A color-tunable polymer thin film and a preparation method and application thereof

Abstract

The application provides a color-adjustable polymer film and a preparation method and application thereof, and belongs to the technical field of functional polymer materials and organic electrochromic technology. Three kinds of electrochromic polymers respectively showing red, green and blue are dissolved in appropriate organic solvents to prepare three kinds of primary color solutions, which are sequentially named as primary color solution (R), primary color solution (G) and primary color solution (B). Two of the three kinds of primary color solutions are blended according to a certain proportion, and are coated on the surface of a substrate to form a wet film. Then, the wet film is finally obtained through heat curing to obtain the color-adjustable polymer film. As the electrochromic material, the film can realize reversible conversion of a variety of colors from transparent to red, green and blue three primary colors obtained by binary blending, and has high optical contrast, fast response time and good cycle stability.

Description

Technical Field

[0001] This invention relates to the field of functional polymer materials and organic electrochromic technology, and particularly to a color-tunable polymer film, its preparation method, and its applications. Background Technology

[0002] Electrochromic materials are functional materials whose optical absorption properties can reversibly change under the influence of an applied electric field, thus exhibiting changes in color or transparency. These materials have broad application prospects in fields such as intelligent dimming windows, low-power displays, anti-glare mirrors, adaptive camouflage, and information encryption due to their low energy consumption, sustainable controllability, and good visual response characteristics. Among the many electrochromic material systems, organic electrochromic polymers have become a current research hotspot due to their advantages such as strong structural designability, fast response speed, and high optical contrast. Specifically, electrochromic units, represented by triphenylamine, phenothiazine, and their derivatives, can produce significant absorption changes during electrochemical redox processes, thereby achieving electrochromic behavior.

[0003] However, existing electrochromic polymer systems still have shortcomings. First, they offer limited color variety. Most current electrochromic materials are typically built based on a single chromophore, and their color changes are mostly limited to transitions between colorless and a single chromatic color (such as blue or green), making it difficult to meet the application requirements of multicolor displays or complex visual modulation. Second, multicolor modulation relies on complex molecular design. To achieve multicolor electrochromism, it is usually necessary to construct complex conjugated structures or multi-block polymer systems to adjust the energy level structure and absorption spectrum. This not only increases the complexity of the synthesis steps but also raises the material preparation cost, hindering large-scale applications. Furthermore, the material stability and processing performance are also limited. Traditional electrochromic polymers based on conjugated backbones typically have rigid structures, poor solubility, and limited processing performance; their films are prone to swelling or peeling in electrolyte environments, affecting the cycling stability and lifespan of devices. In addition, although there are research reports on the regulation of material properties through blending strategies in the existing technology, most of them focus on improving conductivity or mechanical properties. Research on achieving continuous control of electrochromic color through simple blending is still relatively limited, especially in systems that take into account high transparency, good processability and high stability, there is still a lack of effective solutions.

[0004] Therefore, developing an electrochromic material system that has a simple structural design, convenient processing technology, can achieve multicolor changes through simple ratio control, and has good electrochemical performance and structural stability is of great research significance and application value. Summary of the Invention

[0005] The purpose of this invention is to provide a color-tunable polymer film, its preparation method, and its application, in order to solve the above-mentioned technical problems.

[0006] To achieve the above-mentioned objectives, the present invention provides the following technical solution: This invention provides a method for preparing a color-tunable polymer film, comprising the following steps: 1) Prepare primary color solutions R, G, and B respectively using primary color polymer R, G, and B; 2) Take two of the above three base color solutions and mix them together. Then add an amine crosslinking agent and a solvent. Coat the resulting mixed solution onto the surface of the substrate and obtain a color-tunable polymer film by thermosetting. The molecular structural formulas of the primary color polymers R, G, and B are as follows: ; Where a, b, x, y, m, and n are independent integers from 5 to 15.

[0007] Furthermore, the amine crosslinking agent comprises one or more of 4,4'-diaminodiphenylmethane, tetraethylenepentamine, and polyethyleneimine; the solvent comprises one or more of chloroform, dichloromethane, and tetrahydrofuran.

[0008] Furthermore, the concentrations of the primary color solution R, primary color solution G, and primary color solution B are independently 5~15 mg / mL.

[0009] Furthermore, the concentration of the amine crosslinking agent in the mixed solution is 0.5~1.5 mg / mL.

[0010] Furthermore, the coating method is spraying, spin coating, or screen printing.

