JPH0578575B2 - - Google Patents

Description

[Detailed description of the invention]

[Technical Field] The present invention relates to an improved electrolytic oxidative polymerization method for heterocyclic compounds. [Prior Art and its Problems] It has been known that a polymer film can be obtained on an electrically conductive electrode substrate by electrolytically oxidizing and polymerizing a heterocyclic compound or the like in an organic solvent. These polymers exhibit various electroactivities and are considered promising materials for new electrodes for batteries, electrochemical sensors, electrochromic displays, etc. However, polymer films obtained by conventional methods have problems with surface smoothness, adhesion with electrode substrates, etc., and it has been difficult to obtain stable characteristics. [Object of the Invention] An object of the present invention is to provide an electrolytic oxidative polymerization method for obtaining a polymer film of a heterocyclic compound having excellent surface smoothness and adhesion to an electrode substrate. [Structure of the Invention] The present invention provides an improved electrolytic polymerization method characterized in that an amine is added during electrolytic oxidative polymerization of a heterocyclic compound selected from pyrrole, indole, carbazole, dibenzofuran, and dibezothiophene in an organic solvent. This invention relates to an oxidative polymerization method. In the present invention, electrolytic oxidation polymerization is carried out using an apparatus as shown in FIG. This is called a three-electrode electrolytic cell, which is very commonly used when performing electrolytic reactions, and does not necessarily require a glass filter between each chamber. By injecting an electrolytic oxidation polymerization solution into this electrolytic cell and applying a predetermined voltage between the working electrode and the counter electrode, a polymerization reaction is started and a polymer film is formed on the working electrode. The thickness of the membrane (the amount of polymer) is adjusted by the amount of electricity applied. The magnitude of the voltage applied between the two electrodes can be determined to be the most efficient value by measuring the voltage-current characteristics of the electrolytically oxidized polymerization solution. An electrically conductive material such as platinum, carbon, Nesa glass, or stainless steel is used for the working electrode and the counter electrode. In this case, higher efficiency can be obtained if the surface area of the counter electrode is as large as possible. The reference electrode is a potassium chloride saturated calomel electrode.
A sodium chloride saturated calomel electrode, a silver/silver chloride electrode, etc. that can provide a reference potential are used, but depending on the type of supporting electrolyte in the electrolytic oxidation polymerization solution used, they may react with the internal solution of the electrode and cause precipitates. In such cases, it is necessary to select an appropriate one. The electrolytic oxidation polymerization solution used in the present invention is prepared by dissolving a heterocyclic compound as a polymerization monomer, a supporting electrolyte, and an amine additive in an organic solvent. Nitrogen gas is bubbled through this solution for 10 to 20 minutes before it is used for the reaction. Supporting electrolytes include lithium perchlorate, sodium perchlorate, sodium sulfate, tetraalkylammonium tetrafluoroborate, sodium trifluoroacetate, etc., but they are soluble in the solvent used and are compatible with polymeric monomers and additives. Requires no reaction. The amount added is usually about 0.1 mol/. The organic solvent that can be used in the present invention is not particularly limited as long as it can dissolve all of the polymerized monomer, supporting electrolyte, and amine additive. Specific examples include acetonitrile, tetrahydrofuran, propylene carbonate, and benzonitrile. The amine additive used in the present invention is not particularly limited as long as it does not undergo electrolytic oxidation polymerization, but specific examples include methylamine, ethylamine, dimethylamine, trimethylamine, allylamine, cyclohexylamine, pyridine, pyrazine, and quinoline. It will be done. The amount of these additives is preferably in the range of 0.1 mol to 5.0 mol per 1 mol of polymerized monomer, and addition of 5.0 mol or more inhibits the polymerization reaction. The amount of additive to the reaction solvent is preferably in the range of 0.01 to 10.0 mol/. [Effects of the Invention] The polymer film obtained using the present invention has superior uniformity, surface smoothness, and adhesion to the electrode substrate compared to conventional ones, and this makes it possible to obtain stable and stable polymer films in practical use. There are effects such as improved performance. EXAMPLES The present invention will be explained in more detail with reference to Examples below. Examples 1 to 3 Electrolytic oxidative polymerization was carried out using the apparatus shown in FIG.
The working electrode has a size of 1 x 4 cm, a thickness of 1 mm, and a surface resistance of 10.
Ω indium oxide Nesaglass was used and installed so that the contact area with the electrolytic oxidation polymerization solution was 2 cm ² . A platinum plate with a thickness of 0.1 mm and a surface area of 15 cm ² was used as the counter electrode. A sodium chloride saturated calomel electrode was used as the reference electrode. The electrolytic oxidation polymerization solution contains 0.67 g (0.1 mol/) of pyrrole and 2.45 g (0.2 mol/) of sodium perchlorate.
), pyridine 0.79g (0.1mol/) ~ 3.16g
(0.4 mol/) was dissolved in acetonitrile to make a total volume of 100 ml. Addition amount of pyridine is 0.1
Example 1 was determined to be 0.2 mol/mole, and Example 3 was 0.4 mol/mole/mole/mole. After bubbling nitrogen gas into each of these solutions for 15 minutes, they were poured into a three-electrode electrolytic cell. Each to the working electrode
Polymerization is started by applying a voltage of 1.1V, and the amount of current applied is
The reaction was terminated when the temperature reached 0.2 coulombs/cm ² . The polymer film formed on the working electrode was washed with acetonitrile and dried before being used for evaluation. A thin film profilometer was used to measure the film thickness and surface smoothness. The measurement results of Examples 1 to 3 were as shown in Table 1. Here, R is the pyridine addition rate and represents the molar ratio of monomer to pyridine. T ₁ and T ₂ represent the film thickness 9 and the surface protrusion 10, respectively, as shown in FIG. Therefore, the smaller the value of the surface protrusion T ₂ , the more smooth the film surface becomes. Comparative example 1 Not adding pyridine and reducing the applied voltage
The same method as in Example 1 was carried out except that the voltage was 0.9V. The properties of the obtained membrane were as shown in Table 1. Pyridine addition rate R, film thickness T ₁ and surface protrusion T ₂
3 and 4 respectively, and the characteristics of the film of Comparative Example 1 are B in the diagram.
Represented by points. On the other hand, the characteristics of the films obtained in Examples 1 to 3 are expressed by P ₁ to P ₃ points, respectively.
The results show that although the film thickness tends to decrease slightly by adding pyridine, the surface smoothness of the film is dramatically improved. It was also observed that the addition of pyridine improved the adhesion of the polymer film to the electrode substrate. That is, when the electrode with the polymer film attached was immersed in water for several minutes and then dried several times, the electrode obtained in Comparative Example 1 was completely peeled off, but in Examples 1 to 3, it was completely peeled off. None of the results were changed. Example 4 Electrolytic oxidation polymerization solution contains 1.86 g of dibenzothiophene
(0.1 mol/), sodium perchlorate 2.45 g (0.2
2.37 g (0.3 mol/) of pyridine was dissolved in acetonitrile to make a total volume of 100 ml. Polymerization was started by applying a voltage of 2.2 V to the working electrode, and the reaction was terminated when the amount of current applied reached 0.50 coulombs/cm ² . Other operations were performed in the same manner as in Example 1. The obtained polymer film adhered uniformly to the electrode substrate. The measurement results of the film properties were as shown in Table 1. Comparative Example 2 The same procedure as Example 4 was carried out except that pyridine was not added. Almost no polymer adhered to the electrode. Example 5 The same procedure as in Example 4 was carried out except that 1.17 g (0.1 mol/) of indole was used as the monomer and the applied voltage was 2.0V. A uniform polymer film was obtained. The properties of the membrane were as shown in Table 1. Comparative Example 3 No pyridine was added and the applied voltage was
The same procedure as in Example 5 was carried out except that the voltage was set to 1.35V. Although polymer was produced, most of it fell off from the electrode substrate. Example 6 The electrolytic oxidation polymerization solution contained 0.84 g of carbazole (0.05 g
mol/), 7.74 g (0.2 mol/) of tetrabutylammonium hexafluorophosphate, and 1.19 g (0.15 mol/) of pyridine were dissolved in acetonitrile to make a total volume of 100 ml. Polymerization was initiated by applying a voltage of 2.5 V to the working electrode, and the reaction was terminated 10 minutes later. Other operations were performed in the same manner as in Example 1. A uniform polymer film was obtained. The properties of the membrane were as listed in Table 1. Comparative Example 4 The same procedure as Example 6 was carried out except that pyridine was not added. The polymer did not adhere uniformly to the electrode substrate. The membrane properties are shown in Table 1. Example 7 0.84 g of dibenzofuran (0.05 mol/
) and the applied voltage was 3.5V. A uniform and shiny polymer film was obtained. The membrane properties are shown in Table 1. Comparative Example 5 The same procedure as Example 7 was carried out except that pyridine was not added. The polymer was non-uniform and easily fell off, resulting in a weak film.

