JPS60197729A - Electroconductive organic polymer - Google Patents

Abstract

PURPOSE:An acid-doped electroconductive organic polymer, prepared by subjecting aniline containing a protonic acid to electrolytic oxidative polymerization in an aqueous medium under specified conditions. CONSTITUTION:An acid-doped electroconductive organic polymer having an electric conductivity >=10<-6>S/cm and showing excellent moldability. This polymer is formed by subjecting an aniline solution containing a protonic acid in an amount at least equivalent to that of aniline to electrolytic oxidative polymerization at an electrolytic potential which is by at least 1V higher than the standard calomel electrode potential (current density of about 0.01-1A/cm<2>).

Description

[Detailed description of the invention] The present invention relates to a conductive organic polymer and a method for producing the same.

Most organic materials are electrically insulating, however, a group of organic polymers with electrical conductivity known as organic semiconductors have received attention in recent years. Organic materials that are themselves electrically conductive are generally classified into three types. The first is graphite. Although graphite is not strictly considered an organic material, it can be considered to have the ultimate structure of an organic conjugated system. Graphite itself already has fairly high conductivity, but by intercalating it with various compounds, it can be made to have even higher conductivity, eventually becoming a superconductor. However, graphite has a strong two-dimensionality and is difficult to mold, which poses an obstacle in its application.

The second type is a charge transfer complex.For example, a crystalline material obtained using tetrathiafulvalene and tetracyanoquinodimethane as an electron donor and an electron acceptor, respectively, has a very large electrical conductivity of 400 to 500 S/am at room temperature. However, since such charge transfer complexes are not polymers, they have the same difficulty in moldability as graphite for practical application.

The third type is a π-electron conjugated organic polymer that becomes highly conductive through doping, as typified by polyacetylene. The conductivity of -5 polyacetylene before doping is 10=937 cm for the trans type and 103/cm for the cis type, and has properties close to that of a semiconductor or an insulator. However, such polyacetylene contains arsenic pentafluoride, iodine, sulfur dioxide,
By doping with an electron-accepting compound such as ferric chloride or an electron-donating compound such as an alkali metal, a p-type semiconductor and an n-type semiconductor can be formed, respectively. It can also provide high conductivity on the level of a metal conductor. The above-mentioned polyacetylene is theoretically an interesting conductive organic polymer, but on the other hand, polyacetylene is extremely susceptible to oxidation and is easily oxidized and deteriorated in the air, causing its properties to change significantly. In the doped state, it is more sensitive to oxidation, and even a small amount of moisture in the air causes a sharp decrease in conductivity. This tendency is particularly remarkable for n-type semiconductors.

In addition, poly(p-phenylene) and poly(p-phenylene sulfide) have conductivities of 10S/cI11 and lOS/cIII, respectively, before doping.
However, by doping with the aforementioned arsenic pentafluoride, the conductivity can be increased to 500S/K and Is, respectively.
/cm. The electrical properties of these doped organic polymers are also unstable to varying degrees.

The electrical properties of such doped conductive organic polymers are generally very unstable to the environment.
This phenomenon is common to this type of conductive organic polymers, and is an obstacle to their practical application.

As described above, various organic conductive substances have been known so far, but from the viewpoint of developing practical applications, polymer forms with excellent moldability are preferred.

On the other hand, research on oxidized polymers of aniline as oxidized dyes has been conducted for a long time in connection with aniline black. In particular, as an intermediate for the production of aniline black,
The aniline octamer represented by formula (1) has been confirmed as emeraldine (A
, G., Green et al., +J.

Che+s, Soc, 97.2388 (1910
) S issue 1, 1117 (1912) ), this is 8
Soluble in 0% acetic acid, cold pyridine and N,N-dimethylformamide. Furthermore, this emeraldine is oxidized in an ammoniacal medium to produce nigraniline represented by formula (II), which is also known to have dissolution properties similar to those of emeraldine.

Furthermore, in recent years, it has been discovered by R. Buvet et al. that this sulfate of emeraldine has high conductivity (J. Polymer Sci, C.
+ 16+2931; 2943 (1967);
22.11B? (1969)).