[0011] Furthermore, the heat curing is carried out under argon or nitrogen atmosphere, the heat curing temperature is 120~170℃, and the heat curing time is 4~5.5h.

[0012] The present invention also provides a color-tunable polymer film prepared by the above preparation method.

[0013] The present invention also provides an application of a color-tunable polymer film in smart windows, car rearview mirrors, information encryption, flat panel displays, and flexible wearable devices.

[0014] The beneficial effects of this invention are: Compared with existing technologies, the beneficial effects of the present invention are as follows: the method of the present invention is simpler, more intuitive and controllable than existing technologies, and the multi-color adjustable polymer electrochromic material prepared exhibits better electrochromic performance compared with existing materials. It is expected to be used in smart windows, car rearview mirrors, information encryption, flat panel displays and flexible wearable devices. Attached Figure Description

[0015] Figure 1 The molecular structures of the red, green, and blue primary color polymers used in Example 1 are shown. Figure 2 The cyclic voltammetry curve of the polymer film prepared in Example 1 is shown below. Figure 3 The images show the UV-Vis absorption spectra of the polymer film prepared in Example 1 under different voltages. Figure 4 The images show the chromaticity of the polymer film prepared in Example 1 and two other polymer films with different blending ratios at different voltages. Figure 5 The cyclic voltammetry curve of the polymer film prepared in Example 2 is shown below. Figure 6 The images show the UV-Vis absorption spectra of the polymer film prepared in Example 2 under different voltages. Figure 7 The images show the chromaticity of the polymer film prepared in Example 2 and two other polymer films with different blending ratios under different voltages. Figure 8 The graph shows the transmittance of the polymer film prepared in Example 2 as a function of time under multiple potential steps from 0 to 1.0 V at a specific wavelength. Figure 9 The cyclic voltammetry curve of the polymer film prepared in Example 3 is shown below. Figure 10 The images show the UV-Vis absorption spectra of the polymer film prepared in Example 3 under different voltages. Figure 11 The images show the chromaticity of the polymer film prepared in Example 3 and another polymer film with different blending ratios under different voltages. Figure 12 This is a graph showing the transmittance of the polymer film prepared in Example 3 as a function of time under multiple potential steps from 0 to 1.0 V at a specific wavelength. Detailed Implementation

[0016] This invention provides a method for preparing a color-tunable polymer film, comprising the following steps: 1) Prepare primary color solutions R, G, and B respectively using primary color polymer R, G, and B; 2) Take two of the above three base color solutions and mix them together. Then add an amine crosslinking agent and a solvent. Coat the resulting mixed solution onto the surface of the substrate and obtain a color-tunable polymer film by thermosetting. The molecular structural formulas of the primary color polymers R, G, and B are as follows: ; Where a, b, x, y, m, and n are independent integers from 5 to 15, preferably 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, and 15.

[0017] In this invention, the amine crosslinking agent comprises one or more of 4,4'-diaminodiphenylmethane, tetraethylenepentamine, and polyethyleneimine, preferably polyethyleneimine; the solvent comprises one or more of chloroform, dichloromethane, and tetrahydrofuran, preferably chloroform.

[0018] In this invention, the concentrations of the primary color solution R, primary color solution G, and primary color solution B are independently 5~15 mg / mL, preferably 5 mg / mL, 6 mg / mL, 7 mg / mL, 8 mg / mL, 9 mg / mL, 10 mg / mL, 11 mg / mL, 12 mg / mL, 13 mg / mL, 14 mg / mL, and 15 mg / mL.

[0019] In this invention, the volume ratio of the two primary color solutions is 1~5:1~5, preferably 2~4:2~4, and more preferably 2~3:2~3.

[0020] In this invention, the concentration of the amine crosslinking agent in the mixed solution is 0.5~1.5 mg / mL, preferably 0.6 mg / mL, 0.7 mg / mL, 0.8 mg / mL, 0.9 mg / mL, 1.0 mg / mL, 1.1 mg / mL, 1.2 mg / mL, 1.3 mg / mL, or 1.4 mg / mL.

[0021] In this invention, the coating method is spraying, spin coating or screen printing, preferably spraying.

[0022] In this invention, the heat curing is carried out under argon or nitrogen atmosphere, and the heat curing temperature is 120~170℃, preferably 130℃, 140℃, 150℃, 160℃, or 170℃; the heat curing time is 4~5.5h, preferably 4h, 4.5h, 5h, or 5.5h.

