JP7709702B2 - Method for producing conductive polymer solution - Google Patents

Description

The present invention relates to a method for producing a conductive polymer solution and a conductive polymer.

In recent years, semiconductor technology has undergone rapid development, leading to the creation of a huge electronics-related industry and a highly information-oriented society. As examples of applications of conductive polymers in electronics products, liquid crystal displays (LCDs) and organic electroluminescence (OLEDs) are widely used in a variety of fields, including televisions, computers, and the various mobile devices that have become popular in recent years. In this way, the electronics-related industry that uses conductive polymers has achieved remarkable development.

As materials that underpin these electronics-related industries, externally doped conductive polymers have been developed in which π-conjugated polymers, such as polyacetylene, polythiophene, polyaniline, and polypyrrole, are doped with electron-accepting compounds as dopants. However, these externally doped conductive polymers have issues such as being difficult to purify due to their low solubility, and it is difficult to maintain stable doping.

So, so-called self-doped conductive polymers have been developed, which have a substituent (sulfo group, sulfonate group, etc.) that combines water solubility and doping action in the polymer main chain, either directly or via a spacer. Known examples of self-doped conductive polymers include sulfonated polyaniline and sulfonated polythiophene (see, for example, Non-Patent Documents 1 and 2). Among these, poly(4-(2,3-dihydrothieno[3,4-b][1,4]dioxin-2-ylmethoxy)-1-butanesulfonic acid) (PEDT-S) substituted with linear alkylenesulfonic acid groups has been reported (see, for example, Patent Document 1, Non-Patent Documents 3 and 4). The applicant of the present application has also reported a self-doped conductive polymer that combines high conductivity and excellent water solubility (see, for example, Patent Document 2).

JP 2001-261795 A International Publication No. 2014/007299

Journal of the American Chemical Society, 117, 10055-10062(1995) Journal of the Chemical Society, Chemical Communications, 23, 1694-1695(1990) Chemistry of Materials, 21, 1815-1821(2009) Advanced Materials, 23, 4403-4408(2011)

In the above-mentioned prior art (Patent Document 2), a self-doped conductive polymer is synthesized by chemical oxidative polymerization, but this method tends to leave metal ions, especially iron ions, derived from the catalyst or oxidizing agent as impurities in the polymerization product. Such iron ion impurities can cause a decrease in device characteristics and durability in applications such as organic EL and LCD. For this reason, a treatment to remove iron ions using a cation exchange resin has been proposed for conductive polymers obtained by chemical oxidative polymerization. However, there are issues with the removal treatment using a cation exchange resin, such as an increase in the number of manufacturing steps, an increase in variable costs, and an increase in environmental load, which are preferable to reduce.

On the other hand, electrochemical oxidative polymerization is known as a synthesis method that does not require a catalyst or oxidizing agent and is less likely to leave metal ions, especially iron ions, as impurities. However, it has been difficult to achieve the high conductivity required for solid electrolytic capacitors and the like with self-doped conductive polymers obtained by the conventional electrochemical oxidative polymerization method. If the conductivity of self-doped conductive polymers can be increased, it will be possible to further improve the performance of solid electrolytic capacitors and the like.

One aspect of the present invention aims to provide a method for producing a conductive polymer that achieves high conductivity using an electrochemical oxidative polymerization method.

As a result of intensive research into solving the above problems, the inventors discovered that by heating a solution of self-doped polythiophene obtained by electrochemical oxidative polymerization reaction, it is possible to develop extremely high conductivity that could not be achieved with self-doped conductive polymers obtained by conventional electrochemical oxidative polymerization methods, and thus completed the present invention.

That is, one aspect of the present invention relates to a method for producing a self-doped conductive polymer with higher electrical conductivity by heat treating a polythiophene containing structural units represented by at least the following general formula (2) and the following general formula (3) obtained by electrochemical oxidative polymerization.

That is, one aspect of the present invention includes the following [1] to [7].

[1]
A method for producing a conductive polymer solution containing polythiophene having at least two repeating units selected from the group consisting of a repeating unit represented by the following general formula (2) and a repeating unit represented by the following general formula (3),
(i) a polymerization step of bringing at least one pair of electrodes into contact with a solution containing at least a thiophene monomer represented by the following general formula (1), a solvent, and an acid, and applying a potential difference between the electrodes to obtain a polymer solid or a polymer solution that is a polymer of the monomers;
(ii) a dissolving step of mixing the polymer solid with the solvent to obtain the polymer solution when the polymer obtained in the polymerization step is a polymer solid;
(iii) a heat treatment step of heating the polymer solution obtained in the polymerization step or the dissolution step;
A manufacturing method comprising the steps of:

[In the general formulae (1) and (2), M ⁺ each independently represents a hydrogen ion, an alkali metal ion, an ammonium ion, a conjugate acid of an amine compound, or a quaternary ammonium cation. In the general formulae (1), (2), and (3), R ² represents a hydrogen atom, a linear or branched alkyl group having 1 to 6 carbon atoms, or a halogen atom. m represents an integer of 1 to 6, and n represents 0 or 1.]
[2]
In the general formulas (1), (2), and (3), m is 2 or 3.

[3]
The method according to [1] or [2], wherein in the general formulas (1), (2), and (3), the R ² is a methyl group.

[4]
The method according to any one of [1] to [3], wherein in the polymerization step, a concentration of the monomer is 0.1 to 30% by weight.

[5]
The manufacturing method according to any one of [1] to [4], wherein in the polymerization step, the current density is in the range of 0.01 to 10 mA/ ^cm2 .

[6]
The method according to any one of [1] to [5], wherein in the heat treatment step, the heating temperature is in the range of 50 to 250° C.

[7]
A conductive polymer comprising polythiophene containing at least two or more repeating structures selected from the group consisting of repeating structures represented by the following general formula (2) and repeating structures represented by the following general formula (3), characterized in that the conductive polymer has a carrier mobility of 1.5 to 10 cm ² /Vs.

[In the general formula (2), M ⁺ each independently represents a hydrogen ion, an alkali metal ion, an ammonium ion, a conjugate acid of an amine compound, or a quaternary ammonium cation. In the general formulas (2) and (3), R ² represents a hydrogen atom, a linear or branched alkyl group having 1 to 6 carbon atoms, or a halogen atom. m represents an integer of 1 to 6, and n represents 0 or 1.]

