Conjugated polymer material capable of realizing neutral state green / black color-transparent electrochromic performance and preparation method and application thereof

Abstract

The application discloses a conjugated polymer material capable of realizing neutral state green / black-transparent electrochromic performance and a preparation method and application thereof. The conjugated polymer material (IV) is prepared through copolymerization of a cyclic ether modified p-dibromobenzene ring monomer (I), a thiophene derivative ProDOT monomer (II) and a D-A-D unit ProDOT-BTD-ProDOT coupling monomer (III). The electrochromic polymer thin film processed from the conjugated polymer material has application prospects in the fields of intelligent windows, intelligent glasses, displays, electronic paper and the like. In the material, the cyclic ether modified p-dibromobenzene ring monomer effectively reduces the oxidation potential of the conjugated polymer, improves the electrochromic performance of the black / green-transparent electrochromic thin film, and realizes stable and reversible conversion.

Description

Technical Field

[0001] This invention relates to the field of electrochromic materials, specifically to a conjugated polymer material capable of achieving neutral green / black-transparent electrochromic properties, its preparation method, and its applications. Background Technology

[0002] Electrochromic materials, as a novel type of functional material, have gradually attracted widespread attention. In recent years, electrochromic displays, as a typical non-emissive (passive) display technology, have received considerable attention and are expected to become one of the next-generation displays. Within the field of electrochromism, materials that can reversibly switch between black and high-transmittance states have received extensive attention and research due to their wide range of applications (e.g., electronic paper, smart windows, electrochromic glasses). Solution-processable conjugated polymers, as a new generation of electrochromic materials, possess advantages such as easy color adjustment, good mechanical flexibility, fast response time, and good processing performance, providing a good platform for the preparation of materials that can switch from black to high transmittance. Compared with conjugated polymer materials that can switch from red and green to high transmittance, achieving materials that can switch from black to high transmittance is more difficult because they not only need to have full absorption across the entire visible light region in the neutral state but also need to achieve high transmittance within the same wavelength range in the oxidized state. To date, the preparation of high-performance black-to-high-transmittance conjugated polymer materials remains a significant challenge.

[0003] Thanks to the efforts of numerous researchers, many strategies have been developed to prepare conjugated polymer materials that switch from black to high transmittance, such as donor-acceptor (DA) design theory, side-chain suspension, and color blending. Among these, DA design theory is the most commonly used approach for designing and preparing black-to-high transmittance materials. Researchers reported the first soluble black-to-high transmittance conjugated polymer material based on the DA design method by controlling the feed ratio of the D-unit ProDOT and the DAD unit ProDOT-BTD-ProDOT using random oxidative polymerization with ferric chloride. This pioneering work opened the door to the design and preparation of black conjugated polymer materials. Subsequently, based on different donor or acceptor units and combined with different polymerization methods, researchers have designed and synthesized many black-to-high transmittance conjugated polymers.

[0004] By comparing the above results, we found a common feature: all current black-to-high-transmission conjugated polymers are achieved by random copolymerization of multiple units. This invention, by adjusting the feed ratio of monomers with different absorption segments in DA and introducing cyclic ether-modified dibromobenzene ring monomers, can reduce the oxidation potential of the polymer, thus synthesizing a highly stable green / black conjugated polymer with an absorption spectrum extending throughout the visible light region (400-780 nm). Summary of the Invention

[0005] This invention provides a conjugated polymer material capable of achieving neutral green / black-transparent electrochromic properties, along with its preparation method and applications. Electrochromic polymer films processed from this conjugated polymer material show promising applications in fields such as smart windows, smart glasses, displays, and electronic paper.

[0006] The technical solution of the present invention is as follows:

[0007] A conjugated polymer material capable of achieving neutral green / black-transparent electrochromic properties, as shown in formula (IV):

[0008]

[0009] In equation (IV),

[0010] R1 and R2 are independently one of C1-C30 alkyl chains or alkoxy chains;

[0011] R3 and R4 are independently one of C1-C30 alkyl chains or alkoxy chains;

[0012] n = 1 to 9;

[0013] a = 1 to 70, b = 1 to 70, c1 = 1 to 70, c2 = 1 to 70, and a + b = c1 + c2.