[0023] The color-tunable polymer film of the present invention is a colorless and transparent electrochromic material in the neutral state and can display a variety of transparent colors in the oxidized state. Furthermore, a stable and reversible color switching can occur between these two states. At the same time, the material has high optical contrast and fast response time at a specific wavelength.

[0024] The color-tunable polymer film has an optical contrast of 50% to 80% at 750 nm; The color-tunable polymer film has a coloring time of 1.0s to 1.5s and a fading time of 1.5s to 2.0s at 538nm.

[0025] The present invention also provides a color-tunable polymer film prepared by the above preparation method.

[0026] The present invention also provides an application of a color-tunable polymer film in smart windows, car rearview mirrors, information encryption, flat panel displays, and flexible wearable devices.

[0027] The technical solutions provided by the present invention will be 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.

[0028] Example 1

[0029] The molecular structures of the three primary color polymers used (red, green, and blue) are as follows: Figure 1 As shown. In this example, the volume ratio of primary color solution R to primary color solution B is 1:2. 100 mg each of the freshly prepared R, G, and B substances were measured and diluted to volume with chloroform in a 10 mL volumetric flask, then sonicated for 10 min. 0.33 mL of the above primary color solution R and 0.67 mL of primary color solution B were dissolved in chloroform with polyethyleneimine (PEI) (polymer to crosslinking agent mass ratio of 10:1), and then sprayed onto an ITO substrate to form a film. The solution concentration was 10 mg / mL.

[0030] The film was thermocured in a tubular furnace. Curing was performed at 150 °C for 5 h in an argon atmosphere to form a dense cross-linked network. After thermocrosslinking, the uncrosslinked portions were washed away with dichloromethane to obtain the final polymer film.

[0031] Electrochromic properties of polymer films: Using an electrochemical workstation coupled with a UV-Vis spectrophotometer, the cyclic voltammetry curves and UV-Vis absorption and colorimetric maps of the prepared films were measured in a 0.1 M tetrabutylammonium hexafluorophosphate / acetonitrile solution. The data processing results are as follows: Figure 2-4 As shown.

[0032] from Figure 2It can be seen that the oxidation voltage of the polymer film with R:B=1:2 is 0.9 V, which shows good electrochemical behavior.

[0033] from Figure 3-4 It can be seen that the polymer film is colorless and highly transparent in the neutral state, and turns blue-violet under oxidation voltage, exhibiting electrochromic properties with high optical contrast from colorless to colored.

[0034] Example 2

[0035] Measure 100 mg each of the newly prepared substances R, G, and B, and dilute to volume with chloroform in a 10 mL volumetric flask. Sonicate for 10 min. Take 0.4 mL of the above-mentioned primary color solution G and 0.6 mL of the primary color solution B, dissolve them in chloroform with polyethyleneimine (PEI) (polymer to crosslinking agent mass ratio of 10:1), and then spray the solution onto an ITO substrate to form a film with a solution concentration of 10 mg / mL.

[0036] The film was thermocured in a tubular furnace. Curing was performed at 150 °C for 5 h in an argon atmosphere to form a dense cross-linked network. After thermocrosslinking, the uncrosslinked portions were washed away with dichloromethane to obtain the final polymer film.

[0037] Electrochromic properties of polymer films: Using an electrochemical workstation coupled with a UV-Vis spectrophotometer, the cyclic voltammetry curves, UV-Vis absorption and chromaticity diagrams at different voltages, and the stability of the films under step voltage were measured in a 0.1 M tetrabutylammonium hexafluorophosphate / acetonitrile solution. The data processing results are shown below. Figure 5-8 As shown.

[0038] from Figure 5 It can be seen that the oxidation voltage of the polymer film with G:B=2:3 is 0.9 V, which shows good electrochemical behavior.

[0039] from Figure 6-7 It can be seen that the polymer film is colorless and highly transparent in the neutral state (transmittance ≥ 97%), and turns blue-green under oxidation voltage, exhibiting electrochromic properties with high optical contrast from colorless to colored.

[0040] from Figure 8 It can be seen that the film retains 44.4% of its contrast after 1000 seconds in the stability test at 750 nm.

[0041] Example 3

[0042] Measure 100 mg each of the freshly prepared substances R, G, and B, and dilute to volume with chloroform in a 10 mL volumetric flask. Sonicate for 10 min. Take 0.8 mL of the above primary color solution R and 0.2 mL of the primary color solution B, dissolve them in chloroform with polyethyleneimine (PEI) (polymer to crosslinking agent mass ratio of 10:1), and then spray the solution onto an ITO substrate to form a film with a solution concentration of 10 mg / mL.

