A black-transparent electrochromic compound and its preparation method and application

Abstract

The present invention provides a black-transparent electrochromic compound and its preparation method and application, which belongs to the field of electrochromic material technology. The following steps are included: under a protective atmosphere, 4,7-bis(3,3-dimethyl-3,4-dihydro-2H-thieno[3,4-b][1,4]dioxopyran-6-yl)benzo[c][1,2,5]thiadiazole, 3,4-bis((2-ethylhexyl)oxy)thiophene, 2,6-dibromo-4,4-bis(2-ethylhexyl)-4H-cyclopentadien-[2,1-b:3,4-b']bithiophene, potassium carbonate, pivalic acid, Pd(OAc)2 and DMAc are mixed to obtain the black-transparent electrochromic compound. The film made of the compound is black in a neutral state and highly transparent in an oxidized state, with an optical contrast of 27% under a wavelength range of 600nm, a coloring time of 1s, and a fading time of 0.45s.

Description

Technical Field

[0001] The present invention relates to the technical field of electrochromic materials, and in particular to a black-transparent electrochromic compound and a preparation method and application thereof. Background Art

[0002] Electrochromism refers to the phenomenon in which a material undergoes a reversible color change under the influence of an applied electric field. Solution-processable electrochromic polymers have attracted research interest due to their bistability, rich color palette, and the ability to fabricate large-scale electrochromic films using solution processing. While numerous researchers have developed a relatively complete system of electrochromic materials capable of switching from base color to colorless, few have demonstrated high-performance, intermediate-color-free electrochromic polymers capable of switching from black to high transparency. Summary of the Invention

[0003] The object of the present invention is to provide a black-transparent electrochromic compound and its preparation method and application, which has the characteristics of low driving voltage, no intermediate color and high cycle stability.

[0004] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0005] The present invention provides a black-transparent electrochromic compound, the structure of the black-transparent electrochromic compound is:

[0006]

[0007] R is The weight average molecular weight of the compound is 80,000 to 150,000.

[0008] The present invention also provides a method for preparing the black-transparent electrochromic compound, comprising the following steps:

[0009] Under a protective atmosphere, 4,7-bis(3,3-dimethyl-3,4-dihydro-2H-thieno[3,4-b][1,4]dioxopyran-6-yl)benzo[c][1,2,5]thiadiazole, 3,4-bis((2-ethylhexyl)oxy)thiophene, 2,6-dibromo-4,4-bis(2-ethylhexyl)-4H-cyclopenta[2,1-b:3,4-b']bithiophene, potassium carbonate, pivalic acid, Pd(OAc)2 and DMAc are mixed and reacted to obtain the black-transparent electrochromic compound.

[0010] Preferably, the structural formula of the 4,7-bis(3,3-dimethyl-3,4-dihydro-2H-thieno[3,4-b][1,4]dioxopin-6-yl)benzo[c][1,2,5]thiadiazole is:

[0011]

[0012] Preferably, the structural formula of the 2,6-dibromo-4,4-bis(2-ethylhexyl)-4H-cyclopenta[2,1-b:3,4-b']bithiophene is:

[0013]

[0014] Preferably, the mass ratio of the 4,7-bis(3,3-dimethyl-3,4-dihydro-2H-thieno[3,4-b][1,4]dioxopin-6-yl)benzo[c][1,2,5]thiadiazole, 3,4-bis((2-ethylhexyl)oxy)thiophene and 2,6-dibromo-4,4-bis(2-ethylhexyl)-4H-cyclopenta[2,1-b:3,4-b']bithiophene is 0.17-0.18:0.4-0.5:1.

[0015] Preferably, the mass ratio of potassium carbonate, pivalic acid and 2,6-dibromo-4,4-bis(2-ethylhexyl)-4H-cyclopenta[2,1-b:3,4-b']bithiophene is 0.5-0.7:0.06-0.08:1.

[0016] Preferably, the mass volume ratio of the Pd(OAc)2, DMAc and 2,6-dibromo-4,4-bis(2-ethylhexyl)-4H-cyclopenta[2,1-b:3,4-b']bithiophene is 5-6 mg:8-12 mL:280 mg.

[0017] Preferably, the temperature of the mixing reaction is 125-135° C., and the time of the mixing reaction is 18-22 hours.

[0018] The present invention also provides application of the black-transparent electrochromic compound in automobile sun visors.

