Yellow-transparent display electrochromic polymer as well as preparation method and application thereof

Abstract

The invention provides a yellow-transparent display electrochromic polymer as well as a preparation method and application thereof, and belongs to the technical field of electrochromic materials. The electrochromic polymer shown in the formula (I) is used in the electrochromic polymer film, the obtained electrochromic polymer film can be reversibly switched from yellow to transparent under different voltage windows, the optical contrast ratio in the wavelength range of 640 nm is 5.82%, the film shows pure yellow in the neutral state, and the film has the advantages that the film is bright in color, good in color fastness and the like. In the color changing process, the film always keeps high transmissivity, and the film is expected to be applied to the display fields of electronic paper, electronic tags and the like.

Description

Technical Field

[0001] The invention relates to the technical field of electrochromic materials, and in particular to an electrochromic polymer with yellow-transparent display and a preparation method and application thereof. Background Art

[0002] Electrochromic materials can be divided into inorganic electrochromic materials and organic electrochromic materials. Conductive polymer electrochromic materials (ECPs) have developed rapidly due to their many advantages over inorganic or organic small molecule materials, including simple structural design, diverse coloring, high coloring efficiency, and great potential for manufacturing large-area or flexible devices. The thiophene derivative 3,3-bis(((2-ethylhexyl)oxy)methyl)-3,4-dihydro-2H-thieno[3,4-B][1,4]dioxepene (ProDOT) allows substitution and introduction of large steric substituents in the structure, which is conducive to forming a more "open" surface morphology and promoting balanced ion transport, ultimately resulting in higher optical contrast, faster response speed and better coloring efficiency, which helps polymer materials achieve "colored-transparent", which is of great significance for display applications. In addition, the access of long alkyl chains improves the overall solubility of the polymer, which helps to realize the solution-processable polymer to be processed into a film by spraying or spin coating.

[0003] Yellow is the basic component color of the subtractive three primary colors (cyan, magenta, and yellow), and plays a very important role in color regulation and rich display effects. In the neutral state, the yellow polymer needs to have a high band gap value, and the absorption band needs to be located in the range of 380 to 550nm. In the oxidized state, the absorption band must cross the entire visible light region and transfer to the near-infrared region to achieve high transmittance. Existing yellow-transparent conductive polymer electrochromic materials often have more 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 electrochromic polymer and its preparation method and application, so that it can present a pure yellow in the neutral state. Summary of the invention

[0004] The purpose of the present invention is to provide an electrochromic polymer with yellow-transparent display and a preparation method and application thereof, so as to solve the problem in the prior art that the conductive polymer electrochromic material with yellow-transparent display has a large amount of absorption residue 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 object of the invention, the present invention provides the following technical solutions:

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

[0007]

[0008] Here, n represents the average degree of polymerization, and n is an integer ranging from 100 to 2000.

[0009] The present invention provides a method for preparing the above-mentioned yellow-transparent electrochromic polymer, comprising the following steps:

[0010] (1) dissolving 3,6-dibromo-1,2-phenylenediamine, benzaldehyde and zirconium chloride in chloroform to carry out 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 methyl iodide in tetrahydrofuran to carry out a substitution reaction to obtain 4,7-dibromo-1-methyl-2-phenyl-1H-benzimidazole;

[0012] (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 a palladium catalyst are mixed in dimethylacetamide to carry out an aromatic coupling reaction to obtain an 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 amount of chloroform added is 10-20 mL / g based on the mass of benzaldehyde.

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

[0015] Preferably, 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; and the amount of tetrahydrofuran added is 10-30 mL / g based on the mass of 4,7-dibromo-2-phenyl-1H-benzimidazole.

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

[0017] Preferably, 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.

[0018] Preferably, in step (3), the temperature of the aromatic coupling reaction is 130-150° C. and the time is 34-38 hours.

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

[0020] Preferably, the concentration of the electrochromic polymer represented by formula (I) is 3-10 mg / mL; and the solvent is one or more of chloroform, dichloromethane, tetrahydrofuran and toluene.

[0021] Beneficial effects of the present invention:

[0022] (1) The present invention uses a benzimidazole derivative as a conjugated core to undergo an aromatic coupling reaction with a thiophene derivative 3,3-bis(((2-ethylhexyl)oxy)methyl)-3,4-dihydro-2H-thieno[3,4-B][1,4]dioxepene (ProDOT), and the resulting electrochromic polymer with a structure as shown in (I) is a D-π type conductive polymer.