【table】

[Table] *Marked: Cannot be evaluated because the adhesion between the polymer and the electrode substrate is weak and a satisfactory film cannot be obtained.
As is clear from the examples in Table 1, the polymer film obtained when an amine is added in the electrolytic oxidative polymerization of a heterocyclic compound in an organic solvent has a small value of surface protrusions T ₂ . In other words, it has excellent surface smoothness. On the other hand, in a comparative example in which no amine was added, not only the surface smoothness was poor, but also the adhesion to the electrode substrate was weak, making it difficult to form a satisfactory polymer film.

[Brief explanation of drawings]

FIG. 1 shows the three-electrode electrolytic oxidation polymerization tank used in the present invention, and FIG. 2 shows an enlarged sectional view of the polymer membrane used for evaluation. 1 is a working electrode, 2 is a counter electrode, 3 is a reference electrode, 4 is a glass filter, 5 is an electrolytic oxidation polymerization solution, 6 is a polymer film, 7 is an electrode substrate, and 8 is a mechanical membrane for measuring film thickness. 9 is the film thickness T ₁ , 1
0 is the surface protrusion _T2 . Figure 3 shows the relationship between the thickness of the polymer film obtained by electrolytic oxidative polymerization of pyrrole and the amount of pyridine added, and Figure 4 shows the relationship between the surface protrusions of the pyrrole polymer film and the amount of pyridine added. show. P ₁ to _{P 3} were obtained in Examples 1 to 3, respectively, and B was obtained in Comparative Example 1.

Claims (1)

[Scope of Claims] 1. An electrolytic oxidative polymerization method characterized in that an amine is added during the electrolytic oxidative polymerization of a heterocyclic compound selected from pyrrole, indole, carbazole, dibenzofuran, and dibenzothiophene in an organic solvent. . 2 The amine is methylamine, ethylamine, dimethylamine, trimethylamine, allylamine,
The electrolytic oxidative polymerization method according to claim 1, wherein cyclohexylamine, pyridine, pyrazine or quinoline is used. 3. The electrolytic oxidative polymerization method according to claim 1, wherein the amount of the amine added is 0.1 to 5 mol per mol of the heterocyclic compound.