It is also already known that an organic substance similar to emeraldine can be obtained by electrolytic oxidation of aniline (
D., M., Mohilner et al., J.
Amer.

Chew, Soc, 84.3618 (1962
)) According to this, an aqueous solution of aniline in sulfuric acid is prepared using a platinum electrode, and in order to avoid electrolysis of water, +〇, with respect to a standard calomel electrode (hereinafter referred to as SCE).
Electrolytic oxidative polymerization at an oxidation potential of 8 V yields a material that is 80% soluble in acetic acid, pyridine and N,N-dimethylformamide.

In addition, Dfaz et al. (J, Electroanal,
Cheta, + l1l (1980)'), Koyama et al. (Proceedings of the Society of Polymer Science and Technology, Utsubo, (71°1524
1)) also attempted electrolytic polymerization of aniline, but both aimed at polymer-coated chemically modified electrodes, and electrolysis was performed at a potential of 1 V or less relative to SCH.

The present inventors have conducted intensive research on electrolytic oxidation polymerization of aniline in order to obtain stable and highly conductive organic materials, especially conductive organic polymers.
By electrolytically oxidizing and polymerizing aniline at a predetermined current density and an electrolytic potential higher than 1 V, new emeraldine is produced, which has a higher molecular weight than emeraldine and has already been doped at the oxidative polymerization stage. The present invention was achieved by discovering that it is possible to obtain a stable and highly conductive polymer without requiring a doping operation.

The conductive organic polymer according to the present invention is prepared by applying an aniline solution containing aniline and a protic acid in an amount equivalent to or more than aniline to a standard calomel electrode at a current density of 0.01 mA/- to IA at an electrolytic potential higher than +IV. A polymer obtained by electrolytic oxidation polymerization at /-, doped with the above acid, and characterized by having an electrical conductivity of IO8/c+n or more.

The protonic acid used in the present invention is preferably a protonic acid whose oxidation potential is higher than the oxidation potential in the present invention, and therefore, specifically, hydrochloric acid, hydrobromic acid, sulfuric acid, nitric acid, per-IM acid, Tetrafluoroboric acid (HBF4
), in order to obtain a hexafluoroelectrically conductive organic polymer, the above-mentioned protonic acid should be used in an amount equal to or more than the equivalent of aniline, usually 1 to
It is necessary to use a 5-fold range and to electrolytically oxidize the aniline solution at an electrolytic potential higher than +1 V relative to a standard calomel electrode. When the oxidation electrolytic potential is below +1V or when the current density is outside the above range,
This is because the resulting polymer has a low molecular weight and low conductivity.

Further, it is desirable that the aniline concentration in the aniline solution is 1% by weight or more. Even when the aniline concentration is less than 1 weight, the resulting polymer has a low molecular weight,
It also has low conductivity. However, the upper limit of the aniline concentration is not particularly limited, but is usually up to 50% by weight.

The solvent is preferably a solvent that can dissolve both the protonic acid and aniline and whose decomposition potential is stable at the oxidation potential during electrolytic oxidative polymerization of aniline. Group lower alcohols, nitriles such as acetonitrile and benzonitrile, ketones such as methyl ethyl ketone, N, N-
Amides such as dimethylformamide are preferably used.

The decomposition potential of water is 1.23 V, which is higher than the electrolytic oxidation potential in the present invention in some cases, but in the present invention, even when water is used as a solvent, the oxidation electrolytic potential of aniline is set to be higher than +1 V. By increasing the molecular weight, an aniline oxidized polymer having a high molecular weight and high conductivity can be obtained.

That is, the oxidation potential of aniline can be determined by a so-called cyclic portammogram in which the potential is scanned at a constant speed and the current value at each potential is plotted, but as shown in Figure 4, the oxidation potential for scE is approximately Near 1v,
Approximately 2v and 3v are observed. These oxidation potentials correspond to the oxidizing power of chemical oxidants; at each oxidation potential, polymers at that oxidation potential are preferentially produced, and in the middle of each oxidation potential, polymers at each oxidation potential are competitively produced. to be generated.