[0019] The present invention has the following beneficial effects:

[0020] The black-transparent electrochromic compound provided by the present invention appears black in its neutral state and highly transparent in its oxidized state. Its optical contrast ratio at a wavelength of 600 nm is 27%, with a coloring time of 1 second and a fading time of 0.45 seconds. After 600 cycles of a step voltage of 0 V and 1 V, the optical contrast at 600 nm still maintains 91.1% of its original contrast ratio, making it a black-transparent electrochromic material with excellent properties. Furthermore, this black-transparent electrochromic compound can be applied to automobile sun visors, where the transmittance of the film can be varied by applying different voltages, thereby achieving different shading effects. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a synthetic route for the black-transparent electrochromic compound of Example 1 of the present invention;

[0022] Figure 2 CV curve of the black-transparent electrochromic film of Example 1;

[0023] Figure 3 The UV-visible absorption spectra of the black-transparent electrochromic film of Example 1 at different voltages;

[0024] Figure 4 This is a response time graph of the black-transparent electrochromic film of Example 1 at 600 nm;

[0025] Figure 5 This is a stability test graph of the black-transparent electrochromic film of Example 1 at 600nm;

[0026] Figure 6 This is a color coordinate diagram of the black-transparent electrochromic film of Example 1 at different voltages;

[0027] Figure 7 This is a curve diagram of the brightness change of the black-transparent electrochromic film in Example 1 under different voltages. DETAILED DESCRIPTION

[0028] The present invention provides a black-transparent electrochromic compound, the structure of the black-transparent electrochromic compound is:

[0029]

[0030] R is The weight average molecular weight of the compound is 80,000 to 150,000.

[0031] The present invention also provides a method for preparing the black-transparent electrochromic compound, comprising the following steps:

[0032] Under a protective atmosphere, 4,7-bis(3,3-dimethyl-3,4-dihydro-2H-thieno[3,4-b][1,4]dioxopyran-6-yl)benzo[c][1,2,5]thiadiazole, 3,4-bis((2-ethylhexyl)oxy)thiophene, 2,6-dibromo-4,4-bis(2-ethylhexyl)-4H-cyclopenta[2,1-b:3,4-b']bithiophene, potassium carbonate, pivalic acid, Pd(OAc)2 and DMAc are mixed and reacted to obtain the black-transparent electrochromic compound.

[0033] In the present invention, the protective atmosphere is preferably nitrogen.

[0034] In the present invention, the structural formula of the 4,7-bis(3,3-dimethyl-3,4-dihydro-2H-thieno[3,4-b][1,4]dioxopin-6-yl)benzo[c][1,2,5]thiadiazole is:

[0035]

[0036] In the present invention, the structural formula of the 3,4-bis((2-ethylhexyl)oxy)thiophene is:

[0037]

[0038] In the present invention, the structural formula of the 2,6-dibromo-4,4-bis(2-ethylhexyl)-4H-cyclopenta[2,1-b:3,4-b']bithiophene is:

[0039]

[0040] In the present invention, the mass ratio of 4,7-bis(3,3-dimethyl-3,4-dihydro-2H-thieno[3,4-b][1,4]dioxopin-6-yl)benzo[c][1,2,5]thiadiazole, 3,4-bis((2-ethylhexyl)oxy)thiophene and 2,6-dibromo-4,4-bis(2-ethylhexyl)-4H-cyclopenta[2,1-b:3,4-b']bithiophene is preferably 0.17-0.18:0.4-0.5:1, more preferably 0.172-0.178:0.42-0.48:1, and more preferably 0.174-0.176:0.44-0.46:1.

[0041] In the present invention, the mass ratio of potassium carbonate, pivalic acid and 2,6-dibromo-4,4-bis(2-ethylhexyl)-4H-cyclopenta[2,1-b:3,4-b']bithiophene is preferably 0.5-0.7:0.06-0.08:1, more preferably 0.55-0.65:0.065-0.075:1, and more preferably 0.58-0.62:0.068-0.072:1.

[0042] In the present invention, the mass volume ratio of Pd(OAc)2, DMAc and 2,6-dibromo-4,4-bis(2-ethylhexyl)-4H-cyclopenta[2,1-b:3,4-b']bithiophene is preferably 5-6 mg:8-12 mL:280 mg, more preferably 5.2-5.8 mg:9-11 mL:280 mg, and more preferably 5.4-5.6 mg:9.5-10.5 mL:280 mg.

[0043] In the present invention, the temperature of the mixing reaction is preferably 125-135°C, more preferably 127-133°C, and even more preferably 129-131°C.

[0044] In the present invention, after the mixing reaction is completed, post-treatment is performed to obtain the black-transparent electrochromic compound.

