JPH0645673B2 - Method for producing highly conductive thiophene-based polymer - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing a highly conductive thiophene-based polymer, and more specifically, it can be easily industrially mass-produced and molded into an arbitrary shape to obtain a primary product. The present invention relates to a method for producing a highly conductive thiophene-based polymer which can be used as an electrode for batteries, secondary batteries, solar cells or various electric or electronic devices.

[Conventional technology]

Conventional methods for producing thiophene-based polymers are generally classified into the following two methods.

The first method is a method in which a thiophene compound is dissolved in an appropriate electrolytic solution and electropolymerization is performed to obtain it from the electrode (Synthetic Metals, Vol. 14, 1986, p. 279).

The second method is a chemical polymerization method in which a thiophene compound is treated with an appropriate oxidizing agent (synthetic metals No. 1).
Vol. 18, 1987, p. 227).

[Problems to be Solved by the Invention]

Among such conventional methods, the first method can produce a highly conductive thiophene-based polymer, but compared with the second method, it requires a special apparatus and an electrolyte, and thus the production cost is extremely high. It has the disadvantage that it is expensive and only a film of the same size as the electrode area can be obtained. Moreover, the obtained film has nonuniformity such that the central portion is thin and the peripheral portion is thick, which is not a realistic method.

On the other hand, although the second method has a low production cost, there is a problem that a polymer having high conductivity cannot be obtained by the conventional method.

[Means for Solving the Problems]

The present inventors have diligently studied the difference between chemical polymerization and electrolytic polymerization in order to elucidate the reason why a highly conductive polymer cannot be obtained by the chemical polymerization method. It is possible to obtain high conductivity by uniformly oxidizing the monomers and the like by controlling the amount of the polymer. In the case of chemical polymerization, by controlling the potential value appropriately, a high conductivity polymer similar to electrolytic polymerization can be obtained. This has led to the completion of the present invention.

According to the present invention, a thiophene-based monomer is stirred in an inert gas atmosphere at -20 to 40 ° C in an oxidant solution in which an oxidizing agent and a solvent are combined to maintain the oxidation potential at 1.0 to 1.6V. A highly conductive thiophene polymer is easily produced by polymerizing and doping the produced thiophene polymer with a dopant.

[Operation and Example]

Examples of the oxidizing agent used in the present invention include sulfuric acid,
Inorganic acids such as hydrochloric acid and chlorosulfonic acid; ordinary Lewis acids; and chlorides and sulfates of metals such as aluminum, chromium, tin, titanium, zirconium, manganese, iron, copper, molybdenum, tungsten, ruthenium, palladium and platinum. , Metal salts such as nitrates and acetylacetonates. These oxidizing agents can be used alone or as a mixture of two or more kinds.

As the solvent, those capable of dissolving thiophene-based monomers such as alcohols, halogenated hydrocarbons, aromatic hydrocarbons and ethers are preferably used.

Examples of the thiophene-based monomer include thiophene and alkylthiophene, and the alkylthiophene is preferably one in which the β-position is substituted with an alkyl group.

An electron accepting compound and an electron donating compound can be used as a dopant used for doping the polymer obtained by polymerization. As a specific example,
For example, halogen such as iodine and bromine; arsenic pentafluoride,
Metal halide compounds such as antimony pentafluoride, silicon tetrafluoride, phosphorus pentachloride, phosphorus pentafluoride, aluminum chloride, aluminum bromide and aluminum fluoride; oxidizing agents such as sulfur trioxide, nitrogen dioxide and difluorosulfonyl peroxide Protic acids such as sulfuric acid, nitric acid, fluorosulfuric acid, trifluorosulfuric acid, chlorosulfuric acid; silver perchlorate, tetracyanoethylene, chloranil, 2,3-dichloro-
5,6-dicyanobenzoparaquinone, 2,3-dibromo-5,6
-Dicyanobenzoparaquinone; and other alkali metals such as lithium, sodium and potassium.

In the present invention, the oxidation potential of the oxidant solution is SEC.
It measures using the S electrode type potentiostat which used the electrode.

It is important to keep the oxidation potential of the oxidant solution in the range of 1.0 to 1.6V. If the oxidation potential is less than 1.0 V, the reaction is unlikely to occur, while if it is higher than 1.6 V, side reactions may occur, which is not preferable.

