JPH059271A - Manufacture of highly conductive organic polymer - Google Patents

Abstract

PURPOSE:To provide a method for manufacturing an organic polymer having high conductivity from a monomer comprising an aromatic compound through chemical oxidative polymerization, which can ease restrictions on the kinds of antioxidants and solvents to be used and can produce a polymer with improved conductivity as compared with the prior art methods. CONSTITUTION:In manufacturing a highly conductive organic polymer by the chemical oxidative polymerization of a monomer comprising a five- or six- membered ring aromatic compound containing nitrogen, oxygen, sulfur or selemium atom(s) as heteroatom(s) in a solution, a mixture of at least two solvents are used to control the oxidation potential of the polymerization solution and to effect the chemical oxidative polymerization of the aromatic compound.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method for producing a highly conductive organic polymer.

[0002]

2. Description of the Related Art As a method for producing a conductive organic polymer, an electrolytic oxidative polymerization method and a chemical oxidative polymerization method are known, and each method has advantages and disadvantages. 63-55659). The inventors of the present invention have studied the method of enhancing the conductivity of a conductive polymer and the method of processing the chemical oxidation polymerization method, which is particularly efficient in productivity (Japanese Patent Application No. 63-55659, Japanese Patent Application No. 63-55659). Japanese Patent Application No. 63-85706, Japanese Patent Application No. 63-175969). Japanese Patent Application Sho 63-556
As described in No. 59, in the chemical oxidative polymerization reaction in a solution, the initial oxidation potential is determined by the kind of oxidant, its concentration,
Alternatively, it is possible to dramatically increase the conductivity of the produced polymer by adding a reductant corresponding to the oxidant and controlling it to a constant value depending on the type of solvent. However, the range of the oxidation potential that can be controlled by the type of solvent and the concentration of the oxidizing agent is narrow, and the selectability of the type of oxidizing agent and the type of solvent that can be used is limited.

[0003]

SUMMARY OF THE INVENTION The present inventors have made an aromatic compound, particularly an aromatic compound containing a heteroatom such as nitrogen, oxygen, sulfur and selenium, a monomer, and have a high conductivity by a chemical oxidative polymerization method. As a result of diligent research to obtain an organic polymer, the use of an appropriate mixed solvent as the oxidative polymerization solvent makes it easier to control the oxidation potential, and the oxidant and solvent species are restricted as compared with the conventional method. Relaxed,
And found that the conductivity of the resulting polymer is improved,
The present invention has been completed. The monomers used in the present invention are selected from 5- and 6-membered aromatic compounds containing nitrogen, oxygen, sulfur or selenium as heteroatoms.
As an example of such a compound, a pyrrole derivative, a furan derivative, a thiophene derivative or a selenophene derivative can be cited as the 5-membered heterocyclic compound. Suitable compounds as pyrrole derivatives are unsubstituted pyrrole, N-substituted pyrrole such as N-alkylpyrrole, or the 3-position or 3,4.
Position an alkyl group C ₁ -C _6, 3-alkyl-pyrrole having an alkoxy group or a halogen atom, 3,4-dialkyl pyrrole, 3-alkoxy-pyrrole, 3,4-dialkoxy-pyrrole, 3-chloro-pyrrole and 3, 4-dichloropyrrole and the like can be mentioned. The furan derivative, the thiophene derivative and the selenophene derivative include unsubstituted furan, unsubstituted thiophene, unsubstituted selenophene and 3-alkyl having a C _{1 to} C ₆ alkyl group, an alkoxy group or a halogen atom at the 3rd or 3rd and 4th positions. Furan, 3,4-dialkylfuran, 3-alkoxyfuran, 3,4-dialkoxyfuran, 3-chlorofuran, 3,4-dichlorofuran, etc., or
3-alkylthiophene, 3,4-dialkylthiophene, 3-
Alkoxythiophene, 3,4-dialkoxythiophene,
3-chlorothiophene, 3,4-dichlorothiophene, etc., and further 3-alkylselenophene, 3,4-dialkylselenophene, 3-alkoxyselenophene, 3,4-dialkoxyselenophene, 3-chloroselenophene, 3 1,4-dichloroselenophene and the like can be mentioned. Further, examples of the 6-membered aromatic compound include aniline, toluidine, chloroaniline, benzidine and the like.

Examples of the oxidizing agent include iron (III) salt, molybdenum (V) salt and ruthenium (III) salt for pyrrole, furan, thiophene and selenophene. Examples of the aniline oxidizing agent include chromic acid (IV) salts, dichromic acid (VII) salts, permanganic acid (VII) salts and the like. On the other hand, in the present invention, the control of the oxidation potential becomes very easy, and therefore the range of the oxidizing agent suitable for use is not limited to the above range.