According to one aspect of the present invention, a method for producing a conductive polymer that achieves high conductivity using electrochemical oxidative polymerization can be provided.

One embodiment of the present invention will be described in detail below. Note that unless otherwise specified in this specification, "A to B" representing a numerical range means "A or more, B or less."

A method for producing a conductive polymer solution according to one embodiment of the present invention is a method for producing a conductive polymer solution containing a polythiophene containing at least two or more repeating structures selected from the group consisting of a repeating structure represented by the following general formula (2) and a repeating structure represented by the following general formula (3),
(i) a polymerization step of bringing at least one pair of electrodes into contact with a solution containing at least a thiophene monomer represented by the following general formula (1), a solvent, and an acid, and applying a potential difference between the electrodes to obtain a polymer solid or a polymer solution that is a polymer of the monomers;
(ii) a dissolving step of mixing the polymer solid with the solvent to obtain the polymer solution when the polymer obtained in the polymerization step is a polymer solid;
(iii) a heat treatment step of heating the polymer solution obtained in the polymerization step or the dissolution step;
A manufacturing method comprising the steps of:

[In the general formulae (1) and (2), M ⁺ each independently represents a hydrogen ion, an alkali metal ion, an ammonium ion, a conjugate acid of an amine compound, or a quaternary ammonium cation. In the general formulae (1), (2), and (3), R ² represents a hydrogen atom, a linear or branched alkyl group having 1 to 6 carbon atoms, or a halogen atom. m represents an integer of 1 to 6, and n represents 0 or 1.]
In the general formulas (1) and (2), each M ⁺ independently represents a hydrogen ion, an alkali metal ion, an ammonium ion (NH ₄ ⁺ ), a conjugate acid of an amine compound, or a quaternary ammonium cation.

The alkali metal ions are not particularly limited, but examples of preferred ions include Li ions, Na ions, and K ions.

The conjugate acid of the amine compound is an amine compound which becomes a cationic species by addition of a hydron (H ⁺ ) to the amine compound, and may be any amine compound which reacts with a sulfonic acid group to form a conjugate acid.

The amine compound in the conjugate acid of the amine compound is not particularly limited, but examples thereof include amine compounds having an ^sp3 hybrid orbital represented by the general formula N(R ¹ ) ₃ , and amine compounds having an ^sp2 hybrid orbital such as pyridines or imidazoles.

The above-mentioned substituents R ¹ each independently represent a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, or an alkyl group having 1 to 6 carbon atoms and a substituent.

The alkyl group having 1 to 6 carbon atoms is not particularly limited, but examples thereof include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, an n-pentyl group, an isopentyl group, a neopentyl group, a tert-pentyl group, a cyclopentyl group, an n-hexyl group, a 2-ethylbutyl group, and a cyclohexyl group.

The alkyl group having 1 to 6 carbon atoms and having a substituent is not particularly limited, but examples thereof include an alkyl group having 1 to 6 carbon atoms and having a group selected from the group consisting of a halogen atom, an alkyl group having 1 to 6 carbon atoms, an amino group, and a hydroxy group. Specific examples thereof include, but are not particularly limited to, a trifluoromethyl group, a 2-hydroxyethyl group, etc.

Of these, from the viewpoint of availability, the substituents R ¹ are preferably each independently a hydrogen atom, a methyl group, an ethyl group, or a 2-hydroxyethyl group.

The amine compound represented by the general formula N(R ¹ ) ₃ is not particularly limited, but examples thereof include ammonia, methylamine, dimethylamine, trimethylamine, ethylamine, diethylamine, triethylamine, normal-propylamine, isopropylamine, normal-butylamine, tertiary-butylamine, hexylamine, aminoethanol, dimethylaminoethanol, methylaminoethanol, diethanolamine, N-methyldiethanolamine, triethanolamine, 3-amino-1,2-propanediol, 3-methylamino-1,2-propanediol, 3-dimethylamino-1,2-propanediol, and 1,4-butanediamine.

The amine compound having an sp ² hybrid orbital that forms a conjugate acid of the amine compound is not particularly limited, and examples thereof include imidazole, N-methylimidazole, 1,2-dimethylimidazole, pyridine, picoline, and lutidine.

Among the amine compounds that form the conjugate acids of these amine compounds, ammonia, ethanolamine compounds, and imidazole compounds are preferred from the viewpoint of availability.

The quaternary ammonium cation is not particularly limited, but examples thereof include tetramethylammonium cation, tetraethylammonium cation, tetra-n-propylammonium cation, tetra-n-butylammonium cation, and tetra-n-hexylammonium cation. Among these, the tetramethylammonium cation and tetraethylammonium cation are preferred from the viewpoint of availability.

As described above, each M ⁺ is preferably independently a hydrogen ion, a Li ion, a Na ion, a K ion, an ammonium ion, a monoethanolammonium ion, a diethanolammonium ion, a triethanolammonium ion, an imidazolium ion, an N-methylimidazolium ion, or a 1,2-dimethylimidazolium ion.

In the above general formulas (1), (2), and (3), R ² each independently represents a hydrogen atom, a linear or branched alkyl group having 1 to 6 carbon atoms, or a halogen atom.

The linear or branched alkyl group having 1 to 6 carbon atoms is not particularly limited, but examples thereof include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl, isopentyl, neopentyl, tert-pentyl, cyclopentyl, n-hexyl, 2-ethylbutyl, cyclohexyl, and n-octyl groups.

Halogen atoms include, but are not limited to, fluorine atoms, chlorine atoms, bromine atoms, etc.

With respect to ^R2 , from the viewpoint of film-forming properties, each independently is preferably a hydrogen atom, a methyl group, an ethyl group, or a fluorine atom, more preferably a methyl group, an ethyl group, or a fluorine atom, and more preferably a methyl group.

Each m independently represents an integer from 1 to 6, preferably an integer from 1 to 4, and more preferably 2 or 3.

Each n is independently 0 or 1, preferably 1.

The structural unit represented by the general formula (3) represents the doped state of the structural unit represented by the general formula (2). In the conductive polymer of one embodiment of the present invention, during electrolytic oxidation polymerization, a part of the structural unit represented by the general formula (2) undergoes a self-doping reaction and changes to the structural unit represented by the general formula (3). This action causes the resulting polymer to exhibit electrical conductivity.

