RU2528841C2 - Polymer electrochromic device - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to a polymer electrochromic device which is capable of varying light absorption in a controlled manner when voltage is applied. The polymer electrochromic device includes at least two electrodes and an electrochromic composition. The electrochemical composition contains a cathode component(s) and an anode component(s), at least one of which is an electrochromic component, and an electrolyte. The electrochromic component is a dispersion of nanoparticles of an insoluble electrochromic polymer in an organic solvent.

EFFECT: invention ensures easy production of the device by using a more readily available insoluble electrochromic polymer compared to insoluble electrochromic polymers currently used.

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Description

This invention relates to the field of electrochemistry of organic compounds of electrochromic devices, i.e. devices capable of controlling the amount of light absorption in a controlled manner when an electrical voltage is applied. More specifically, the present invention relates to polymer electrochromic devices containing, as an electrochromic component, a dispersion of nanoparticles of an insoluble electrochromic polymer, with dispersion as a system in which particles of an insoluble (dispersed) phase are uniformly distributed in a liquid dispersion medium (solvent).

Electrochromic materials are included in the group of chromogenic materials, including photochromic (changing the level of light absorption under the influence of light) and thermochromic (changing the level of light absorption under the influence of heat) materials.

Electrochromic devices based on inorganic compounds, organic compounds, oligomers and polymers are known (Roger J. Mortimer. Elrctrochromic materials // Chemical Society Reviews, 1997, v. 26, pp. 147-156; AAArgun, P. - H., Aubert , BCThompson, Multicolored Electrochromism in Polymers: Structures and Devices // Chem. Mater. - 2004. - V.16. - P. 1264-1272.). The main disadvantages of inorganic devices based on metal oxides, in particular tungsten, molybdenum, and vanadium oxides, include their fragility, which does not allow the manufacture of a flexible device, large response times, a weak change in transmission when voltage is applied and when it is removed, and also significant manufacturing difficulties. Therefore, in recent years, the main attention has been paid to organic electrochromic devices that use conductive electrochromic polymers, which can significantly overcome the above disadvantages.

Polymers in electrochromic devices are used in the form of solutions or layers that are obtained from solutions. However, with the exception of polyviologenes, all of the above polymers are not soluble in water or in organic solvents. Therefore, a fundamental condition for the suitability of polymers for electrochromic devices is the ability to transfer them into solution. Today, the generally accepted method is the chemical modification of polymers and / or monomers, as a result of which the polymers acquire the ability to dissolve in organic solvents. Typically, to convert electrochromic polymers into soluble form, their alkyl derivatives, aryl derivatives, cycloalkyl and cycloaryl derivatives, ether and cycloether derivatives, etc. are prepared. (A.Kumar, JRReynolds, Macromolecules, 1996, 29, 7629-7630; T. Inagaki, M. Hunter, XQYang, TASkotheim, Y. Okamoto, J. Chem. Soc, Chem. Commun., 1988, 126 )

The fundamental drawback of this approach is the need for chemical modification of polymers and / or monomers, which is a laborious, lengthy and expensive process. For example, a typical procedure for producing polyalkylthiophenes according to (J. Roncali, Chem Rev, 1992, 92, 711) involves the following steps: 3-hexylthiophene from thiophene chloride is obtained by the Grignard reaction by adding hexylmagnesium chloride to a solution of thiophene chloride and a NiCl ₂ catalyst ( Ph ₂ P (CH _{2) 3} PPh _2, boiling the resulting mixture at reflux for several hours, the resulting product was purified by distillation or recrystallization. hexylthiophene obtained Bromination using N-bromosuccinimide in dimethylsulfoxide under stirring mixtures within 24 hours, the resulting mixture was poured into water and extracted with dichloromethane. The extract was washed thoroughly with water, dried over magnesium sulfate and evaporated under reduced pressure. 2-bromo-3-hexylthiophene was purified by extraction in chloroform, the extract in chloroform was washed with sodium hydroxide solution to neutral pH, dried over magnesium sulfate, evaporated on a rotary evaporator and distilled twice .. The 2-bromo-3-hexylthiophene obtained in the previous step is coupled with 2,5-dibromothiophene in the presence of a dichloro [1,3-bis (diphenylphosphino) opaen] nickel to obtain 3,3 ”-dihexylthiophene. The resulting alkylated monomer 3,3-dihexylthiophene is polymerized in the presence of anhydrous iron (III) chloride in chloroform or carbon tetrachloride in a stream of nitrogen for 8 hours. The obtained polymer is precipitated from the solution by the addition of methanol, and the unreacted monomer and catalyst are first purified in the Soxhlet apparatus first in vapors of methanol, then acetone and dried. The disadvantage of this method is that the synthesis includes 4 stages with complex intermediate cleaning procedures at each stage. The total yield of the final product does not exceed 10-20%.

