Electrochromic polymer, preparation method and application thereof, and electrochromic polymer film

Abstract

The invention discloses an electrochromic polymer, a preparation method and application thereof and an electrochromic polymer film. The high-performance electrochromic polymer HBpro is prepared by adopting an arylation polycondensation process, and large-scale preparation of a thin film material can be realized by adopting a solution processing method; the prepared electrochromic polymer film is blue in a neutral state and colorless in an oxidation state, the optical contrast ratio in the wavelength range of 660 nm is 28.2%, the coloring time is 0.61 s, and the color fading time is 0.25 s; the optical contrast at 660nm after 1500s circulation under the step voltage of 0V and 1.2 V can keep 71% of the initial contrast, and the material has the advantages of high color changing speed, high stability and the like, and has potential application value in the fields of intelligent windows, electronic tags and the like.

Description

Technical Field

[0001] The present invention belongs to the technical field of electrochromic materials, and in particular relates to an electrochromic polymer and a preparation method and application thereof, and an electrochromic polymer film. Background Art

[0002] Electrochromism refers to the phenomenon that when a material is subjected to an external electric field, it undergoes a redox reaction through the injection or extraction of ions and electrons, and its appearance shows a reversible change in color. As a type of electrochromic material, electrochromic polymers have the advantages of designable colors, fast response speed, high optical contrast, and high coloring efficiency. Currently, most electrochromic polymer materials are insoluble polymers obtained by electrochemical or chemical polymerization, and cannot be prepared at low cost and on a large scale through solution processing methods such as spin coating, spray coating, and inkjet printing. Therefore, people have begun to devote themselves to the design and synthesis of electrochromic polymers that can be processed by solution.

[0003] The invention patent with the authorization announcement number CN111303387B discloses an electrochromic polymer and its preparation and an electrochromic polymer film. Although the electrochromic polymer can be processed by solution, it takes a long time for coloring and fading. Therefore, it is very necessary to provide a high-performance, solution-processable electrochromic polymer. Summary of the invention

[0004] To solve the above problems, in a first aspect, the present invention provides an electrochromic polymer and a preparation method thereof. The prepared electrochromic polymer has high performance and can be processed by solution.

[0005] The technical solution of the present invention to solve the above problems is as follows:

[0006] An electrochromic polymer, the structural formula of the electrochromic polymer is:

[0007]

[0008] The degree of polymerization n=150-200.

[0009] The electrochromic polymer adopts a donor-acceptor-donor (DA-D') method to achieve an orderly alternating structure, so that the polymer has a strong intramolecular charge transfer characteristic, thereby having a low optical band gap, excellent redox activity and stability, etc.

[0010] The method for preparing the electrochromic polymer comprises the following steps:

[0011] S1. The compound 4,7-dibromo-2,1,3-benzothiadiazole represented by formula (II) undergoes a coupling reaction with the compound (3,3-bis(((2-ethylhexyl)oxy)methyl)-3,4-dihydro-2H-thieno[3,4-b][1,4]dioxepane-6-yl)tributylstannane represented by formula (III) to generate the compound 4-(3,3-bis(((2-ethylhexyl)oxy)methyl)-3,4-dihydro-2H-thieno[3,4-b][1,4]dioxepane-6-yl)-7-bromobenz[c][1,2,5]thiadiazole represented by formula (IV);

[0012]

[0013] S2. Brominate the compound 4-(3,3-bis(((2-ethylhexyl)oxy)methyl)-3,4-dihydro-2H-thiophene[3,4-b][1,4]dioxepane-6-yl)-7-bromobenz[c][1,2,5]thiadiazole represented by formula (IV) with NBS to obtain the compound 4-bromo-7-(8-bromo-3,3-bis(((2-ethylhexyl)oxy)methyl)-3,4-dihydro-2H-thiophene[3,4-b][1,4]dioxepane-6-yl)benzo[c][1,2,5]thiadiazole represented by formula (V);

[0014]

[0015] S3. The compound 4-bromo-7-(8-bromo-3,3-bis(((2-ethylhexyl)oxy)methyl)-3,4-dihydro-2H-thiophene[3,4-b][1,4]dioxepan-6-yl)benzo[c][1,2,5]thiadiazole represented by formula (V) and the compound 4,4-di(2-ethylhexyl)-dithiophenecyclopentadiene represented by formula (VI) are reacted through arylation polycondensation to produce the electrochromic polymer HBpro represented by formula (I).

