JP2957692B2 - Electrolytic polymerization method - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to an electrolytic polymerization method, and more particularly to an electrolytic polymerization method using an improved cathode in electrolytic polymerization.

[Prior art] In recent years, polymer formation by electrolytic oxidation polymerization of polyaniline, polypyrrole, polythiophene, and the like has been actively performed, and organic conductive polymers having particularly excellent electron conductivity have been produced. I have. Applications of such conductive polymers to electrode active materials for batteries, switching elements, electrochromic materials, or electrode materials for capacitors have been attempted.

The electrolytic oxidation polymerization of such an organic compound will be described in detail below by taking, for example, a typical electrolytic oxidation polymerization of polypyrrole.

FIG. 3 shows a commonly used electrolytic polymerization apparatus. In the figure, 1 is an electrolytic solution, 2 is an electrolytic cell, 3 is an anode, 4
Is a cathode, 5 is a circulation pump for stirring and circulating the electrolyte, 6 is a power supply, 7 and 8 are conducting leads, 9
Numerals 10 and 10 denote connectors for making connection with each electrode, and 12 denotes a circulation pipe for circulating the electrolyte.

Usually, as the electrolytic solution 1, an organic solvent such as acetonitrile, dimethylformamide, propylene carbonate or an aqueous solvent is used, and as a supporting electrolyte for these solvents, for example, tetra-n-butylammonium perchlorate and boron tetrafluoride A salt such as tetra-n-butylammonium is dissolved in, for example, about 0.1 to 0.6 mol / L to impart ionic conductivity to the solvent. In the case of an aqueous solvent, for example, sodium p-toluenesulfonate, sodium alkylnaphthalenesulfonate and the like are used.

In this way, a monomer (pyrrole) is dissolved or dispersed in, for example, about 0.05 to 0.3 mol / L in a solution having ion conductivity and used as an electrolyte. In order to carry out polymerization using such an electrolytic solution, first, a pair of electrodes (anode 3 and cathode 4) are immersed in the electrolytic solution, and a voltage of about several volts is applied between the electrodes so that the electrolytic solution is applied to the surface of the anode 3. Pyrrole in the solution is oxidized and polypyrrole is electrolytically deposited. On the other hand, the electrolyte itself is reduced on the cathode 4 surface.

Therefore, the magnitude of the voltage applied for electrolytic oxidation changes depending on the level of the oxidation-reduction potential of the electrolytic solution and the reducible substance present in the electrolytic solution. If no reducible substance is added to the electrolytic solution, cations coming from the electrolytic solution itself or from the supporting electrolyte are reduced as described above. As described above, in the electrolytic oxidation reaction, an electrochemical oxidation-reduction reaction is performed on the anode and cathode surfaces in accordance with the amount of electricity supplied.

[Problem to be Solved by the Invention] In the above-mentioned conventional technology, even if the anode 3 is made of platinum, stainless steel or the like, which has a low electric resistance, a portion where the shape of the anode protrudes (in this case, a connector and the like) is included. If it has, when electrolyzed in the electrolytic solution, the polymer is preferentially deposited on the protruding portion. Conversely, when using an anode having a depressed portion or using a cylindrical anode, it is difficult to deposit a polymer in these depressions and the inside of the tube, and it is not possible to form a uniform polymer film. There was a drawback to say.

In many cases, the connector 9 is usually immersed in an electrolytic solution, and it is also common practice to use an anode having an oxide film formed on its surface as an anode, or depending on the type of metal of the anode. In some cases, an anode is electrolytically oxidized during electrolytic polymerization to form an oxide film, and these anodes generally have high electric resistance. For example, when it is desired to carry out electrolytic polymerization on a conductive polymer which has been thinly chemically deposited on an anode, a transparent electrode or an insulator having an oxide film formed on a surface having a high electric resistance, an electrolytic polymer is provided on the connector 9 portion. It has been preferentially deposited, and it has been difficult to uniformly deposit the electrolytic polymer on the electrode surface having a high electric resistance.

