JPH0555532B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a conductive organic polymer obtained by oxidative polymerization of aniline. 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 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, 2931; 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 oxidative polymerization of aniline, aniline has a much higher molecular weight than the above-mentioned emeraldine, and since it has already been doped in the oxidative polymerization stage, no new doping operation is required. The present invention was achieved by discovering that a stable and highly conductive polymer can be obtained by using the same method. The present invention provides a method for producing a conductive organic polymer by oxidatively polymerizing aniline or a water-soluble salt of aniline with dichromate in a protonic acid-containing reaction medium, in which the protonic acid/dichromate molar ratio is 1.2.
As above, the conductivity is 10 ^-6 S/cm or more, usually
A high molecular weight polymer having a molecular weight of 10 ⁻³ to ^{10 1} S/cm,
A 0.5g/dl solution of concentrated sulfuric acid has a concentration of 0.10dl/dl at 30°C.
The method is characterized by obtaining a polymer having a logarithmic viscosity of 100 g or more. The conductive oxidized aniline polymer obtained by the method of the present invention usually exhibits a green to blackish green color in a dry powder state, and generally, the higher the conductivity, the higher the conductivity.
It has a bright green color. However, pressure-molded products usually exhibit a shiny blue color. The conductive organic polymers produced by the method of the present invention are insoluble in water and most organic solvents, but are usually slightly soluble or contain portions that are 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 to 10% by weight.
in the range of 0.25 to 5% by weight in most cases. 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. Polymers produced by the method of the invention can be prepared using 0.5 ml of concentrated sulfuric acid.
The g/dl solution has a logarithmic viscosity at 30°C in the range 0.1-1.0, most often 0.2-0.6. 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. Although the structure of the polymer according to the present invention has not yet been determined, its infrared absorption spectrum is similar to that of emeraldine, while it has a high molecular weight and high conductivity. It appears to be a substantially linear π-electron conjugated polymer as shown in the following formula that forms a chain. Furthermore, although the polymer according to the present invention has high electrical conductivity, the electrical conductivity is significantly reduced by compensating with ammonia, and the original high electrical conductivity is restored by doping with sulfuric acid again. It is confirmed that doping with protonic acid has already occurred 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 according to the invention is thus compensated with ammonia and the sign of the thermoelectromotive force, this polymer is p-type. As described above, since the conductive organic polymer obtained by oxidative polymerization of aniline according to the method of the present invention has already been doped with protonic acid during the polymerization stage, a new doping treatment is required. It is a conventionally known doped conductive organic polymer that has high conductivity without requiring a It has a uniquely high stability compared to According to the present invention, the conductive organic polymer can be obtained by oxidative polymerization of aniline or a water-soluble salt of aniline in a reaction medium containing a protic acid and an oxidizing agent dichromate. 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, as the oxidizing agent, dichromate salts, particularly sodium dichromate and potassium dichromate are suitable, and potassium dichromate is especially optimal. Further, as the 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 type or a mixture of two or more of water, a water-miscible organic solvent, and a water-immiscible organic solvent can be used. Usually, when an aniline water-soluble salt is used, the reaction medium is Water, a water-miscible organic solvent, or a mixture thereof that dissolves the aniline water-soluble salt is used, and when aniline itself is used, the reaction medium is a water-miscible organic solvent that dissolves the aniline or a water-immiscible organic solvent. 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 the present invention, a particularly preferred method for producing a conductive organic polymer is a method for producing a conductive organic polymer by oxidatively polymerizing aniline or a water-soluble salt of aniline with an oxidizing agent in a protonic acid-containing reaction medium. A high molecular weight polymer having an electrical conductivity of 10 ^-6 S/cm or more when the protic acid/dichromate molar ratio in the reaction medium containing the agent, in particular, the protic acid/potassium dichromate molar ratio is 1.2 or more. So, a 0.5g/dl solution of concentrated sulfuric acid has a concentration of 0.10 at 30°C.
The above is characterized in that in most cases a polymer having a logarithmic viscosity of 0.2 to 0.6 is obtained. 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 less conductive the obtained oxidized polymer tends to be. Preferably near room temperature. In the method of the present invention, the reaction is preferably carried out by dropping an aqueous solution of a protonic acidic oxidizing agent into an organic solution of aniline or an aqueous solution of a water-soluble salt of aniline with stirring, or by adding it all at once. usually,
After an induction period of several minutes, the polymer precipitates immediately. In this way, the reaction ends immediately, but the mixture is usually stirred for several minutes to several hours afterwards 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. Dry,
A conductive organic polymer according to the invention is obtained. In the method of the present invention, the electrical conductivity of the resulting electrically conductive organic 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 an oxidized polymer, it is necessary to optimally select the composition of the reaction medium according to the present invention, and in order to obtain a highly conductive polymer with an electrical conductivity of 10 ^-6 S/cm or more. The protonic acid/dichromate molar ratio in the reaction medium in which the reaction is carried out is 1.2, preferably 2.
