A viologen compound, a hydrogel display device and application thereof

Abstract

The application discloses a display device composed of a viologen compound and a hydrogel and application thereof, and synthesizes a novel viologen derivative electrochromic material (I) by modifying a viologen N position with a proper substituent group, and then assembles the viologen derivative into a sodium carboxymethyl cellulose hydrogel to obtain a hydrogel with electrochromic properties; the electrochromic hydrogel material is in a high-transmittance state in a neutral state, and when an external voltage is applied, the absorption peak value has a significant rising change; the reduced state is purple, and the electrochromic hydrogel material has a potential application prospect in the field of electrochromism.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of electrochromic materials, and particularly relates to a display device composed of a viologen compound and a hydrogel and application thereof. BACKGROUND

[0002] Electrochromism (EC) refers to a phenomenon that the optical properties (reflectivity, transmittance, absorptivity, etc.) of a material change stably and reversibly under the action of an applied electric field, and in appearance, the phenomenon is a reversible change in color and transparency.

[0003] A viologen compound (1,1'-disubstituted-4,4'-bipyridine) is a common organic small molecule material with a bipyridine molecular structure. The viologen compound shows obvious color change under voltage driving, has good optical contrast, high coloring efficiency and redox stability, and is therefore widely used as an organic optoelectronic functional material in the field of electrochromism. As a kind of electron-deficient material, the color change of the viologen is caused by the electron transfer in the molecule, and the viologen shows different colors in three different states, namely, a neutral state, a monovalent cation state and a divalent cation state.

[0004] An electrochromic device generally has a five-layer sandwich structure, and is sequentially composed of a transparent conductive electrode, an electrolyte layer, an electrochromic layer, an ion storage layer and a transparent conductive electrode II. The electrochromic device is relatively complicated to manufacture.

[0005] Therefore, it is an important technical problem to provide an integrated environmentally friendly electrochromic hydrogel and an electrochromic device from the perspective of green safety. SUMMARY

[0006] The application provides a display device composed of a viologen compound and a hydrogel and application thereof. The device is in a high-transmittance state in a neutral state and shows purple color in a reduced state, and the types of electrochromic materials are enriched.

[0007] The technical scheme of the application is as follows:

[0008] A viologen derivative, as shown in formula I:

[0009]

[0010] The preparation method of the viologen derivative shown in formula I includes the following steps:

[0011] (1) 4,7-dibromo-2,1,3-benzothiadiazole, 4-pyridine boronic acid, tetrakis(triphenylphosphine)palladium, potassium carbonate and 1,4-dioxane are mixed, heated to 100-130 DEG C under N2 protection and refluxed for 20-30 h, and then treated to obtain a compound shown in formula II;

[0012] The molar ratio of 4,7-dibromo-2,1,3-benzothiadiazole to 4-pyridineboronic acid is 1:1.5-3, preferably 1:2-3, more preferably 1:3;

[0013] Tetrakis(triphenylphosphine)palladium is used as a catalyst, and the amount of catalyst used is generally 0.01 to 0.1% of the molar amount of 4,7-dibromo-2,1,3-benzothiadiazole;

[0014] Potassium carbonate (which can be added in the form of an aqueous solution) is used as an alkaline balancing substance to improve the catalytic activity of the catalyst; the molar ratio of 4,7-dibromo-2,1,3-benzothiadiazole to potassium carbonate is 1:1.5-3, preferably 1:2-3, and more preferably 1:3;

[0015] 1,4-dioxane is used as the reaction solvent; the volume mass ratio of 1,4-dioxane to 4,7-dibromo-2,1,3-benzothiadiazole is 27 to 30:1, mL / g; preferably 28 to 30:1, mL / g; more preferably 29:1, mL / g;

[0016] The reaction temperature is preferably 105-125°C, more preferably 120°C; the reaction time is preferably 24h;

[0017] The post-treatment method is as follows: after the reaction is completed, the reaction solution is cooled to room temperature, water and dichloromethane are added for extraction, the organic phase is dehydrated with anhydrous sodium sulfate, concentrated under reduced pressure, and then subjected to column chromatography separation, using a mixture of petroleum ether and dichloromethane in a volume ratio of 2:1 as the eluent, collecting the eluate containing the target compound, and removing the solvent by rotary evaporation to obtain the compound represented by Formula II;

[0018]

[0019] (2) mixing the compound represented by formula II, propane sultone, and N,N-dimethylformamide, heating to 110-130° C. and reflux for 10-15 hours, and post-treating to obtain the viologen derivative represented by formula I;

[0020] The molar ratio of the compound represented by formula II to propane sultone is 1:2 to 4, preferably 1:2 to 3, more preferably 1:3;

[0021] N,N-dimethylformamide is used as the reaction solvent; the volume mass ratio of N,N-dimethylformamide to the compound represented by Formula II is 27 to 30:1, mL / g; preferably 28 to 30:1, mL / g; more preferably 29:1, mL / g;

[0022] The post-treatment method is as follows: after the reaction is completed, the reaction mixture is cooled to room temperature, the precipitate generated by the reaction is separated by vacuum filtration, washed with acetonitrile and N,N-dimethylformamide, and dried at 50° C. to obtain the viologen derivative shown in formula I.