When the monomer is pyrrole, the above-mentioned ferric chloride, ferric bromide, ferric iodide, ferric perchlorate and other iron (III) salts, ruthenium trichloride are used as oxidants. , Ruthenium tribromide, ruthenium triiodide, ruthenium triperchlorate, etc. or molybdenum pentachloride, molybdenum (V) salts such as molybdenum pentabromide, other aluminum chloride, aluminum chloride / second chloride Examples thereof include inorganic halogen salts such as copper and titanium tetrachloride, and protic acids such as hydrochloric acid, sulfuric acid, hydrofluoric acid, perchloric acid, trichloroacetic acid, trifluoroacetic acid and phosphoric acid. Of these, iron (III) salts, particularly ferric chloride, are preferably used from the viewpoints of economy and ease of handling. Stoichiometrically, a quantitative polymerization reaction occurs when 2 mol or more of ferric chloride is used with respect to 1 mol of the monomer.

The solvent used in the polymerization reaction must be one that is not subject to the oxidation reaction by the oxidizing agent, and the selection is important because the potential of the oxidizing agent depends on the type of the solvent used. When the monomer is pyrrole and the oxidant is ferric chloride, a single solvent such as methanol gives an appropriate oxidation potential to pyrrole (for example, in the case of ferric chloride / methanol, 600 mV (vs SCE) a2.5M, 560mV
(vs. SCE) a1M), the resulting polymer shows high conductivity,
At this time, it is necessary to adjust the oxidation potential to an appropriate value by adding the concentration of the oxidizing agent or the addition of ferrous chloride, which is a reductant thereof. Considering the solubility of the oxidant or its reductant and the preferable concentration of the monomer, it is not easy to create the conditions where the oxidation potential is at an appropriate value in a single solvent system, and the types of solvents that can be used are quite limited. . When acetonitrile is used as a solvent for ferric chloride, its oxidation potential is around 1300 mV (vs. SCE), which is an unsuitable solvent in a single solvent system. However, according to the present invention, the second solvent can be further added to this solution to change the oxidation potential of the solution to realize an appropriate oxidation potential and obtain a highly conductive polymer. The oxidation potential of the solution decreases when a first solvent, that is, a solvent having a higher coordination ability for Fe ³⁺ than acetonitrile is added, and conversely, when a solvent having a lower coordination ability is added, the oxidation potential increases.
For example, when 1 M ferric chloride is dissolved in acetonitrile, its oxidation potential is 1360 mV (vs. SCE). The oxidation potential measured here shows the average value in the mixed solvent system, is different from the local effective oxidation potential in the oxidation reaction, and the difference between the two oxidation potentials is different from that of the oxidizing agents of both kinds of solvents. It depends on the interaction difference, ie the combination of solvents. Therefore, the oxidation potential suitable for obtaining a highly conductive polymer seems to be different for each combination of solvents in the mixed solvent system. For example, in a single solvent system, a polymer showing high conductivity is obtained at an oxidation potential of about 500 mV (vs. SCE), but in an acetonitrile / methanol mixed solvent system, it is 95%.
Maximum conductivity is obtained at 0 mV (vs. SCE). Therefore, it is necessary to determine the optimum oxidation potential for each combination of solvents, and the method according to the present invention slightly complicates the adjustment of the optimum conditions. There are advantages that the restrictions on the concentration of the above-mentioned and the concentration of the monomer are alleviated, and the conductivity of the obtained product is improved as compared with the conventional method.

The first solvent described above is selected from those which dissolve a monomer and an oxidizing agent when mixed with a second solvent in addition to being less susceptible to an oxidation reaction, and other than acetonitrile, water, methanol, Ethanol, propanols, butanols, pentanol, hexanol,
Octanol, aliphatic alcohols such as ethylene glycol, ethers such as diethyl ether and dibutyl ether, halogenated hydrocarbons such as chloroform, dichloromethane, 1,1-dichloroethane and 1,1-dichloroethylene,
Benzene, aromatic compounds such as 4-chloropyridine and its derivatives, N, N-dimethylformamide, N, N-dimethylacetamide and other aprotic polar solvents, methyl acetate, esterified products such as ethyl acetate, nitromethane, nitroethane, Nitro compounds such as nitrobenzene can be mentioned. The requirements for the second solvent described above are the same as for the first solvent. Further, if necessary, third and fourth solvents can be added.

The polymer obtained by the above-mentioned chemical oxidation method is generally brown to black powder, which can be put to practical use after being washed and dried and then molded by a compression molding method or the like. The electrical conductivity of the molded product is from several tens to over 300 S / cm. Further, depending on the purpose, the present polymer may be used as a composite with another type of polymer by blending.

