CN115636924A - Blue to transparent electrochromic polymer and preparation method and application thereof - Google Patents
Blue to transparent electrochromic polymer and preparation method and application thereof Download PDFInfo
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- CN115636924A CN115636924A CN202211139720.7A CN202211139720A CN115636924A CN 115636924 A CN115636924 A CN 115636924A CN 202211139720 A CN202211139720 A CN 202211139720A CN 115636924 A CN115636924 A CN 115636924A
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Abstract
The invention relates to a blue to transparent electrochromic polymer, which has the following structure:
wherein n represents the degree of polymerization, and n is a natural number of 8-100. The polymer can realize the conversion from blue to transparent states, and has the characteristics of low driving voltage (step potential is 0V and 1.0V), high optical contrast (generally more than 40 percent and maximally up to 45 percent) and high stability (the stability is still kept after 200 times of square wave potential scanning); the polymer is easy to dissolve in organic solvents such as toluene, dichloromethane and the like for solution treatment, and is convenient to adopt spraying or blade coating and other modesLarge-area film forming is beneficial to the process treatment and application.
Description
Technical Field
The invention relates to the technical field of electrochromic polymers, in particular to a blue to transparent electrochromic polymer and a preparation method and application thereof.
Background
The electrochromic is a phenomenon that under the action of an external electric field, ions and electrons are injected or extracted to generate redox reaction, so that the material is switched between an oxidation state and a neutral state, and the appearance shows reversible color change. The electrochromic material has wide application prospect in the fields of intelligent windows, military intelligent camouflage and the like. Compared with inorganic metal oxide and viologen organic micromolecule electrochromic materials, the electrochromic polymer has the advantages of easy molecular structure design, rich color conversion, high optical contrast, high response speed, high stability and the like. Blue is one of the primary colors of the three primary colors, and the electrochromic polymer displaying blue has important significance for electrochromic display. Therefore, the development of blue to transparent electrochromic materials has been the focus of research in the electrochromic field.
In general, polymer materials such as polyaniline and polythiophene are difficult to dissolve due to their rigid main chains, and are difficult to form a large-area film by solution treatment; in addition, the electrochromic material of the primary color generally needs to be dissolved so as to be combined with other color-changing materials to exert color matching performance. In order to realize the solution treatment of the polymer, long-chain alkyl or ionic groups can be introduced into the side chain of the polymer, so as to achieve the purpose of dissolving in an oily solvent and water. However, the polymer dissolved in water still has the problems of poor stability and the like, while the polymer capable of being treated by the oily solvent has the advantages of no influence on the main chain color change, high stability and the like, but the variety of the polymer capable of being treated by the oily solvent, particularly the high-performance blue, green, red and other primary color polymers is still less, and the industrialization promotion of the electrochromic polymer is severely limited. However, the existing soluble blue to transparent electrochromic polymer is mainly realized based on a main chain structure of propylenedioxythiophene, and has the problems of single structure, few types, low contrast, slow response rate and the like.
Disclosure of Invention
Technical problem to be solved
In view of the above disadvantages and shortcomings of the prior art, the present invention provides a blue to transparent electrochromic polymer and a preparation method thereof, wherein mainly by introducing an ethylenedioxythiophene structure into a thienothiophene derivative, an electrochromic polymer with blue to transparent conversion and color change contrast ratio of more than 40% is successfully prepared, and the polymer has the advantages of good stability, low potential required for color change, high response efficiency, etc. The electrochromic polymer can be subjected to solution treatment to exert color matching performance, and is favorable for process treatment and application, such as large-area film formation or preparation of electrochromic devices and the like.
(II) technical scheme
In order to achieve the purpose, the invention adopts the main technical scheme that:
in a first aspect, the present invention provides a blue to transparent electrochromic polymer having the following structural formula:
wherein n represents the degree of polymerization, and n is a natural number of 8 to 100.
In a second aspect, the invention provides a preparation method of a blue to transparent electrochromic polymer shown in formula I, the method specifically comprises:
dissolving one of 2, 5-dibromo-3, 4-ethylenedioxythiophene, 2, 5-dichloro-3, 4-ethylenedioxythiophene and 2, 5-diiodo-3, 4-ethylenedioxythiophene and a compound shown in a formula II in an organic solvent as a synthetic monomer, adding an organic acid, an inorganic weak base and a palladium catalyst, and heating under the protection of inert gas to perform a polymerization reaction to obtain a blue to transparent electrochromic polymer with a structure shown in a formula I;
the reaction process is as follows, wherein R = Br, cl or I;
according to the preferred embodiment of the present invention, wherein the organic acid is pivalic acid or tert-decanoic acid; the inorganic weak base is potassium carbonate, cesium carbonate or potassium acetate; the palladium catalyst is palladium acetate.