It is necessary to do the above. Oxidative polymerization under these conditions typically results in conductivities ranging from 10 ^-3 to
A conductive aniline polymer with a conductivity of 10 ¹ S/cm can be obtained. 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. In the process of the present invention, if the protonic acid/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 polymers is substantially the same. . That is, according to the method of the present invention, a polymer having a predetermined conductivity can be obtained with good reproducibility. On the other hand,
The amount of dichromate relative to aniline determines the yield of polymer obtained. However, the electrical conductivity of the polymer is not substantially affected by the amount of dichromate used. Therefore, for a given protonic acid/
When using an oxidizing agent aqueous solution having a molar ratio of dichromate and using an equivalent or more amount of dichromate to aniline, an organic polymer having a predetermined conductivity can be obtained almost quantitatively. 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 polymer 45 g of water was placed in a 300 ml flask, 4 ml of concentrated hydrochloric acid was added, and 5 g (0.0537 mol) of aniline was further dissolved to prepare an aqueous solution of aniline hydrochloride. Separately, 4.61 g (0.047 mol) of concentrated sulfuric acid in 28.8 g of water.
and 1.84g of potassium dichromate.
An oxidizing agent aqueous solution (protonic acid/potassium dichromate molar ratio 7.5) in which (0.00625 mol) was dissolved was prepared, and this was added dropwise to the above aniline hydrochloride aqueous solution at room temperature with stirring. It took 30 minutes. dripped. After the start of the dropwise addition, the solution was only colored yellow for the first 2 to 3 minutes, but after that, a green solid was quickly precipitated, and the reaction liquid took on a dark green color. After the addition was completed, the mixture was stirred for an additional 30 minutes, and then the reaction mixture was poured into 400 ml of acetone, stirred for 2 hours, and then the polymer was filtered off. The resulting polymer was washed with stirring in distilled water, filtered off, and washing was repeated in this manner until the filtrate became neutral. Next, the filtered polymer was washed repeatedly with acetone until the filtrate was no longer colored.
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 Figure 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 FIGS. 2 and 3, respectively.
In addition, emeraldine was prepared by the method of AGGreen et al. (AGGreen et al., J.Chem.
Soc., 97 , 2388 (1910)). This polymer was added to 97% concentrated sulfuric acid at room temperature, stirred, and its solubility was examined, and the amount dissolved was 1.2% by weight. Also, the concentration
The logarithmic viscosity of a 97% concentrated sulfuric acid solution of this polymer at 0.5 g/dl was 0.46 at a temperature of 30°C.
For comparison, the viscosities of Emeraldine and Diamond Black under the same conditions are
They were 0.02 and 0.005. 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, about 120 mg of the polymer powder obtained above was crushed in an agate mortar, and then pressure-molded into a disk with a diameter of 13 mm at a pressure of 6000 Kg/cm ² using a tablet molding machine for an infrared spectrophotometer. Four pieces of copper foil with a width of about 1 mm were adhered to the four corners of the disk using silver paste or graphite paste, and the conductivity was measured in air according to the van der Pauw method, and the conductivity was 0.40 S/cm. Even when measured in a vacuum of 10 ^-2 Torr, they showed almost the same conductivity. The disk was left in air for 4 months with virtually no change in conductivity. Further, FIG. 5B shows an infrared absorption spectrum of the above-mentioned polymer according to the present invention when compensated with ammonia, and FIG. 5C shows an infrared absorption spectrum after doping the polymer again with 5N sulfuric acid. The spectrum after this redoping is exactly the same as the original one shown in Figure 5A, and furthermore,
The conductivity is also the same as before ammonia compensation. It is therefore shown that the polymer according to the invention is already doped by the protic acid used in its oxidative polymerization step. Example 2 (1) Effect of the sulfuric acid/potassium dichromate molar ratio in a sulfuric acid acidic oxidizing agent aqueous solution with a constant sulfuric acid concentration on the conductivity of the polymer 45 g of water was added to a 300 mm capacity flask, and 4 ml of concentrated hydrochloric acid was added. was added, and 5 g (0.0537 mol) of aniline was further dissolved to prepare an aqueous aniline hydrochloride solution. Separately, 1.84 g of potassium dichromate (0.00625
mol) in various amounts of 3N sulfuric acid and