[0016]

[0017] Preferably, the reaction in step S1 is as follows: under the protection of an inert gas, the compound represented by formula (II), the compound represented by formula (III), a palladium catalyst, and ultra-dry DMF are added to a reaction container, reacted at 110 to 130° C. for 10 to 14 hours, and post-treated to obtain a compound represented by formula (IV).

[0018] Preferably, the inert gas is nitrogen.

[0019] Preferably, in step S1, the molar ratio of the compound represented by formula (II) to the compound represented by formula (III) is (0.8-1.2):(0.8-1.2); the added volume of ultra-dry DMF is 30-100 mL / g based on the mass of the compound represented by formula (II).

[0020] Preferably, the palladium catalyst is selected from any one of palladium acetate, tetrakis(triphenylphosphine)palladium or dichlorobis(triphenylphosphine)palladium.

[0021] Preferably, in step S1, the specific method of post-treatment is: extracting the reaction mixture with dichloromethane, washing it three times with saturated brine. 2 SO 4 After drying, the organic phase was purified by column chromatography to obtain the target product 4-(3,3-bis(((2-ethylhexyl)oxy)methyl)-3,4-dihydro-2H-thiophene[3,4-b][1,4]dioxepan-6-yl)-7-bromobenz[c][1,2,5]thiadiazole.

[0022] Preferably, the reaction in step S2 is as follows: adding the compound represented by formula (IV), NBS and chloroform into a reaction container, reacting at room temperature for 0.5 to 4 hours, and post-treating to obtain the compound represented by formula (V).

[0023] Preferably, in step S2, the molar ratio of NBS to the compound represented by formula (IV) is (0.8-1.2):(0.8-1.2); the added volume of chloroform is 10-100 mL / g based on the mass of the compound represented by formula (IV).

[0024] Preferably, in step S2, the specific method of post-treatment is: adding water to quench the reaction, extracting the reaction mixture with dichloromethane, and washing three times with saturated brine. 2 SO 4 The organic phase was dried and purified by column chromatography to obtain the target product 4-bromo-7-(8-bromo-3,3-bis(((2-ethylhexyl)oxy)methyl)-3,4-dihydro-2H-thiophene[3,4-b][1,4]dioxepan-6-yl)benzo[c][1,2,5]thiadiazole.

[0025] Preferably, the reaction in step S3 is as follows: the compound represented by formula (V), the compound represented by formula (VI), anhydrous potassium carbonate, pivalic acid, Pd(OAc) 2 , ultra-dry DMAc are added into the reaction container, reacted at 120-160° C. for 22-26 hours, and post-treated to obtain the electrochromic polymer HBpro represented by formula (I).

[0026] Preferably, in step S3, the molar ratio of the compound represented by formula (V) to the compound represented by formula (VI) is (0.8-1.2):(0.8-1.2); the molar ratio of anhydrous potassium carbonate to the compound represented by formula (VI) is (1.5-2.5):1; the molar ratio of pivalic acid to the compound represented by formula (VI) is (0.01-0.4):1; Pd(OAc) 2 The molar ratio of the super dry DMAc to the compound represented by formula (VI) is (0.01-0.05):1; the added volume of the super dry DMAc is 30-60 mL / g based on the mass of the compound represented by formula (VI).

[0027] Preferably, in step S3, the specific method of the post-treatment is: adding the reaction solution to methanol, filtering the mixture with a Buchner funnel, washing the filter cake with methanol, wrapping the filter cake with filter paper and extracting polymers of different polymerization degrees therein with a Soxhlet extractor, during which solvents with different solubility are replaced, and the order of using the solvents is methanol, acetone, petroleum ether, and chloroform, and the part extracted with chloroform is rotary evaporated to remove the solvent to obtain HBpro.