In order to keep the oxidation potential at a constant level, it is necessary to keep the concentration of the oxidant at a constant level. As a method of keeping the concentration of the oxidant constant, for example, there is a method of saturating or supersaturating the oxidant, or adding an oxidant consumed by the reaction during the reaction. It is preferred to use a saturated or supersaturated solution of the oxidant, with the addition of the oxidant as needed. When the oxidant is in an unsaturated state, the potential becomes low as the reaction proceeds, and the polymerization in the initial and final stages becomes non-uniform, resulting in poor conductivity. Here, saturated or supersaturated means a state in which the undissolved oxidizing agent remains in the sufficiently stirred solution. Since the supplement of the oxidant consumed by the polymerization is achieved by the dissolution of the undissolved oxidant, stirring is extremely demanding and it is preferable to stir as much as possible.

The thiophene-based monomer is polymerized by adding the monomer to the above oxidant solution at a ratio of 0.01 to 0.3 mol with respect to 1 mol of the oxidant and at a temperature of -20 to 40 ° C under an atmosphere of an inert gas such as nitrogen. Done. The molar ratio of monomer to oxidant is
If it is larger than 0.3, unreacted substances remain and conductivity deteriorates.
If it is less than 0.01, its utility value is small in terms of productivity.

A polymerization time of 3 hours or less is sufficient, and the thiophene polymer can be obtained by filtering the reaction mixture, washing it with methyl alcohol, ethanol, acetone or the like, and drying it under reduced pressure.

As a method of doping the obtained polymer, a method of contacting the dopant in a gaseous state, a solid state or a liquid state, a method of dissolving the dopant in a suitable solvent and contacting it, and subjecting the conductive polymer to electrolysis Electrochemical methods such as doping.

The doping amount and the doping time vary depending on the type, size, amount and apparent specific gravity of the thiophene-based polymer and are not particularly limited.

The method for producing a thiophene-based polymer of the present invention can easily and industrially mass-produce a highly conductive thiophene-based polymer by a chemical polymerization method, and the obtained highly conductive thiophene-based polymer can be molded into an arbitrary shape. Then, it can be used as an electrode of primary batteries, secondary batteries and solar cells or as various electric and electronic devices.

Next, the method of the present invention will be described more specifically with reference to Examples and Comparative Examples. The electric conductivity is a value measured by a known four-terminal method on a sample piece formed by molding a thiophene-based polymer powder at a pressure of 2.000 kg / cm ² .

Example 1 0.5 mol of anhydrous ferric chloride in 50 ml of supersaturated chloroform solution
Was placed in a flask under a nitrogen atmosphere, and the oxidation potential was measured with stirring.

A thiophene monomer (2.5 mmol) was added to the above solution to react with stirring at room temperature for 2 hours, filtered, washed with methyl alcohol or acetone, and dried under reduced pressure to obtain a polythiophene powder.

Next, the polythiophene powder was doped with iodine and pressed to form a sample piece, and the electric conductivity was measured and found to be 70 scm ⁻¹ .

Example 2 Polymerization was carried out in the same manner as in Example 1 except that molybdenum pentachloride was used instead of ferric hydroxide.

At this time, the oxidation potential was 1.1 V, and the conductivity of the obtained sample was 20 scm ^-1 .

Example 3 Polymerization was carried out in the same manner as in Example 1 except that the amount of the thiophene monomer was 7.5 mmol. The conductivity of the obtained sample was 23 scm ^-1 .

Example 4 A conductive polymer was obtained in the same manner except that the polythiophene powder obtained in Example 1 was doped with arsenic pentafluoride. The conductivity of the obtained polymer was 85 scm ^-1 .

Example 5 Example 1 except that 2.5 mmoles of 3-methylthiophene was used in place of the thiophene monomer in Example 1.
Polymerization was carried out in the same manner as in (1) to give poly-3-methylthiophene powder. The conductivity of the sample obtained by iodine doping is
It was 100 scm ^-1 .

Example 6 A conductive polymer was obtained in the same manner except that the poly-3-methylthiophene powder obtained in Example 5 was doped with sulfuric acid. The electric conductivity of the polymer was 54 scm ^-1 .

