JPH0330618B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing highly conductive organic polymers. 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 substance, it can be considered to have the ultimate structure of an organic conjugated system. This graphite already has a fairly high conductivity by itself, but by intercalating it with various compounds, it can be made to have even higher conductivity, eventually becoming a superconductor. However, graphite has strong two-dimensionality and is difficult to mold, which poses an obstacle in its application. The second type is a charge transfer complex, and for example, a crystalline material obtained using tetrathiafulvalene and tetracyanoquinodimethane as an electron donor and an electron acceptor, respectively, has a very high conductivity of 400 to 500 S/cm 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 polyacetylene before doping is that the transformer type
10 ^-5 S/cm, and 10 ^-9 S/cm for the cis type, and has properties close to semiconductors or insulators. However, such polyacetylene contains arsenic pentafluoride, iodine,
By doping with an electron-accepting compound such as sulfur trioxide, 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.
Furthermore, it is possible to provide high conductivity at a conductor level of 10 ³ S/cm. The above polyacetylene is an interesting conductive organic polymer in theory, 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 its conductivity decreases rapidly even with the slightest amount of moisture in the air. This tendency is particularly remarkable for n-type semiconductors. Furthermore, poly(p-phenylene) and poly(p-phenylene sulfide) have conductivities of 10 ^-9 S/cm and 10 ^-16 S/cm, respectively, before doping, but By doping with arsenic, the conductivity is 500S/cm and
It can be a conductive organic polymer with a conductivity of 1 S/cm. The electrical properties of these doped organic polymers are also unstable to varying degrees. The fact that the electrical properties of such doped conductive organic polymers are generally very unstable with respect to the environment is a common phenomenon among these types of conductive organic polymers, and it is difficult to use them for practical purposes. This has become an obstacle to practical applications. 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 the formula () is emeraldine.
(AGGreen et al., J.
Chem.Soc., 97 , 2388 (1910); 101 , 1117
(1912)), which consists of 80% acetic acid, cold pyridine and N,
Soluble in N-dimethylformamide. It is also known that this emeraldine is oxidized in an ammoniacal medium to produce nigraniline represented by the formula (), which also has similar solubility properties to emeraldine. Furthermore, in recent years, R. Buvet et al. discovered that this sulfate of emeraldine has high conductivity (J. Polymer Sci., C.
16, 2331; 2943 (1967); 22 , 1187 (1969)). The present inventors have conducted intensive research on the oxidative polymerization of aniline in order to obtain stable and highly conductive organic materials, particularly conductive organic polymers.
By selecting the reaction conditions for the oxidative polymerization of aniline, aniline, which has a much higher molecular weight than the above-mentioned emeraldine and is already doped in the oxidative polymerization stage, can be produced without the need for a new doping operation. We found that it was possible to obtain a stable and highly conductive aniline oxidized polymer, but as a result of further intensive research, we found that after reducing this polymer, we reoxidized it with an oxidizing agent effective as an acceptor and doped it. The inventors have discovered that a polymer with even higher conductivity can be obtained by doing so, leading to the present invention. The method for producing a conductive organic polymer according to the present invention includes:
A polymer having an electrical conductivity of 10 ^-6 S/cm or more, obtained by oxidative polymerization of aniline or a water-soluble salt of aniline with an oxidizing agent in a protonic acid-containing reaction medium, and doped with a protonic acid during the oxidative polymerization. A 0.5g/dl solution of concentrated sulfuric acid is heated at 30°C.