[0014] The preparation method of the conjugated polymer material (IV) of the present invention is as follows:

[0015] A cyclic ether-modified p-dibromophenyl ring monomer (I), a thiophene derivative ProDOT monomer (II), a DAD unit ProDOT-BTD-ProDOT coupling monomer (III), Pd(OAc)2, an inorganic base, neopentanoic acid, and an organic solvent are mixed and polymerized at 110–160°C (preferably 120–140°C) for 20–100 h (preferably 40–72 h) under nitrogen protection. After post-treatment, a conjugated polymer material (IV) is obtained.

[0016] in,

[0017] The molar ratio of cyclic ether modified dibromophenyl ring monomer (I), thiophene derivative ProDOT-type monomer (II), DAD unit ProDOT-BTD-ProDOT coupling monomer (III), Pd(OAc)2, inorganic base, and neopentanoic acid is x:1:1-x:0.01~0.1:0.5~5:0.1~1, x=0.2~0.8; preferably x:1:1-x:0.05:2.5:0.4, x=0.3~0.5;

[0018] The inorganic base is selected from one or more of potassium carbonate, cesium carbonate, potassium bicarbonate, sodium bicarbonate, and sodium carbonate, with potassium carbonate being preferred;

[0019] The preferred organic solvent is anhydrous N,N-dimethylacetamide (DMAc);

[0020] The specific post-processing method is as follows: After the reaction is completed, the reaction mixture is cooled to room temperature, then washed in methanol, filtered, and the precipitate is collected and purified by Soxhlet extraction. The precipitate is extracted sequentially with methanol, acetone, petroleum ether, and dichloromethane. The petroleum ether extract and the dichloromethane extract are collected, the solvent is evaporated, and the conjugated polymer material (IV) is obtained.

[0021]

[0022] In equations (I) to (III),

[0023] The definitions of R1, R2, R3, R4, and n are the same as in equation (IV).

[0024] The conjugated polymer material (IV) of this invention can be prepared into an electrochromic polymer film by spin coating or spray coating, and the resulting film exhibits neutral green / black-transparent electrochromic properties. Specifically, the preparation method of the electrochromic polymer film is as follows:

[0025] The conjugated polymer material (IV) is dissolved in a solvent and sprayed onto a conductive substrate through a spray gun. After drying, an electrochromic polymer film is obtained.

[0026] The solvent is selected from dichloromethane, trichloromethane, tetrahydrofuran, methanol, or water, with dichloromethane being preferred;

[0027] The concentration of the conjugated polymer material (IV) in the solvent is 1–30 mmol / L, preferably 5 mmol / L;

[0028] The conductive substrate can be ITO glass, ITO-PET substrate, FTO glass, or FTO-PET substrate, etc.

[0029] The thickness of the thin film spraying is 50-200 nm.

[0030] The beneficial effects of this invention are as follows:

[0031] The material provided by this invention utilizes cyclic ether modification of the dibromophenyl ring monomer to effectively reduce the oxidation potential of the conjugated polymer, improving the electrochromic properties of the black / green-transparent electrochromic film and enabling a stable and reversible transition from neutral green / black to transparent. Specifically, the polymer film exhibits a coloring time of 2.1 s and a fading time of 2.2 s at 650 nm; a contrast ratio of 39.35%, and maintains 91% contrast ratio after 1626 cycles. This material represents a novel functional material with significant potential applications in fields such as smart windows, smart glasses, displays, and electronic paper. Attached Figure Description

[0032] Figure 1 NMR of the polymer prepared in Example 1.

[0033] Figure 2 The optical absorption of the polymer film prepared in Example 2 under different voltages.

[0034] Figure 3 The curve of transmittance of the polymer film prepared in Example 2 as a function of time under multiple potential steps from 0 to 0.9V in the range of 300 to 1100 nm.

[0035] Figure 4 Cyclic voltammetry curves of the polymer film prepared in Example 2.

[0036] Figure 5 Response time of the polymer film prepared in Example 2.

[0037] Figure 6 The relationship between the L* value of the polymer film prepared in Example 2 and the applied voltage.

[0038] Figure 7 : a*b* values ​​of the polymer film prepared in Example 2. Detailed Implementation

[0039] The present invention is further described below through specific embodiments, but the scope of protection of the present invention is not limited thereto.

