Display device composed of viologen compound and hydrogel and application of display device

Abstract

The invention discloses a viologen compound, a display device composed of hydrogel and application of the viologen compound and the display device. A novel viologen derivative electrochromic material (I) is synthesized by selecting a proper substituent group to modify the N position of viologen, then the viologen derivative is assembled into sodium carboxymethyl cellulose hydrogel, and the display device is prepared. The hydrogel with the electrochromic property is obtained; the electrochromic hydrogel material is in a high-transmittance state in a neutral state, when an external voltage is applied, an absorption peak value has an obvious rising change, the electrochromic hydrogel material is purple in a reduction state, and the electrochromic hydrogel material has a potential application prospect in the field of electrochromism; # imgabs0 #

Description

Technical Field

[0001] The invention belongs to the technical field of electrochromic materials, and in particular relates to a display device composed of a viologen compound and a hydrogel and applications thereof. Background Art

[0002] Electrochromism (EC) refers to the phenomenon that the optical properties of a material (reflectivity, transmittance, absorptivity, etc.) undergo stable and reversible changes under the action of an external electric field, which manifests itself in appearance as reversible changes in color and transparency.

[0003] Viologen compounds (1,1'-disubstituted-4,4'-bipyridine) are a common class of organic small molecule materials with bipyridine molecular structure. They show obvious color changes under voltage drive, have good optical contrast, high coloring efficiency and redox stability, so they are widely used in the field of electrochromism as an organic photoelectric functional material. As a class of electron-deficient materials, the electron transfer within the molecule causes the color change of viologen, which specifically includes three different states, namely neutral state, monovalent cationic state and divalent cationic state, showing different colors in different states.

[0004] Electrochromic devices are generally five-layer sandwich structures, which are transparent conductive electrode 1, electrolyte layer, electrochromic layer, ion storage layer, and transparent conductive electrode 2, respectively. The production is relatively cumbersome and complicated.

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

[0006] The present invention provides a display device composed of a viologen compound and a hydrogel and application thereof. The device is highly transparent in a neutral state and displays purple in a reduced state, thus enriching the types of electrochromic materials.

[0007] The technical solution of the present invention 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 comprises the following steps:

[0011] (1) 4,7-dibromo-2,1,3-benzothiadiazole, 4-pyridineboronic acid, tetrakis(triphenylphosphine)palladium, potassium carbonate, and 1,4-dioxane are mixed, heated to 100-130° C. under N2 protection, and refluxed for 20-30 hours, followed by post-treatment to obtain a compound represented by 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 the 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 fed 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, and the organic phase is concentrated under reduced pressure and then separated by column chromatography, and a mixed solution of petroleum ether and dichloromethane in a volume ratio of 2:1 is used as an eluent, and the eluate containing the target compound is collected, and the solvent is removed by rotary evaporation to obtain a 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 shown in 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 shown in 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, specifically, by attaching 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 supplement material, sodium carboxymethyl cellulose as a polymer electrolyte matrix, and a viologenin derivative shown in formula I as an electrochromic material, thereby assembling a green and safe viologenin-based electrochromic device.

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

[0028] The present invention synthesizes a novel viologen derivative, uses benzothiadiazole as a bridge structure of the viologen derivative, and interrupts the original 4,4'-bipyridine structure. By introducing propane sultone, alkyl modification is performed on the N positions on both sides. The substitution at the N position in viologen can effectively adjust the original bandgap width of viologen, shift the absorption of viologen in the visible light region, and enhance the solubility of viologen derivatives in water.

[0029] As an electrochromic material, the viologen derivative is in a highly transparent state in a neutral state, and the absorption peak increases with the increase of the applied negative voltage, and appears purple in a reduced state; and when the voltage is reduced, the color gradually changes from purple to a transparent state, and this is repeated. The ultraviolet absorption spectrum of the viologen derivative was tested using an electrochemical workstation and an ultraviolet-visible spectrophotometer, showing a high contrast ratio and good electrochromic performance. The novel viologen derivative provided by the present invention enriches viologen compound materials and has potential application prospects in the field of electrochromism.