The closest analogue of this invention is the polymer electrochromic device described in RF application 2007109282. The electrochromic device includes a solution of a cathodic electrochromic polymer based on polypyridine or its copolymer and anodic electrochromic material, which is an aniline-based oligomer introduced into the compartment between the electrodes. The disadvantage of this device is the complex multi-stage organic synthesis of polyviologens (Harris F.W .; Chuang K.C .; Huang S.A.X .; Janimak J.J .; Cheng S.Z.D. Polymer 1994, 35, 4940).

An object of the present invention is to provide a polymer electrochromic device. The technical result of the invention is to significantly simplify the manufacturing process of the device by eliminating the multi-stage organic synthesis of a soluble electrochromic polymer, which is an electrochromic component of the device.

The problem is solved in that the electrochromic component (s) are not true solutions of chemically modified polymers, but dispersions of nanoparticles of insoluble electrochromic polymers, the synthesis of which is not a multi-stage process. This approach can significantly simplify the creation of polymer electrochromic devices.

 Figure 1 shows a schematic representation of the electrochromic device according to this invention (1 - transparent electrode, 2 - electrochromic composition containing the cathode and anode components and electrolyte, 3 - gasket, 4 - voltage application section, 5 - power source)

Figure 2 shows an electron micrograph of nanoparticles (nano-needles) obtained by interfacial polymerization according to Example 1.

Figure 3 shows an electron micrograph of nanoparticles obtained according to Example 2.

Figure 4 shows an electron micrograph of nanofibers obtained according to Example 3.

According to the invention, the electrochromic component (s) are nanoparticles of various conductive polymers, for example polyethylenedioxythiophene (PEDOT), polyaniline (PANI), polythiophene, polypyrrole, etc., as well as their copolymers and derivatives, including nanoparticles of a poly (aniline- co-3,4-ethylenedioxythiophene) / poly (4-styrenesulfonic acid), as dispersions in an organic solvent such as, for example, propylene carbonate (PC), dimethylformamide (DMF), dimethyl sulfoxide (DMSO), dimethylacetamide (DMAA), N -methylpyrrolidone (MP), etc., with the end Ntration of nanoparticles can be from about 0.1 wt. % to about 10 wt. %

The polymer nanoparticles of the present invention are prepared by any known method, for example, interfacial polymerization (Kai Su, Nurxat Nuraje, Lingzhi Zhang, I-Wei Chu, Hiroshi Matsau, Nan-Loh Yang, Macromol Symp, 2009, 279, 1-6; Jiaxing Huang and Richard B. Kaner, J. AM. CHEM. SOC. 2004, 126, 851-855), matrix chemical polymerization and copolymerization (Boeva J.A., Pyshkina O.A., Lezov A.A., Polushina G.E. ., Lezov A.V., Sergeev V.G. High-molecular compounds 2010. T. 52. No. 6. C.1-10.), Polymerization in the presence of organizing agents, such as, for example, low molecular weight electrolytes (Ji Hye Kim , Fei Fei Fang, Ki-Ho Lee and Hyoung Jin Choi, Korea-Australia Rheo logy Journal, Vol. 18, No. 2, June 2006 pp. 103-107), organic acids and alcohols (MVKulkarni, AKViswanath, RCAiyer, PKKhanna, Journal of Polymer Science: Part B: Polymer Physics, Vol. 43, 2161-2169 (2005)), etc. Thus, the synthesis of nanoparticles is a one-stage polymerization, often not requiring additional stages of isolation and / or purification. Polymer nanoparticles can be beads, threads, needles, fibers, rods, tubes, etc.

