Photo-crosslinkable polymerization processable electrochromic polymer, method for preparing the same, and use thereof

Abstract

The present application relates to the technical fields of organic chemistry and organic photoelectric functional material, and provides a photo-crosslinkable polymerization processing type electrochromic polymer, a preparation method thereof and application thereof.The present application provides a photo-crosslinkable polymerization processing type electrochromic polymer, and a structural formula of the photo-crosslinkable polymerization processing type electrochromic polymer is as formula (d): x is 5-10, and y is 2x.The photo-crosslinkable polymerization processing type electrochromic polymer provided by the present application has simple synthesis steps, low preparation cost, and can realize transparent-black state switching, and has wide application prospect.The photo-crosslinkable polymerization processing type electrochromic polymer provided by the present application can occur reversible crosslinking reaction under ultraviolet light without additional photoinitiator, and can be prepared into a polymer film by using the photo-crosslinking reaction, is energy-saving and environment-friendly, easy to initiate, and can be mass-produced to obtain an electrochromic film with crosslinking structure, excellent performance and strong cycle stability.

Description

Technical Field

[0001] This invention relates to the fields of organic chemistry and organic optoelectronic functional materials, specifically to a photocrosslinkable polymerizable electrochromic polymer, its preparation method, and its applications. Background Technology

[0002] Electrochromic technology, as a smart color-changing technology, works by controlling an applied voltage to alter the optical properties of electrochromic materials, enabling them to reversibly switch between transparent and colored states. Electrochromic materials have broad application prospects, especially suitable for fabricating transmission-type electrochromic devices, such as smart windows, electronic tags, and photochromic glasses.

[0003] From the perspective of practical applications of electrochromic devices, the most widely applicable materials are those that can reversibly switch between transparent and black. Currently, organic conjugated electrochromic polymers have been extensively studied in experiments to achieve black-to-transparent color change due to their advantages in optical contrast and coloring efficiency. However, these polymers typically have complex molecular structures, leading to high synthesis difficulty and high film preparation costs. Furthermore, the inability to achieve a truly colorless and transparent state usually limits their development and application.

[0004] Therefore, how to obtain transparent-black electrochromic polymer films through molecular structure design and expand their applications has become a research hotspot. Summary of the Invention

[0005] This invention is made to solve the above-mentioned problems. The purpose is to provide a photocrosslinkable polymer that is easy to synthesize, has low preparation cost, and can achieve a transparent-to-black color change. Furthermore, a transparent-to-black electrochromic polymer film with a crosslinked structure with excellent performance, simple preparation method, and large-scale production can be prepared through a photocrosslinking process, so as to be used to prepare high-performance electrochromic devices.

[0006] The inventors discovered that polymer films prepared by chemical polymerization have strict requirements on the degree of polymerization of the polymer. If the polymerization is too low, the prepared polymer film will be easily soluble in organic solvents and difficult to use; if the polymerization is too high, it will be difficult to find a suitable solvent to process the polymer. However, polymers prepared by photocrosslinking can change the solubility of the polymer itself and have the advantages of energy saving, environmental protection, and easy initiation. Therefore, the inventors attempted to design a photocrosslinkable polymer that can be polymerized and processed into an electrochromic polymer.

[0007] During the research, the inventors discovered that cinnamic acid and its derivatives can undergo reversible crosslinking reactions under ultraviolet light without the addition of an external photoinitiator. Therefore, the inventors used cinnamic acid esters as photocrosslinking units to modify the structure of triphenylamine and synthesized electrochromic units, preparing a photocrosslinkable polymer that can achieve a transparent-to-black color change. Furthermore, the inventors conducted a photocrosslinking reaction on the photocrosslinkable polymer to prepare an electrochromic polymer film with a crosslinked structure. By optimizing the preparation method, the performance of the electrochromic polymer film was improved.

[0008] In a first aspect, the present invention provides a photocrosslinkable polymerizable electrochromic polymer, wherein the structural formula of the photocrosslinkable polymerizable electrochromic polymer is as shown in formula (d):

[0009]

[0010] x is 5-10, y is 2x.