Dopants that cause an insulator-metal transition by doping can be divided into acceptors and donors. The former enter close to the polymer chain of a conductive polymer and take away π electrons from the conjugated system of the main chain. As a result, a positive charge (positive hole) is injected into the main chain, so it is also called a p-type dopant. Conversely, the latter donates electrons to the conjugated system of the main chain, and these electrons move through the conjugated system of the main chain, so it is also called an n-type dopant.

In one embodiment of the present invention, the dopant is a sulfo group or a sulfonate group covalently bonded within the polymer molecule, and is a p-type dopant. A polymer that exhibits conductivity without the addition of an external dopant is called a self-doped polymer.

The thiophene monomer represented by the general formula (1) is not particularly limited, but examples thereof include sodium 3-[(2,3-dihydrothieno[3,4-b]-[1,4]dioxin-2-yl)methoxy]-1-methyl-1-propanesulfonate, sodium 3-[(2,3-dihydrothieno[3,4-b]-[1,4]dioxin-2-yl)methoxy]-1-ethyl-1-propanesulfonate, sodium 3-[(2,3-dihydrothieno[3,4-b]-[1,4]dioxin-2-yl)methoxy]-1-propyl-1-propanesulfonate, sodium 3-[( Sodium 2,3-dihydrothieno[3,4-b]-[1,4]dioxin-2-yl)methoxy]-1-butyl-1-propanesulfonate, sodium 3-[(2,3-dihydrothieno[3,4-b]-[1,4]dioxin-2-yl)methoxy]-1-pentyl-1-propanesulfonate, sodium 3-[(2,3-dihydrothieno[3,4-b]-[1,4]dioxin-2-yl)methoxy]-1-hexyl-1-propanesulfonate, sodium 3-[(2,3-dihydrothieno[3,4-b]-[1,4]dioxin-2-yl)methoxy]-1-isopropyl -1-propanesulfonic acid sodium salt, 3-[(2,3-dihydrothieno[3,4-b]-[1,4]dioxin-2-yl)methoxy]-1-isobutyl-1-propanesulfonic acid sodium salt, 3-[(2,3-dihydrothieno[3,4-b]-[1,4]dioxin-2-yl)methoxy]-1-isopentyl-1-propanesulfonic acid sodium salt, 3-[(2,3-dihydrothieno[3,4-b]-[1,4]dioxin-2-yl)methoxy]-1-fluoro-1-propanesulfonic acid sodium salt, 3-[(2,3-dihydrothieno[3,4-b]-[1,4]dioxin-2-yl)methoxy]-1-fluoro-1-propanesulfonic acid sodium salt, ]dioxin-2-yl)methoxy]-1-methyl-1-propanesulfonic acid potassium, 3-[(2,3-dihydrothieno[3,4-b]-[1,4]dioxin-2-yl)methoxy]-1-methyl-1-propanesulfonic acid, 3-[(2,3-dihydrothieno[3,4-b]-[1,4]dioxin-2-yl)methoxy]-1-methyl-1-propanesulfonic acid ammonium, or 3-[(2,3-dihydrothieno[3,4-b]-[1,4]dioxin-2-yl)methoxy]-1-methyl-1-propanesulfonic acid triethylammonium.

The thiophene monomers exemplified above can be produced, for example, according to the following general formula (4) using thieno[3,4-b]-1,4-dioxine-2-methanol and a branched sultone compound, which can be synthesized based on known methods (e.g., Journal of Electroanalytical Chemistry, 443, 217-226 (1998)).

[In the general formula (4), ^R2 has the same meaning as ^R2 in the general formula (1), and ^M2 represents an alkali metal ion (Li ion, K ion, Na ion, Cs ion, or the like).]
Furthermore, the thiophene monomer represented by the general formula (4) thus produced can be converted to a sulfonic acid in which ^M2 is a hydrogen atom (the thiophene monomer represented by the general formula (1)) by acid treatment (contact with an acid or an H ion type cation exchange resin, etc.). Furthermore, the thiophene monomer represented by the general formula (1) can be obtained by contacting this sulfonic acid in which ^M2 is a hydrogen atom with an alkali metal compound, ammonia, an amine compound, or a quaternary ammonium compound.

In the method for producing a conductive polymer solution containing a conductive polymer according to one embodiment of the present invention, a monomer other than the thiophene monomer represented by the general formula (1) can be used in combination. The monomer is not particularly limited, but examples thereof include thiophene, 3-hexylthiophene, 3,4-ethylenedioxythiophene, hydroxymethyl-3,4-ethylenedioxythiophene, hydroxy-3,4-propyleneoxythiophene, bromomethyl-3,4-ethylenedioxythiophene, N-(2,3-dihydrothieno[3,4-b][1,4]dioxin-2-ylmethyl)-2-aminoethanesulfonic acid, and N-methyl-N-(2,3-dihydrothieno[3,4-b][1,4]dioxin-2-ylmethyl)-2-aminoethanesulfonic acid. Examples of such sulfonic acid include 2,3-dihydrothieno[3,4-b][1,4]dioxin-2-ylmethanesulfonic acid, 6-(2,3-dihydrothieno[3,4-][1,4]dioxin-2-yl)-1-hexene, 6-(2,3-dihydrothieno[3,4-][1,4]dioxin-2-yl)-1-hexanesulfonic acid, 6-(2,3-dihydrothieno[3,4-][1,4]dioxin-2-yl)-1-butanesulfonic acid, and O-(2,3-dihydrothieno[3,4-b][1,4]dioxin-2-ylmethyl)-4-phenolsulfonic acid.

The method for producing a conductive polymer solution according to one embodiment of the present invention is characterized by including the steps (i), (ii), and (iii) described above.

Hereinafter, the polymerization step (i) of one embodiment of the present invention will be described, in which at least one pair of electrodes is brought into contact with a solution containing at least a monomer containing a thiophene monomer represented by the general formula (1), a solvent, and an acid, and a potential difference is applied (a potential is applied) between the electrodes to polymerize the monomer and obtain a polymer.

In the polymerization step, a monomer containing at least the thiophene monomer represented by the general formula (1) is polymerized. The concentration range of the monomer in the polymerization reaction is not particularly limited, but is preferably 0.1 to 30% by weight, more preferably 0.2 to 20% by weight, more preferably 0.3 to 10% by weight, and even more preferably 0.5 to 8% by weight.

The "monomer concentration" referred to here is a value expressed as weight of (monomer containing thiophene monomer represented by the general formula (1)) / weight of (monomer containing thiophene monomer represented by the general formula (1) + solvent + acid) x 100 (wt%).