The object of the present invention is to solve such a problem, and even if there is a portion having a projection or a depression or a cylindrical portion in the shape of the anode, the polymer is relatively uniformly formed on the anode by electrolytic polymerization. It is an object of the present invention to provide an electrolytic polymerization method capable of precipitating a polymer.

[Means for Solving the Problems] In order to achieve the above object, in the electrolytic polymerization method of the first invention of the present invention, when a conductive polymer is formed on a hollow cylindrical anode by electrolytic oxidation, In order to make the current density flowing per unit area uniform, a cylindrical cathode having a shape corresponding to the anode is provided outside the anode, and an auxiliary cathode is provided inside the anode to perform electrolytic polymerization. And

Further, the electrolytic polymerization method of the second invention of the present invention is characterized in that, when a conductive polymer is formed on a flat anode by electrolytic oxidation, the current density per unit area of the anode is made uniform. Is characterized in that a cathode having an inverted V-shaped cross section is provided at the lower part of the substrate to perform electrolytic polymerization.

In the first and second methods of the present invention, it is preferable that the surface of the anode is an anode having a thin film of a metal oxide or a chemically formed conductive polymer.

[Action] The present invention provides an electrolytic polymerization method in which a monomer capable of oxidative electrolytic polymerization is contained in an electrolytic solution and a polymer is deposited on the anode by applying a voltage between the anode and the cathode. Since the electrolytic polymerization is carried out using a cathode or an auxiliary cathode having a shape corresponding to the shape of the anode, it is possible to deposit the polymer by the electrolytic polymerization almost uniformly on the anode.

That is, during the electrolytic oxidation polymerization, the flowing current produces a strong or weak current flow on the electrode surface according to the shape of the anode. For example, in the case of an anode having a projection, current concentrates on the projection. By forming the cathode portion corresponding to the protruding portion of the anode as a cathode arranged or arranged away from the protruding portion, it is possible to reduce the current flowing through that portion. Conversely, the flow of electric current is deep inside the concave or cylindrical inner surface of the anode. In this case, by installing the auxiliary cathode on the inner surface of the anode, it is possible to uniformly supply current to the inner surface of the anode having a depressed portion or the inner surface of the cylindrical anode, and to deposit a uniform polymer inside the anode. It is possible.

That is, in the electrolytic polymerization method of the first invention of the present invention, a cylindrical cathode having a shape corresponding to the anode is provided outside the hollow cylindrical anode, and an auxiliary cathode is provided inside the anode to perform the electrolytic polymerization. By doing so, the current density can be made uniform, so that a polymer having a uniform thickness can be deposited on the entire surface of the cylindrical anode.

In the electrolytic polymerization method according to the second aspect of the present invention, a current density can be similarly made uniform by providing an inverted V-shaped cathode below the plate-shaped anode and performing electrolytic polymerization. Can be deposited on the entire surface of the flat anode.

In addition, these anodes generally have high electric resistance, and therefore, in addition to the above-described uneven polymer deposition due to the anode shape, current concentrates and flows easily due to the electrode connector. According to a preferred example, the anode having a thin film of a metal oxide or a conductive polymer formed chemically can reduce the current distribution to the connector and make the current distribution to the anode substantially uniform. Therefore, the polymer can be deposited almost uniformly on the anode by electrolytic polymerization.

[Examples] Hereinafter, the present invention will be described in more detail based on examples.