Further, according to the present invention, after the polypyrrole is chemically or electrochemically reduced and dedoped,
The conductivity of the polypyrrole can be further increased by performing the oxidation and the doping by chemical oxidation or electrolytic oxidation. Examples of the reducing agent used for the chemical reduction include hydrazines such as hydrazine, hydrazine hydrate, and phenylhydrazine; pyridines such as pyridine and chloropyridine; and metal hydrides such as lithium aluminum hydride and sodium borohydride. it can. The chemical reducing agent is usually used in a molar amount of 1 to 10 times the nitrogen atom of the polymer, but is not necessarily limited thereto. The reduction reaction may be carried out in the temperature range of −50 to 100 ° C. for several tens of minutes to several hours, but it is usually sufficient to carry out the reaction at room temperature for about 1 hour.

In electrolytic reduction, neutral polypyrrole which is dedoped can be obtained by applying an applied voltage having a polarity opposite to that of ordinary electrolytic polymerization. The higher the applied voltage is, the faster the dedoping is performed. Usually, 0.01 to -2.0 V (vs. SCE) is preferable.

After reduction, the neutral polypyrrole is again chemically reoxidized with an oxidizing agent and doped. As the dopant used for such re-doping, any compound having an oxidizing power sufficient for re-oxidizing a reduced neutral polymer and having an electron accepting property effective as a dopant can be used.

Examples of such oxidizing agents include halogens such as iodine, bromine and chlorine, arsenic pentafluoride, antimony pentafluoride, boron trifluoride, boron trichloride, ferric chloride, stannic chloride and tetrachloride. Lewis acid of titanium chloride, zinc chloride, cupric chloride, hydrochloric acid, sulfuric acid and salts thereof (eg potassium hydrogen sulfate, sodium hydrogen sulfate etc.), perchloric acid and salts thereof (eg lithium perchlorate, sodium perchlorate, Potassium perchlorate, iron perchlorate, etc.) or borofluoric acid and its salts (eg sodium borofluoride,
Examples thereof include potassium boron fluoride, ammonium boron fluoride, tetraalkylammonium fluoride boron, trichloroacetic acid, trifluoroacetic acid, and the like.
It should not necessarily be limited to these.

It is also possible to carry out oxidation and doping again electrochemically. In this case, the above-mentioned oxidizing agent may be used as a supporting electrolyte, and an applied voltage having the same polarity as in ordinary electrolytic polymerization may be applied.

[0014]

The highly conductive polymer obtained by the present invention is molded by compression molding or the like to be used as a conductive structural component or as a conductive thermoplastic resin by adding it to another resin, an electromagnetic shielding material, etc. Can be used for.

[0015]

EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to the scope of these examples.

Example 1 Ferric chloride acid dissolved in acetonitrile / methanol
Chemical potential A mixed solvent is prepared by changing the component volume ratio of acetonitrile (manufactured by Tokyo Kasei) and methanol (manufactured by Tokyo Kasei). Ferric chloride (anhydrous, manufactured by Tokyo Kasei) is added to this solvent so as to have a concentration of 1 M, and after stirring well, 1 dm ³ of the solution is placed in a beaker. A platinum plate (3 mm × 3 mm) and a salt bridge connected to a saturated calomel electrode were inserted into this solution to serve as working or reference electrodes, and the potential of each solution was measured at room temperature with stirring. Fig. 1 shows the measurement results of the oxidation potential for each solution composition. The oxidation potential of 1360 mV (vs. SCE) for acetonitrile alone decreased with the increase of the amount of methanol, and 560 mV (vs. SCE) for methanol alone. ). Synthesis of Polypyrrole The solution whose oxidation potential was measured in Example 1 is cooled to 0 ° C. A solution prepared by dissolving 0.1 mol (6.7 g) of pyrrole, which was purified by vacuum distillation and stored in the dark under a nitrogen atmosphere, in each of the above acetonitrile / methanol mixed solvents (5 times the volume of pyrrole) was added to the above oxidation. It was added to the agent solution with stirring. At this time, the oxidation potential was also measured at the same time.
The produced polymer was precipitated as a brown to black powder. After 20 minutes, the polymerization reaction was stopped by filtering the produced polymer, and then washing with methanol was repeated until the filtrate became transparent. The obtained polypyrrole was vacuum dried at room temperature for 24 hours. The polypyrrole powder was press-molded into a disk shape (diameter 10 mm × thickness 2 mm) at a pressure of 400 kg / cm ² , and its conductivity (direct current) was measured at 20 ° C. by the four-terminal method. FIG. 2 shows the relationship between the initial oxidation potential of the polymerization reaction and the conductivity of the obtained polypyrrole in each composition of methanol / acetonitrile. The conductivity of the produced polymer changes with the initial oxidation potential, and at 950 mV (vs. SCE), the highest conductivity 326 S /
cm was obtained. This value is 10 compared with the conventional method shown in Comparative Example 1.
It exceeds 0 S / cm.