[0011] The photocrosslinkable polymer-processable electrochromic polymer provided by this invention has a simple synthesis step, low preparation cost, and can achieve switching between transparent and black states, showing broad application prospects. On one hand, this photocrosslinkable polymer-processable electrochromic polymer can undergo a reversible crosslinking reaction under ultraviolet light without the addition of an external photoinitiator, and can be used to prepare polymer films via photocrosslinking, which is energy-saving, environmentally friendly, and easy to initiate. On the other hand, this photocrosslinkable polymer-processable electrochromic polymer is soluble in dichloromethane, and can be processed into films using solution processing, which is simple to operate. Furthermore, the prepared electrochromic film with a crosslinked structure is insoluble in dichloromethane, enabling large-scale production of high-performance, highly cycling-stable electrochromic films with a crosslinked structure.

[0012] A second aspect of the present invention provides a method for preparing a photocrosslinkable polymerizable electrochromic polymer, comprising the following steps:

[0013] (1) Substance a is reacted with 4-(N,N-dimethylamino)phenylboronic acid pinacol ester to obtain substance b, with the structural formula shown in formula (b). The chemical reaction equation is as follows:

[0014]

[0015] (2) React substance b obtained in step (1) with methacrylic acid to obtain substance c, with the structural formula shown in formula (c), and the chemical reaction equation is as follows:

[0016]

[0017] (3) The substance c obtained in step (2) is polymerized with melamine cyanurate and azobisisobutyronitrile to obtain photocrosslinkable polymerized electrochromic polymer d, with the structural formula as shown in formula (d). The chemical reaction equation is as follows:

[0018]

[0019] The method for preparing photocrosslinkable polymeric electrochromic polymers provided by this invention is simple to operate and has low preparation cost. This method introduces cinnamic acid ester as a photocrosslinking unit and modifies the structure of triphenylamine to synthesize an electrochromic unit. The prepared electrochromic polymer can be processed into thin films by photocrosslinking polymerization, and the prepared thin films can achieve switching between transparent and black states, which has broad application prospects.

[0020] A third aspect of the present invention provides a method for preparing an electrochromic polymer film having a cross-linked structure.

[0021] An electrochromic polymer film with a crosslinked structure was prepared by photocrosslinking reaction of the photocrosslinkable polymer d as described in the first aspect. The chemical reaction equation is as follows:

[0022]

[0023] In some embodiments of the method for preparing an electrochromic polymer film with a cross-linked structure provided in the third aspect of the present invention, the specific steps are as follows:

[0024] A photocrosslinkable polymer was dissolved in a solvent to prepare a polymer solution. An ITO conductive glass was placed in an ultraviolet ozone generator, and the polymer solution was then spin-coated onto the surface of the ITO conductive glass to form a thin film. After the film dried, a photocrosslinking reaction was carried out under ultraviolet light to obtain a polymer film. After purification, an electrochromic polymer film with a crosslinked structure was obtained.

[0025] The method for preparing electrochromic polymer films with cross-linked structures provided by this invention does not require the addition of photoinitiators. Electrochromic polymer films with cross-linked structures can be prepared under ultraviolet light, which is easy to initiate and energy-saving and environmentally friendly.

[0026] In some embodiments of the method for preparing an electrochromic polymer film with a cross-linked structure provided in the third aspect of the present invention, the solvent is dichloromethane, and the concentration of the polymer solution is 40-45 mg / mL.

[0027] In some embodiments of the method for preparing an electrochromic polymer film with a cross-linked structure provided in the third aspect of the present invention, the spin coating speed is 900-1000 rpm.

[0028] This invention limits the spin coating speed during the preparation process. On the one hand, it prevents the film thickness from being too thin due to excessive spin coating speed, which would reduce the contrast of the film and affect its electrochromic properties. On the other hand, it prevents the film thickness from being uneven due to excessive spin coating speed.

[0029] In some embodiments of the method for preparing an electrochromic polymer film with a cross-linked structure provided in the third aspect of the present invention, the wavelength of the ultraviolet lamp is 310-312 nm.