[0023] (2) The electrochromic polymer as shown in (I) of the present invention is dissolved in a solvent and sprayed to form a film to obtain an electrochromic polymer film. The polymer film can achieve reversible switching from yellow to transparent under different voltage windows, and the optical contrast within the wavelength range of 640nm is 5.82%. In addition, the film presents a pure yellow color in the neutral state with almost no absorption residue. During the color change process, the film always maintains high transmittance, and is expected to be used in display fields such as electronic paper and electronic tags. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 The cyclic voltammetry curves of the electrochromic polymer film of Application Example 1 at different current sweep rates;

[0025] Figure 2 The UV-visible absorption spectra of the electrochromic polymer film of Application Example 1 at different voltages;

[0026] Figure 3 The spectral dynamic stability diagram of the electrochromic polymer film of Application Example 1 in the 640nm band;

[0027] Figure 4 is a chromaticity curve diagram of the electrochromic polymer film of Application Example 1;

[0028] Figure 5 This is a brightness curve diagram of the electrochromic polymer film of Application Example 1. DETAILED DESCRIPTION

[0029] The present invention provides an electrochromic polymer with yellow-transparent display, the structure of the electrochromic polymer is shown in formula (I):

[0030]

[0031] Here, n represents the average degree of polymerization, and n is an integer ranging from 100 to 2000.

[0032] The present invention provides a method for preparing the above-mentioned yellow-transparent electrochromic polymer, comprising the following steps:

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

[0034] (2) dissolving 4,7-dibromo-2-phenyl-1H-benzimidazole, potassium tert-butoxide, and methyl iodide in tetrahydrofuran to carry out 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]dioxepene, potassium carbonate, pivalic acid, and a palladium catalyst are mixed in dimethylacetamide to carry out an aromatic coupling reaction to obtain an electrochromic polymer as shown in formula (I).

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

[0037]

[0038] In the present invention, 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, and more preferably 1:1:0.1; based on the mass of benzaldehyde, the amount of chloroform added is 10-20 mL / g, preferably 12-18 mL / g, and more preferably 13-15 mL / g.

[0039] In the present invention, in step (1), the cyclization reaction time is 44 to 52 hours, preferably 46 to 50 hours, and more preferably 48 hours.

[0040] In the present invention, 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, preferably 1:1.1:1.2; based on the mass of 4,7-dibromo-2-phenyl-1H-benzimidazole, the amount of tetrahydrofuran added is 10-30 mL / g, preferably 15-25 mL / g, and more preferably 20 mL / g.

[0041] In the present invention, in step (2), the substitution reaction time is 22 to 26 hours, preferably 23 to 25 hours, and more preferably 24 hours.

[0042] In the present invention, 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; It is preferably 1:1:2.4-2.6:0.3:0.035-0.045, and more preferably 1:1:2.5:0.3:0.038-0.042; based on the mass of 4,7-dibromo-1-methyl-2-phenyl-1H-benzimidazole, the added amount of dimethylacetamide is 30-60 mL / g, preferably 40-50 mL / g, and more preferably 42-48 mL / g.

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

[0044] The present invention provides an application of the above-mentioned yellow-transparent electrochromic polymer in an electrochromic polymer film, wherein the electrochromic polymer as shown in formula (I) is dissolved in a solvent and then sprayed to form a film.

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

[0046] The technical solutions provided by the present invention are described in detail below in conjunction with the embodiments, but they should not be construed as limiting the protection scope of the present invention.

[0047] Example 1

[0048] 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) were dissolved in 25 mL of chloroform and stirred at room temperature for 48 h for cyclization reaction. After the reaction, the solvent was removed under reduced pressure and the crude compound was recrystallized from acetonitrile to obtain 5.05 g of 4,7-dibromo-2-phenyl-1H-benzimidazole (b) with a yield of 85% as a light orange solid.

[0049] Potassium tert-butoxide (0.35 g, 3.125 mmol) and 4,7-dibromo-2-phenyl-1H-benzimidazole (b) (1 g, 2.84 mmol) were added to a double-mouthed tube, and hydrogen was filled after vacuuming. 20 mL of anhydrous tetrahydrofuran was added, and the temperature was cooled to -10 ° C., stirred for half an hour to remove hydrogen, and methyl iodide (0.484 g, 3.41 mmol) was added. The mixture was stirred at room temperature for 24 hours for substitution reaction. After the reaction was completed, the reaction solution obtained was poured into deionized water and mixed, and the precipitate was collected by filtration. The precipitate was then extracted with saturated sodium chloride and dichloromethane, and the organic phase was collected and dried with anhydrous sodium sulfate. Finally, petroleum ether and ethyl acetate were used as mobile phases (the volume ratio of petroleum ether to ethyl acetate in the mobile phase was 8:1), and purified by silica gel column chromatography to obtain 4,7-dibromo-1-methyl-2-phenyl-1H-benzimidazole (c).

