JPH0437090B2 - - Google Patents

Description

[Detailed description of the invention]

<Industrial application field> In 1977, MacDiarmid of the University of Pennsylvania,
Conductive polymers have attracted worldwide attention since Shirakawa et al. discovered that when polyacetylene was exposed to electron-accepting compounds such as iodine and AsF ₅ , it developed high conductivity comparable to that of metals. . These polymers can electrochemically introduce and remove dopants and control the amount, making it possible to control conductivity over a wide range. Therefore, by utilizing these properties, various applications can be considered for various sensors, batteries, electrochromic materials, electronic devices, etc. Thiophene, like pyrrole, is mainly 2,
Although it is said that a polymer is formed by bonding at the 5-position, the possibility of reaction at the 3- or 4-position has also been pointed out. Moreover, since thiophene generally has a higher oxidation potential than pyrrole and the like, polymerization is carried out under harsh conditions. Therefore, intervention for side effects is considered unavoidable. The present inventors have conducted extensive studies to obtain a thiophene polymer that has excellent reaction regioselectivity in polymerization, good regularity, and excellent mechanical properties and electrical conductivity. As a result, 3,4
- By introducing an alkoxy group into dialkoxythiophene, the oxidation potential is lowered, side reactions are suppressed, and the bonding site is limited to the 2,5-position, resulting in disordered regulation due to molecular symmetry. The present inventors have completed the present invention by discovering that the resulting film has high electrical conductivity and excellent mechanical properties, and that the electrical conductivity can be further improved by stretching and orientation treatment. <Structure of the Invention> The present invention is directed to a 3,4-dialkoxy group consisting of a repeating unit represented by the following general formula (), which does not completely dissolve in a dipolar aprotic solvent at 25°C in an oxidized state. Thiophene polymer film (However, R ¹ and R ² each independently have 1 to 4 carbon atoms.
represents an alkyl group. ). Hereinafter, specific contents of the present invention will be explained in detail. The 3,4-dialkoxy polymer of the present invention comprises 3,
It is obtained by electrolytically oxidizing and polymerizing 4-dialkoxythiophene using an organic solvent in the presence of an electrolyte, thereby depositing it in the form of a film on an anode plate. Furthermore, according to this method, anions coexisting in the reaction system are taken in as dopants, so high conductivity can be achieved even without doping with an electron-accepting compound. The 3,4-dialkoxythiophene used in the present invention is a compound represented by the following general formula (). (However, R ¹ and R ² each independently have 1 to 4 carbon atoms.
represents an alkyl group. ) The 3,4-dialkoxythiophene used in the present invention is prepared by the method of Fager et al. (Journal of the American Chemical Society, Vol. 67).
2217, 1945), it can be synthesized by the following route (wherein, R is the above-mentioned R ¹ or R ² ). Thiodiglycolic acid diethyl ester can be synthesized by ethyl esterifying thiodiglycolic acid in the presence of a sulfuric acid catalyst. This was condensed with diethyl oxalate by Hinsberg reaction,
The resulting tetrasodium 3,4-dihydroxythiophene-2,5-dicarboxylic acid salt is recrystallized and converted into dialkyl sulfate without purification. By o-alkylating with, hydrolyzing with caustic soda, and precipitating with acid,
Convert to 3,4-dialkoxythiophene-2,5-dicarboxylic acid. Then, the desired 3,4-dialkoxythiophene can be obtained by decarboxylating this dicarboxylic acid in quinoline using Cu-Cr oxide as a catalyst. Cu−Cr
Oxide was determined by the method of Connor et al. (Journal of the American Chemical Society 54)
Vol. 1132, 1932). Specifically, the 3,4-dialkoxythiophene includes 3,4-dimethoxythiophene,
Examples include 3,4-diethoxythiophene, 3,4-dipropylthiophene, and 3,4-dibutoxythiophene. Examples of the electrolyte include tetraalkylammonium salts of inorganic and organic acids, alkali metal salts of inorganic and organic acids, and the like. Specifically, tetraethylammonium perchlorate, tetraethylammonium borofusate, tetramethylammonium hexafluorophosphate, tetramethylammonium hexafluoroarcetate, tetrabutylammonium sulfonate, tetraethylammonium trifluoromethylsulfonate, tetraethylammonium p-toluenesulfonate. , lithium trifluoromethylsulfonate, lithium perchlorate, sodium p-toluenesulfonate, and the like. The organic solvent that is the polymerization catalyst is preferably one that easily dissolves the electrolyte, such as acetonitrile, henzonitrile, nitrobenzene, tetrahydrofuran, nitromethane, propylene carbonate, ethylene carbonate, sulfolane, dimethoxyethane, but is not necessarily limited thereto. The 3,4-dialkoxythiophene is 0.0001 mol/liter to 1 mol/liter based on the solvent,
Preferably, the polymerization is carried out using 0.001 mol/liter to 0.5 mol/liter. Electrolyte is 0.0001 mol/liter to solvent
Polymerization is carried out using 1 mol/liter. Electrolyte is 0.0001 mol/liter to solvent
1 mol/liter, preferably 0.001 mol/liter to 0.5 mol/liter is used. The reaction temperature is -50°C to 100°C. A temperature of -50°C to 50°C is preferably employed. The reaction time is appropriately selected from the relationship between the amount of current and the time of current application in order to produce a film with a desired thickness. Suitable anode materials for electrolytic polymerization include platinum plates,
Glassy carbon plates, palladium plates, etc. are used, but are not limited thereto. 3,4- obtained by electrolytic oxidation polymerization in the present invention
The dialkoxythiophene polymer film is 2,5