[0030] This invention limits the wavelength of the ultraviolet lamp during the preparation process to prevent the wavelength of the ultraviolet lamp from being too high or too low, which would reduce the degree of cross-linking of the film and affect the electrochromic properties of the film.

[0031] In some embodiments of the method for preparing an electrochromic polymer film with a cross-linked structure provided in the third aspect of the present invention, the specific purification step is as follows: placing the polymer film in the solvent, removing it and drying it to obtain an electrochromic polymer film with a cross-linked structure.

[0032] The present invention further purifies the prepared polymer film, dissolving the oligomers in the film in a solvent, thereby improving the purity of the electrochromic polymer film with cross-linked structure and obtaining better electrochromic performance.

[0033] A fourth aspect of the present invention provides an electrochromic polymer having a cross-linked structure constituting a film as described in the third aspect, the electrochromic polymer having a cross-linked structure having the structural formula of formula (e):

[0034]

[0035] The electrochromic polymer with a cross-linked structure provided by this invention is insoluble in dichloromethane, and can be used to prepare high-performance electrochromic polymer films with a cross-linked structure. Furthermore, the electrochromic polymer with a cross-linked structure can switch between transparent and black states by controlling the applied voltage, and can be used to prepare electrochromic devices, such as smart windows, electronic tags, and photochromic glasses.

[0036] The electrochromic polymer described in this invention can be used to prepare high-performance electrochromic devices.

[0037] A fifth aspect of the present invention provides an application of the electrochromic polymer having a cross-linked structure as described in the fourth aspect, characterized in that the electrochromic polymer having a cross-linked structure is used to prepare an electrochromic device.

[0038] By implementing the above technical solution, the present invention has the following beneficial effects:

[0039] This invention synthesizes an electrochromic unit by structurally modifying triphenylamine, and prepares a photocrosslinkable polymeric electrochromic polymer using cinnamate as the photocrosslinking unit. The synthesis method is simple, with few byproducts and easy separation.

[0040] The photocrosslinkable polymer-processable electrochromic polymer provided by this invention can obtain a stable and insoluble electrochromic polymer film with a crosslinked structure under ultraviolet light irradiation.

[0041] The electrochromic polymer film with a cross-linked structure prepared by this invention can exhibit transparent-to-black color-changing properties and has high optical contrast, making it widely applicable in the fields of smart windows, smart glasses, and electronic tags. Attached Figure Description

[0042] Figure 1 This is the cyclic voltammetry curve of the electrochromic polymer film with a cross-linked structure in Example 7 of the present invention;

[0043] Figure 2 Cyclic voltammetry curves of the electrochromic polymer film with a cross-linked structure at different scan rates in Example 8 of the present invention;

[0044] Figure 3 These are the ultraviolet-visible absorption spectra of the electrochromic polymer film with a cross-linked structure in Example 9 of the present invention under different voltages;

[0045] Figure 4 This is an electrochromic optical contrast diagram of the electrochromic polymer film with a cross-linked structure in Example 10 of the present invention. Detailed Implementation

[0046] To make the technical means, creative features, objectives and effects of this invention easy to understand, the invention will be specifically described below in conjunction with embodiments and accompanying drawings.

[0047] Example 1: Preparation of photocrosslinkable polymerizable electrochromic polymer

[0048] (1) Weigh substance a (2.00 g, 4.6 mmol), 4-(N,N-dimethylamino)phenylboronic acid pinacol ester (2.80 g, 11.3 mmol), and tetra(triphenylphosphine)palladium (0.10 g, 0.09 mmol) into a 100 mL two-necked round-bottom flask. Under nitrogen protection, add tetrahydrofuran (30 mL) and 10 mL of potassium carbonate aqueous solution (2 M), and heat to reflux for 12 h. After the reaction is complete, add the resulting reaction solution to saturated brine and extract with dichloromethane. Combine the extracted organic solutions and remove water with anhydrous sodium sulfate. Filter the filtrate and dry it with coarse silica gel. Pack fine silica gel into a column as the stationary phase, and use dichloromethane and petroleum ether in a 1:1 volume ratio as the eluent. Separate and purify by column chromatography to obtain 1.04 g of yellow solid product substance b, with a yield of 44%.