Comparative Example 1 According to Example 1 of Japanese Patent Application No. 63-55659, the oxidizing potential of the solution was controlled by adding the reductant to the solution of the oxidizing agent. Ferric chloride 3.5M methanol solution 1dm ³ (liquid temperature 0
C.), a predetermined amount of ferrous chloride is added. A solution of 0.1 mol (6.7 g) of pyrrole in 5 volumes of methanol was added to this solution with stirring. At this time, the oxidation potential of the reaction solution was measured by the method described in Example 1. After 20 minutes, the reaction was stopped in the same manner as in Example 1, and after washing, drying and molding, the conductivity of the molded product was measured. The results are shown in FIG. 3. The oxidation potential of the polymerization reaction liquid changed with the addition of ferrous chloride, and the conductivity of the produced polymer also changed. At the initial oxidation potential of 500 mV (vs. SCE),
The highest conductivity of 200 S / cm was obtained.

Comparative Example 2 The same oxidation potential control as in Comparative Example 1 was tried in an acetonitrile solvent, but the control of the oxidation potential was unsuccessful because ferrous chloride was insoluble in acetonitrile.

Comparative Example 3 According to Example 1 of Japanese Patent Application No. 63-55659, the polymerization reaction was carried out while controlling the oxidation potential by changing the solvent for the polymerization reaction. Add 2.5 M ferric chloride to various solvents and cool to 0 ° C. A solution prepared by dissolving 0.1 mol (6.7 g) of pyrrole in 5 times the volume of each solvent was added to this solution with stirring. At this time, the oxidation potential of the reaction solution was measured by the method described in Example 1. After 20 minutes, the reaction was stopped in the same manner as in Example 1, washed with a reaction solvent, dried and molded, and the conductivity of the molded product was measured. The results are shown in FIG. 3. The oxidation potential of the polymerization reaction liquid changed with the addition of ferrous chloride, and the conductivity of the produced polymer also changed.
The initial oxidation potential changed, and the conductivity of the produced polymer also changed. The highest conductivity of 200 S / cm was obtained at the initial oxidation potential of 530 mV (vs. SCE).

Example 2 1.0 g of the polypyrrole powder obtained in Example 1 was added to a solution of 2.0 g of phenylhydrazine in 50 ml of diethyl ether solution, and the mixture was stirred at room temperature and reacted for about 1 hour. After completion of the reaction, the reduced polypyrrole was filtered off, washed thoroughly with ether, and dried in vacuum. This pyrrole was exposed to iodine vapor at room temperature all day and night for oxidative doping. The re-doped polypyrrole was press-molded in the same manner as in Example 1 and the conductivity was measured.
A value of 610 S / cm was shown, and an increase in conductivity due to re-doping was observed.

[Brief description of drawings]

FIG. 1 is a graph showing the relationship between each solution composition and the oxidation potential of a solution prepared by dissolving ferric chloride in a mixed solvent of acetonitrile and methanol in Example 1.

FIG. 2 is a graph showing the relationship between the initial oxidation potential of a polymerization reaction and the conductivity of the obtained polypyrrole when polypyrrole is synthesized using acetonitrile and methanol in Example 1.

FIG. 3 is a graph showing the relationship between the oxidation potential and the conductivity of the obtained polypyrrole when synthesizing the polypyrrole by the methods of Comparative Examples 1 to 3.

Claims (7)

[Claims] 1. When producing a highly conductive organic polymer by chemically oxidatively polymerizing a monomer consisting of a 5-membered or 6-membered aromatic compound containing nitrogen, oxygen, sulfur or selenium as a hetero atom in a solution. A method for producing a highly conductive organic polymer, which comprises controlling the oxidation potential of a polymerization solution by mixing two or more kinds of solvents to carry out chemical oxidative polymerization of an aromatic compound. 2. The method for producing a highly conductive organic polymer according to claim 1, wherein the monomer is pyrrole or a derivative thereof. 3. The method for producing a highly conductive organic polymer according to claim 1, wherein an iron (III) salt is used as the oxidizing agent. 4. The method for producing a highly conductive organic polymer according to claim 3, wherein the oxidizing agent is ferric chloride. 5. The method for producing a highly conductive organic polymer according to claim 1, wherein the solvent for chemical oxidative polymerization contains acetonitrile and methanol. 6. The initial oxidation potential during chemical oxidative polymerization is
The method for producing a highly conductive organic polymer according to claim 5, which is 560 to 1300 mV (vs. SCE). 7. The highly conductive organic polymer obtained by chemical oxidative polymerization is further reduced, and then oxidized and doped with an oxidizing agent effective as an acceptor.
7. The method for producing a highly conductive organic polymer according to any one of 6 above.