[0040] In the following embodiments,

[0041] The structural formula of the dibromophenyl ring monomer modified with the cyclic ether is as follows:

[0042]

[0043] The preparation method is as follows:

[0044] 1,2-Dihydroxybenzene (0.11 g, 1 mmol) was mixed with 1,3-dibromopropane (0.20 g, 1 mmol) and 50 mg of 18-crown ether-6 in 30 mL of 1 mol / L NaOH ethanol solution, and the mixture was heated to 80 °C and reacted for 8 h. After the reaction, the mixture in the reaction flask was poured into deionized water, and the mixture was extracted thoroughly with dichloromethane. The organic phase was evaporated to dryness and then purified by silica gel column chromatography with dichloromethane:petroleum ether = 3:1 as the eluent, yielding 0.12 g of product (82% yield). 1 NMR δ = 6.8 (s, 4H), δ = 4.3 (m, 4H), δ = 2.34 (m, 2H).

[0045] The above product (0.15 g, 1 mmol) was dissolved in 50 mL of anhydrous THF. Tetraethylethylenediamine (0.70 g, 6 mmol) was added dropwise at -78 °C, and after thorough stirring, a solution of n-butyllithium (containing 0.38 g, 6 mmol) was slowly added. The reaction was maintained at -78 °C for 3 h, then transferred to room temperature and reacted for another 3 days. The reaction apparatus was then transferred to -78 °C, and liquid bromine (0.48 g, 3 mmol) was added dropwise, and the mixture was stirred at -78 °C for 1 h. The reaction apparatus was then transferred to room temperature and reacted for another day. After the reaction was complete, the reaction solution was poured into water and extracted with dichloromethane. The liquid phase was separated, evaporated to dryness, and purified by silica gel column chromatography using dichloromethane:petroleum ether = 3:1 as the eluent, yielding 0.04 g of an oily liquid product (13% yield). 1 NMR δ = 7.08 (s, 2H), δ = 4.3 (m, 4H), δ = 2.34 (m, 2H).

[0046] The structural formula of the thiophene derivative ProDOT monomer is as follows:

[0047]

[0048] Purchased from Audtech (10g)

[0049] The structural formula of the raw material DAD unit ProDOT-BTD-ProDOT coupling monomer is as follows:

[0050]

[0051] Purchased from Bid Pharmaceutical (10g)

[0052] Example 1: Synthesis of conjugated polymer materials:

[0053]

[0054] Under nitrogen protection, the following were added to the reaction flask: a cyclic ether-modified p-dibromophenyl ring monomer (0.23 g, 0.71 mmol), a thiophene derivative ProDOT monomer (0.43 g, 1 mmol), a DAD unit ProDOT-BTD-ProDOT coupling monomer (0.21 g, 0.29 mmol), a catalyst palladium acetate (11 mg, 0.05 mmol), K₂CO₃ (0.35 g, 2.5 mmol), neopentanoic acid (40 mg, 0.4 mmol), and 9 mL DMAc. The temperature was raised to 130-140 °C, and the reaction was stirred for 48 h. After the reaction was completed, the cooled mixture was thoroughly washed in methanol and purified using a Soxhlet extractor. The crude product was packaged in filter paper and placed in a Soxhlet extraction apparatus. Extraction was performed successively with 500 mL of pure methanol, 500 mL of acetone, 500 mL of petroleum ether, and 500 mL of dichloromethane to obtain the extract. The products in petroleum ether and dichloromethane were retained, with yields of 35% in petroleum ether and 45% in dichloromethane. The solvent was removed by evaporation, and 0.533 g of conjugated polymer material was finally obtained with a molecular weight distribution of 2.9–102 kDa.

[0055] Example 2: Preparation of electrochromic polymer thin film:

[0056] 5 mg of the conjugated polymer material obtained in Example 1 was dissolved in 1 mL of dichloromethane. The resulting solution was used to prepare a thin film on an ITO conductive substrate using a spray gun. After drying, an electrochromic polymer film with a thickness of 150 nm was obtained.

[0057] Compared to existing black-to-transparent electrochromic films, the polymer film prepared in this invention exhibits a significant decrease in absorption near 650 nm and 430 nm as the voltage increases under operating voltage conditions of 0-0.9V, and displays a color change from black / green to transparent. This prepared film expands upon existing black / green polymer systems, pioneering the use of benzene ring ether structures in the preparation of black / green electrochromic polymer materials.