[0023] An electrochromic hydrogel is composed of a viologen derivative represented by formula I, 1,1'-ferrocenedimethanol, sodium carboxymethyl cellulose and deionized water in a mass ratio of 2:1:17:200.

[0024] The preparation method of the electrochromic hydrogel is as follows: at room temperature, the viologen derivative represented by formula I and 1,1'-ferrocenedimethanol are ultrasonically dissolved in deionized water, and then sodium carboxymethyl cellulose is added and stirred until a uniform and transparent state is obtained to obtain an electrochromic hydrogel with a light yellow color.

[0025] The electrochromic hydrogel can be further assembled into an electrochromic device by affixing 3M tape around the conductive surface of the conductive ITO glass, evenly applying the electrochromic hydrogel into the adhesive frame, and then covering the conductive surface of another conductive ITO glass on the adhesive frame to obtain the electrochromic device.

[0026] The present invention uses conductive ITO glass as a conductive layer, 1,1'-ferrocenedimethanol as an anode supplementary material, sodium carboxymethyl cellulose as a polymer electrolyte matrix, and a viologen derivative shown in formula I as an electrochromic material, thereby assembling a green and safe viologen-based electrochromic device.

[0027] The technical principles of the present invention include:

[0028] This invention synthesizes a novel viologen derivative that uses benzothiadiazole as a bridge structure, interrupting the original 4,4'-bipyridine structure. Alkyl groups are introduced at both N positions by introducing propane sultone. This N-position substitution effectively modulates the original band gap of the viologen, shifting its absorption in the visible light region and enhancing its solubility in water.

[0029] As an electrochromic material, the viologen derivative is highly transparent in its neutral state, with its absorption peak increasing with applied negative voltage, appearing purple in the reduced state. When the voltage is reduced, the color gradually changes from purple to transparent, and this cycle repeats. The ultraviolet absorption spectrum of the viologen derivative, measured using an electrochemical workstation and a UV-visible spectrophotometer, exhibits high contrast and good electrochromic properties. The novel viologen derivatives provided by the present invention enrich the viologen family of compound materials and have potential applications in the field of electrochromism.

[0030] The beneficial effects of the present invention are:

[0031] This study synthesized a novel electrochromic material derived from a viologen derivative by modifying the N-position of the viologen with appropriate substituents. The material was then applied to an electrochromic hydrogel and device. The resulting device exhibited high transparency in its neutral state. When an external voltage of -0.9 V was applied, the absorption peak showed a significant upward shift, becoming purple in the reduced state. When the voltage was reduced, the color gradually shifted from purple to transparent, and this cycle repeated. Electrochemical performance tests demonstrated excellent reversible, non-diffusion-controlled redox properties.

[0032] The device's UV absorption spectrum, measured using an electrochemical workstation and UV-visible spectrophotometer, showed high contrast and excellent electrochromic performance. This new electrochromic device combines both electrochromic and excellent electrochemical properties, and has potential application prospects in the electrochromic field. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 : Cyclic voltammogram of electrochromic device.

[0034] Figure 2 : UV-visible absorption spectra of electrochromic devices at different voltages.

[0035] Figure 3 : Response time and stability diagram of electrochromic device at 532nm wavelength. DETAILED DESCRIPTION

[0036] The present invention is further described below by way of specific examples, but the scope of protection of the present invention is not limited thereto. In the examples of the present invention, unless otherwise specified, the methods used are conventional methods, and the reagents used can be obtained from commercial sources.

[0037] Example 1

[0038] (1) 4,7-Dibromo-2,1,3-benzothiadiazole (0.67 g, 2.28 mmol), 4-pyridineboronic acid (0.84 g, 6.84 mmol), tetrakis(triphenylphosphine)palladium (0.05 g, 0.001 mmol), potassium carbonate (0.94 g, 6.8 mmol) and 20 mL of 1,4-dioxane were added to a reaction flask in sequence, heated to 100 ° C under N2 protection, and refluxed for 24 h. After the reaction was completed, water and dichloromethane were extracted three times, the extract was concentrated and dehydrated with anhydrous sodium sulfate, and separated by column chromatography using petroleum ether and dichloromethane as mobile phases. After the solvent was removed by rotary evaporation, 0.29 g of the compound shown in formula II was obtained, with a yield of 44.2%.

[0039] (2) The compound represented by formula II (0.46 g, 1.4 mmol), propane sultone (0.51 g, 4.13 mmol), and 5 mL of N,N-dimethylformamide were added to the reaction flask in sequence, and the mixture was heated to 120°C and refluxed for 12 h. After the reaction was completed, the yellow precipitate was separated by vacuum filtration, and the solid product was washed with acetonitrile and N,N-dimethylformamide to remove residual impurities. The solid was collected and dried in a 50°C forced air oven to obtain 0.322 g of the violacein derivative represented by formula I, with a yield of 70%.