[0049] (2) Weigh substance b (1.00 g, 1.9 mmol), methacrylic acid (0.26 g, 3.0 mmol), 4-dimethylaminopyridine (0.03 g, 0.3 mmol), dicyclohexylcarbodiimide (0.64 g, 3.1 mmol), and tetrahydrofuran (30 mL) into a 100 mL round-bottom flask and stir at room temperature for 24 h. After the reaction is complete, the resulting reaction solution is added to saturated brine and extracted with dichloromethane. Combine the extracted organic solutions and remove water with anhydrous sodium sulfate. Filter the solution and dry it with coarse silica gel. Pack fine silica gel into a column as the stationary phase and use dichloromethane as the eluent. Separate and purify the product by column chromatography to obtain 0.72 g of pale yellow solid product c, with a yield of 65%.

[0050] (3) Weigh substance c (0.30 g, 0.5 mmol), melamine cyanurate (0.18 g, 0.5 mmol), and azobisisobutyronitrile (0.08 g, 0.5 mmol) into a 50 mL two-necked round-bottom flask. Under nitrogen protection, add anhydrous tetrahydrofuran (10 mL), heat to 60 °C, and stir for 48 h. After the reaction is complete, add the resulting reaction solution into a 250 mL Erlenmeyer flask containing 100 mL of methanol and let stand for 2 h. Collect the precipitate by vacuum filtration, wash with methanol, and dry in an oven to obtain 0.31 g of white solid product d.

[0051] The structural formula of substance a is shown in formula (a); the structural formula of substance b is shown in formula (b); the structural formula of substance c is shown in formula (c); the structural formula of substance d is shown in formula (d);

[0052]

[0053] Example 2: Preparation of electrochromic polymer films with cross-linked structures

[0054] The substance d prepared in Example 1 was dissolved in dichloromethane to prepare a polymer solution with a concentration of 40 mg / mL. ITO conductive glass was treated in a UV ozone generator for 25 min. The polymer solution was spin-coated onto the surface of the ITO conductive glass at 1000 rpm for 1 min. After the film dried naturally, it was crosslinked under 312 nm UV light for 40 min, and then soaked in dichloromethane to remove uncrosslinked oligomers, yielding an electrochromic polymer film with a crosslinked structure composed of electrochromic polymer e, the structural formula of which is shown in formula (e).

[0055]

[0056] Example 3: Screening of polymer solution concentration

[0057] In this embodiment, an electrochromic polymer film with a cross-linked structure was prepared according to the method in Example 2, and the concentration of the polymer solution was further screened.

[0058] Table 1. Changes in reaction effect with polymer solution concentration

[0059]

[0060]

[0061] As shown in Table 1, the films prepared by substance d in a 40-42 mg / mL dichloromethane solution have a suitable film thickness and exhibit the best performance in subsequent tests. Too low a solution concentration results in an excessively thin film, while too high a concentration results in an excessively thick film; both excessively thin and excessively thick films will further degrade film performance.

[0062] Example 4: Screening of reaction solvents

[0063] In this embodiment, an electrochromic polymer film with a cross-linked structure was prepared according to the method in Example 2, and the reaction solvent was further screened.

[0064] Table 2 shows the changes in reaction effect with reaction solvent.

[0065] Serial Number reaction solvent reaction effect 1 dichloromethane Suitable film morphology 2 chloroform The surface morphology of the thin film is not dense and smooth. 3 Tetrahydrofuran The surface morphology of the thin film is not dense and smooth.

[0066] As shown in Table 2, substance d is soluble in dichloromethane, trichloromethane, and tetrahydrofuran. However, the surface morphology of films prepared using trichloromethane and tetrahydrofuran as solvents is not dense and uneven, therefore dichloromethane is used as the solvent.

[0067] Example 5: Screening of spin coating speed

[0068] In this embodiment, an electrochromic polymer film with a cross-linked structure was prepared according to the method in Example 2, and the spin coating speed was further screened.

[0069] Table 3. Changes in reaction effect with spin coating speed.