[0058] Furthermore, this polymer material exhibits high stability. Current experimental results show that it can achieve over 1600 stable cycles under an applied voltage of 0-0.9V, while existing black polymers typically show significant degradation in optical contrast after only 500 cycles. This significant difference is attributed to the introduction of a phenyl ring ether structure, which enhances the material's spatial distortion and further improves its voltage tolerance. This provides a promising approach for the future development of highly stable black-to-transparent electrochromic polymer materials.

Claims

1. A conjugated polymer material capable of achieving neutral green / black-transparent electrochromic properties, as shown in formula (IV): In equation (IV), R1 and R2 are independently one of C1-C30 alkyl chains or alkoxy chains; R3 and R4 are independently one of C1-C30 alkyl chains or alkoxy chains; n＝1～9； a = 1 to 70, b = 1 to 70, c1 = 1 to 70, c2 = 1 to 70, and a + b = c1 + c2.

2. The method for preparing the conjugated polymer material (IV) as described in claim 1, characterized in that, The preparation method is as follows: Cyclic ether-modified p-dibromophenyl ring monomer (I), thiophene derivative ProDOT-type monomer (II), DAD unit ProDOT-BTD-ProDOT coupling monomer (III), Pd(OAc)2, inorganic base, neopentanoic acid and organic solvent were mixed and polymerized at 110-160℃ for 20-100h under nitrogen protection. After post-treatment, conjugated polymer material (IV) was obtained. in, The molar ratio of cyclic ether modified dibromophenyl ring monomer (I), thiophene derivative ProDOT-type monomer (II), DAD unit ProDOT-BTD-ProDOT coupling monomer (III), Pd(OAc)2, inorganic base, and neopentanoic acid is x:1:1-x:0.01~0.1:0.5~5:0.1~1, x=0.2~0.8; In equations (I) to (III), The definitions of R1, R2, R3, R4, and n are the same as in equation (IV).

3. The method for preparing the conjugated polymer material (IV) as described in claim 2, characterized in that, The molar ratio of cyclic ether modified p-dibromophenyl ring monomer (I), thiophene derivative ProDOT-type monomer (II), DAD unit ProDOT-BTD-ProDOT coupling monomer (III), Pd(OAc)2, inorganic base, and neopentanoic acid is x:1:1-x:0.05:2.5:0.4, where x = 0.3 to 0.

5.

4. The method for preparing the conjugated polymer material (IV) as described in claim 2, characterized in that, The inorganic base is selected from one or more of potassium carbonate, cesium carbonate, potassium bicarbonate, sodium bicarbonate, and sodium carbonate.

5. The method for preparing the conjugated polymer material (IV) as described in claim 2, characterized in that, The organic solvent is anhydrous N,N-dimethylacetamide.

6. The method for preparing the conjugated polymer material (IV) as described in claim 2, characterized in that, The polymerization reaction is carried out at a temperature of 120–140°C for 40–72 hours.

7. The method for preparing the conjugated polymer material (IV) as described in claim 2, characterized in that, The post-processing method is as follows: After the reaction is completed, the reaction mixture is cooled to room temperature, then washed in methanol, filtered, and the precipitate is collected and purified by Soxhlet extraction. The precipitate is extracted sequentially with methanol, acetone, petroleum ether, and dichloromethane. The petroleum ether extract and the dichloromethane extract are collected, and the solvent is evaporated to obtain the conjugated polymer material (IV).

8. An electrochromic polymer film, characterized in that, The conjugated polymer material (IV) as described in claim 1 is prepared by spin coating or spray coating.

9. The method for preparing the electrochromic polymer film as described in claim 8, characterized in that, The preparation method is as follows: The conjugated polymer material (IV) is dissolved in a solvent and sprayed onto a conductive substrate through a spray gun. After drying, an electrochromic polymer film is obtained. The solvent is selected from dichloromethane, trichloromethane, tetrahydrofuran, methanol, or water; The concentration of the conjugated polymer material (IV) in the solvent is 1–30 mmol / L; The conductive substrate is selected from ITO glass, ITO-PET substrate, FTO glass, or FTO-PET substrate; The thickness of the thin film spraying is 50-200 nm.

10. The application of the electrochromic polymer film as described in claim 8 in the fields of smart windows, smart glasses, displays, and electronic paper.

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