The solvent used in the polymerization step is not particularly limited, but is preferably water, a solvent containing water, or a water-soluble solvent, and more preferably water, a water-water-soluble alcohol mixed solvent, or a water-soluble alcohol.

Examples of water include pure water, distilled water, and ion-exchanged water.

Water-soluble alcohols include, but are not limited to, alcohols such as methanol, ethanol, propanol, and butanol.

Of these solvents, water or methanol is preferred, and water is more preferred. The solvent may be degassed or substituted with an inert gas such as nitrogen.

The acid used in the polymerization step is not particularly limited, but may be, for example, an inorganic acid or an organic acid. Examples of inorganic acids include hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid, and boric acid. Examples of organic acids include methanesulfonic acid, paratoluenesulfonic acid, formic acid, acetic acid, lactic acid, and benzoic acid. Among these, sulfuric acid, methanesulfonic acid, and paratoluenesulfonic acid are preferred, and sulfuric acid is more preferred, in terms of the excellent polymerization reaction rate.

A solution containing at least a monomer containing a thiophene monomer represented by the general formula (1), a solvent, and an acid can be produced by mixing these components in any order. Such a solution containing a monomer containing a thiophene monomer represented by the general formula (1), a solvent, and an acid before contact with an electrode may be referred to as a "feed solution" below.

The amount of acid added (content) is not particularly limited, but the normality of the acid in the starting solution (=molar concentration of acid x valence of the acid) is preferably 0.01 to 10 [N], more preferably 0.01 to 5 [N], and even more preferably 0.01 to 2 [N]. When the starting solution is an aqueous solution, it is preferable to add (contain) acid so that the pH of the starting solution is in the range of 0 to 6.5, more preferably so that the pH is in the range of 0 to 5, and even more preferably so that the pH is in the range of 0 to 3.

The method of contacting at least one pair of electrodes with the solution is not particularly limited, but for example, the solution is placed in the container, and an anode and a cathode are immersed in the solution to apply a potential difference. A three-electrode method using a reference electrode or a two-electrode method may be used. Alternatively, the container itself may be used as an electrode, and the counter electrode may be brought into contact with the solution.

The potential difference applied between the electrodes is a potential difference that can electrochemically oxidize and polymerize the thiophene monomer represented by the general formula (1) above, and is not particularly limited. However, the potential of the anode, as determined by the three-electrode method, is preferably in the range of 0 to +5 V relative to the reference electrode, and more preferably in the range of +0.5 to +2.5 V.

The current density during polymerization is not particularly limited, but is preferably in the range of 0.01 to 10 mA/cm ² , and more preferably in the range of 0.1 to 6 mA/cm ² .

The material of the container is not particularly limited as long as it is sufficiently durable against the solution. For example, glass, glass-lined containers, Teflon (registered trademark), polyethylene, polypropylene, polyvinyl chloride, stainless steel, etc. are preferred.

The shape of the container may be any shape capable of holding the solution inside, and may have a structure in which the anode and cathode can be separated by a porous partition or ionic bridge.

The electrodes used in the polymerization process can be ones that allow an electrochemical oxidation reaction to proceed on their surfaces by applying a potential difference between the electrodes. Such electrodes are not particularly limited, but examples include gold, platinum, nickel, titanium, stainless steel, glassy carbon, ITO, etc., and these may be used alone or in combination of two or more types.

The reaction pressure in the polymerization process may be normal pressure, reduced pressure, or increased pressure.

The reaction atmosphere in the method for producing a conductive polymer solution according to one embodiment of the present invention is not particularly limited, but may be an air atmosphere or an inert gas atmosphere such as nitrogen or argon. An inert gas atmosphere is more preferable.

The reaction temperature of the polymerization step is, for example, a temperature at which the thiophene monomer represented by the general formula (1) can be electrochemically oxidatively polymerized, and is not particularly limited, but is preferably in the range of -10 to 50°C, and more preferably in the range of 0 to 40°C.

The reaction time of the polymerization step is not particularly limited, but may be, for example, a time during which the oxidative polymerization of the thiophene monomer represented by the general formula (1) proceeds sufficiently. Although not particularly limited, the reaction time is preferably in the range of 0.5 to 200 hours, and more preferably in the range of 0.5 to 80 hours.

The polymerization step can be carried out in a state containing a surfactant in addition to the thiophene monomer represented by the general formula (1), the solvent, and the acid. The addition of the surfactant is preferable in terms of improving the solubility and dispersibility in the solvent of the thiophene monomer used as the raw material and the thiophene polymer produced.

The surfactant is not particularly limited, but may be, for example, an anionic surfactant, a cationic surfactant, a nonionic surfactant, or an amphoteric surfactant, and more preferably at least one selected from the group consisting of an anionic surfactant and a nonionic surfactant.

Anionic surfactants are not particularly limited, but examples include carboxylic acid type, sulfonic acid type, sulfate ester type, and phosphate ester type.

The carboxylic acid type is not particularly limited, but examples include sodium octanoate, sodium decanoate, sodium palmitate, sodium stearate, etc.

The sulfonic acid type is not particularly limited, but examples include sodium hexanesulfonate, sodium decane sulfonate, sodium toluenesulfonate, sodium octylbenzenesulfonate, sodium dodecylbenzenesulfonate, sodium naphthalenesulfonate, etc.

The above-mentioned sulfate ester type is not particularly limited, but examples thereof include sodium lauryl sulfate, sodium laureth sulfate, ammonium lauryl sulfate, etc.

The phosphate ester type is not particularly limited, but examples include sodium lauryl phosphate, potassium lauryl phosphate, etc.

Nonionic surfactants are not particularly limited, but examples include polyethylene glycol type surfactants, acetylene glycol type surfactants, polyhydric alcohol type surfactants, polymer type nonionic surfactants, etc.

The polyethylene glycol surfactant is not particularly limited, but examples thereof include higher alcohol ethylene oxide adducts, alkylphenol ethylene oxide adducts, fatty acid ethylene oxide adducts, polyhydric alcohol fatty acid ester ethylene oxide adducts, higher alkylamine ethylene oxide adducts, ethylene oxide adducts of fats and oils, and polypropylene glycol ethylene oxide adducts.

The acetylene glycol surfactant is not particularly limited, but examples thereof include 2,4,7,9-tetramethyl-5-decyne-4,7-diol, Surfynol (registered trademark, manufactured by Air Products Co., Ltd.), and Olfine (registered trademark, manufactured by Nissin Chemical Industry Co., Ltd.).