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

[0031] The present invention synthesizes a novel electrochromic material of viologen derivative by selecting a suitable substituent to modify the N position of viologen. The material is applied to electrochromic hydrogel and device. The obtained device is in a high-transmittance state in a neutral state. When the external voltage is applied to -0.9V, the absorption peak value has a significant upward change, and it is purple in the reduced state; and when the voltage is reduced, the color gradually changes from purple to transparent state, and so on repeatedly; in the electrochemical performance test, it shows good reversible and non-diffusion-controlled redox properties.

[0032] At the same time, the ultraviolet absorption spectrum of the device was tested using an electrochemical workstation and a UV-visible spectrophotometer, showing a high contrast ratio and good electrochromic performance. This new type of electrochromic device has both electrochromic performance and excellent electrochemical performance, and has potential application prospects in the field of electrochromism. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0034] Figure 2 : UV-visible absorption spectra of electrochromic devices under 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 specific examples, but the protection scope 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, and the yield was 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 bottle 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 the 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, and perform ultrasonic treatment to completely dissolve 1,1'-ferrocenedimethanol. Then slowly add sodium carboxymethyl cellulose (0.17 g, 0.2 mmol) and stir until the mixture is homogeneous and transparent, and the gel color is light yellow.

[0042] (2) Secondly, the electrochromic hydrogel is assembled into an electrochromic device. 3M tape is attached around the conductive surface of the conductive ITO glass. The electrochromic hydrogel is evenly applied to 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 scanned by cyclic voltammetry with a scanning voltage of 0 to -1.2 V and a scanning speed of 100 mV / s. The results are shown in FIG. Figure 1 As shown, Figure 1 This is an electrochemical property test diagram. From the figure, we can see that the device has a pair of obvious redox peaks, and as the voltage decreases, the color of the device is observed to change from high transparency to dark 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 subjected to electrochemical workstation and UV spectrometer coupling technology. The electrochemical workstation was set to constant potential electrolysis, the UV spectrum was set to full-band absorbance, and the scanning range was 400-1100nm. The results are as follows: Figure 2 As shown, Figure 2The visible ultraviolet spectrum shows that there is almost no absorption at 400-1100nm in the neutral state at 0V, and two absorption peaks appear at 532nm and 752nm at 0.7V, and the electrochromic device completes the transition from colorless to purple. As the voltage increases further, 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 subjected to the electrochemical workstation and UV spectrometer coupling technology. The electrochemical workstation was set to the multi-potential step method: the initial potential was 0 V, the end potential was 0.8 V, the potential pulse width was 10 s, and the scanning time was 50000 s. The UV spectrum was set to spectral dynamics, and the wavelength was set to 532 nm. The data finally obtained are as follows: Figure 3 As shown, it can be seen that the coloring time of the electrochromic device is 4s, the fading time is 5s, and the film still maintains a contrast ratio of 99.4% after 5000 cycles. According to the results, it can be seen 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, characterized in that: The steps include: (1) 4,7-dibromo-2,1,3-benzothiadiazole, 4-pyridineboronic acid, tetrakis(triphenylphosphine)palladium, potassium carbonate, and 1,4-dioxane are mixed, heated to 100-130° C. under N2 protection, and refluxed for 20-30 hours, followed by post-treatment to obtain a compound represented by 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, characterized in that: 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, characterized in that: In step (1), the amount of tetrakis(triphenylphosphine)palladium used is 0.01 to 0.1% of the molar amount of 4,7-dibromo-2,1,3-benzothiadiazole.

5. The preparation method according to claim 2, characterized in that: 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, characterized in that: 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 shown in formula I, 1,1'-ferrocenedimethanol, sodium carboxymethyl cellulose and deionized water.

8. The electrochromic hydrogel according to claim 7, characterized in that: 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 attached around the conductive surface of the conductive ITO glass, the electrochromic hydrogel described in claim 7 is evenly applied to the glue frame, and then the conductive surface of another conductive ITO glass is covered on the glue frame to obtain an electrochromic device.

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