It should be emphasized that during the transition from true solutions to dispersions (i.e., so-called colloidal solutions, which are systems in which particles of an insoluble (dispersed) phase are uniformly distributed in a liquid dispersion medium (solvent), many can change as physical, the chemical properties of the substance.Moreover, during the transition from the bulk phase of solids to nanostructures, significant, ambiguous and unpredictable changes in many functional properties are often observed that cannot be explained only an increase in the specific surface and an increase in the number of surface atoms (A.A. Eliseev, A.V. Lukashin, “Functional Nanomaterials.” Ed. by Academician Yu.D. Tretyakova. M., FIZMATLIT, 2010). it is not at all obvious that the electrically conductive and electrochromic properties of polymers, which are an indispensable condition for their use in electrochromic devices, will be preserved during the transition from true solutions to dispersions of nanoparticles.

To achieve this goal, an electrochromic device is made, schematically shown in FIG. The device contains at least two optically transparent electrodes (1) (transparent plates with an electrically conductive layer), the space between which is filled with an electrochromic composition (2), including the anode and cathode components, at least one of which is electrochromic and represents a dispersion of nanoparticles of an electrochromic insoluble polymer in a suitable solvent, as well as an electrolyte providing electron transport between the cathode and anode components. The electrolyte can be introduced into the electrochromic composition or used in layers, for example, in the form of a paste, swelling film or physical gel.

The device is assembled by placing the electrochromic composition (2) between the electrodes (1), separated from each other by a gasket (3) of insulating material, and fasten the device at the edges. The resulting device through voltage application sections (4), which in this case serve as terminals, is connected to a direct current source (5), voltage is applied and the coloring time is measured, then the voltage is removed and the bleaching time of the device is measured.

A distinctive feature of this invention compared with those known from the prior art is that the electrochromic component is not a true solution of the electrochromic polymer, but a dispersion of nanoparticles of an insoluble electrochromic polymer in an organic solvent, while the other component may or may not possess electrochromic properties and represent both a true solution and a dispersion. In any case, the second component of the electrochromic device (anodic or cathodic) must have electroactivity, i.e. have the ability to receive / give at least one electron when voltage is applied.

As the second component of the electrochromic device, any electroactive organic compound known in the art can be used.

Thus, for example, phenazine derivatives, in particular dihydrodialkylphenazines, tetramethylphenyldiamine and its derivatives, tetraalkylbenzidines and their derivatives, tetrathiafulvalenes and its derivatives, metallocenes, for example, ferrocenes and their derivatives, etc., can be used as the anode component. As the anode component, commercial N-diphenyl-1,4-phenylenediamine (DFFD) can be used.

As the cathode component can be used as electrochromic compounds, for example derivatives of viologen, aniline oligomers, derivatives of thiophene, etc., and electroactive compounds that are not electrochromic, such as organopolydisulfides, such as poly-2-mercaptoethyl ether, poly-2 , 5-dimercapto-1,3,4-thiadiazole, polytritio-cyanuric acid, poly-1,2-ethanedithiol and the like, sulfa-containing polymers and tetrafluoroethylene copolymers, for example, a nafion product, etc.

The second component (cathodic or anodic) is dissolved in any suitable organic solvent, such as propylene carbonate, DMF, DMSO, MP, etc. The concentration of the second component is selected in accordance with the nature and concentration of the electrochromic dispersion and the solvent used.