As explained earlier, Mohilner et al. carried out electrolytic oxidation of aniline at an oxidation potential of +8 V relative to SCE in order to avoid electrolysis of water. Electrolytic potential higher than , preferably 2~
By performing electrolytic oxidation at an electrolytic potential of IOV, it is possible to obtain an aniline polymer with a molecular weight much higher than that of emeraldine and a high conductivity.

In the present invention, the current density in electrolytic oxidation is also important. When the current density is less than 0.01 mA/-, the obtained polymer is dissolved in concentrated sulfuric acid, so it is considered to be a low molecular weight polymer, and such a polymer also has low conductivity.

In the present invention, the aniline solution may contain a supporting electrolyte other than the above-mentioned protonic acid.

Specific examples include perchlorate metal salts such as lithium perchlorate and sodium perchlorate, and organic salts such as tetrabutylammonium perchlorate. In addition to the above, salts such as nitrates, sulfates, hydrochlorides, tetrafluoroborates, hexafluorophosphates, etc. can also be used as supporting electrolytes.

The conductive organic polymer according to the present invention usually exhibits a green to black edge color in a dry powder state, and generally, the higher the conductivity, the brighter the green color.

However, pressure-molded products usually exhibit a shiny blue color. Further, the polymer according to the present invention has already been doped with the protic acid used in the electrolytic oxidation polymerization stage, and its electrical conductivity is usually 103/el1 or more, and in most cases 10-3
It is in the range of ~103101.

The conductive organic polymer according to the present invention includes those soluble in concentrated sulfuric acid as long as the conductivity is within the above range, but particularly high conductivity with a conductivity of 10-3'S/cs or more. The polymers according to the invention having . As mentioned above, such a polymer contains emeraldine containing 80% acetic acid,
In sharp contrast to its solubility in cold pyridine and N,N-dimethylformamide, it is indicative of a high molecular weight polymer. Furthermore, polymers that are insoluble in concentrated sulfuric acid are
Differential thermal analysis results also indicate that it is a high molecular weight polymer.

Although the structure of the polymer according to the present invention has not yet been determined,
While the infrared absorption spectrum is similar to that of emeraldine, W4 has a high molecular weight and high conductivity, so it has a substantially linear polymer chain in which aniline continuously forms a polymer chain with head-to-tail bonds, as shown in the following formula. It appears to be a π-electron conjugated polymer.

Although the polymer according to the present invention has high electrical conductivity, the electrical conductivity is significantly reduced by compensating with ammonia, and almost the original high electrical conductivity is recovered by doping with hydrochloric acid again. It is confirmed that the material is doped with protonic acid at this stage. Also,
The infrared absorption spectrum of the polymer obtained by doping the polymer again with hydrochloric acid after compensating it with ammonia is substantially the same as that of the polymer before compensation with ammonia, indicating that the polymer according to the present invention is doped with protonic acid. It is confirmed that Furthermore, due to the fact that the polymer according to the invention is thus compensated with ammonia and the sign of the thermoelectromotive force, this polymer is p-type.

As described above, the conductive organic polymer obtained by the oxidative polymerization of aniline according to the present invention has already been doped with protonic acid during the polymerization stage, and therefore has high conductivity without the need for a new doping treatment. Furthermore, even if left in the air for a long period of time, its conductivity does not change at all, making it uniquely stable compared to conventionally known doped conductive organic polymers. It has a sexual nature.

The present invention will be explained below with reference to Examples, but the present invention is not limited to these Examples in any way.

Example 1 (Experiment No. 1) (1) Production of polymer An anode and a cathode made of platinum were inserted into an aqueous solution in which the aniline concentration was 10 fi% and contained an equivalent amount of hydrochloric acid to aniline, and initial electrolysis for SCH was performed. Potential +1.8v,
Electrolytic oxidation polymerization was carried out by applying current at a constant current density of 5 mA/- for 8 hours. It is well known that when electrolytic polymerization is carried out at a constant current density, the electrolytic potential gradually increases, and therefore the electrolytic potential is usually expressed as the initial potential as shown above. .

The aniline polymer produced on the anode in the above reaction was peeled off and pulverized, washed with stirring in distilled water, filtered, and then the filtered polymer was washed with acetone. The filtered polymer was vacuum dried over phosphorus pentoxide at room temperature for 10 hours to obtain a conductive organic polymer according to the present invention as a green powder.

