate, and finally purify 4,7-dibromo-1-methyl-2-phenyl-1H-benzimidazole (c) through silica gel column chromatography with petroleum ether and ethyl acetate as the mobile phase (the volume ratio of petroleum ether to ethyl acetate in the mobile phase is 8:1).

[0050] 1H NMR (400 MHz, CDCl3) δ 7.74-7.69 (m, 2H), 7.57-7.51 (m, 3H), 7.33 (q, J = 8.3 Hz, 2H), 4.12 (s, 3H).

[0051] Take 3,3-bis(((2-ethylhexyl)oxy) methyl)-3,4-dihydro-2H-thieno[3,4-B][1,4] dioxepine (0.5 g, 1.13 mmol), 4,7-dibromo-1-methyl-2-phenyl-1H-benzimidazole (c) (0.413 g, 1.13 mmol), anhydrous potassium carbonate (0.39 g, 2.83 mmol), pivalic acid (33.9 mg, 0.34 mmol) and Pd(OAc)2(10 mg, 0.045 mmol) into a 50 mL two-port round-bottom flask, add 20 mL of ultra-dry dimethylacetamide under nitrogen protection, react at 140°C for 36 h, cool to room temperature, add the obtained reaction solution into 200 mL of methanol, perform suction filtration with a Buchner funnel, and wash the filter cake with methanol, wrap the filter cake with filter paper, and extract the polymers of different polymerization degrees in the filter cake with a Soxhlet extractor, during which the solvents with different solubilities are changed, and the solvents used in the order of methanol, acetone, petroleum ether, chloroform, and the amount of each solvent used is 300 mL, finally, the part extracted by chloroform is rotary evaporated to remove the solvent, to obtain an electrochromic polymer as shown in formula (I), denoted as PBMHT, the M n = 2501.

[0052] Application Example 1

[0053] Add 10 mg of PBMHT prepared in Example 1 into a 10 mL beaker, then add 2 mL of chloroform, mix with an ultrasonic machine at 50 kHz for 10 min, and finally spray a film on the conductive surface of a 25*40 mm ITO glass using a spray gun, to obtain a PBMHT electrochromic polymer film.

[0054] Verify the performance of the PBMHT electrochromic polymer film prepared in Application Example 1:

[0055] (1) Electrochemical test: use Chenhua 660 electrochemical workstation for electrochemical test, parameter setting: CV mode, the highest and lowest voltages of scanning are 1.0 V and 0 V respectively.

[0056] The test results are shown in Table 1. Figure 1 The starting oxidation potential of the PBMHT electrochromic film is 0.7 V, which presents yellow in the neutral state and transparent in the oxidized state.

[0057] (2) Optical and electrochromic performance test:

[0058] The optical and electrochromic performance test is carried out by using the CHI660 electrochemical workstation and the ultraviolet-visible spectrophotometer in combination, and the specific process is as follows: tetrabutylammonium hexafluorophosphate (0.387g, 1mmol) is added into a 10mL volumetric flask, and is diluted with chromatographic grade acetonitrile to serve as a blank solution. The ITO glass covered with the above-mentioned PBMHT electrochromic film is used as a working electrode, a platinum sheet is used as a counter electrode, and an Ag / AgCl electrode is used as a reference electrode, and the optical and electrochromic performance test is carried out on the film, and the results are shown in Figure 2 、 Figure 3 It can be seen that the film has a maximum absorption value at 640nm when the working voltage is 1V, and the optical contrast under the wavelength range of 640nm is 5.82%.

[0059] (3) Chroma and brightness test:

[0060] The chroma test is carried out by using the CHI660 electrochemical workstation and the ultraviolet-visible spectrophotometer in combination, and the specific process is as follows: tetrabutylammonium hexafluorophosphate (0.387g, 1mmol) is added into a 10mL volumetric flask, and is diluted with chromatographic grade acetonitrile to serve as a blank solution. The ITO glass covered with the above-mentioned PBMHT electrochromic film is used as a working electrode, a platinum sheet is used as a counter electrode, and an Ag / AgCl electrode is used as a reference electrode, and the chroma test is carried out on the film, and the test results are shown in Figure 4 、 Figure 5 It can be seen from Figure 4 that the PBMHT electrochromic polymer film presents a pure yellow color in a neutral state, and almost no absorption residue remains; it can be seen from Figure 5 that the film has a very high relative brightness under different voltages. It can be seen from Figure 4 and Figure 5 that the film always maintains high transmittance during the color change process, and can realize reversible switching between yellow and transparent.