According to a preferred embodiment of the present invention, wherein the organic solvent is N, N-dimethylacetamide or N, N-dimethylpropionamide.
According to a preferred embodiment of the present invention, the molar ratio of one of 2, 5-dibromo-3, 4-ethylenedioxythiophene, 2, 5-dichloro-3, 4-ethylenedioxythiophene and 2, 5-diiodo-3, 4-ethylenedioxythiophene to the monomer of the compound represented by formula II is 1:1.
according to a preferred embodiment of the present invention, the molar ratio of the weak inorganic base to the compound represented by formula II is 3 to 4:1; the molar ratio of the organic acid to the compound shown in the formula II is 0.5-1:1; the molar ratio of the palladium catalyst to the compound shown in the formula II is 0.05-0.1:1.
according to the preferred embodiment of the present invention, the polymerization temperature is 120-140 ℃ and the reaction time is 36-72 hours.
According to a preferred embodiment of the present invention, after the reaction is completed, the reaction mixture is cooled to room temperature, the reaction mixture is dropped into cold methanol for precipitation, and the precipitate is dried and filtered; and then carrying out Soxhlet extraction by respectively using methanol, n-hexane and chloroform, concentrating the chloroform extract, dripping into cold methanol for precipitation, filtering and drying to obtain the blue to transparent electrochromic polymer shown in the formula I.
In a third aspect, the invention also provides application of the blue to transparent electrochromic polymer shown in the formula I in preparation of electrochromic films and electrochromic devices.
Preferably, the electrochromic film is prepared by dissolving the fused ring thiophene electrochromic polymer shown in the formula I in an organic solvent to obtain a mixed solution, coating the mixed solution on the surface of a substrate and drying, and the film thickness is 80-400nm. The organic solvent can be toluene, chloroform and other low-polarity solvents.
Preferably, the electrochromic device comprises an upper electrode layer, an electrolyte layer, an electrochromic thin film layer and a lower electrode layer which are sequentially stacked, wherein the electrochromic thin film layer is a thin film layer formed by the fused ring thiophene electrochromic polymer shown in formula I.
(III) advantageous effects
The method utilizes 2, 5-dibromo-3, 4-ethylenedioxythiophene (or 2, 5-dichloro-3, 4-ethylenedioxythiophene or 2, 5-diiodo-3, 4-ethylenedioxythiophene) and a compound shown as a formula II as synthetic monomers to carry out arylation coupling polymerization reaction, so that the 3, 4-ethylenedioxythiophene is introduced into a main chain of a thienothiophene derivative as an embedded unit, and the absorption spectrum of a polymer is red-shifted and shows blue under a neutral state by utilizing the electron supply characteristic and the conjugated planarity of the 3, 4-ethylenedioxythiophene; meanwhile, long-chain alkyl groups in the side chain structure of the thienothiophene derivative are combined to weaken the interaction among molecules, so that the polymer is easy to dissolve in organic solvents such as toluene, dichloromethane and the like for solution treatment, large-area film formation by adopting modes such as spraying or blade coating and the like is facilitated, and the method is favorable for technological treatment and application.
The polymer can realize the conversion from blue to transparent states, has the characteristics of low driving voltage (step potential is 0V and 0.8V), high optical contrast (usually more than 40 percent and can reach 45 percent at most) and high stability (the stability is still kept after 200 times of square wave potential scanning), and is suitable for the assembly application of electrochromic devices.
Drawings
Fig. 1 is a nuclear magnetic hydrogen spectrum of a blue to transparent electrochromic polymer of the present invention.
FIG. 2 shows the molecular weight and distribution of the polymer of formula I as determined by gel permeation chromatography, with reference sample being polystyrene, solvent being tetrahydrofuran, and the ordinate being the detected intensity and the abscissa being the retention time.
FIG. 3 is a spectral absorption curve and color photograph of a blue to transparent electrochromic polymer of formula I dissolved in chloroform.
FIG. 4 is a photograph of the UV-VIS absorption spectrum and color shift of the blue to transparent electrochromic polymer film of formula I at different potentials.
FIG. 5 is a cyclic voltammogram of a blue to transparent electrochromic polymer film of formula I.
FIG. 6 is a square wave potential cycling curve for a blue to transparent electrochromic polymer film according to formula I.
Fig. 7 is a thermal stability curve for a blue to transparent electrochromic polymer of formula I.