[0045] The post-treatment method is preferably as follows: after the mixing reaction is completed, the reaction solution is poured into methanol for suction filtration, the filter cake is washed with methanol and then wrapped with filter paper, and polymers of different polymerization degrees are extracted using a Soxhlet extractor. During the process, solvents with different solubility are replaced, and the order of using the solvents is methanol, acetone, petroleum ether and chloroform. The part extracted with chloroform is rotary evaporated to remove the solvent to obtain a black-transparent electrochromic compound.

[0046] The present invention also provides application of the black-transparent electrochromic compound in automobile sun visors.

[0047] In the present invention, unless otherwise specified, the raw materials required for preparation are all commercially available products well known to those skilled in the art.

[0048] The technical solutions provided by the present invention are described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0049] Example 1

[0050] 50.1 mg of 4,7-bis(3,3-dimethyl-3,4-dihydro-2H-thieno[3,4-b][1,4]dioxopin-6-yl)benzo[c][1,2,5]thiadiazole, 136.23 mg of 3,4-bis((2-ethylhexyl)oxy)thiophene, 280 mg of 2,6-dibromo-4,4-bis(2-ethylhexyl)-4H-cyclopenta[2,1-b:3,4-b']bithiophene, 172.5 mg of anhydrous potassium carbonate, 20 mg of pivalic acid, and 25.6 mg of Pd(OAc) were weighed and added to a Schlenk tube. Under nitrogen protection, 10 mL of ultra-dry DMAc was added, and the mixture was mixed and reacted at 130°C for 20 h, and then cooled to 25°C. The reaction solution was added to 300 mL of methanol, filtered with a funnel and the filter cake was washed with methanol. The filter cake was wrapped with filter paper and polymers of different polymerization degrees were extracted using a Soxhlet extractor. During the process, solvents with different solubility were replaced in the order of methanol, acetone, petroleum ether and chloroform. The amount of each solvent used was 250 ml. Finally, the part extracted with chloroform was rotary evaporated to remove the solvent to obtain a black-transparent electrochromic compound, marked as RB.

[0051] The preparation process of this embodiment 1 is as follows Figure 1 shown.

[0052] Application Examples

[0053] 10 mg of the black-transparent electrochromic compound RB prepared in Example 1 was ultrasonically mixed with 1 mL of chloroform in a 50 kHz ultrasonic machine for 10 min, and then spin-coated on the conductive surface of a 25*40 mm ITO glass using a spin coater (spin coater speed of 1000 r / min, spin coating time of 30 s) to obtain a black-transparent electrochromic film.

[0054] Performance Testing

[0055] 1. Electrochemical testing

[0056] The electrochemical test was performed using a Chenhua 660 electrochemical workstation with the following parameters: CV mode, scan rate of 100 mv / s, and the highest and lowest scan voltages of 1 V and 0 V, respectively. Figure 2 shown

[0057] from Figure 2 It can be seen that the film obtained from the black-transparent electrochromic compound has an initial oxidation potential of 0.2 V and a pair of obvious redox peaks, which proves that it has excellent electrochemical properties.

[0058] 2. Optical and electrochromic performance test

[0059] The electrochromic performance test was carried out using a Chenhua 660 electrochemical workstation in conjunction with a UV-visible spectrophotometer. The specific process was as follows: 0.387 g of tetrabutylammonium hexafluorophosphate was added to a 10 mL volumetric flask, and the volume was adjusted with chromatographic grade acetonitrile to use it as a blank solution. Two portions of blank solution and two portions of blank ITO glass were placed in two cuvettes, and the cuvettes were placed in a UV-visible spectrophotometer to scan the baseline. After the scan, one of the blank ITO glasses was replaced with an ITO glass covered with a polymer film, and a platinum wire was placed in it as a counter electrode, and an Ag / AgCl electrode was used as a reference electrode. Different voltages were applied for 10 seconds using a Chenhua 660 electrochemical workstation, and then a UV-visible spectrophotometer was used to complete the scan in the wavelength range of 350 to 780 nm to obtain the spectrum of the polymer film at different voltages. The results are shown in FIG. Figures 3 to 5 As shown, Figure 3 is the UV-visible absorption spectrum at different voltages, Figure 4 The response time diagram of the film at 600nm is shown in Figure 2. Figure 5 This is a stability test diagram of the film at 600nm.

[0060] from Figures 3 to 5It appears black in its neutral state and highly transparent in its oxidized state. Furthermore, as voltages are continuously applied, the absorption curve in the visible light range is very smooth with no distinct peaks, demonstrating that the film exhibits no intermediate colors during the color change process. The optical contrast at 600nm is 27%, with a coloring time of 1s and a fading time of 0.45s. Even after 600 cycles of step voltages from 0V to 1.0V, the optical contrast at 600nm still maintains 91.1% of its original contrast.