Example 7 A poly-3-methylthiophene powder was obtained by polymerization in the same manner as in Example 2 except that 3-methylthiophene was used in place of the thiophene monomer in Example 1. The conductivity of the sample obtained by iodine doping was 90 scm ^-1 .

Example 8 Example 1 except that 2.5 mmol of 3-ethylthiophene was used in place of the thiophene monomer in Example 1.
Polymerization was carried out in the same manner as in (3) to give poly-3-ethylthiophene powder. The conductivity of the sample obtained by iodine doping is
It was 36 scm ^-1 .

Comparative Example 1 A sample piece was prepared in the same manner as in Example 1 except that the concentration of the oxidizing agent was changed to 0.08 molar unsaturated solution.
The oxidation potential was 1.1 V and the conductivity was 0.01 scm ^-1 .

Comparative Example 2 Polymerization was carried out in the same manner as in Example 1 except that 50 ml of a 0.5 molar iron perchlorate solution in methyl alcohol was used as the oxidant solution. The oxidation potential of the oxidant solution is 0.
It was 9 V and almost no reaction occurred.

Comparative Example 3 A sample piece was obtained in the same manner as in Example 1 except that the amount of thiophene monomer was changed to 10 mmol. The conductivity of the obtained sample was 0.03 scm ^-1 .

The polymerization conditions and results of the above Examples and Comparative Examples are summarized in Table 1.

[Effects of the Invention] The method of the present invention does not require a special device required in the conventional method for producing a highly conductive thiophene-based polymer, so that not only the production cost is greatly reduced, but also the obtained film is It is a polymer having higher conductivity and higher conductivity than conventional ones. Further, since it is a chemical polymerization method, it is simple and can be industrially mass-produced.

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Claims (8)

[Claims] 1. A thiophene-based monomer is polymerized while stirring in an inert gas atmosphere at -20 to 40 ° C. in an oxidant solution in which an oxidant and a solvent are combined to maintain an oxidation potential value of 1.0 to 1.6 V. And a method for producing a highly conductive thiophene-based polymer, which comprises doping the obtained thiophene-based polymer with a dopant. 2. The method according to claim 1, wherein the oxidant is saturated or supersaturated to keep the concentration of the oxidant constant, or the oxidant consumed by the reaction is added during the reaction. 3. The method according to claim 1, wherein the molar ratio of the thiophene-based monomer and the oxidizing agent is in the range of 0.01 to 0.3 with respect to the oxidizing agent. 4. An inorganic acid such as sulfuric acid, hydrochloric acid or chlorosulfonic acid; a Lewis acid; and aluminum, chromium, tin, titanium, zirconium, manganese, iron, copper, molybdenum, tungsten, ruthenium, palladium, platinum. 2. The method according to claim 1, which is at least one selected from the group consisting of metal chlorides, sulfates, nitrates, and metal compounds such as acetylacetonate. 5. The solvent according to claim 1, wherein the solvent is selected from the group consisting of alcohols, halogenated hydrocarbons, aromatic hydrocarbons and ethers and is capable of dissolving a thiophene-based monomer. Production method. 6. The production method according to claim 1, wherein the thiophene-based monomer is selected from the group consisting of thiophene and alkylthiophene substituted at the β-position with an alkyl group. 7. The method according to claim 1, wherein the dopant is an electron accepting compound or an electron donating compound. 8. The dopant is halogen; a metal halogen compound such as arsenic pentafluoride, antimony pentafluoride, silicon tetrafluoride, phosphorus pentachloride, phosphorus pentafluoride, aluminum chloride, aluminum bromide, aluminum fluoride; Oxidizing agents such as sulfur trioxide, nitrogen dioxide, difluorosulfonyl peroxide; protic acids such as sulfuric acid, nitric acid, fluorosulfuric acid, trifluorosulfuric acid, chlorosulfuric acid; silver perchlorate; tetracyanoethylene; chloranil; 2,3 -Dichloro-5,6-dicyanobenzoparaquinone; 2,3-dibromo-5,6-dicyanobenzoparaquinone; and lithium,
The production method according to claim 1, which is selected from the group consisting of alkali metals such as sodium and potassium.