After reducing the aniline oxidized polymer having a logarithmic viscosity of 0.10 or more, it is oxidized with an oxidizing agent effective as an acceptor and doped. It is characterized by The aniline oxidized polymer used in the method of the present invention is a polymer obtained by oxidative polymerization of aniline or a water-soluble salt of aniline in a reaction medium containing a protonic acid and an oxidizing agent. As the aniline water-soluble salt, mineral acid salts such as hydrochloric acid and sulfuric acid are usually suitable, but are not limited to these. Further, the oxidizing agent is not particularly limited, but chromium oxide () and dichromates such as potassium dichromate and sodium dichromate are suitable, and potassium dichromate is particularly optimal. . However, chromium-based oxidizing agents such as chromic acid, chromate, and chromyl acetate, and manganese-based oxidizing agents such as potassium permanganate can also be used as necessary. In addition, as a protonic acid,
Sulfuric acid, hydrochloric acid, hydrobromic acid, tetrafluoroboric acid (HBF ₄ ), hexafluorophosphoric acid (HPF ₆ ), etc. are used, and sulfuric acid is particularly preferred. When a mineral acid is used to form the aniline water-soluble salt, the mineral acid may be the same as or different from the protic acid described above. As the reaction medium, one or a mixture of two or more of water, a water-miscible organic solvent, and a water-immiscible organic solvent can be used; however, when an aniline water-soluble salt is used, the reaction medium usually contains , water, a water-miscible organic solvent, or a mixture thereof that dissolves the aniline water-soluble salt, and when aniline itself is used, the reaction medium may be a water-miscible organic solvent that dissolves the aniline, or a water-miscible organic solvent or a water-miscible organic solvent that dissolves the aniline. Miscible organic solvents are used. Incidentally, it is necessary that the above organic solvents are not oxidized by the oxidizing agent used. For example, as the water-miscible organic solvent, ketones, ethers, or organic acids such as acetone, tetrahydrofuran, and acetic acid are used, and as the water-immiscible organic solvent, carbon tetrachloride, hydrocarbons, etc. are used. In particular, the aniline oxidized polymer that can be preferably used in the present invention contains the above-mentioned oxidizing agent when producing the aniline oxidized polymer by oxidatively polymerizing aniline or an aniline water-soluble salt with an oxidizing agent in a protonic acid-containing reaction medium. It is obtained by setting the protonic acid/potassium dichromate molar ratio in the reaction medium to 1.2 or more, has an electrical conductivity of 10 ^-6 S/cm or more, preferably 10 ^-3 S/cm or more, and has a
A 0.5 g/dl solution is a polymer having a logarithmic viscosity of 0.10 or more, preferably 0.2 to 0.6 at 30°C. The reaction temperature is not particularly limited as long as it is below the boiling point of the solvent, but the higher the reaction temperature, the lower the conductivity of the resulting oxidized polymer tends to be, so from the viewpoint of obtaining a polymer with high conductivity, It is preferably at room temperature or below. In the above method, preferably, an aqueous solution of a protonic acidic oxidizing agent is dropped into an organic solution of aniline or an aqueous solution of a water-soluble salt of aniline with stirring,
Alternatively, the reaction may be carried out by adding all at once. Usually, the polymer precipitates immediately after an induction period of several minutes. Although the reaction terminates immediately in this way, usually
The mixture is then stirred for several minutes to several hours for ripening.
Next, the reaction mixture was poured into a large amount of water or an organic solvent, the polymer was filtered out, and the filtrate was washed with water until it became neutral, and then washed with an organic solvent such as acetone until it was no longer colored, and the polymer was evaporated under vacuum. After drying, an aniline oxidized polymer is obtained. In the above method, the electrical conductivity of the obtained aniline oxidized polymer is closely related to the composition of the reaction medium containing a protonic acid and an oxidizing agent in which the oxidative polymerization of aniline is carried out. In order to obtain a polymer, it is necessary to optimally select the composition of the above reaction medium, and the conductivity
In order to obtain a polymer with high conductivity of 10 ^-6 S/cm or more, it is necessary to set the protonic acid/potassium dichromate molar ratio in the reaction medium in which the reaction is carried out to 1.2, preferably 2 or more. . Oxidative polymerization under these conditions typically results in a conductivity of 10 ^-3
It is possible to obtain aniline oxidized polymers with ˜10 ¹ S/cm. As mentioned above, when a reaction is carried out by adding an acidic oxidizing agent aqueous solution to an organic solution of aniline or an aqueous solution of an aniline water-soluble salt, the concentration of protonic acid in the oxidizing agent aqueous solution is particularly limited. However, it is usually in the range of 1 to 10N. As mentioned above, if the protonic acid/potassium dichromate molar ratio in the reaction medium in which the oxidative polymerization of aniline is carried out is constant, the electrical conductivity of the resulting oxidized aniline polymers will be substantially the same. On the other hand, the amount of potassium dichromate relative to aniline determines the yield of polymer obtained. but,
The conductivity of the polymer is substantially unaffected by the amount of potassium dichromate used. Therefore,
When using an oxidizing agent aqueous solution with a predetermined protonic acid/potassium dichromate molar ratio and using an equivalent or more amount of potassium dichromate to aniline, an oxidized aniline polymer having a predetermined conductivity can be produced almost quantitatively. can be obtained. The aniline oxidized polymer obtained as described above is insoluble in water and most organic solvents, but usually contains a portion that is slightly soluble or soluble in concentrated sulfuric acid. The solubility in concentrated sulfuric acid varies depending on the reaction conditions for producing the polymer, but is usually 0.2
~10% by weight, in most cases 0.25-5
% by weight. However, this solubility should be understood, especially in the case of polymers of high molecular weight, to include portions where the polymer has a solubility in the above range. In addition, the above aniline oxidized polymer can be treated with concentrated sulfuric acid.