The polyhydric alcohol surfactant is not particularly limited, but examples thereof include fatty acid esters of glycerol, fatty acid esters of pentaerythritol, fatty acid esters of sorbitol and sorbitan, fatty acid esters of sucrose, alkyl ethers of higher alcohols, fatty acid amides of alkanolamines, etc.

The polymeric nonionic surfactant is not particularly limited, but examples thereof include polyvinylpyrrolidone and copolymers of polyvinylpyrrolidone. The copolymer of polyvinylpyrrolidone is not particularly limited, but is preferably one having both hydrophilic and hydrophobic parts in the polymer chain, and examples thereof include copolymers in which polyvinylpyrrolidone is grafted to polyvinyl alcohol, [vinylpyrrolidone-vinyl acetate] block copolymers, [vinylpyrrolidone-methyl methacrylate] copolymers, [vinylpyrrolidone-normal butyl methacrylate] copolymers, and [vinylpyrrolidone-acrylamide] copolymers.

By carrying out the above-mentioned polymerization reaction, a polymer of a monomer containing a thiophene monomer represented by the general formula (1) can be produced, and the polymer is obtained as a polymer solution or a polymer solid. When the polymer is obtained as a polymer solid, all or part of the solid tends to be obtained as a deposit on the anode.

When the polymer is obtained as a polymer solid, the dissolution step represented by the following (ii) is carried out to obtain a polymer solution.

Next, we will explain (ii) a dissolution step of the present invention, which is carried out when the polymer obtained in the polymerization step is a polymer solid, in which the polymer solid is mixed with a solvent to obtain a polymer solution.

If the polymer solid obtained in the polymerization step is precipitated on the electrode, it is preferable to separate the polymer solid from the electrode in advance. The method of separation is not particularly limited, but examples include peeling by impact, peeling by ultrasonic waves, peeling using a spatula, and dissolving and peeling using a good solvent. Regardless of whether the polymer solid is precipitated on the electrode, it is preferable to filter the obtained polymer solid. The filtration method is not particularly limited, but examples include suction filtration, pressure filtration, centrifugal filtration, and natural filtration.

The filter used to filter the polymer solid may be any filter capable of separating the polymer solid from the solvent after the polymerization process, and examples of such filters include, but are not limited to, filter paper, membrane filters, glass filters, and filter cloth.

The polymer solid separated above is then mixed with a solvent to obtain a polymer solution.

The solvent is not particularly limited, but is preferably water, a solvent containing water, or a water-soluble solvent, and more preferably water, a water-water-soluble alcohol mixed solvent, or a water-soluble alcohol.

Examples of water include pure water, distilled water, and ion-exchanged water.

Water-soluble alcohols include, but are not limited to, alcohols such as methanol, ethanol, propanol, and butanol.

Of these solvents, water, a water-methanol mixed solvent, or methanol is preferred, and water is more preferred. The solvent may be degassed or substituted with an inert gas such as nitrogen.

It is preferable that the viscosity of the polymer solution is in the range of 0.1 to 1000 mPa·s.

The polymer concentration in the polymer solution is not particularly limited, but is preferably in the range of 0.01 to 20% by weight. The polymer concentration is preferably 0.1 to 10% by weight, and more preferably 0.2 to 5% by weight, in terms of excellent processing efficiency in the heat treatment step (iii) below.

Next, we will explain (iii) the heat treatment step of heating the polymer solution obtained in the polymerization step or the dissolution step according to one embodiment of the present invention.

As for the polymer solution to be heated in the heat treatment process, the polymer solution produced in the polymerization process (i) or the dissolution process (ii) can be used as is, or the polymer solution produced in the polymerization process (i) or the dissolution process (ii) can be purified by a commonly known purification method before use.

The purification method includes, but is not limited to, ultrafiltration, dialysis, ion exchange resin treatment, etc. These purification methods may be performed alone or in combination of two or more types.

The ion exchange resin is not particularly limited, but examples thereof include weakly acidic cation exchange resins, strongly acidic cation exchange resins, weakly basic anion exchange resins, and strongly basic anion exchange resins. These resins may be used alone or in combination of two or more kinds.

The heating temperature in the heat treatment step is preferably higher than the polymerization reaction temperature of polythiophene in order to obtain high conductivity, and is not particularly limited, but is preferably 50 to 200°C, more preferably 60 to 180°C, and even more preferably 70 to 150°C.

Regarding the heating in the heat treatment process, it is preferable to heat to a temperature that is the maximum temperature reached in the polymerization process (°C) + 10°C or more, more preferably to heat to a temperature that is the maximum temperature reached in the polymerization process (°C) + 20°C or more, and even more preferably to heat to a temperature that is the maximum temperature reached in the polymerization process (°C) + 50°C or more.

The heating in the heat treatment step may be performed in a closed system or an open system. When heating at high temperatures, evaporation of the solvent may occur, so it is preferable to perform the heating in a closed system, and a pressure-resistant container may be used as necessary.

The heating time is not particularly limited, but is preferably from 0.1 hours to 1000 hours. More preferably, it is from 0.5 hours to 100 hours, and even more preferably from 1 hour to 50 hours.

By carrying out the above steps (i), (ii), and (iii), the desired conductive polymer solution can be produced.

In addition to the above-mentioned steps (i), (ii), and (iii), the method for producing a conductive polymer according to one embodiment of the present invention may further include an anion exchange step (iv) in which the polymer solution obtained in the heat treatment step is contacted with an anion exchange resin to exchange the anions in the polymer solution for hydroxide ions (so-called purification step). The anion exchange step (iv) is preferably carried out between the polymerization step (i) and the heat treatment step (iii), between the dissolution step (ii) and the heat treatment step (iii), or after the heat treatment step (iii), and may be carried out once or in combination multiple times.

The anion exchange resin is not particularly limited, but examples thereof include weakly basic anion exchange resins and strongly basic anion exchange resins. Weakly basic anion exchange resins are preferred because they are excellent in efficiently increasing the purity of the conductive polymer. Furthermore, the weakly basic anion exchange resin is not particularly limited, but an amine-type weakly basic anion exchange resin is preferred. As the amine-type weakly basic anion exchange resin, commercially available products can be used, and there is no particular limitation. For example, Diaion (registered trademark) WA20, Diaion (registered trademark) WA21, Diaion (registered trademark) WA30 (manufactured by Mitsubishi Chemical Corporation), Amberlite (registered trademark) IRA67, Amberlite (registered trademark) IRA96SB, Amberlite (registered trademark) IRA98 (manufactured by Organo Corporation), Dowex (registered trademark) 66 (manufactured by Dow), Duolite (registered trademark) A368MS (manufactured by Rohm and Haas Company), LEWATIT (registered trademark) MP62WS, LEWATIT (registered trademark) Monoplus MP64, etc. can be suitably used.