[0070] Serial Number Spin coating speed (rpm) reaction effect 1 800 Uneven film thickness 2 850 Uneven film thickness 3 900 The film thickness is moderate and uniform 4 950 The film thickness is moderate and uniform 5 1000 The film thickness is moderate and uniform 6 1050 The film is relatively thin. 7 1100 The film is relatively thin. 8 1150 thin film 9 1200 thin film

[0071] As shown in Table 3, when the spin coating speed is between 900-100 rpm, the prepared electrochromic polymer film with cross-linked structure has a moderate thickness and uniform texture, exhibiting excellent electrochromic properties. However, when the spin coating speed is below 900 rpm, the prepared electrochromic polymer film with cross-linked structure has uneven thickness and an uneven surface, affecting its electrochromic properties. When the spin coating speed is above 1000 rpm, the excessively fast speed results in insufficient solution on the spin coating, leading to a thinner prepared electrochromic polymer film with cross-linked structure, which also affects its electrochromic properties.

[0072] Example 6: Screening of UV Lamp Wavelengths

[0073] In this embodiment, an electrochromic polymer film with a cross-linked structure was prepared according to the method in Example 2, and the wavelength of the ultraviolet lamp was further screened.

[0074] Table 4. Changes in reaction effect with the wavelength of the ultraviolet lamp.

[0075] Serial Number Wavelength (nm) of ultraviolet lamp reaction effect 1 308 Low degree of cross-linking of thin films 2 309 Low degree of cross-linking of thin films 3 310 High degree of cross-linking of thin films 4 311 High degree of cross-linking of thin films 5 312 High degree of cross-linking of thin films 6 313 Low degree of cross-linking of thin films 7 314 Low degree of cross-linking of thin films 8 315 Low degree of cross-linking of thin films

[0076] As shown in Table 4, when the wavelength of the ultraviolet lamp is between 310 and 312 nm, the electrochromic polymer film with cross-linked structure prepared has a high degree of cross-linking and excellent electrochromic performance.

[0077] Example 7: Cyclic voltammetry testing of electrochromic polymer films with cross-linked structures

[0078] 0.391 g of 0.1 mol / L [BMIM]BF4 was added to a 10 mL volumetric flask and diluted to volume with chromatographic grade PC to serve as a blank supporting electrolyte solution. The electrochromic polymer film with a cross-linked structure prepared in Example 2 was used as the working electrode, Ag / AgCl as the reference electrode, and platinum wire as the counter electrode. Cyclic voltammetry curves of the film at a scan rate of 50 mV / s were measured on an electrochemical workstation. The test results are as follows: Figure 1 As shown.

[0079] Depend on Figure 1 It can be seen that the film has two redox pairs. The first oxidation peak corresponds to the oxidation of the nitrogen atom at the center of triphenylamine, and the second oxidation peak corresponds to the oxidation of two dimethylamino groups.

[0080] Example 8: Cyclic voltammetry testing of electrochromic polymer films with cross-linked structures at different scan rates

[0081] 0.391 g of 0.1 mol / L [BMIM]BF4 was added to a 10 mL volumetric flask and diluted to volume with chromatographic grade PC to serve as a blank supporting electrolyte solution. The electrochromic polymer film with a cross-linked structure prepared in Example 2 was used as the working electrode, Ag / AgCl as the reference electrode, and platinum wire as the counter electrode. Cyclic voltammetry curves of the film at scan rates of 10, 20, 50, 100, and 200 mV / s were measured in an electrochemical workstation. The test results are as follows: Figure 2 As shown.

[0082] Depend on Figure 2 It can be seen that at low scan rates, the differences between different oxidation peaks are less pronounced. When the scan rate increases from 10 mV / s to 200 mV / s, the oxidation peak current is proportional to the half power of the potential scan rate. Since the oxidation peaks of the polymer film contain oxidation at multiple sites, the shift in peak potential is not significant.

[0083] Example 9: UV-Vis absorption spectroscopy of electrochromic polymer films with cross-linked structures

[0084] 0.391 g of 0.1 mol / L [BMIM]BF4 was added to a 10 mL volumetric flask and diluted to volume with chromatographic grade PC to serve as a blank supporting electrolyte solution. The electrochromic polymer film with a cross-linked structure prepared in Example 2 was used as the working electrode, Ag / AgCl as the reference electrode, and platinum wire as the counter electrode. The UV-Vis absorption spectra of the polymer film at different voltages were measured, and the results are as follows: Figure 3 As shown.