A 0.5 g/dl solution has a logarithmic viscosity at 30°C ranging from 0.1 to 1.0, most often from 0.2 to 0.6. In this case too, it is to be understood that, especially in the case of polymers of high molecular weight, the portion soluble in concentrated sulfuric acid has a logarithmic viscosity in the above range. As mentioned above, emeraldine is 80% acetic acid,
In sharp contrast to the solubility in cold pyridine and N,N-dimethylformamide, the viscosity of concentrated sulfuric acid solutions of the polymers according to the invention is also much higher than that of emeraldine and aniline black under the same conditions. These show that the polymer according to the present invention is a high molecular weight polymer. Furthermore, the results of differential thermal analysis also indicate that the polymer according to the invention is a high molecular weight polymer. The structure of such an aniline oxidized polymer has not yet been determined, but its infrared absorption spectrum is similar to that of emeraldine, while it has a high molecular weight and high conductivity, so it is possible that the aniline is connected in a head-to-tail bond. It appears to be a substantially linear π-electron conjugated polymer as shown in the following formula that forms a polymer chain. In addition, although aniline oxidized polymers have high conductivity, the conductivity is significantly reduced by compensating with ammonia, and the original high conductivity is restored by doping with sulfuric acid. It is confirmed that the material is doped with protonic acid at the stage of oxidative polymerization. Furthermore, the infrared absorption spectrum of the polymer that was compensated with ammonia and then doped again with sulfuric acid completely matched that of the polymer before compensation with ammonia. It is confirmed that Furthermore, due to the fact that the polymer is compensated with ammonia and the sign of the thermoelectromotive force, this polymer is p-type. Since the aniline oxidation polymers described above are already doped with protonic acids during the polymerization stage, they have high conductivity without the need for any new doping treatment, and can be used for long periods of time. Even if it is exposed to air, its conductivity does not change at all, and it has a uniquely high stability compared to conventionally known doped conductive organic polymers. In powder form, it usually exhibits a green to dark green color, and generally, the higher the conductivity, the brighter the green color. However, pressure-molded products usually exhibit a shiny blue color. According to the present invention, by chemically reprocessing the aniline oxidized polymer, its conductivity can be further improved. That is, after reducing the aniline oxidized polymer obtained as described above, it is oxidized with an oxidizing agent effective as an acceptor and doped. In the process of the invention, it is preferred that the aniline oxidized polymer is compensated with a base prior to its reduction. As the base used for this compensation, inorganic bases such as aqueous ammonia and sodium bicarbonate, and organic bases such as lower aliphatic amines such as triethylamine can be used, but preferably aqueous ammonia is used. In order to compensate the aniline oxidized polymer with such a base, for example, the polymer powder may be added to a 0.1N or higher solution of these bases and stirred, although there is no particular limitation. The reaction time required for the compensation reaction is several minutes to several hours, but usually about 30 minutes is sufficient. Thereafter, the polymer is filtered and dried to usually obtain a reddish-purple polymer. The thus compensated polymer is then reduced with a reducing agent. The method is not particularly limited, but
Generally, it is sufficient to stir the polymer powder while suspending it in a solution of the reducing agent. As the reducing agent, hydrazines such as hydrazine, hydrazine hydrate, and phenylhydrazine, and metal hydrides such as lithium aluminum hydride and sodium borohydride can be used, but metal hydrides are generally insoluble in solvents. However, since the reduction efficiency is poor, hydrazines that are soluble in a solvent, particularly phenylhydrazine, are preferably used. The reducing agent is preferably used in an amount that provides an equivalent amount of hydrogen to the nitrogen atoms contained in the polymer, usually 1.5 to 3 times the equivalent amount of nitrogen atoms contained in the polymer, but this It is not limited to. The time required for this reduction reaction is usually several tens of minutes to several hours, and in many cases, the reaction may be carried out for one hour. Since the reduction proceeds sufficiently rapidly at room temperature, no particular heating is required, but it is of course possible to carry out the reduction reaction under heating if necessary. After the reduction reaction is completed, the polymer powder is filtered, washed with a solvent of the same type as the reaction solvent, and dried at room temperature after removing the reducing agent. The reduced polymer thus obtained usually has a gray color and is highly susceptible to oxidation. After this, the reduced polymer is reoxidized and doped. The dopant used in this doping must have sufficient oxidizing power to reoxidize the reduced polymer and must also have the function of an electron-accepting reagent effective as a dopant, that is, an acceptor. As mentioned above, the reduced polymer is sensitive to oxidation and is even oxidized by oxygen in the air.