The conductive polymer solution produced through the above-mentioned steps can be further adjusted for viscosity or composition to prepare a conductive polymer solution suitable for the intended application.

The method for adjusting the viscosity is not particularly limited, but examples thereof include a method of removing the solvent by ultrafiltration or distillation, a method of adding a solvent, and a homogenization treatment (using an ultrasonic homogenizer, a high-pressure homogenizer, etc.). When a solvent is added, the solvent is not particularly limited, but examples thereof include the same solvent as that used in the polymerization process, and water is more preferable.

The above-mentioned component adjustment is not particularly limited, but may include operations such as adding conventionally known additives that are commonly used in the field of conductive polymer compositions based on conventionally known methods.

The conductive polymer solution produced by the above-mentioned production method is characterized in that it contains a polythiophene containing at least two or more repeating structures selected from the group consisting of the repeating structures represented by the general formula (2) and the repeating structures represented by the general formula (3), and further characterized in that it has a low iron ion content. Since the iron ion content is low, the production method according to one embodiment of the present invention does not require a purification operation by a cation exchange process that was routinely performed in the conventional technology, and has the effect of reducing the number of processes and reducing the environmental burden.

It is desirable for the conductive polymer solution to have a low iron ion content when used for its intended purpose, and the iron content is preferably 10 ppm or less, more preferably 5 ppm or less, more preferably 2 ppm or less, even more preferably 0.5 ppm or less, and even more preferably 0.2 ppm or less.

The conductive polymer produced by the above-mentioned production method preferably has high carrier mobility, and although there are no particular limitations, the carrier mobility is preferably 1.5 to 10 cm ² /Vs, and more preferably 1.8 to 5 cm ² /Vs.

Furthermore, according to one embodiment of the present invention, a highly efficient manufacturing method that reduces the manufacturing process makes it possible to manufacture a conductive polymer solution with excellent conductivity. This leads to the realization of a highly efficient manufacturing method for energy-efficient electronics products, and can contribute to the achievement of the Sustainable Development Goals (SDGs), such as Goal 7 "Affordable and Clean Energy."

The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope of the claims. The technical scope of the present invention also includes embodiments obtained by appropriately combining the technical means disclosed in different embodiments.

Next, one aspect of the present invention will be described in detail using examples, but the present invention should not be interpreted as being limited to these.

(Electrical Conductivity Measurement Method)
A vinyl tape was applied to a slide glass (26 x 70 mm) so as to divide it into two in the middle of the longitudinal direction, and a conductive polymer solution (concentration of conductive polymer is about 1.0 wt%) was dropped onto one of the sections (26 x 35 mm) divided by the vinyl tape, and the solution was dried at 60°C for 30 minutes and at 120°C for 10 minutes. Then, the solution was heat-treated in a vacuum at 200°C for 1 hour to produce a conductive polymer cast film with a thickness d of about 5 μm. The produced conductive polymer cast film was cut into 10 x 10 mm. The thickness d was measured using a stylus step gauge D-100 (KLA-Tencor) in dry air (dried for 10 minutes at a humidity of 10% or less).

Conductivity was evaluated using electrical conductivity as an index. First, a four-probe probe PSP (Mitsubishi Chemical Corporation) connected to a resistivity meter Loresta GP (Mitsubishi Chemical Corporation) was fixed with a crank, and the cast film was lifted using a lab jack to press it directly against the probe and measure the resistance R. The resistance R measured by the four-probe method was multiplied by the resistivity correction factor (RCF value), which is a correction value determined by the film shape (film thickness, size, measurement coordinates), and the electrical conductivity σ was calculated using the following formula.

where σ is electrical conductivity (S/cm), I is current (A), U is voltage (V), RCF is resistivity correction factor, and d is film thickness (μm).

(Molecular weight measurement method)
Weight average molecular weight (Mw), number average molecular weight (Mn), and polydispersity index (PDI) were measured by GPC (gel permeation chromatography), and a high performance liquid chromatography apparatus (Prominence, Shimadzu Corporation) and columns TSKgel α-M and guardcolumn α (Tosoh Corporation) were used. Poly(4-styrenesulfonic acid) (PSS, American polymer standard) was used as the standard sample. Dimethyl sulfoxide (DMSO) in which 10 mM tetrabutylammonium bromide (TBABr) and 10 mM N-diisopropylamine (DIPA) were dissolved was used as the eluent. The measurement sample was neutralized and diluted with the eluent to a conductive polymer concentration of 5×10 ⁻³ wt%, and then ultrasonicated at 50° C. for 20 minutes, reacted at 50° C. for 18 hours, and then ultrasonicated for 20 minutes to perform dedoping.

(Reflection Spectrum Measurement and Carrier Mobility Calculation)
The conductive polymer cast film thus prepared was used as a measurement sample and the reflection spectrum was measured in the wavelength range of 300 to 2500 nm using an ultraviolet-visible spectrophotometer (V-670, manufactured by JASCO Corporation). The intersection point of the extrapolated line of the reflection spectrum and the reflectance of 0% was defined as the plasma frequency _fp , and the carrier density _Nc was calculated from the plasma frequency _fp using the following formula.

Here, f _p is the plasma frequency (ω _p /2π) (Hz), N _c is the carrier density (/cm ³ ), e is the elementary charge (1.6×10 ^-19 C), ε ₀ is the dielectric constant (8.85×10 ^-12 F/m), m ^* is the effective mass (0.82 m ₀ ), and m ₀ is the free electron mass (9.11×10 ^-31 kg).

Furthermore, the carrier mobility μ was calculated from the electrical conductivity σ and carrier density _Nc obtained above using the following formula.

Here, it is electrical conductivity σ (S/cm), carrier density N _c (/cm ³ ), and elementary charge e (1.6×10 ⁻¹⁹ C).

(Viscosity measurement)
The viscosity of the conductive polymer solution (concentration of conductive polymer: about 1.0 wt %) was measured at 25° C. using a torsional vibration viscometer (Viscomaid VM-10A-L, Sekonic).