Example 1 Polypyrrole was formed by electrolytic oxidation on the surface of a stainless steel metal cylinder having a diameter of 5 mm, a length of 1 cm, and a thickness of 0.1 mm.
FIG. 1 shows a configuration of a main part of an electrolytic cell provided with a cathode and an auxiliary cathode according to the present invention. In the figure, 1 is an electrolytic solution containing pyrrole, 2 is an electrolytic cell, 3 is a cylindrical stainless steel anode for depositing polypyrrole, 4 is a cylindrical stainless steel cathode having a shape corresponding to the cylindrical anode, and 4 'is inside the cylindrical anode. The auxiliary cathode having a diameter of 1 mm was installed. The auxiliary cathode 4 ′ was used by making electrical contact with the cathode 4 at point A. Reference numeral 11 denotes an electrode hanger connector having a titanium oxide film formed on its surface except for electrical contacts, and the cylindrical anode 3 and the lead wire 7 are electrically connected by a clip-shaped connector 9. Also, 10 is a clip-shaped connector of the cathode,
8 is a lead wire. As a result of applying a voltage of 3 V to the cathode for 10 minutes and depositing an electrolytic oxidation polymerization film on the cylindrical anode,
A uniform polymer film could be deposited on the outer and inner surfaces. Here, the composition of the electrolytic solution, pyrrole 0.3m
ol / L, sodium p-toluenesulfonate as supporting electrolyte
An aqueous solution of 0.15 mol / L was used.

For comparison, a polymer was deposited on a cylindrical electrode under the same electrolysis conditions by a conventional electrolysis method. The main part of the electrolytic cell used was configured as shown in FIG. In the figure, 1 is an electrolytic solution containing pyrrole, 2 is an electrolytic cell, 3 is a cylindrical stainless steel anode for depositing polypyrrole, 4 is a flat stainless steel cathode, 11 is a titanium oxide film formed on the surface except for electrical contacts. In the electrode hanger connector, the cylindrical anode 3 and the lead wire 7 are electrically connected by a clip-shaped connector 9. Reference numeral 10 denotes a clip-shaped connector for the cathode, and reference numeral 8 denotes a lead wire. As a result, the polymer was deposited unevenly inside the cylindrical anode, and there were many undeposited portions.

Example 2 Aluminum foil formed with aluminum oxide (thickness of 0.
1 mm, a width of 5 mm, and a length of 1 cm) were used as the anode, and the surface of the anode was made of polypyrrole which had been chemically thinned beforehand. That is, after immersing an aluminum foil formed with aluminum oxide in an aqueous solution of manganese nitrate, it is heated and oxidized in the air to form manganese dioxide, immersed in an N, N-dimethylformamide solution of polypyrrole, and chemically oxidized polypyrrole on the anode surface. A thinly formed anode was used.

The configuration of the main part of the electrolytic cell used is shown in FIG. In the figure, 1 is an electrolytic solution containing pyrrole, 2 is an electrolytic cell, 3 is a plate-shaped anode for depositing polypyrrole, 4 is an inverted V-shaped stainless steel cathode, 11 is a titanium oxide film on the surface except for electrical contacts. The formed electrode hanger connectors, 7 and 8 are lead wires, and 9 and 10 are clip-shaped connectors. As shown in FIG. 2, the cathode 4 is located at the anode position furthest from the energized portion B of the electrode hanger connector 11 of the anode 3,
The inverted V-shaped apex was set closest. The electrolytic polymerization was performed under the same conditions as in Example 1. As a result, a large amount of polypyrrole was deposited on the electrode hanger connector 11 and its anode contact portion (B), but could be deposited on the entire surface of the anode.

For comparison with a conventional method, polypyrrole was electrolytically deposited using the same electrolytic cell as shown in FIG. However,
As the anode, an aluminum foil in which polypyrrole was previously chemically thinly formed on the same aluminum oxide film as described above was used, and the electrode 3 was used as in the usual electrolytic polymerization.
Since connector 4 was immersed in the electrolyte, connectors 9 and 10
Was also immersed in the electrolytic solution, and the electrolytic polymerization was performed under the same conditions as in the present invention. As a result, polypyrrole almost deposited on the connector 9 and its anode contact portion, and could not be deposited on the entire surface of the anode within the same time. It has been found that at least 30 minutes or more of electrolysis time is required for deposition on the entire surface.