[0040] Example 2

[0041] (1) Dissolve a water-soluble viologen derivative (0.02 g, 0.01 mmol) and 1,1'-ferrocenedimethanol (0.01 g, 0.04 mmol) in 2 mL of deionized water. Ultrasonicate to completely dissolve the 1,1'-ferrocenedimethanol. Then, slowly add sodium carboxymethylcellulose (0.17 g, 0.2 mmol) and stir until the mixture is homogeneous and transparent, with a light yellow gel.

[0042] (2) Secondly, the electrochromic hydrogel is assembled into an electrochromic device. 3M tape is affixed around the conductive surface of the conductive ITO glass. The electrochromic hydrogel is evenly coated into the adhesive frame with a coating thickness of 3 mm. Then, the conductive surface of another conductive ITO glass is covered on the adhesive frame to obtain the electrochromic device.

[0043] Example 3

[0044] Testing of electrochemical properties of electrochromic devices:

[0045] The device prepared in Example 2 was connected to an electrochemical workstation and cyclic voltammetry was used for scanning. The scanning voltage was 0 to -1.2 V and the scanning speed was 100 mV / s. The results are shown in FIG. Figure 1 As shown, Figure 1 The electrochemical properties test diagram is Figure 1 It can be seen that the device has a pair of obvious redox peaks, and as the voltage decreases, the color of the device can be observed to change from high transmittance to deep purple. The device can achieve purple color change at 0.8V.

[0046] Example 4

[0047] Spectroelectrochemical testing of electrochromic devices:

[0048] The device prepared in Example 2 was analyzed by combining an electrochemical workstation with an ultraviolet spectrometer. The electrochemical workstation was set to constant potential electrolysis, the ultraviolet spectrum was set to full-band absorbance, and the scanning range was 400-1100 nm. The results are shown in FIG. Figure 2 As shown, Figure 2This is a visible-ultraviolet spectrum. In the neutral state at 0V, there is almost no absorption between 400 and 1100nm. At 0.7V, two absorption peaks appear at 532nm and 752nm, indicating that the electrochromic device has completed the colorless to purple transition. As the voltage increases, the two absorption peaks become stronger, and the ECD color deepens.

[0049] Example 5

[0050] Test of response speed and stability of electrochromic devices:

[0051] The device prepared in Example 2 was analyzed using an electrochemical workstation coupled with an ultraviolet spectrometer. The electrochemical workstation was set to a multi-potential step method with an initial potential of 0 V, a final potential of 0.8 V, a potential pulse width of 10 s, and a scan time of 50,000 s. The ultraviolet spectrum was set to spectrodynamics with a wavelength of 532 nm. The data obtained are shown in the figure below. Figure 3 As shown, the electrochromic device has a coloring time of 4 seconds and a fading time of 5 seconds, and the film still maintains a contrast ratio of 99.4% after 5000 cycles. The results show that the electrochromic device provided by the present invention has good stability under multiple cycles.

Claims

1. A viologen derivative, as shown in Formula I: 。 2. The method for preparing the viologen derivative according to claim 1, wherein: The steps include: (1) 4,7-dibromo-2,1,3-benzothiadiazole, 4-pyridineboronic acid, tetrakis(triphenylphosphine)palladium, potassium carbonate, and 1,4-dioxane were mixed, heated to 100-130°C under N2 protection and refluxed for 20-30 hours, and post-treated to obtain the compound of formula II; (2) Mixing the compound represented by formula II, propane sultone, and N,N-dimethylformamide, heating to 110-130°C and reflux for 10-15 hours, and post-treating to obtain the viologen derivative represented by formula I; 。 3. The preparation method according to claim 2, wherein In step (1), the molar ratio of 4,7-dibromo-2,1,3-benzothiadiazole to 4-pyridineboronic acid is 1:1.5-3.

4. The preparation method according to claim 2, wherein In step (1), the amount of tetrakis(triphenylphosphine)palladium used is 0.01-0.1% of the molar amount of 4,7-dibromo-2,1,3-benzothiadiazole.

5. The preparation method according to claim 2, wherein In step (1), the molar ratio of 4,7-dibromo-2,1,3-benzothiadiazole to potassium carbonate is 1:1.5-3.

6. The preparation method according to claim 2, wherein In step (2), the molar ratio of the compound represented by formula II to propane sultone is 1:2-4.

7. An electrochromic hydrogel, characterized in that: The invention is composed of a viologen derivative represented by formula I, 1,1'-ferrocenedimethanol, sodium carboxymethyl cellulose and deionized water; 。 8. The electrochromic hydrogel according to claim 7, wherein: The mass ratio of the viologen derivative shown in formula I, 1,1'-ferrocenedimethanol, sodium carboxymethyl cellulose and deionized water is 2:1:17:

200.

9. An electrochromic device, characterized in that: The electrochromic device is assembled as follows: 3M tape is applied around the conductive surface of the conductive ITO glass, the electrochromic hydrogel according to claim 7 is evenly applied to the adhesive frame, and then the conductive surface of another conductive ITO glass is covered on the adhesive frame to obtain an electrochromic device.

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