Aqueous oxidant solutions with different molar ratios of potassium dichromate were prepared. This oxidizing agent aqueous solution was added dropwise to the above aniline hydrochloride aqueous solution from a dropping funnel at room temperature while stirring. After the addition was completed, the mixture was stirred for an additional 30 minutes, and then the reaction mixture was poured into 400 ml of acetone, stirred for 2 hours, and then the polymer was filtered off and dried. The electrical conductivity (σ) of the unpurified electrically conductive polymer obtained in this manner is indicated by a circle in FIG. The above polymer was also washed with distilled water and filtered off, and washing was repeated in this manner until the filtrate was neutral. The electrical conductivity of the purified polymer thus obtained is shown in FIG. 6 by the symbol ●. In addition, in the following drawings, the unpurified polymer as described above is similarly shown with a circle, and the purified polymer is shown with a black mark. From the results shown in Figure 6, it is clear that the protonic acid/potassium dichromate molar ratio in the oxidizing agent aqueous solution is
By setting it to 1.2 or more, the conductivity is 10 ^-6 S/cm
It is understood that the above conductive organic polymers can be obtained. (2) Influence of sulfuric acid/potassium dichromate molar ratio in a sulfuric acid acidic aqueous solution with a constant potassium dichromate concentration on the conductivity and yield of the polymer.1.84 g of potassium dichromate is added to a constant weight of sulfuric acid with different concentrations. (0.00625 mol) was dissolved to prepare an aqueous solution having a potassium dichromate concentration of 5.2% by weight. This oxidizing agent aqueous solution was added dropwise to an aqueous solution containing 0.0537 mol of aniline hydrochloride aqueous solution at room temperature while stirring, as in Example 1, to obtain a polymer according to the present invention. FIG. 7 shows the relationship between the sulfuric acid/potassium dichromate molar ratio in the oxidizing agent aqueous solution and the polymer yield and conductivity. When the above molar ratio is 1.2 or more, a polymer with an electrical conductivity of 10 ^-6 S/cm or more can be obtained, while when the amount of potassium dichromate to aniline is constant, the yield of the polymer is is shown to be almost constant. (3) Effect of potassium dichromate concentration on conductivity and yield of polymers Potassium dichromate was dissolved in sulfuric acid aqueous solutions with different concentrations so that the molar ratio of sulfuric acid/potassium dichromate was 7.5, and various An aqueous solution of potassium dichromate was prepared. This oxidizing agent aqueous solution was added dropwise at room temperature to an aqueous solution containing aniline hydrochloride in a molar amount about 9 times that of potassium dichromate to obtain a polymer according to the present invention. As the results are shown in Figure 8, even if the potassium dichromate concentration in the oxidizing agent aqueous solution was different,
When the sulfuric acid/potassium dichromate molar ratio is constant and the amount of potassium dichromate relative to aniline is constant, the polymer can be obtained at a nearly constant yield and its electrical conductivity is also almost constant. is shown. (4) Effect of the amount of potassium dichromate relative to aniline on the conductivity and yield of the polymer Potassium dichromate was dissolved in 3N sulfuric acid to prepare an oxidizing agent aqueous solution with a sulfuric acid/potassium dichromate molar ratio of 7.5. . Various amounts of the above oxidizing agent aqueous solution were added to the same aniline hydrochloride aqueous solution as in Example 1 to obtain polymers. The influence of the amount of potassium dichromate relative to aniline on the conductivity and yield of the polymer is shown in FIG. In addition, 1 mole of potassium dichromate in acidic sulfuric acid corresponds to 3 equivalents, and the equivalence of potassium dichromate in the drawings means the equivalence of potassium dichromate as an oxidizing agent with respect to aniline. Since the oxidant aqueous solution used has a constant molar ratio of sulfuric acid/potassium dichromate, the conductivity of the obtained polymer is almost constant, while the yield of the obtained polymer is the same as that of the aniline in the oxidant aqueous solution. It is understood that it is approximately proportional to the amount of potassium dichromate. (5) Effect of aniline concentration on conductivity and yield of polymer Potassium dichromate was dissolved in 3N sulfuric acid, and an oxidizing agent aqueous solution with a sulfuric acid/potassium dichromate molar ratio of 7.5 and a potassium dichromate concentration of 5.2% by weight was prepared. was prepared. This oxidizing agent aqueous solution was added so that the number of equivalents of potassium dichromate to aniline was 1/3 to obtain a polymer according to the present invention. The results are shown in FIG. When the sulfuric acid/potassium dichromate molar ratio in the oxidizing agent aqueous solution is constant and the amount of potassium dichromate relative to aniline is constant, almost constant conductivity occurs with almost constant yield regardless of the aniline concentration. It is possible to obtain a polymer having a certain degree of strength. Example 3 6.48 g (0.050 mol) of aniline hydrochloride was dissolved in 3N sulfuric acid.