(2) Evaluation of physical properties The obtained polymer was insoluble not only in concentrated sulfuric acid but also in N-methyl-2-pyrrolidone.

Next, FIG. 1 shows the infrared absorption spectrum of the polymer obtained above. For comparison, the infrared absorption spectra of Emeraldine and commercially available Diamond Black are shown in Figures 2 and 3, respectively. In addition, Emeraldine beam 0M,
Prepared by the method of Mohilner et al. (Do
M., Mohilner at al., J.

Aa+, Cheap, Soc, , 84. 3618 (
1962).

In addition, emeraldine and diamond black 30
It is understood that the logarithmic viscosities of concentrated sulfuric acid solutions at a concentration of 0.5 g/di at °C are 0.02 and 0.005, respectively, which are of low molecular weight.

Furthermore, FIG. 4 shows a cyclic portammogram in electrolytic oxidation of aniline.

Furthermore, the results of thermogravimetric analysis in air of the above polymer according to the present invention and emeraldine are shown in FIG. The temperature increase rate is 10°C/min.

Next, 120 μg of the polymer powder obtained above was crushed in a 1 gll mortar, and then used in an infrared spectrophotometer tablet molding machine under a pressure of 6 mm.
000 kg/- to form a disk with a diameter of 13 cranes. Glue four pieces of copper foil with a width of about 1fi to the four corners of the disc with silver paste or graphite paste, and heat it with a fan in the air.
As a result of measurement according to the Del Bou method, the conductivity was 4. IS
/cs+. Even when measured in a vacuum of 120 Torr, they showed almost the same conductivity. This disk was left in the air for 4 months,
The conductivity remained virtually unchanged.

In addition, the above polymer according to the present invention (electrical conductivity 6.6S/cm
) with ammonia compensation (conductivity 3.3×1O-9
The infrared absorption spectrum of S/c11) is shown in Figure 6,
This was doped again with 5N hydrochloric acid (conductivity 0.15
The infrared absorption spectrum after S/e1m) is shown in FIG. The spectrum after this redoping is found to be substantially the same as the original shown in FIG. 1, and furthermore, the conductivity is also approximately the same as before ammonia compensation. This shows that the polymer according to the invention is already doped by the protic acid used in its oxidative polymerization stage.

Example 2 (Experiment numbers 2 to 7) Example 1 except that the protonic acid in Example 1 was replaced with hydrochloric acid and the acid shown in the table was used in an equivalent amount to aniline.
Aniline was electrolytically oxidized in the same manner as above. The electrical conductivity of these polymers is shown in the table. Moreover, both polymers were insoluble in both concentrated sulfuric acid and N-methyl-2-pyrrolidone.

Example 3 (Experiment Nos. 8 and 9) Experiments according to the present invention were carried out in the same manner as in Example 1, except that the aniline concentration in the aniline solution was changed and, accordingly, hydrochloric acid was used in an equivalent amount to aniline. A conductive organic polymer was obtained. The electrical conductivity of the polymer is shown in the table. These polymers were also insoluble in concentrated sulfuric acid and N-methyl-2-pyrrolidone.

Comparative Example 1 (Experiment No. 12 and 13) For comparison, the aniline concentration in the aniline solution was set to 0.
．． Example 1 except that the aqueous solution containing hydrochloric acid or sulfuric acid at a concentration of 1 mol/l as the acid was used.
Electrolytic oxidation was carried out in the same manner. The electrical conductivity of the obtained polymer is shown in the table. Additionally, these polymers can be dissolved in concentrated sulfuric acid and N-
It was partially dissolved in methyl-2-pyrrolidone.

Example 4 (Experiment Nos. 14 to 16) Example 1 The aniline solution having the composition of Experiment No. 1 was subjected to electrolytic oxidation with the initial electrolytic potential set to the value shown in the table. The resulting polymer was insoluble in concentrated sulfuric acid and N-methyl-2-pyrrolidone.

Furthermore, the electrical conductivity of the polymer is shown in the table.

Comparative Example 2 (Experiment No. 17) Similarly to Example 3, electrolytic oxidation was performed on the aniline solution having the composition of Example 1 with the initial electrolytic potential set to +IV with respect to SCE. The results are shown in the table.