[0061] 3. Color coordinates and brightness measurement

[0062] The color coordinates of RB were determined using a Chenhua 660 electrochemical workstation coupled with a CM-3600D-spectrophotometer. The specific process was as follows: 0.387 g of tetrabutylammonium hexafluorophosphate was added to a 10 mL volumetric flask, and the volume was fixed with chromatography-grade acetonitrile, which was used as a blank solution. ITO glass covered with a polymer film was used as the working electrode, platinum wire as the counter electrode, and Ag / AgCl electrode as the reference electrode. Different voltages were applied for 10 seconds using a Chenhua 660 electrochemical workstation, and the color coordinates and brightness of the RB film were determined using a CM-3600D-spectrophotometer. The test results are shown in Figure 2. Figure 6 and Figure 7 As shown, Figure 6 is the color coordinate diagram of the film at different voltages, Figure 7 This is a curve of the brightness change of the film under different voltages.

[0063] from Figure 6 and Figure 7 It can be seen that its a* and b* values ​​between 0 and 1 V are both less than 4; the brightness also changes from 62.5 to 81.5, proving that RB has no obvious color tendency in the color changing process, only obvious changes in light and dark.

[0064] As can be seen from the above examples, the present invention provides a black-transparent electrochromic compound that appears black in a neutral state and highly transparent in an oxidized state. It has an optical contrast ratio of 27% at a wavelength of 600nm, a coloring time of 1s, and a fading time of 0.45s. After 600 cycles of step voltages of 0V and 1V, the optical contrast at 600nm still maintains 91.1% of the original contrast ratio, making it a black-transparent electrochromic material with excellent properties. In addition, this black-transparent electrochromic compound can be applied to automobile sun visors, where different voltages are applied to change the transmittance of the film to achieve different shading effects.

[0065] 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 principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A black-transparent electrochromic compound, characterized in that The structure of the black-transparent electrochromic compound is: R is The weight average molecular weight of the compound is 80,000 to 150,000.

2. The method for preparing the black-transparent electrochromic compound according to claim 1, characterized in that: It includes the following steps: Under a protective atmosphere, 4,7-bis(3,3-dimethyl-3,4-dihydro-2H-thieno[3,4-b][1,4]dioxopyran-6-yl)benzo[c][1,2,5]thiadiazole, 3,4-bis((2-ethylhexyl)oxy)thiophene, 2,6-dibromo-4,4-bis(2-ethylhexyl)-4H-cyclopenta[2,1-b:3,4-b']bithiophene, potassium carbonate, pivalic acid, Pd(OAc)2 and DMAc are mixed and reacted to obtain the black-transparent electrochromic compound.

3. The method for preparing the black-transparent electrochromic compound according to claim 2, wherein: The structural formula of the 4,7-bis(3,3-dimethyl-3,4-dihydro-2H-thieno[3,4-b][1,4]dioxopin-6-yl)benzo[c][1,2,5]thiadiazole is:

4. The method for preparing a black-transparent electrochromic compound according to claim 2 or 3, wherein: The structural formula of the 2,6-dibromo-4,4-bis(2-ethylhexyl)-4H-cyclopenta[2,1-b:3,4-b']bithiophene is:

5. The method for preparing the black-transparent electrochromic compound according to claim 4, wherein: The mass ratio of the 4,7-bis(3,3-dimethyl-3,4-dihydro-2H-thieno[3,4-b][1,4]dioxopin-6-yl)benzo[c][1,2,5]thiadiazole, 3,4-bis((2-ethylhexyl)oxy)thiophene and 2,6-dibromo-4,4-bis(2-ethylhexyl)-4H-cyclopenta[2,1-b:3,4-b']bithiophene is 0.17-0.18:0.4-0.5:

1.

6. The method for preparing the black-transparent electrochromic compound according to claim 5, wherein: The mass ratio of the potassium carbonate, pivalic acid and 2,6-dibromo-4,4-bis(2-ethylhexyl)-4H-cyclopenta[2,1-b:3,4-b']bithiophene is 0.5-0.7:0.06-0.08:

1.

7. The method for preparing a black-transparent electrochromic compound according to claim 5 or 6, wherein: The mass volume ratio of the Pd(OAc)2, DMAc and 2,6-dibromo-4,4-bis(2-ethylhexyl)-4H-cyclopenta[2,1-b:3,4-b']bithiophene is 5-6 mg:8-12 mL:280 mg.

8. The method for preparing a black-transparent electrochromic compound according to claim 7, wherein: The temperature of the mixed reaction is 125-135° C., and the time of the mixed reaction is 18-22 hours.

9. Use of the black-transparent electrochromic compound according to claim 1 in automobile sun visors.

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