Detailed Description
For the purpose of better explaining the present invention and to facilitate understanding, the present invention will be described in detail by way of specific embodiments with reference to the accompanying drawings.
Example 1
This example is a preparation method of a blue to transparent electrochromic polymer of the present invention, and the specific process is as follows:
(1) Synthesis of a compound of formula ii:
under the protection of nitrogen at-78 ℃, dropwise adding a hexane solution of n-butyllithium into a THF solution of thieno (3-2-b) thiophene, then adding TIPSCl (triisopropylchlorosilane), and carrying out quenching, extraction, washing and drying to obtain an intermediate product 1; continuously adding a hexane solution of n-butyllithium and a THF solution of trimethyltin chloride into the THF solution of the intermediate product 1 at the temperature of-78 ℃ under the protection of nitrogen, and quenching, extracting, washing and drying to obtain an intermediate product 2; adding the intermediate product 2 into a mixture containing the compound 3 (2, 5-dibromothieno [3, 2-B) under the protection of nitrogen]Thiophene-3, 6-dicarboxylic acid ethyl ester: CAS: 1800376-55-9), pd 2 (dba) 3 And P (o-tol) 3 Extracting, washing and drying the obtained product in a toluene solution to obtain an intermediate product 4; adding the intermediate product 4 into THF solution of 4-hexyl-1-bromobenzene and hexane solution of n-butyl lithium at-78 ℃ under the protection of nitrogen, extracting, washing and drying to obtain the compound shown in the formula II. The detailed synthesis process can be referred to Chinese patent application CN201980006127.5 (Specification [0245 ]]-[0255])。
(2) The synthesis of the blue to transparent electrochromic polymers of formula I is as follows:
placing 0.1mmol of 2, 5-dibromo-3, 4-ethylenedioxythiophene, 0.1mmol of compound shown in formula II, 0.006mmol of palladium acetate, 0.3mmol of potassium carbonate and 0.05mmol of pivalic acid in a 25mL double-neck bottle, pumping gas, injecting nitrogen, injecting 15mL of anhydrous N, N-Dimethylacetamide (DMAC), pumping gas, filling nitrogen, heating to 120 ℃, refluxing for reaction for 72 hours, cooling to room temperature after the reaction is finished, dripping the reaction liquid into cold methanol for precipitation, filtering the precipitate, and drying; and then respectively carrying out Soxhlet extraction by using methanol, n-hexane and chloroform, wherein the extraction time of each extraction is 24 hours, concentrating the chloroform extract to 15mL, then dripping the chloroform extract into cold methanol to precipitate to obtain a black solid, filtering and drying to obtain the blue to transparent electrochromic polymer shown in the formula I.
As shown in fig. 1, is the nmr hydrogen spectrum of the blue to transparent electrochromic polymer of formula I. As shown in FIG. 2, the molecular weight and the distribution diagram of the target polymer having the structure shown in formula I are determined by gel permeation chromatography, the reference sample is polystyrene, the solvent is tetrahydrofuran, the ordinate of the figure is the detected intensity, and the abscissa of the figure is the retention time. The molecular weight of the polymer of formula I was measured to be Mn 19590 daltons, mw 47973 daltons, and PDI 2.44885.
Example 2
The blue to transparent electrochromic polymer shown in the formula I prepared in example 1 is dissolved in chloroform to prepare a solution of 8mg/ml, insoluble substances are filtered out through a filter tip, the solution is placed in a spray gun, the air pressure is controlled to be 2MPa, spraying is carried out on conductive glass, the absorbance of a film is about 0.8, and the sprayed film is placed in a vacuum drying oven to be dried in vacuum at 40 ℃ for later use.
The following performance tests were carried out on the polymers obtained and on the polymer films:
(1) Solution spectroscopic measurements were performed on the fused ring thiophene electrochromic polymer of formula I prepared in example 1:
dissolving polymer in chloroform to obtain solution with concentration of 2 × 10 -4 The absorption curve and the photo of the solution of mg/mL are shown in FIG. 3, the absorption peak of the polymer is at 560nm (absorbing yellow-green light), and the polymer solution appears bluish-purple.
(2) The polymer film is subjected to spectrum electrochemical performance tests under different voltages:
a three-electrode system is adopted, a platinum wire is used as a counter electrode, a calibrated silver wire is used as a reference electrode, the polymer film in the embodiment 1 is used as a working electrode, and the supporting electrolyte is as follows: 0.1mol/L of lithium perchlorate/propylene carbonate solution. The spectroelectrochemical spectrum and the color loss (oxidation state) coloring (neutral state) photo of the copolymer film under different applied voltages are shown in figure 4, which indicates that the polymer film has obvious electrochromic performance.