The organic solvent is selected taking into account the nature of the components of the device, and also taking into account the possible use of the electrochromic composition obtained on its basis for the manufacture of a flexible or rigid electrochromic device. The solvents used in the present invention are preferably dimethylformamide (DMF), propylene carbonate (PC), N-methylpyrrolidone (MP), dimethyl sulfoxide (DMSO), dimethylacetamide (DMAA), acetonitrile, tetrahydrofuran (THF), etc., or mixtures thereof.

The electrolyte used in the electrochromic device provides the transport of electrons (ions) between the cathode and anode components. As the electrolyte according to this invention, any organic and inorganic salts can be used in the form of a solution, or in the form of a paste, a swelling film or in the form of a gel, deposited on at least one of the electrodes or in layers.

Thus, the aim of the invention is achieved by a polymer electrochromic device comprising at least two electrodes, and an electrochromic composition comprising a cathode component (s) and anode component (s), at least one of which is an electrochromic component, as well as an electrolyte, moreover, the electrochromic component is a dispersion of nanoparticles of an insoluble electrochromic polymer in an organic solvent. The electrochromic polymer nanoparticles used as a dispersion in the device are nano needles, nanofibers, nanowires, nanorods, nanobots or nanotubes, and the electrochromic polymer is selected from the group consisting of polyethylene dioxithiophene, polyaniline, polypyrrole copolymers and derivatives thereof.

The following examples are intended to illustrate the present invention and do not limit its scope.

Example 1

Stage 1. Obtaining PEDOT nanoparticles

PEDOT nano-needles in propylene carbonate were prepared by interfacial polymerization of EDOT as described in (Kai Su, Nurxat Nuraje, Lingzhi Zhang, I-Wei Chu, Hiroshi Matsau, Nan-Loh Yang, Macromol Symp, 2009, 279, 1-6). For this, 5 mg of EDOT was dissolved in 5 ml of dichloromethane, 5 mg of FeCb was dissolved in 5 ml of water; the aqueous phase was layered on top of the organic phase and kept for 2 days without stirring at room temperature. The aqueous layer containing PEDOT and FeCl ₃ nanoparticles was carefully selected and 5 drops of concentrated hydrochloric acid were added to prevent hydrolysis of iron chloride. Nanoparticles (nano-needles) were isolated by evaporation of the solvent on a rotary evaporator at 90 ° C. It was believed that the polymerization reaction was complete, and the resulting dried material contains a mixture of PEDOT and FeCl ₃ in a mass ratio of 1: 1. The resulting material was investigated using transmission electron microscopy (TEM). TEM photographs of a nano-needle PEDOT are shown in FIG. 2. It can be seen that the length of the nano needles ranges from 100 to 150 nm, and their thickness is about 20 nm. The resulting PEDOT nano-needles were stored in a closed vial.

Stage 2. Obtaining a dispersion of nanoparticles PEDOT

To obtain a dispersion, 20 mg of the unwashed material obtained in stage 1, containing a mixture of nanoparticles and iron chloride, was weighed and 1 ml of PC was poured. The mixture was stirred at room temperature for 3 hours and left overnight. The resulting dispersion with a concentration of PEDOT nanoparticles of 10 mg / ml (1%) was used in the assembly of the electrochromic device.

Stage 3. Assembly and testing of a polymer electrochromic device

An electrochromic device was assembled (see FIG. 1) containing two optically transparent electrodes, which were a 1.4 mm thick glass substrate coated with an ITO conductive coating (90% In ₂ O ₃ and 10% SnO ₂ ). An insulating pad of polypropylene 0.016 mm thick with a hole cut in the center was placed on the first electrode. A 0.005 M solution of N'-diphenyl-1,4-phenylenediamine (DPPD, anode component) in PC was applied to the central part of the electrode thus prepared. Before use, DPPD was purified by recrystallization from ethanol. Then, a 1% dispersion of nano-needles PEDOT in propylene carbonate (PC) was applied to the same electrode. Both components were thoroughly mixed. A layer of physical gel was applied to the second electrode, which was a 0.05 M solution of LiCl in a mixture containing 7.22 wt. % polymethylmethacrylate, 36.08 wt. % acetonitrile, 20.62 wt. % propylene carbonate and 36.08 wt. % tetrahydrofuran. The electrodes were superimposed on each other and fixed with clamps. Then, a direct current voltage of 2.8 V was applied to the device, and the time of staining and bleaching of the device was recorded. The change in the transmission intensity (ΔT,%) was calculated as the difference between the transmission of the working part of the device in the absence of current and when DC voltage was applied to the device. For the device described in this example, the dyeing time was 0.5 s, the bleaching time was 0.8 s, and the change in transmittance was 23%.