(pH measurement)
The pH of the conductive polymer solution (conductive polymer concentration: approximately 1.0 wt %) was measured at 25° C. using a pH meter (F-53, Horiba, Ltd.).

(particle size measurement)
The particle size of the conductive polymer was evaluated using a dynamic light scattering measurement device (Nanotrac UPA-UT151, Nikkiso). After measurement with about 2 ml of pure water as the background, the sample was diluted 100 to 200 times by adding 10 to 20 μl of a conductive polymer solution (concentration of conductive polymer: about 1.0 wt %) and then measured. The particle size distribution and the median diameter (D ₅₀ ) at which the integrated particle size distribution curve crosses the horizontal axis at 50% were calculated using the software Microtrac II DMS.

Example 1
(Electrochemical oxidation polymerization method)
Polymerization was carried out using a three-electrode system consisting of a platinum working electrode (35 cm ² ), a titanium counter electrode (690 cm ² ), and a silver-silver chloride reference electrode. First, 10 g of sodium 3-[(2,3-dihydrothieno[3,4-b]-[1,4]dioxin-2-yl)methoxy]-1-methyl-1-propanesulfonate (thiophene monomer represented by the following general formula (5), produced according to a conventional method) was dissolved in 990 g of 1 M dilute sulfuric acid solution. The concentration of the thiophene monomer at this time was 1.0% by weight. The mixture in which the thiophene monomer was completely dissolved was added to a reaction vessel. The temperature of the mixture in the reaction vessel was adjusted to 0° C., and nitrogen was flowed for 2 hours. After that, a potential of +0.8 V was applied to the working electrode with respect to the reference electrode at a current density of 1 mA/cm ² for 20 hours, resulting in the precipitation of a solid. Analysis of the precipitate revealed that it was polythiophene (a polymer having repeating units represented by the following general formula (6) and general formula (7)) formed by polymerization of the thiophene monomer.

(Purification of electrochemically oxidized polymer)
Polythiophene (a polymer consisting of repeating structures represented by the general formula (6) and the general formula (7)) precipitated by electrochemical oxidation polymerization was collected by glass filter filtration. Next, 3 kg of pure water was added to the obtained polythiophene, and the mixture was stirred overnight, and then homogenized for 10 minutes by an ultrasonic homogenizer to obtain a polymer solution. The polymer solution was purified by ultrafiltration (molecular weight cutoff = 10 kD), and undissolved solids were removed by suction filtration. The polymer solution obtained by suction filtration was further concentrated by ultrafiltration (molecular weight cutoff = 10 kD) to obtain a deep ultramarine aqueous solution (conductive polymer solution) containing 1.0 wt% polythiophene (a polymer consisting of repeating structures represented by the general formula (6) and the general formula (7), a conductive polymer).

(Heat treatment of conductive polymer solution)
The aqueous solution containing the polythiophene (a polymer having repeating units represented by the general formula (6) and the general formula (7)) adjusted to a concentration of 1.0% by ultrafiltration was heated with stirring at 100° C. for 24 hours to obtain a conductive polymer solution.

(Electrical Conductivity)
The electrical conductivity of the conductive polymer contained in the conductive polymer solution obtained by the production method according to one embodiment of the present invention was measured by the above-mentioned electrical conductivity measurement method, and was found to be 322 S/cm.

(molecular weight)
When the molecular weight of the conductive polymer contained in the conductive polymer solution obtained by the production method according to one embodiment of the present invention was measured by the above-mentioned molecular weight measurement method, the weight average molecular weight was 15,706 g/mol.

(carrier density, carrier mobility)
The carrier density and carrier mobility of the conductive polymer contained in the conductive polymer solution obtained by the production method according to one embodiment of the present invention were measured by the reflectance spectrum method, and the carrier density was 1.23×10 ²¹ /cm ³ and the carrier mobility was 1.81 cm ² /Vs.

(viscosity)
The viscosity of the conductive polymer solution obtained by the production method according to one embodiment of the present invention was measured by the above-mentioned viscosity measurement method, and was found to be 2.68 mPa·s.

(pH)
The pH of the conductive polymer solution obtained by the production method according to one embodiment of the present invention was measured by the above-mentioned pH measurement method, and was found to be 1.87.

(particle size)
The viscosity of the conductive polymer solution obtained by the production method according to one embodiment of the present invention was measured by the above-mentioned particle size measurement method, and was found to be 2.07 nm.

The results are shown in Tables 1, 2 and 3.

Example 2
The same polymerization operation, purification operation, and heat treatment of the polymerization solution as in Example 1 were performed, except that the condition of the current density of 1 mA/ ^cm2 in Example 1 was changed to a current density of 2 mA/ ^cm2 , to obtain a deep ultramarine aqueous solution (conductive polymer solution) containing polythiophene (a polymer having repeating structures represented by the general formula (6) and the general formula (7), which is a conductive polymer) at a concentration of 1.0 wt%. The results of the physical property evaluation are shown in Tables 1, 2, and 3.

Example 3
The same polymerization operation, purification operation, and heat treatment of the polymerization solution as in Example 1 were performed, except that the condition of the current density of 1 mA/ ^cm2 in Example 1 was changed to a current density of 3 mA/ ^cm2 , to obtain a deep ultramarine aqueous solution (conductive polymer solution) containing polythiophene (a polymer having repeating structures represented by the general formula (6) and the general formula (7), which is a conductive polymer) at a concentration of 1.0 wt%. The results of the physical property evaluation are shown in Tables 1, 2, and 3.

Example 4
The same polymerization operation, purification operation, and heat treatment of the polymerization solution as in Example 1 were performed, except that the condition of the current density of 1 mA/ ^cm2 in Example 1 was changed to a current density of 4 mA/ ^cm2 , to obtain a deep ultramarine aqueous solution (conductive polymer solution) containing polythiophene (a polymer having repeating structures represented by the general formula (6) and the general formula (7), which is a conductive polymer) at a concentration of 1.0 wt%. The results of the physical property evaluation are shown in Tables 1, 2, and 3.

Example 5
The same polymerization operation, purification operation, and heat treatment of the polymerization solution as in Example 1 were performed, except that the condition of the current density of 1 mA/ ^cm2 in Example 1 was changed to a current density of 5 mA/ ^cm2 , to obtain a deep ultramarine aqueous solution (conductive polymer solution) containing polythiophene (a polymer having repeating structures represented by the general formula (6) and the general formula (7), which is a conductive polymer) at a concentration of 1.0 wt%. The results of the physical property evaluation are shown in Tables 1, 2, and 3.