Furthermore, the obtained polymer was soluble in both concentrated sulfuric acid and N-methyl-2-pyrrolidone.

Example 5 (Experiment Nos. 18 to 21) Electrolytic oxidation was performed in the same manner as in Example 1, except that the aniline concentration was changed and the solvent used was replaced with the organic solvent shown in the table.

The electrical conductivity of these polymers is shown in the table. Moreover, both polymers are concentrated sulfuric acid and N-methyl-2-pyrroli.

It was insoluble in tons.

Example 6 (Experiment No. 22) An aniline solution having an aniline concentration of 10% by weight, containing hydrochloric acid in an equivalent amount to aniline, and additionally containing 0.5% by weight of tetrabutylammonium perchlorate as a supporting electrolyte. is the initial electrolytic potential with respect to SCE +1.7■,
Electrolytic oxidation polymerization was carried out by applying current at a constant current density of 11.1 mA/- for 30 hours. The aniline polymer formed on the anode was peeled off and treated in the same manner as in Example 1 to obtain a conductive polymer. This polymer had an electrical conductivity of 4.43/ell and was insoluble in both concentrated sulfuric acid and N-methyl-2-pyrrolidone.

Example 7 (Experiment Nos. 23 to 26) An aniline solution having an aniline concentration of 25% by weight and containing an equivalent amount of hydrochloric acid to aniline was electrolytically oxidized by passing current at the constant current density shown in the table. The electrical conductivity of the obtained polymer is shown in the table. Moreover, both polymers were insoluble in both concentrated sulfuric acid and N-methyl-2-pyrrolidone.

[Brief explanation of drawings]

Figure 1 is the infrared absorption spectrum of the conductive organic polymer according to the present invention, Figures 2 and 3 are the infrared absorption spectra of emeraldine and aniline black, respectively.
The figure shows a cyclic portammogram during electrolytic oxidation of aniline, Figure 5 is a graph showing the weight residual rate of the polymer according to the present invention and emeraldine upon heating, and Figure 6 is a graph obtained by compensating the polymer according to the present invention with ammonia. Infrared absorption spectrum of polymer. FIG. 7 is an infrared absorption spectrum of a polymer obtained by redoping the polymer of FIG. 6 with hydrochloric acid. Procedural amendment (formality) April 24, 1985 Director-General of the Patent Office 2 Name of invention Conductive organic polymer 3 Relationship to the person making the amendment Patent applicant address 1-chome Shimohozumi, Ibaraki City, Osaka Prefecture No. 1 and 2 Name: Nitto Electric Industry Co., Ltd. 4, Agent address: 1-8-3-5, Shinmachi, Nishi-ku, Osaka City, Date of amendment order: February 8, 1980 (Shipping date: 1988)
(February 28) Contents of amendment (1) Submit an application for correction as shown in the attached sheet. (2) On page 19 of the specification, lines 12 to 20, delete "-[4. Brief description of the drawings. Figure 1 shows the resulting polymer."] (3) Delete "The infrared absorption spectrum of..." from lines 1 to 3 on page 2.0 of the specification and add the following sentence in its place. [4. Brief description of the drawings] Figure 1 shows the infrared absorption spectrum of the conductive organic polymer according to the present invention, Figures 2 and 3 show the infrared absorption spectra of emeraldine and aniline black, respectively.
The figure shows a cyclic portammogram in the electrolytic oxidation of aniline, Figure 5 is a graph showing the weight residual rate of the polymer according to the present invention and emeraldine upon heating, and Figure 6 is the graph obtained by ammonia compensation of the polymer according to the present invention. Infrared absorption spectrum of polymer. FIG. 7 is an infrared absorption spectrum of a polymer obtained by redoping the polymer of FIG. 6 with hydrochloric acid. ”

Claims (1)

[Claims] (An aniline solution containing 11 aniline and a protonic acid equivalent to or more than aniline is applied to a standard calomel electrode at an electrolytic potential higher than +1 V at a current density of 0.01 mA/
A conductive organic polymer obtained by electrolytic oxidation polymerization in CD to IA/-, doped with the above acid, and having an electrical conductivity of 1O-6510i1 or more.