Stage 1. Obtaining a copolymer [poly (ANI-co-EDOT)] / PSS

The [poly (ANI-co-EDOT)] / PSS copolymer was prepared by matrix polymerization in the presence of polystyrenesulfonic acid (PSS) as follows. 1 ml (1.11 g) of a commercial aqueous solution of PSS (“Sigma Aldrich”, M _w = 7.5 × 10 ⁴ ) containing 18 wt. % polymer, was diluted with 9 ml of distilled water and kept for a day. Comonomer was introduced into the resulting solution: 0.0704 g of aniline hydrochloride (ANI, Sigma Aldrich) and 59.8 μl of 3,4-ethylenedioxythiophene (EDOT, Sigma Aldrich). Ammonium persulfate (APS, MP Biomedicals, 0.2528 g APS in 0.8 ml of water) initiated the copolymerization with stirring at room temperature. The concentrations of the components in the resulting mixture were: [APS] = [PSS] = 0.1 M, [ANI] = [EDOT] = 0.05 M). The mixture was kept at room temperature for one day.

To study the obtained nanoparticles, the reaction mixture was dialyzed against 3 L of distilled water during the day to remove oligomers and decay products of the initiator using a dialysis bag with an exclusion limit of 20 kDa. A TEM photograph of the obtained dispersion of a “nano-needle” copolymer is shown in FIG. 3. It can be seen that the diameter of the nano-needle varies in the range of 6-10 nm.

Stage 2. The selection of the copolymer and obtaining a dispersion

The copolymer was precipitated from the initial reaction mixture in 50 ml of acetone, and then centrifuged; the precipitate was washed with 20 ml of isopropanol and dried in air. To obtain a dispersion, 11 mg of the obtained copolymer was suspended in 4 ml of DMSO, then the suspension was sonicated on a pestle for 2 minutes while cooling in an ice bath. The resulting dispersion (0.275%) was stored in a closed vial at room temperature.

Stage 3. Assembly and testing of a polymer electrochromic device

The polymer electrochromic device was assembled as described in Example 1. The electrochromic component was the dispersion of the copolymer nanoparticles obtained in stage 2, the second electroactive component was a 0.09 M solution of DPPD in PC, and the gel described in Example 1 was used as the electrolyte.

The assembled device, as described above in Example 1, was supplied with a direct current voltage of 2.8 V and the time of staining and discoloration of the device was recorded. For the device described in this example, the dyeing time was 0.7 s, the bleaching time was 0.4 s, and the change in light transmission was 36%.

Polyaniline nanoparticles (PANI) in the form of fibers were obtained by interfacial polymerization of aniline (ANI) in accordance with the procedure described in the article (Jiaxing Huang and Richard B. Kaner, J. AM. CHEM. SOC. 2004, 126, 851-855), as follows Thus: 0.29 ml of ANI was dissolved in 20 ml of dichloromethane, 1.9 g of para-toluenesulfonic acid and 0.1824 g of ammonium persulfate were dissolved in 20 ml of water. The aqueous solution was layered on the organic and kept for 3 hours at room temperature without stirring. The aqueous phase was carefully separated and the resulting polymer was isolated from the aqueous phase by filtration through a paper filter and washed with water (5 × 100 ml). The resulting PANI nanofibre material was dried in vacuo. A TEM photograph of the obtained PANI nanofibres is shown in FIG. 4. It can be seen that the length of the fibers ranges from 80 to about 200 nm, and their diameter is about 12 nm.