Example 6
The same polymerization operation, purification operation, and heat treatment of the polymerization solution as in Example 1 were performed, except that the condition of the current density of 1 mA/ ^cm2 in Example 1 was changed to a current density of 6 mA/ ^cm2 , to obtain a deep ultramarine aqueous solution (conductive polymer solution) containing polythiophene (a polymer having repeating structures represented by the general formula (6) and the general formula (7), which is a conductive polymer) at a concentration of 1.0 wt%. The results of the physical property evaluation are shown in Tables 1, 2, and 3.

Reference example 1
The polymerization and purification procedures were the same as in Example 1, except that the heat treatment was not performed, to obtain a deep ultramarine aqueous solution containing polythiophene (a polymer having repeating units represented by the general formula (6) and the general formula (7)) at a concentration of 1.0% by weight. The results of the physical property evaluation are shown in Tables 1, 2, and 3.

Reference example 2
The polymerization and purification procedures were the same as in Example 2, except that the heat treatment was not performed, to obtain a deep ultramarine aqueous solution containing polythiophene (a polymer having repeating units represented by the general formula (6) and the general formula (7)) at a concentration of 1.0% by weight. The results of the physical property evaluation are shown in Tables 1, 2, and 3.

Reference example 3
The polymerization and purification procedures were the same as in Example 3, except that the heat treatment was not performed, to obtain a deep ultramarine aqueous solution containing polythiophene (a polymer having repeating units represented by the general formula (6) and the general formula (7)) at a concentration of 1.0% by weight. The results of the physical property evaluation are shown in Tables 1, 2, and 3.

Reference example 4
The polymerization and purification procedures were the same as in Example 4, except that the heat treatment was not performed, to obtain a deep ultramarine aqueous solution containing polythiophene (a polymer having repeating units represented by the general formula (6) and the general formula (7)) at a concentration of 1.0% by weight. The results of the physical property evaluation are shown in Tables 1, 2, and 3.

Reference example 5
The polymerization and purification procedures were the same as in Example 5, except that the heat treatment was not performed, to obtain a deep ultramarine aqueous solution containing polythiophene (a polymer having repeating units represented by the general formula (6) and the general formula (7)) at a concentration of 1.0% by weight. The results of the physical property evaluation are shown in Tables 1, 2, and 3.

Reference example 6
The polymerization and purification procedures were the same as in Example 6, except that the heat treatment was not performed, to obtain a deep ultramarine aqueous solution containing polythiophene (a polymer having repeating units represented by the general formula (6) and the general formula (7)) at a concentration of 1.0% by weight. The results of the physical property evaluation are shown in Tables 1, 2, and 3.

As can be seen from Table 1, the electrical conductivity of the coating film could be improved by heat-treating the conductive polymer solution containing polythiophene. In addition, as can be seen from Table 2, the carrier mobility of the coating film could also be improved by heat-treating the conductive polymer solution containing polythiophene.

As can be seen from the above tables, the conductive polymer and its solution produced by the production method according to one embodiment of the present invention exhibited the characteristic of having a lower viscosity, despite the fact that the molecular weight and electrical conductivity were improved compared to those not subjected to heat treatment. Generally, the viscosity of conductive polymers increases with increasing molecular weight and electrical conductivity, which tends to have a negative effect on impregnation into capacitor micropores, application properties, operability, etc. However, according to the production method according to one embodiment of the present invention, it is possible to provide a conductive polymer and its solution that have unprecedented high electrical conductivity and high operability.

Thus, according to one embodiment of the present invention, it is possible to manufacture and provide a self-doped conductive polymer and its solution that exhibit high electrical conductivity that was difficult to achieve using conventional electrochemical oxidative polymerization.

In addition, the conductive polymer produced by the manufacturing method according to one embodiment of the present invention has a remarkable and unique effect of exhibiting unprecedentedly high carrier mobility. For this reason, the conductive polymer is extremely useful industrially in that it can improve the performance of organic electroluminescence (EL), LCDs, capacitors, etc.

The conductive polymer obtained by the method for producing a conductive polymer solution according to one embodiment of the present invention has high electrical conductivity and can be used as an antistatic agent, a solid electrolyte for capacitors, as well as an antistatic film and a separator for wound-type aluminum electrolytic capacitors. In addition, it can be expected to be used in electrochromic elements, transparent electrodes, transparent conductive films, thermoelectric conversion materials, chemical sensors, actuators, electromagnetic wave shielding materials, etc.

Claims (6)

A method for producing a conductive polymer solution containing polythiophene having at least two repeating units selected from the group consisting of a repeating unit represented by the following general formula (2) and a repeating unit represented by the following general formula (3),
(i) a polymerization step of bringing at least one pair of electrodes into contact with a solution containing at least a thiophene monomer represented by the following general formula (1), a solvent, and an acid, and applying a potential difference between the electrodes to obtain a polymer solid or a polymer solution that is a polymer of the monomers;
(ii) a dissolving step of mixing the polymer solid with the solvent to obtain the polymer solution when the polymer obtained in the polymerization step is a polymer solid;
(iii) a heat treatment step of heating the polymer solution obtained in the polymerization step or the dissolution step;
A manufacturing method comprising the steps of:
[In the general formulas (1) and (2), M ⁺ each independently represents a hydrogen ion, an alkali metal ion, an ammonium ion, a conjugate acid of an amine compound, or a quaternary ammonium cation. In the general formulas (1), (2), and (3), ^R2 represents a linear or branched alkyl group having 1 to 6 carbon atoms. m represents an integer of 1 to 6, and n represents 0 or 1.] The method according to claim 1, wherein in the general formulas (1), (2) and (3), m is 2 or 3. The method according to claim 1 or 2, wherein in the general formulas (1), (2) and (3), ^R2 is a methyl group. The manufacturing method according to any one of claims 1 to 3, wherein the concentration of the monomer in the polymerization step is 0.1 to 30% by weight. The method according to any one of claims 1 to 4, wherein in the polymerization step, the current density is in the range of 0.01 to 10 mA/ ^cm2 . The manufacturing method according to any one of claims 1 to 5, wherein the heating temperature in the heat treatment step is in the range of 50 to 250°C.