(3) The initial redox voltage of the prepared polymer film was tested using cyclic voltammetry:
as shown in FIG. 5, the polymer films were prepared to have initial redox voltages of about 0.2V and 0.15V.
(4) The spectral response and the stability of the prepared polymer film are tested by a step method:
as shown in fig. 6, the polymer thin film prepared in example 1 had step potentials of 0V and 0.8V and a maximum transmittance contrast of 45%. The electrochemical stability of the prepared polymer film is tested, and the good stability is still kept after the square wave potential scanning is carried out for 200 times.
(5) Testing of the thermal stability of the electrochromic polymers: as shown in fig. 7, the thermal decomposition temperature of the polymer was greater than 300 ℃, indicating that it can be used in higher temperature working environments.
It can be seen from the above examples and various test results that, the color and the absorption spectrum of the copolymer film prepared by the invention can be regulated and controlled by the kind of the comonomer, the copolymer film can realize the conversion from blue to transparent, and has the characteristics of low driving potential, obvious color change contrast, high coloring efficiency, good stability and the like, and the prepared copolymer film can be applied in the fields of electrochromic display, self-adaptive camouflage and the like.
Finally, it should be noted that: the above embodiments are only used to illustrate the technical solution of the present invention, and not to limit the same; while the invention has been described in detail and with reference to the foregoing embodiments, it will be understood by those skilled in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced; and the modifications or the substitutions do not make the essence of the corresponding technical solutions depart from the scope of the technical solutions of the embodiments of the present invention.
Claims (10)
1. A blue to transparent electrochromic polymer characterized by the following structural formula:
wherein n represents the degree of polymerization, and n is a natural number of 8-100.
2. A preparation method of a blue to transparent electrochromic polymer shown in a formula I is characterized by comprising the following steps: dissolving one of 2, 5-dibromo-3, 4-ethylenedioxythiophene, 2, 5-dichloro-3, 4-ethylenedioxythiophene and 2, 5-diiodo-3, 4-ethylenedioxythiophene and a compound shown in a formula II in an organic solvent as a synthetic monomer, adding an organic acid, an inorganic weak base and a palladium catalyst, and heating under the protection of inert gas to perform a polymerization reaction to obtain a blue to transparent electrochromic polymer with a structure shown in a formula I;
the reaction process is as follows, wherein R = Br, cl or I;
3. the method according to claim 2, wherein the organic acid is pivalic acid or tert-decanoic acid; the inorganic weak base is potassium carbonate, cesium carbonate or potassium acetate; the palladium catalyst is palladium acetate.
4. The method according to claim 2, wherein the organic solvent is N, N-dimethylacetamide or N, N-dimethylpropionamide.
5. The process according to claim 2, wherein the molar ratio of one of 2, 5-dibromo-3, 4-ethylenedioxythiophene, 2, 5-dichloro-3, 4-ethylenedioxythiophene and 2, 5-diiodo-3, 4-ethylenedioxythiophene to the monomer of the compound represented by the formula II is 1:1.
6. the process according to claim 2, wherein the molar ratio of the weak inorganic base to the compound of formula II is 3 to 4:1; the molar ratio of the organic acid to the compound shown in the formula II is 0.5-1:1; the molar ratio of the palladium catalyst to the compound shown in the formula II is 0.05-0.1:1.
7. the process according to claim 2, wherein the polymerization temperature is 120 to 140 ℃ and the reaction time is 36 to 72 hours.
8. The process according to claim 2, wherein the reaction mixture is cooled to room temperature after the completion of the reaction, and the reaction mixture is dropped into cold methanol to precipitate, and the precipitate is dried and filtered; and then respectively carrying out Soxhlet extraction by using methanol, n-hexane and chloroform, concentrating the chloroform extract, dripping into cold methanol for precipitation, filtering and drying to obtain the blue to transparent electrochromic polymer shown as the formula I.
9. Use of the blue to transparent electrochromic polymer of claim 1 in the preparation of electrochromic films and electrochromic devices.
10. The application of claim 9, wherein the electrochromic film is prepared by dissolving a fused ring thiophene electrochromic polymer shown in formula I in an organic solvent to obtain a mixed solution, coating the mixed solution on the surface of a substrate and drying, and the film thickness is 80-400nm;
the electrochromic device comprises an upper electrode layer, an electrolyte layer, an electrochromic thin film layer and a lower electrode layer which are sequentially stacked, wherein the electrochromic thin film layer is a thin film layer formed by a condensed ring thiophene electrochromic polymer shown in a formula I.
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