Example 3 A polypyrrole electrolytic polymerized film was formed in exactly the same manner as in Example 2 except that the material used for the hanger connector 11 was changed from titanium to tantalum using an anode obtained by further adhering manganese dioxide to the aluminum foil used in Example 2. Was.

As a result, polypyrrole was successfully deposited on the anode surface in the same manner as in Example 2.

In the above-described embodiment, an example in which pyrrole is used as a monomer has been described. However, the present invention can be similarly applied to other electrolytically oxidatively polymerizable monomers such as aniline and thiophene. In addition, the conductive polymer film formed in advance on the anode is not limited to polypyrrole, but may be any other polymer such as polyaniline as long as it is a conductive polymer that can be chemically deposited by an oxidizing agent such as manganese dioxide or ferric chloride. Polythiophene and other polymers are also applicable. The material of the anode and cathode is
Any material can be used as long as it can be used for electrolytic polymerization, and it is not particularly limited to those of Examples.

[Effects of the Invention] According to the method of the present invention, even when an anode having a shape in which current distribution is likely to be non-uniform, such as an anode having a protrusion or a depression, or a cylindrical anode, is used, the anode is almost uniformly formed on the anode. A polymer can be deposited by electrolytic polymerization.

That is, in the electrolytic polymerization method of the first invention of the present invention, a cylindrical cathode having a shape corresponding to the anode is provided outside the hollow cylindrical anode, and an auxiliary cathode is provided inside the anode to perform the electrolytic polymerization. By doing so, the current density can be made uniform, so that a polymer having a uniform thickness can be deposited on the entire surface of the cylindrical anode.

In the electrolytic polymerization method according to the second aspect of the present invention, a current density can be similarly made uniform by providing an inverted V-shaped cathode below the plate-shaped anode and performing electrolytic polymerization. Can be deposited on the entire surface of the flat anode.

According to a preferred example of the first or second method of the present invention, wherein the surface of the anode is an anode having a thin film of a metal oxide or a chemically formed conductive polymer,
In addition to the effects described above, even when an anode having a high electric resistance is used in which a current distribution is particularly likely to be concentrated on the connector, it is possible to deposit the polymer almost uniformly by electrolytic polymerization on the anode.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a main portion of an electrolytic polymerization apparatus according to one embodiment of the present invention, FIG. 2 is a schematic configuration diagram of a main portion of an electrolytic polymerization device according to another embodiment of the present invention, and FIG. FIG. 4 is a schematic configuration diagram of a conventional electrolytic polymerization apparatus used, and FIG. 4 is a schematic configuration diagram of main parts of a conventional electrolytic polymerization apparatus of a comparative example. DESCRIPTION OF SYMBOLS 1 ... Electrolyte solution, 2 ... Electrolyzer, 3 ... Anode, 4 ... Cathode, 4 '... Auxiliary cathode, 5 ... Circulation pump, 6 ... Power supply, 7,8 lead wire, 9,10 , 11 …… connector, 12…
... circulation pipe

──────────────────────────────────────────────────続 き Continued on the front page (58) Fields surveyed (Int. Cl. ⁶ , DB name) C25B 1/00-15/08 C25D 9/00-9/12 C25D 13/00-13/24

Claims (3)

(57) [Claims] When forming a conductive polymer on a hollow cylindrical anode by electrolytic oxidation, a shape corresponding to the anode is formed outside the anode in order to make the current density flowing per unit area of the anode uniform. Wherein a cylindrical cathode is provided and an auxiliary cathode is provided inside the anode to perform electrolytic polymerization. 2. A cathode having an inverted V-shaped cross section below the anode in order to make the current density per unit area of the anode uniform when the conductive polymer is formed on the flat anode by electrolytic oxidation. An electrolytic polymerization method, wherein electrolytic polymerization is performed by providing the method. 3. The electrolytic polymerization method according to claim 1, wherein the surface of the anode is an anode having a thin film of a metal oxide or a chemically formed conductive polymer.