[0028] The present invention also provides applications of the electrochromic polymer, such as application of the electrochromic polymer in preparing an electrochromic device.

[0029] In a second aspect, the present invention further provides an electrochromic polymer film, which is made from the electrochromic polymer.

[0030] Preferably, the electrochromic polymer film is obtained by processing the electrochromic polymer into a film through solution processing.

[0031] The preparation method of the electrochromic polymer film is as follows: dissolving the electrochromic polymer HBpro in chloroform, spraying it onto the conductive surface of the ITO glass using a spray gun to form a film, thereby obtaining the electrochromic polymer film.

[0032] The present invention has the following beneficial effects:

[0033] The present invention adopts an arylation polycondensation process to prepare a high-performance electrochromic polymer HBpro, and can realize large-scale preparation of thin film materials by a solution processing method; the prepared electrochromic polymer film is blue in a neutral state and colorless in an oxidized state, and has an optical contrast of 28.2% in a wavelength range of 660nm, a coloring time of 0.61s, and a fading time of 0.25s; its optical contrast at 660nm can maintain 71% of the initial contrast after a 1500s cycle at a step voltage of 0V and 1.2V, and has the advantages of fast color change speed, high stability, etc., and has potential application value in the fields of smart windows, electronic tags, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 The synthetic route of electrochromic polymer HBpro is shown in FIG.

[0035] Figure 2 is the CV curve of the electrochromic polymer film;

[0036] Figure 3 The UV-visible absorption spectra of electrochromic polymer films at different voltages;

[0037] Figure 4 is the response time diagram of the electrochromic polymer film at 660nm;

[0038] Figure 5 This is a dynamic test diagram of the electrochromic polymer film at 660nm. DETAILED DESCRIPTION

[0039] In order to make the purpose, technical scheme and advantages of the present invention more clear, the present invention is further described in detail in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention, rather than all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0040] Example 1: Synthesis of 4-(3,3-bis(((2-ethylhexyl)oxy)methyl)-3,4-dihydro-2H-thiophene[3,4-b][1,4]dioxepan-6-yl)-7-bromophenyl[c][1,2,5]thiadiazole

[0041] Weigh 4,7-dibromo-2,1,3-benzothiadiazole (0.293 g, 1 mmol), (3,3-bis(((2-ethylhexyl)oxy)methyl)-3,4-dihydro-2H-thieno[3,4-b][1,4]dioxepane-6-yl)tributylstannane (0.73 g, 1 mmol) and an appropriate amount of Pd(PPh 3 ) 4 Add to a 50 mL two-necked round-bottom bottle, add 10 mL of ultra-dry DMF under nitrogen protection, react at 120 ° C for 12 hours, and cool to room temperature. Extract the reaction mixture with dichloromethane and wash three times with saturated brine. Combine the organic layers and add anhydrous Na 2 SO 4 After drying, add an appropriate amount of 200-300 mesh silica gel, concentrate and mix the sample under vacuum. Use 300-400 mesh fine silica gel as the stationary phase, chromatograph through a column, and finally obtain a yellow oily substance.

[0042] Example 2: Synthesis of 4-bromo-7-(8-bromo-3,3-bis(((2-ethylhexyl)oxy)methyl)-3,4-dihydro-2H-thieno[3,4-b][1,4]dioxepin-6-yl)benzo[c][1,2,5]thiadiazole

[0043] 4-(3,3-bis(((2-ethylhexyl)oxy)methyl)-3,4-dihydro-2H-thieno[3,4-b][1,4]dioxepin-6-yl)-7-bromobenzo[c][1,2,5]thiadiazole (0.653 g, 1 mmol) and NBS (0.178 g, 1 mmol) were added to 10 ml of chloroform. After reacting at room temperature for 30 min, the reaction was quenched by adding water. The reaction mixture was extracted with dichloromethane and washed three times with saturated brine. The organic layers were combined, dried over anhydrous Na 2 SO 4 dried, an appropriate amount of 200 - 300 mesh silica gel was added, and the mixture was concentrated and stirred under vacuum. Using 300 - 400 mesh fine silica gel as the stationary phase, column chromatography was carried out, and finally a yellow oil was obtained.