The oxidizing power required for the dopant may be small. Therefore, various dopants can be used, including halogens such as iodine, bromine, and chlorine, antimony pentafluoride, boron trifluoride, boron trichloride, ferric chloride, and cupric chloride. ,
Lewis acids, sulfuric acid, hydrochloric acid, which are anhydrides of stannic chloride, titanium tetrachloride, cobalt chloride, zinc chloride, etc.
Protic acids such as sulfuric acid, perchloric acid, hydroborofluoric acid, trifluoroacetic acid, and sulfur trioxide are preferred. Doping of the reduced polymer is carried out in the gas phase or in the liquid phase, depending on the type of dopant. When using a dopant that is a gas or a solid with a high vapor pressure at room temperature, doping can be carried out by placing the polymer powder in a vacuum-pressurized furnace and introducing the dopant into the furnace. In the case of a solid dopant having a low vapor pressure at room temperature, the dopant may be dissolved in a suitable solvent such as acetonitrile or nitromethane, and the polymer powder may be immersed in this dopane solution. Furthermore, when a protonic acid is used as the dopant, the polymer can be doped by immersing the polymer powder in its aqueous solution. The aniline oxidation polymer described above is doped with a protonic acid, such as sulfuric acid, used in the oxidation polymerization step, and has high electrical conductivity, but when this is compensated for, the electrical conductivity decreases significantly and , a remarkable change was also observed in the infrared absorption spectrum. After reduction of this compensation polymer and doping, for example with iodine, the resulting polymer typically has a conductivity several times that of the original aniline oxidized polymer, and its infrared absorption spectrum also differs from that of the original aniline oxidized polymer. Since it is substantially the same as the oxidized polymer, it appears that the aniline oxidized polymer has the same structure as the original one even after being subjected to the series of chemical treatments according to the present invention. However, after compensating the aniline oxidized polymer, without reduction,
Even if it is redoped, its conductivity is low.
The reason for this is not clear, but according to the method of the present invention, the dopant is doped through a direct chemical reaction with the reduced aniline oxidized polymer main chain, so the dopant is simply diffused into the polymer. Compared to the former method, the contact between the polymer backbone and the dopant appears to occur more effectively, resulting in a marked improvement in conductivity. As described above, according to the method of the present invention, a conductive aniline oxidized polymer is preferably compensated with a base, and then reduced, and then oxidized with an oxidizing agent effective as an acceptor and doped. can increase the conductivity of Also, various dopants can be selected. 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 (1) Production of aniline oxidized polymer 90 g of distilled water and concentrated hydrochloric acid were placed in a 300 ml flask.
9.2 ml was added and further 10 g (0.107 mol) of aniline was dissolved to prepare an aqueous aniline hydrochloride solution. Separately, in 92.7 g of distilled water, 26.3 g (0.268 mol) of concentrated sulfuric acid and 10.5 g (0.0357 mol) of potassium dichromate.