A 10% dispersion of PANI nanofibers in MP was obtained by mixing their weighed amount in MP and used as an electrochromic component. A 0.2 M solution of DPPD in MP was used as the second electroactive component. As a physical gel, the mixture described in Example 1 was used.

An electrochromic device was assembled as described in Example 1. A DC voltage of 2.8 V was applied to the assembled device, and the time of staining and bleaching of the device was recorded. For the device described in this example, the dyeing time was 0.5 s, the bleaching time was 1.5 s, and the change in transmittance was 30%.

Example 4

Matrix synthesis of PEDOT on PSS was carried out by mixing a 0.10 M aqueous solution of polystyrenesulfonic acid (PSS) and an equimolar amount of monomer, followed by the addition of an aqueous solution of APS with stirring at room temperature ([PSSC] = [EDOT] = [APS] = 0.10 M). The polymerization was carried out during the day. Nanoparticles of the PEDOT: PSS complex were isolated by centrifugation, the precipitate was washed with isopropyl alcohol and dried in air.

To obtain a dispersion, 20 mg of PEDOT / PSS nanoparticles were suspended in 4 ml of DMSO, the suspension was subjected to ultrasonic treatment on a pestle for 1 min while cooling in an ice bath. Nanoparticles quantitatively transferred to the dispersion (0.5%) and were not precipitated by centrifugation at 14000 rpm for 10 min.

In the electrochromic device, a 0.5% dispersion of PEDOT / PSS in DMSO was used as the cathodic and anodic components. The dispersion was applied to one of the electrodes, an electrolyte was layered on top (the physical gel described in Example 1) and covered with a second electrode coated with a thin dispersion layer on top. A DC voltage of 2.8 V was applied to the assembled device. For the device described in this example, the dyeing time was 0.7 s, the bleaching time was 1.6 s, and the change in transmittance was 18%.

Example 5

The copolymer [poly (ANI-co-EDOT)] / PSS and its dispersion in DMSO were obtained as described in Example 2.

The polymer electrochromic device was assembled as described in Example 2, except that the second electroactive component was a 0.1 M solution of ferrocene in PC.

The assembled device, as described above in Example 1, was supplied with a direct current voltage of 2.8 V and the time of staining and discoloration of the device was recorded. For the device described in this example, the dyeing time was 1.8 s, the bleaching time was 2.5 s, and the change in light transmission rate was 16%.

Example 6

An electrochromic device was assembled as described in Example 2, except that a 0.1 M solution of trimethylammonium hexafluorophosphate in a PC was used as an electrolyte, and a 0.045 M solution of DPPD in a PC was used as a cathodic component.

A voltage of DC 2.8 V was applied to the device, and the time of staining and bleaching of the device was recorded. For the device described in this example, the staining time was 5.0 s, the bleaching time was 2.0 s, and the change in light transmission rate was 12%.

Claims (4)

1. A polymer electrochromic device comprising at least two electrodes and an electrochromic composition comprising a cathode component (s) and an anode component (s), at least one of which is an electrochromic component, as well as an electrolyte, characterized in that it is electrochromic the component is a dispersion of nanoparticles of an insoluble electrochromic polymer in an organic solvent. 2. The polymer electrochromic device according to claim 1, characterized in that the nanoparticles of the electrochromic polymer are either nano-needles, or nanofibers, or nanowires, or nanorods, or nanotubes, or nanotubes. 3. The polymer electrochromic device according to claim 1, characterized in that the electrochromic polymer is selected from the group consisting of polyethylenedioxythiophene, polyaniline, polypyrrole, their copolymers and derivatives. 4. The polymer electrochromic device according to claim 1, characterized in that the concentration of nanoparticles in the organic solvent is from about 0.1 wt. % to about 10 wt. %

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