[0061] The above-mentioned is only the preferred embodiment of the present application, and it should be pointed out that, for ordinary skilled persons in the technical field, several improvements and refinements can be made without departing from the principle of the present application, and these improvements and refinements should also be regarded as the protection scope of the present application.

Claims

1. A yellow-transparent electrochromic polymer, characterized in that: The structure of the electrochromic polymer is shown in formula (I): Here, n represents the average degree of polymerization, and n is an integer ranging from 100 to 2000.

2. The method for preparing the yellow-transparent electrochromic polymer according to claim 1, characterized in that: The steps include: (1) 3,6-dibromo-1,2-phenylenediamine, benzaldehyde and zirconium chloride are dissolved in chloroform to carry out a cyclization reaction to obtain 4,7-dibromo-2-phenyl-1H-benzimidazole; (2) dissolving 4,7-dibromo-2-phenyl-1H-benzimidazole, potassium tert-butoxide, and iodomethane in tetrahydrofuran to carry out a substitution reaction to obtain 4,7-dibromo-1-methyl-2-phenyl-1H-benzimidazole; (3) 4,7-Dibromo-1-methyl-2-phenyl-1H-benzimidazole, 3,3-bis(((2-ethylhexyl)oxy)methyl)-3,4-dihydro-2H-thieno[3,4-B][1,4]dioxepene, potassium carbonate, pivalic acid, and palladium catalyst are mixed in dimethylacetamide to carry out an aromatic coupling reaction to obtain an electrochromic polymer as shown in formula (I).

3. The method for preparing the yellow-transparent electrochromic polymer according to claim 2, characterized in that: In the step (1), the molar ratio of 3,6-dibromo-1,2-phenylenediamine, benzaldehyde and zirconium chloride is 1:0.8-1.2:0.08-0.12; and the amount of chloroform added is 10-20 mL / g based on the mass of benzaldehyde.

4. The method for preparing the yellow-transparent electrochromic polymer according to claim 2 or 3, characterized in that: In the step (1), the cyclization reaction time is 44 to 52 hours.

5. The method for preparing an electrochromic polymer according to claim 4, wherein: In the step (2), the molar ratio of 4,7-dibromo-2-phenyl-1H-benzimidazole, potassium tert-butoxide and methyl iodide is 1:1.0-1.2:1.1-1.3; based on the mass of 4,7-dibromo-2-phenyl-1H-benzimidazole, the amount of tetrahydrofuran added is 10-30 mL / g.

6. The method for preparing the yellow-transparent electrochromic polymer according to claim 3 or 5, characterized in that: In the step (2), the substitution reaction time is 22 to 26 hours.

7. The method for preparing the yellow-transparent electrochromic polymer according to claim 6, characterized in that: In the step (3), the molar ratio of 4,7-dibromo-1-methyl-2-phenyl-1H-benzimidazole, 3,3-bis(((2-ethylhexyl)oxy)methyl)-3,4-dihydro-2H-thieno[3,4-B][1,4]dioxepene, potassium carbonate, pivalic acid and palladium catalyst is 1:1:2.3-2.7:0.2-0.4:0.03-0.05; based on the mass of 4,7-dibromo-1-methyl-2-phenyl-1H-benzimidazole, the amount of dimethylacetamide added is 30-60 mL / g.

8. The method for preparing the yellow-transparent electrochromic polymer according to claim 5 or 7, characterized in that: In the step (3), the temperature of the aromatic coupling reaction is 130-150° C., and the time is 34-38 hours.

9. Use of the yellow-transparent electrochromic polymer according to claim 1 in an electrochromic polymer film, characterized in that: The electrochromic polymer shown in formula (I) is dissolved in a solvent and then sprayed to form a film.

10. Use of the yellow-transparent electrochromic polymer according to claim 9 in an electrochromic polymer film, characterized in that: The concentration of the electrochromic polymer represented by formula (I) is 3-10 mg / mL; the solvent is one or more of chloroform, dichloromethane, tetrahydrofuran and toluene.

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