[0043] The film was thermocured in a tubular furnace. Curing was performed at 150 °C for 5 h in an argon atmosphere to form a dense cross-linked network. After thermocrosslinking, the uncrosslinked portions were washed away with dichloromethane to obtain the final polymer film.

[0044] Electrochromic performance testing of polymer films: Using an electrochemical workstation coupled with a UV-Vis spectrophotometer, the cyclic voltammetry curves, UV-Vis absorption and colorimetry at different voltages, and the response time and stability of the films under step voltage were measured in a 0.1 M tetrabutylammonium hexafluorophosphate / acetonitrile solution. The data processing results are shown below. Figure 9-12 As shown.

[0045] from Figure 9 It can be seen that the oxidation voltage of the polymer film with R:B=4:1 is 0.9 V, which shows good electrochemical behavior.

[0046] from Figure 10-11 It can be seen that the polymer film is colorless and highly transparent in the neutral state (transmittance ≥ 97%), and turns light pink under oxidation voltage, exhibiting electrochromic properties with high optical contrast from colorless to colored.

[0047] from Figure 12 The curves showing the transmittance of the polymer film at 538 nm under multiple potential steps from 0 to 1.0 V as a function of time can be seen. It can be seen that the optical contrast of the film can reach 29.6%, and the coloring / fading times are 1.22 s and 2.00 s, respectively, which shows a fast response time.

[0048] Performance test results show that the color-tunable polymer film prepared by this invention exhibits excellent electrochemical behavior and electrochromic properties. This result strongly demonstrates that by binary blending red, green, and blue primary color solutions and adjusting their respective blending ratios, it is possible not only to prepare electrochromic polymer films with transparent reduced states and multiple colored oxidized states, but also to obtain polymer materials with excellent electrochromic properties by constructing crosslinking networks using amine crosslinking agents.

[0049] This invention provides a color-tunable polymer film, its preparation method, and its applications. This film, as an electrochromic material, can achieve reversible color transitions from transparent to multiple colors, and exhibits high optical contrast, fast response time, and good cycling stability. The method optimizes the concentration of the three primary color solutions, the blending ratio, and the crosslinking conditions, utilizing the efficient thermal crosslinking reaction between epoxy groups and amino groups to form a stable three-dimensional network structure in one step. This provides a promising color adjustment and material preparation solution for the fabrication of high-performance, low-cost flexible color-tunable electrochromic devices (such as smart windows, display and camouflage systems).

[0050] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a color-tunable polymer film, characterized in that, Includes the following steps: 1) Prepare primary color solutions R, G, and B respectively using primary color polymer R, G, and B; 2) Take two of the above three base color solutions and mix them together. Then add an amine crosslinking agent and a solvent. Coat the resulting mixed solution onto the surface of the substrate and obtain a color-tunable polymer film by thermosetting. The molecular structural formulas of the primary color polymers R, G, and B are as follows: ； Where a, b, x, y, m, and n are independent integers from 5 to 15.

2. The method for preparing the color-tunable polymer film according to claim 1, characterized in that, The amine crosslinking agent comprises one or more of 4,4'-diaminodiphenylmethane, tetraethylenepentamine, and polyethyleneimine; the solvent comprises one or more of chloroform, dichloromethane, and tetrahydrofuran.

3. The method for preparing the color-tunable polymer film according to claim 1 or 2, characterized in that, The concentrations of the primary color solutions R, G, and B are independently 5~15 mg / mL.

4. The method for preparing the color-tunable polymer film according to claim 3, characterized in that, The concentration of the amine crosslinking agent in the mixed solution is 0.5~1.5 mg / mL.

5. The method for preparing a color-tunable polymer film according to claim 1, characterized in that, The coating method is spraying, spin coating, or screen printing.

6. The method for preparing a color-tunable polymer film according to claim 1, 4, or 5, characterized in that, The thermosetting process is carried out under argon or nitrogen atmosphere, with a temperature of 120~170℃ and a time of 4~5.5h.

7. A color-tunable polymer film prepared by the preparation method according to any one of claims 1 to 6.

8. The application of the color-tunable polymer film of claim 7 in smart windows, car rearview mirrors, information encryption, flat panel displays, and flexible wearable devices.

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