An aqueous solution of aniline dissolved in 84 ml (0.126 mol) was prepared. The above aniline salt aqueous solution was added dropwise at room temperature to an aqueous solution in which 4.90 g (0.0167 mol) of potassium dichromate was dissolved, and after the addition was completed, the solution was aged for 30 minutes.
Note that the protonic acid/potassium dichromate molar ratio under the above conditions is 7.5. The precipitated polymer was filtered, washed with water and acetone in the same manner as in Example 1, and then vacuum dried to obtain a polymer according to the present invention. The conductivity of this polymer was measured in the same manner as in Example 1 and was found to be 2.8×
It was 10 ^-2 S/cm. Example 4 45% tetrahydrofuran in a 300ml flask
g, and 5 g (0.0537 mol) of aniline was dissolved therein. Separately, 13.17 g (0.134 mol) of concentrated sulfuric acid in 82.2 g of water.
and 5.27g (0.0179g) of potassium dichromate.
Oxidizing agent aqueous solution (protonic acid/
Potassium dichromate molar ratio 7.5) was prepared, and this was added dropwise to the above tetrahydrofuran solution of aniline at room temperature with stirring over a period of 30 minutes. After the dropwise addition was started, the solution was only colored yellow, but after that, a yellowish-greenish brown powder was precipitated, and after a while, this powder turned green. After the addition was completed, the mixture was stirred for an additional 30 minutes, and then the reaction mixture was poured into 600 ml of acetone and stirred for 2 hours.
The polymer was then filtered off. After washing and drying the polymer in the same manner as in Example 1, the conductivity was measured and found to be 0.25 S/cm. Further, the logarithmic viscosity of the concentrated sulfuric acid solution was 0.38. Example 5 Example 4 except that 45 g of carbon tetrachloride was used in place of 45 g of tetrahydrofuran.
A black-green powdery polymer was obtained in exactly the same manner as above.
This polymer had an electrical conductivity of 0.21 S/cm and a logarithmic viscosity of 0.41 in concentrated sulfuric acid solution.

[Brief explanation of the drawing]

FIG. 1 shows the infrared absorption spectrum of the conductive organic polymer according to the present invention, FIGS. 2 and 3 show the infrared absorption spectra of emeraldine and aniline black, respectively, and FIG. 4 shows the infrared absorption spectrum of the conductive organic polymer according to the present invention and emeraldine. It is a graph showing the weight residual rate due to heating. FIG. 5 shows the changes in the infrared absorption spectrum when the polymer according to the present invention is subjected to ammonia compensation and redoping, where A is the polymer according to the present invention, B is the polymer obtained by ammonia compensation, and C is the ammonia compensated polymer. Then, the infrared absorption spectra of each polymer obtained by redoping with sulfuric acid are shown. FIG. 6 shows that in the method of the present invention,
A graph showing the relationship between the sulfuric acid/potassium dichromate molar ratio of an oxidizing agent aqueous solution with a constant sulfuric acid concentration and the electrical conductivity of the obtained polymer. Figure 7 shows a sulfuric acid acidic aqueous solution containing a constant concentration of potassium dichromate. of sulfuric acid/
A graph showing the relationship between the potassium dichromate molar ratio and the yield and conductivity of the obtained polymer. A graph showing the influence of potassium concentration on the yield and electrical conductivity of the obtained polymer. Figure 9 shows the equivalence of a sulfuric acid acidic oxidizing agent aqueous solution with a fixed sulfuric acid/potassium dichromate molar ratio to aniline and the obtained polymer. Figure 10 is a graph showing the relationship between the yield of the polymer obtained and the electrical conductivity. It is a graph showing the relationship between the yield and electrical conductivity of a polymer.

Claims (1)

[Claims] 1. A method for producing a conductive organic polymer by oxidatively polymerizing aniline or a water-soluble salt of aniline with a dichromate in a protonic acid-containing reaction medium,
A high molecular weight polymer with a protonic acid/dichromate molar ratio of 1.2 or more and an electrical conductivity of 10 ^-6 S/cm or more, in which a 0.5 g/dl solution of concentrated sulfuric acid is 0.10 dl/g at 30°C. A method for producing a conductive organic polymer, which comprises obtaining a polymer having a logarithmic viscosity of at least 10%.