Since the reaction proceeds selectively only at the - position, the structure of the resulting polymer has extremely high regularity and excellent mechanical properties. The polymer of the present invention also has extremely high solvent resistance, and does not completely dissolve in dipolar aprotic solvents at 25°C in an oxidized state.
Solvents such as propylene carbonate, acetonitrile, dimethyl sulfoxide, N,N-dimethylformamide, N,N-dimethylacetamide,
Insoluble in N-methyl-2-pyrrolidone, nitromethane, acetone, toluene, and chloroform. A 3,4-dialkoxythiophene polymer film that is oriented in at least one direction can be obtained by carrying out a stretching or orientation treatment using a uniaxial or biaxial stretching machine. As the uniaxial stretching machine, a free end-axial stretching machine and a constant width-axial stretching machine are used, both of which can be automatic or manual. As the biaxial stretching machine, a free end sequential biaxial stretching machine, a constant width sequential biaxial stretching machine, and a simultaneous biaxial stretching machine are used, and all of these machines can be automatic or manual. The 3,4-dialkoxythiophene polymer film has excellent regularity and has high tensile strength itself, but its strength is further improved by stretching and orientation treatment. Moreover, the electrical conductivity is also improved by the stretching and orientation treatment. In the present invention, a tensile strength of 0.5 Kg/mm ² or more is preferably employed regardless of whether or not stretching is performed. Hereinafter, the present invention will be explained in detail with reference to Examples. however,
The present invention is not limited to this. Electrical conductivity was measured by a four-terminal method using silver paste. Example 1 400 ml of freshly distilled propylene carbonate and 8.7 g of tetramethylammonium tetrafluoroborate were placed in a 500 ml separable flask using a platinum plate as an anode and platinum foil as a cathode.
(0.04 mol) was added, and nitrogen gas was introduced to remove oxygen. Then, 3.46 g (0.024 mol) of 3,4-dimethoxythiophene was added. Electrolytic oxidation polymerization was carried out at a current density of 0.25 mA/cm ² for 8 hours while maintaining the temperature at 15° C. under a nitrogen stream. After the polymerization was completed, the resulting 12 μm film was peeled off from the anode plate, washed with acetonitrile, and dried. The conductivity of this material is 50S/cm
The mechanical properties were 0.6 Kg/mm ² .
From the results of elemental analysis, the dopant BF ₄ ^- is 3,
Each 4-dimethoxythiophene unit contained 0.3 units. This material was stretched 1.4 times at 40°C in polypylene carbonate using a manual free end uniaxial stretching machine and then heated to 100°C.
Heat-fixed for 5 minutes. The electrical conductivity of this oriented film was 109 S/cm. As a result of X-ray diffraction, only a halo was observed in the untreated film, but an orientation pattern was observed after the stretching orientation treatment. Example 2 Using a glassy carbon plate as an anode and a platinum foil as a cathode in a 500ml separate flask,
400 ml of freshly distilled propylene carbonate and 9.18 g (0.04 mol) of tetraethylammonium perchlorate were added, and nitrogen gas was introduced to remove oxygen. Then 3,4-dimethoxythiefene 3.46
g (0.024 mol) was added. Electrolytic oxidation polymerization was carried out at a current density of 0.125 mA/cm ² for 24 hours while maintaining the temperature at 15° C. under a nitrogen stream. After the polymerization was completed, a 20 μm film was peeled off from the anode plate, washed with acetonitrile, and dried. The electrical conductivity of this material was 70S/cm, and the mechanical strength was 0.7Kg/ ^mm2 . The elemental analysis results showed that 0.33 dopant perchlorate ions (ClO ₄ ⁻ ) were contained per 3,4-dimethoxythiophene unit. This film was stretched and oriented by 1.2 times in the same manner as in Example 1 to obtain an oriented film with an electrical conductivity of 110 S/cm. Example 3 Using a glassy carbon plate as an anode and a platinum foil as a cathode in a 500ml separable flask,
400 ml of freshly distilled propylene carbonate and 4.09 g (0.02 mol) of tetramethylammonium perchlorate were added, and nitrogen gas was introduced to remove oxygen. Then 1.7g of 3,4-diethoxythiophene
(0.01 mol) was added. Maintained at 15℃ under nitrogen flow.
Electrolytic oxidative polymerization was carried out at a current density of 0.25 mA/cm ² for 8 hours. After the polymerization was completed, a 17 μm film was peeled off from the anode plate, washed with acetonitrile, and dried. The electrical conductivity of this material was 65S/cm, and the mechanical strength was 0.55Kg/ ^mm2 . This film was stretched and oriented by 1.3 times in the same manner as in Example 1 to obtain an oriented film with an electrical conductivity of 89 S/cm. Example 4 The solvent resistance of poly(3,4-dimethoxythiophene) to organic solvents was investigated. The measurements were carried out by immersing CO ₄ ^-doped and dedoped films of poly(3,4-dimethoxythiophene) having structures A and B below in an organic solvent. 60
Table 1 shows the changes after standing for 5 hours at ℃ and after standing for 24 hours at room temperature. It was found that it showed no change in any organic solvent and was extremely stable to organic solvents.

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Claims (1)

[Scope of Claims] 1. Consisting of repeating units represented by the following general (), which do not completely dissolve in a dipolar aprotic solvent at 25°C in an oxidized state,
3,4-dialkoxythiophene polymer film. (However, R ¹ and R ² each independently have 1 to 4 carbon atoms.
represents an alkyl group. 2. The polymer film according to claim 1, which has been subjected to a stretching and orientation treatment in at least one direction. 3. The polymer film according to claim 1 or 2, which has improved conductivity compared to the film before orientation treatment. 4. The polymer film according to any one of claims 1 to 3, having a tensile strength of at least 0.5 Kg/mm ² .