[0044] Example 3: Synthesis of HBpro

[0045] 4-bromo-7-(8-bromo-3,3-bis(((2-ethylhexyl)oxy)methyl)-3,4-dihydro-2H-thieno[3,4-b][1,4]dioxepin-6-yl)benzo[c][1,2,5]thiadiazole (0.732 g, 1 mmol), 4,4-di(2-ethylhexyl)-dithieno[3,2-b:2',3'-d]pyrrole (0.402 g, 1 mmol), anhydrous potassium carbonate (0.276 g, 2 mmol), pivalic acid (33.9 mg, 0.34 mmol) and Pd(OAc) 2 (10 mg, 0.045 mmol) were added to a two-necked round-bottom flask. Under nitrogen protection, 15 mL of ultra-dry DMAc was added, and the reaction was carried out at 140 °C for 24 h and then cooled to room temperature. The reaction solution was added to 300 ml of methanol, filtered by Buchner funnel, and the filter cake was washed with methanol. The filter cake was wrapped with filter paper and extracted with a Soxhlet extractor to obtain polymers with different degrees of polymerization. During this process, solvents with different dissolution abilities were changed. The order of solvent use was methanol, acetone, petroleum ether, and chloroform, and the amount of each solvent used was 300 ml. Finally, the solvent in the chloroform-extracted part was removed by rotary evaporation to obtain HBpro.

[0046] Performance Testing

[0047] 1. Electrochemical Testing of HBpro

[0048] The electrochemical test was performed using a Chenhua 660 electrochemical workstation with the following parameters set: CV mode, scan rate of 100 mv / s, and the highest and lowest scan voltages of 1.2 V and 0 V, respectively. Figure 2 As shown, the initial oxidation potential of the proTh electrochromic film is 0.6 V, and its CV curve has a quasi-reversible redox behavior.

[0049] 2. Optical and electrochromic performance test of HBpro

[0050] The optical and electrochromic performance tests were conducted by using a Chenhua 660 electrochemical workstation in conjunction with a UV-visible spectrophotometer. The specific process was as follows: tetrabutylammonium hexafluorophosphate (0.387 g, 1 mmol) was added to a 10 mL volumetric flask, and the volume was fixed with chromatographic grade acetonitrile to use as a blank solution. Two portions of blank solution and two portions of blank ITO glass were placed in two cuvettes, and the cuvettes were placed in a UV-visible spectrophotometer to scan the baseline. After the scan, one of the blank ITO glasses was replaced with an ITO glass covered with a polymer film, and a platinum sheet was placed therein as a counter electrode, and an Ag / AgCl electrode was used as a reference electrode. A Chenhua 660 electrochemical workstation was used to apply different voltages for 30 seconds, and then a UV-visible spectrophotometer was used to complete the scan in the wavelength range of 300 to 1100 nm to obtain the spectrum of the polymer film at different voltages. The test results are shown in FIG. Figure 3 , 4 , 5. The results show that: its maximum absorption peak in the neutral state (0.0V) is 660nm, and as the voltage continues to increase, the original absorption peak gradually disappears; its color is blue in the neutral state and colorless in the oxidized state; the optical contrast in the 660nm wavelength range is 28.2%, the coloring time is 0.61s, and the fading time is 0.25s. After a 1500s cycle of 0V and 1.2V step voltages, the optical contrast at 660nm can maintain 71% of the initial contrast.

[0051] In summary, the electrochromic polymer film of the present application has the advantages of simple preparation method, fast color change speed, high stability, etc., and has potential application value in the fields of smart windows, electronic tags, etc.

Claims

1. An electrochromic polymer, characterized in that The structural formula of the electrochromic polymer is: The degree of polymerization n=150-200.