[0085] Depend on Figure 3 The ultraviolet-visible absorption spectrum shows that the polymer film is colorless and transparent in the neutral state, yellow in the semi-oxidized state, and black in the fully oxidized state, and also has good electrochromic properties.

[0086] Example 10: Electrochromic performance testing of electrochromic polymer films with cross-linked structures

[0087] 0.391 g of 0.1 mol / L [BMIM]BF4 was added to a 10 mL volumetric flask and diluted to volume with chromatographic grade PC to serve as a blank supporting electrolyte solution. The electrochromic polymer film with a cross-linked structure prepared in Example 2 was used as the working electrode, Ag / AgCl as the reference electrode, and platinum wire as the counter electrode. The optical contrast profile of the polymer film was measured, and the results are shown below. Figure 4 As shown.

[0088] Depend on Figure 4 As shown, the film exhibits a coloring time of 7.1 s, a fading time of 3.9 s, and an optical contrast of 62% at 600 nm, demonstrating excellent electrochromic properties.

[0089] The above embodiments are preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention.

Claims

1. A photocrosslinkable polymerizable electrochromic polymer, characterized in that, The structural formula of the photocrosslinkable polymerizable electrochromic polymer is shown in formula (d): ； x is 5-10, y is 2x.

2. A method for preparing a photocrosslinkable polymerizable electrochromic polymer, characterized in that, Includes the following steps: (1) Substance a is reacted with 4-(N,N-dimethylamino)phenylboronic acid pinacol ester to obtain substance b, with the structural formula shown in formula (b). The chemical reaction equation is as follows: ； (2) React substance b obtained in step (1) with methacrylic acid to obtain substance c, with the structural formula shown in formula (c), and the chemical reaction equation is as follows: ； (3) The substances c, f, and azobisisobutyronitrile obtained in step (2) are subjected to a polymerization reaction to obtain a photocrosslinkable polymeric electrochromic polymer d, with the structural formula shown in formula (d). The chemical reaction equation is as follows: ； x is 5-10, y is 2x.

3. A method for preparing an electrochromic polymer film with a cross-linked structure, characterized in that, The photocrosslinkable polymer d described in claim 1 is prepared by a photocrosslinking reaction, and the chemical reaction equation is as follows: 。 4. The method for preparing an electrochromic polymer film with a cross-linked structure according to claim 3, characterized in that, The specific steps are as follows: A photocrosslinkable polymeric electrochromic polymer d was dissolved in a reaction solvent to prepare a polymer solution. ITO conductive glass was placed in an ultraviolet ozone generator, and the polymer solution was then spin-coated onto the surface of the ITO conductive glass to form a thin film. After the film dried, a photocrosslinking reaction was carried out under an ultraviolet lamp to obtain a polymer film. After purification, an electrochromic polymer film with a crosslinked structure was obtained.

5. The method for preparing the electrochromic polymer film according to claim 4, characterized in that, The reaction solvent is dichloromethane, and the concentration of the polymer solution is 40-45 mg / mL.

6. The method for preparing the electrochromic polymer film according to claim 4, characterized in that, The spin coating speed is 900-1000 rpm.

7. The method for preparing the electrochromic polymer film according to claim 4, characterized in that, The wavelength of the ultraviolet lamp is 310-312 nm.

8. The method for preparing the electrochromic polymer film according to claim 4, characterized in that, The specific purification steps are as follows: the polymer film is placed in the reaction solvent, and after drying, an electrochromic polymer film with a cross-linked structure is obtained.

9. An electrochromic polymer having a cross-linked structure constituting a thin film, characterized in that, The thin film is prepared by the preparation method according to any one of claims 3 to 8 (e): 。 10. The application of an electrochromic polymer having a cross-linked structure as described in claim 9, characterized in that, The electrochromic polymer with the cross-linked structure is used to prepare electrochromic devices.

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