An oxidizing agent aqueous solution (protonic acid/potassium dichromate molar ratio 7.5) was prepared, and this was added dropwise to the above aniline acid salt aqueous solution at room temperature with stirring, taking 30 minutes. did. After the addition was completed, the mixture was stirred for another 30 minutes, and then the reaction mixture was poured into acetone 1.2 and stirred for 2 hours.
The polymer was then filtered off. The obtained polymer was washed with stirring in distilled water, filtered off, and washing was repeated in this manner until the filtrate became neutral. Then,
The filtered polymer was washed repeatedly with acetone until the filtrate became clear and colorless. The filtered polymer was vacuum dried over phosphorus pentoxide at room temperature for 10 hours to obtain 9.5 g of a conductive aniline oxidized polymer as a green powder. This polymer has a logarithmic viscosity of 0.48, and a pressure-molded blue sample has an electrical conductivity of . It was 8S/cm. still,
Conductivity measurement was performed using a tablet molding machine at a pressure of 6000 kg/cm ²
The sample was pressure-formed into a 13 mm diameter disk.
Platinum wires with a width of about 1 mm were adhered to the four corners of the disk using graphite paste, and the process was carried out in air at room temperature according to the van der Pauw method. (2) Evaluation of physical properties (ammonia compensation) 8 g of the polymer obtained in (1) above was stirred in 10% ammonia water for 30 minutes, filtered, washed with water until neutral, and then washed with acetone. Thereafter, it was vacuum dried in a desiccator at room temperature for 8 hours. The resulting powder was purple in color. A sample pressure-molded in the same manner as above was brown in color and had an electrical conductivity of 1.2×10 ⁻⁸ S/cm. (Reduction treatment) 7.2 g of the chemically compensated sample obtained in (2) above was added to a solution of phenylhydrazine (13 g, 0.12 mol) in ethyl ether (138 g), and the mixture was reacted for 1 hour at room temperature with stirring. After that, the polymer was separated by filtration, unreacted phenylhydrazine was thoroughly washed with ethyl ether, and then dried under vacuum. The obtained powder was gray in color, and the conductivity of a sample pressure-molded in the same manner as above was 1.5×1 ⁻⁷ S/cm. (Oxidation and Doping) The reduced polymer obtained above was oxidized and doped with an oxidizing dopant. The method used was either doping the sample polymer powder or doping the sample polymer powder after pressure-molding it into a disk shape. Also,
Depending on the nature of the dopant, it was carried out in the gas phase or in the liquid phase. When conducting in the gas phase, the sample was placed in a sealable glass container connected to a vacuum system, evacuated, and then a dopant gas was introduced into the container. When conducting in liquid phase, the dopant was dissolved in a suitable solvent and the sample was immersed in this solution. All of the polymers after doping had a black-green color. The results are shown in the table. The amount of dopant per repeating unit of the obtained conductive organic polymer was determined from the weight increase, and was expressed as x in [C ₆ H ₄ N.(dopant) _X ]. In addition, the infrared absorption spectra of the aniline oxidized polymer obtained in (1), after compensation with ammonia, after reduction with phenylhydrazine, and after oxidative doping with iodine are shown in Figures 1 and 2, respectively.
It is shown in FIGS. 3 and 4. Comparative Example In the example, the aniline oxidized polymer was compensated and then doped without reduction. The results are shown in the table. 【table】

[Brief explanation of the drawing]

Figures 1, 2, 3 and 4 show the infrared absorption spectra of the aniline oxidized polymer doped with sulfuric acid, after compensation with ammonia, after reduction with hydrazine, and after oxidative doping with iodine, respectively. .

Claims (1)

[Scope of Claims] 1. Obtained by oxidative polymerization of aniline or a water-soluble salt of aniline with an oxidizing agent in a protonic acid-containing reaction medium, the conductivity of which is doped with protonic acid during this oxidative polymerization is 10 ^-6 S/ cm or more, and a 0.5 g/dl solution of concentrated sulfuric acid is 30
1. A method for producing a conductive organic polymer, which comprises reducing an aniline oxidized polymer having a logarithmic viscosity of 0.10 or more at °C, followed by oxidation with an oxidizing agent effective as an acceptor and doping. 2. The method for producing a conductive organic polymer according to claim 1, wherein the reducing agent is hydrazine or metal hydride.