JP2525488B2 - Highly conductive polypyrrole molding - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a highly conductive polypyrrole molded article for a conductive organic material.

<Prior Art> Hetero five-membered ring compounds have recently attracted a great deal of attention because they can easily give a conductive polymer film by electrolytic oxidation polymerization. Doping occurs at the same time during electrolytic polymerization to obtain a polymer film having high conductivity. Further, its stability is also good. The amount of dopant in these polymers can be electrochemically adjusted and the conductivity can be controlled in a wide range. Therefore, by utilizing these properties, they are used for various sensors, batteries, electrochromic materials, electronic devices, wiring materials, and the like. Moreover, it is used for a junction device such as a Josephson device because it exhibits metallic properties at extremely low temperatures.

Polypyrrole obtained by electrolytic oxidation polymerization has excellent electrical conductivity and mechanical strength.

However, when used as a conductive material, it cannot be said that the conductivity is still at a sufficient level. First, it was found that the electroconductivity of pyrrole is electropolymerized at a low temperature and the polypyrrole thus obtained is subjected to a stretch orientation treatment to remarkably improve the conductivity.

In general, polypyrrole is a heat-activated type, so that the apparent activation energy of electric conduction, which shows the temperature dependence of its electric conductivity, is positive. That is, the conductivity decreases as the temperature decreases. In this case, for the purpose of obtaining high electric conductivity, it is desirable that the electric conductivity is less reduced in the low temperature region. Alternatively, on the contrary, it is desirable that the electric conductivity increases as the temperature decreases.

<Problems to be Solved by the Invention> The present invention has been made in view of the above circumstances, and an object thereof is to obtain a highly conductive polypyrrole molded article that exhibits excellent properties as a conductive material, and in particular a film. Is.

<Means for Solving the Problems> The present invention comprises polypyrrole obtained by electrolytic polymerization in the presence of PF ₆ ^{− at} a temperature of 0 ° C. or lower and containing PF ₆ ⁻ as a counter ion, and having a temperature of 100 K or lower. It is a highly conductive polypyrrole molded article that is cooled to preferably 50 K or less. Such a molded body is 100 K or less, preferably a highly conductive polypyrrole molded body characterized by having a temperature reversal temperature of conductivity in which temperature dependence of conductivity exhibits a metallic property in a temperature range of 50 K or less, and Such a polypyrrole molded article is also characterized in that the apparent activation energy of electric conduction is 10 meV or less.

Here, the electric conductivity reversal temperature means a temperature at which the electric conductivity that drops with a decrease in temperature rises again.

Hereinafter, specific contents of the present invention will be described in detail. The "film" will be described below as a representative of the "molded body".

The polypyrrole film of the present invention can be obtained by depositing pyrrole and / or a derivative thereof on an anode plate by carrying out potentiostatic electropolymerization in the presence of an electrolyte using an organic solvent containing water as a solvent. According to this method, anions coexisting in the reaction system are taken in as a dopant, so that high conductivity is exhibited without newly doping an electron-accepting compound.

The pyrrole and its derivatives used in the present invention preferably have a high purity, and are preferably purified by distillation before use. As the derivative of pyrrole, a substitution product at the N position of the pyrrole ring, a mono substitution product at the β position of the pyrrole ring,
A β-, γ-position 2-substituted product or the like is used, and specific examples thereof include N-alkylpyrroles such as pyrrole, N-methylpyrrole and N-ethylpyrrole, N-phenylpyrrole, 3-
Examples thereof include 3-alkylpyrrole such as methylpyrrole, and 3,4-dialkylpyrrole such as 3,4-dimethylpyrrole.

The pyrrole or its derivative is used in an amount of 0.0001 mol / liter (M) to 1 M, preferably 0.001 M to 0.5 M, relative to the solvent, to carry out the polymerization.

Examples of the electrolyte to be introduced as a counter ion include a tetraalkylammonium salt of an inorganic acid of hexafluorophosphate, an alkali metal salt, and the like. Specific examples include hexafluorophosphate tetramethylammonium salt, tetraethylammonium salt, tetrapropylammonium salt, tetrabutylammonium salt, and further lithium salt, sodium salt, potassium salt, etc., but are not limited thereto. is not.

The electrolyte is 0.0001M to 1M with respect to the solvent, preferably 0.001M
M-0.5M is used.

As the organic solvent which is a polymerization solvent, acetonitrile,
It is preferable to use a substance such as benzonitrile, nitrobenzene, tetrahydrofuran, nitromethane, propylene carbonate, ethylene carbonate, sulfolane, or dimethoxyethane, which easily dissolves the electrolyte, but is not limited thereto.

The role of water, which is optionally used, enhances the effect of the electrolyte and improves the morphology of polypyrrole deposition. This amount depends on the type of electrolyte used,
The concentration of water in the electrolyte solution is 0.1M to 5M, preferably 0.
3M to 3M.