2. The method for preparing the electrochromic polymer according to claim 1, comprising the following steps: S1. The compound 4,7-dibromo-2,1,3-benzothiadiazole represented by formula (II) undergoes a coupling reaction with the compound (3,3-bis(((2-ethylhexyl)oxy)methyl)-3,4-dihydro-2H-thieno[3,4-b][1,4]dioxepane-6-yl)tributylstannane represented by formula (III) to generate the compound 4-(3,3-bis(((2-ethylhexyl)oxy)methyl)-3,4-dihydro-2H-thieno[3,4-b][1,4]dioxepane-6-yl)-7-bromobenz[c][1,2,5]thiadiazole represented by formula (IV); S2. Brominate the compound 4-(3,3-bis(((2-ethylhexyl)oxy)methyl)-3,4-dihydro-2H-thiophene[3,4-b][1,4]dioxepane-6-yl)-7-bromobenz[c][1,2,5]thiadiazole represented by formula (IV) with NBS to obtain the compound 4-bromo-7-(8-bromo-3,3-bis(((2-ethylhexyl)oxy)methyl)-3,4-dihydro-2H-thiophene[3,4-b][1,4]dioxepane-6-yl)benzo[c][1,2,5]thiadiazole represented by formula (V); S3. The compound 4-bromo-7-(8-bromo-3,3-bis(((2-ethylhexyl)oxy)methyl)-3,4-dihydro-2H-thiophene[3,4-b][1,4]dioxepan-6-yl)benzo[c][1,2,5]thiadiazole represented by formula (V) and the compound 4,4-di(2-ethylhexyl)-dithiophenecyclopentadiene represented by formula (VI) are reacted through arylation polycondensation to produce the electrochromic polymer HBpro represented by formula (I).

3. The preparation method according to claim 2, characterized in that: The reaction in step S1 is specifically as follows: under the protection of an inert gas, the compound represented by formula (II), the compound represented by formula (III), a palladium catalyst, and ultra-dry DMF are added to a reaction container, reacted at 110 to 130° C. for 10 to 14 hours, and post-treated to obtain a compound represented by formula (IV).

4. The preparation method according to claim 3, characterized in that: In the step S1, the molar ratio of the compound represented by formula (II) to the compound represented by formula (III) is (0.8-1.2):(0.8-1.2); the added volume of ultra-dry DMF is 30-100 mL / g based on the mass of the compound represented by formula (II).

5. The preparation method according to claim 2, characterized in that: The reaction in step S2 is specifically as follows: adding the compound represented by formula (IV), NBS and chloroform into a reaction container, reacting at room temperature for 0.5 to 4 hours, and post-treating to obtain the compound represented by formula (V).

6. The preparation method according to claim 5, characterized in that: In the step S2, the molar ratio of NBS to the compound represented by formula (IV) is (0.8-1.2):(0.8-1.2); the added volume of chloroform is 10-100 mL / g based on the mass of the compound represented by formula (IV).

7. The preparation method according to claim 2, characterized in that: The reaction in step S3 is specifically as follows: adding the compound represented by formula (V), the compound represented by formula (VI), anhydrous potassium carbonate, pivalic acid, Pd(OAc)2, and ultra-dry DMAc into a reaction container, reacting at 120-160°C for 22-26h, and post-treating to obtain the electrochromic polymer HBpro represented by formula (I).

8. The preparation method according to claim 7, characterized in that: In the step S3, the molar ratio of the compound represented by formula (V) to the compound represented by formula (VI) is (0.8-1.2):(0.8-1.2); the molar ratio of anhydrous potassium carbonate to the compound represented by formula (VI) is (1.5-2.5):1; the molar ratio of pivalic acid to the compound represented by formula (VI) is (0.01-0.4):1; the molar ratio of Pd(OAc)2 to the compound represented by formula (VI) is (0.01-0.05):1; the added volume of ultra-dry DMAc is 30-60 mL / g based on the mass of the compound represented by formula (VI).

9. Use of the electrochromic polymer according to claim 1 in preparing an electrochromic device.

10. An electrochromic polymer film, characterized in that: Made from the electrochromic polymer described in claim 1.

Images