[0050] 1H NMR (400MHz, CDCl3) δ7.74–7.69 (m, 2H), 7.57–7.51 (m, 3H), 7.33 (q, J = 8.3Hz, 2H), 4.12 (s, 3H).

[0051] 3,3-bis(((2-ethylhexyl)oxy)methyl)-3,4-dihydro-2H-thieno[3,4-B][1,4]dioxepene (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) were weighed into a 50 mL two-necked round-bottom flask. Under nitrogen protection, 20 mL of Ultra-dry dimethylacetamide was reacted at 140°C for 36 hours, cooled to room temperature, and the obtained reaction solution was added to 200 mL of methanol, filtered with a Buchner funnel, and the filter cake was washed with methanol. The filter cake was wrapped with filter paper and then extracted with a Soxhlet extractor to extract polymers of different polymerization degrees. During this period, solvents with different dissolving powers were replaced in the order of methanol, acetone, petroleum ether, and chloroform. The amount of each solvent used was 300 mL. Finally, the part extracted with chloroform was rotary evaporated to remove the solvent to obtain an electrochromic polymer as shown in formula (I), denoted as PBMHT. The M of the electrochromic polymer obtained in Example 1 is n =2501.

[0052] Application Example 1

[0053] 10 mg of PBMHT prepared in Example 1 was added to a 10 mL beaker, and then 2 mL of chloroform was added, and ultrasonic mixing was performed using a 50 kHz ultrasonic machine for 10 min. Finally, a spray gun was used to spray the conductive surface of a 25*40 mm ITO glass to form a film, thereby obtaining a PBMHT electrochromic polymer film.

[0054] The performance of the PBMHT electrochromic polymer film prepared in Example 1 was verified:

[0055] (1) Electrochemical test: The electrochemical test was performed using a Chenhua 660 electrochemical workstation with the following parameters set: CV mode, with the highest and lowest scan voltages being 1.0 V and 0 V, respectively.

[0056] Test results such as Figure 1 As shown, the initial oxidation potential of the PBMHT electrochromic film is 0.7 V. It appears yellow in the neutral state and transparent in the oxidized state.

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

[0058] The optical and electrochromic performance tests were conducted using a Chenhua 660 electrochemical workstation in conjunction with a UV-visible spectrophotometer. The specific process was as follows: tetrabutylammonium hexafluorophosphate (0.387 g, 1 mmol) was added to a 10 mL volumetric flask, and the volume was fixed with chromatographic grade acetonitrile, which was used as a blank solution. The ITO glass covered with the above-mentioned PBMHT electrochromic film was used as the working electrode, the platinum sheet was used as the counter electrode, and the Ag / AgCl electrode was used as the reference electrode. The optical and electrochromic performance tests of the film were conducted, and the results are shown in FIG. Figure 2 , Figure 3 As shown, it can be seen that when the operating voltage is 1V, the film has a maximum absorption value at 640nm, and the optical contrast ratio in the 640nm wavelength range is 5.82%.

[0059] (3) Chroma and brightness test:

[0060] The colorimetric test was performed using a Chenhua 660 electrochemical workstation in conjunction with a UV-visible spectrophotometer. The specific process was as follows: tetrabutylammonium hexafluorophosphate (0.387 g, 1 mmol) was added to a 10 mL volumetric flask, and the volume was fixed with chromatographic grade acetonitrile, which was used as a blank solution. The ITO glass covered with the above-mentioned PBMHT electrochromic film was used as the working electrode, the platinum sheet was used as the counter electrode, and the Ag / AgCl electrode was used as the reference electrode. The film was tested for colorimetric properties. The test results are shown in Figure 2. Figure 4 , Figure 5 As shown, from Figure 4 It can be seen that the PBMHT electrochromic polymer film shows pure yellow in the neutral state with almost no absorption residue; Figure 5 It can be seen that under different voltages, the film always has a high relative brightness. Figure 4 and Figure 5 It can be seen that the film always maintains high transmittance during the color change process and can achieve reversible switching between yellow and transparent.

[0061] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

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) dissolving 3,6-dibromo-1,2-phenylenediamine, benzaldehyde and zirconium chloride 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 methyl iodide 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 a 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, characterized in that: 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 to 150° C. and the time is 34 to 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 as 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 as shown in formula (I) is 3-10 mg / mL; the solvent is one or more of chloroform, dichloromethane, tetrahydrofuran and toluene.

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