The anode material used in the reaction may be a general-purpose material as long as it does not cause defects or alteration in the electrode reaction, and is not particularly limited, but may be a metal such as platinum, gold, copper, nickel, or the like. A similar conductive material or carbon electrode is used. In addition, the larger the electrode area of the cathode is than that of the anode, the better the state of deposition of polypyrrole generally produced. The ratio of cathode to anode surface area is 1.
The amount is 1 time or more, preferably 1.5 times or more, more preferably 2 times or more, and particularly preferably 3 times or more.

As the polymerization method, a constant voltage electrolysis method or a constant voltage electrolysis method is used. In the potentiostatic electrolysis method, the polymerization potential is silver / silver chloride (Ag / A
gCl) 0.7 volt or more is used for the reference electrode.
Suitably 0.8 to 1.2 volts are used, particularly preferably 0.9 to 1.1 volts. The constant current electrolysis 0.01mA / cm ² ~3mA /
cm ² is used, preferably 0.05 mA / cm ^{2 to 1} mA / cm ² .

The polymerization temperature is 0 ° C (273K) or lower, and -20 ° C (25K
3K) or less is preferably adopted. However, it must be performed above the melting point of the electrolyte.

The polymerization reaction time is appropriately selected from the relationship between the amount of electricity supplied and the time of electricity application in order to produce a film having a desired film thickness.

<Effects of the Invention> The highly conductive polypyrrole molded article that has been cooled to 100 K or less of the present invention exhibits an electric conductivity reversal temperature of 100 K or less, and therefore has excellent performance of maintaining high conductivity in a wide temperature range. Have. Therefore, it can be used particularly in a low temperature range and can be used for various purposes.

<Examples> Hereinafter, the present invention will be described in detail with reference to Examples. However, the present invention is not limited to this. The electric conductivity was measured by a four-terminal method using a silver paste.

[Example 1, Comparative Examples 1 to 4] 400 ml of freshly distilled propylene carbonate using a glass-like carbon plate (GC-20 manufactured by Tokai Carbon Co., Ltd.) whose surface was polished as an anode and a platinum foil as a cathode in a 500 ml separable flask. Then, a mixed solution of 4 ml of water and 5.26 g (0.024 mol) of tetramethylammonium hexafluorophosphate (Example 1) were added, and nitrogen gas was introduced to perform deoxidation. Thereafter, 1.61 g (0.024 mol) of pyrrole was added.
Cooled to -30 ℃, under nitrogen stream, 1.0V against Ag / AgCl electrode
Electrolytic oxidative polymerization was carried out for 24 hours (electricity of 420 clones). The 30 μm film formed after the completion of the polymerization was peeled from the anode plate, washed with acetonitrile and dried.

Then, 6.70 g of tetraethylammonium trifluoromethanesulfonate instead of the electrolyte of the above example
(0.024 mol) (Comparative Example 1), tetraethylammonium perchlorate 5.52 g (0.024 mol) (Comparative Example 2), tetraethylammonium tetrafluoroborate 5.21 g
(0.024 mol) (Comparative Example 3) and tetraethylammonium tosylate (7.22 g, 0.024 mol) (Comparative Example 4) were used, and the polymerization of pyrrole was carried out in the same manner as in the above Examples.

Figure 1 shows the temperature dependence of the electrical conductivity of these polypyrrole films. The electrical conductivity at room temperature and the apparent activation energy (ΔE) of the electrical conductivity by Arrhenius plot at 250K to 200K.
And the temperature at which the electrical conductivity that drops with a decrease in temperature rises again as determined from the temperature dependence of electrical conductivity (conductivity reversal temperature)
Is shown in Table 1.

From FIG. 1 and Table 1, only the polypyrrole of the present invention whose counter ion is hexafluorophosphate is the reversal temperature (20
K) was recognized, and ΔE10 was also shown as a good result.

[Examples 2 to 4 and Comparative Example 5] In Example 1, the polymerization temperature was -40 ° C instead of -30 ° C.
Example 1 except ℃ (233K) (Example 2), -20 ℃ (253K) (Example 3), 0 ℃ (273K) (Example 4), 20 ℃ (293K) (Comparative Example 5) Polymerization of pyrrole was carried out in the same manner as in. The results are shown in Fig. 2 and Table 2.

From FIG. 2 and Table 2, the polymerization temperature of the present invention is −40 ° C. (233 K), −20
In the case of polypyrrole polymerized respectively at ℃ (253K) and 0 ℃ (273K), it was recognized that there was an inversion temperature (20K) of conductivity, and ΔE10meV was also shown.

[Brief description of drawings]

FIG. 1 shows the type of counterion, and FIG. 2 shows the temperature dependence of the electrical conductivity of the polypyrrole film obtained by changing the polymerization temperature.

Claims (1)

(57) [Claims] 1. A polypyrrole obtained by electrolytic polymerization in the presence of PF ₆ ^{− at} a temperature of 0 ° C. or lower and containing PF ₆ ⁻ as a counter ion, and cooled to a temperature of 100 K or lower. Highly conductive polypyrrole molded article.