JP2669622B2 - Manufacturing method of conductive organic polymer - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for electrolytically polymerizing O-aminobenzothiols to obtain a conductive organic polymer. "Prior art and its problems" Conventionally, as a conductive organic polymer, for example, polypyrrole, polyaniline, and the like are known. Such a conductive organic polymer is in the form of a thin film or a film obtained by electrolytic polymerization of a monomer, and exhibits good conductivity, so that it is expected as a promising electronic material. However, such a film made of a conductive organic polymer tends to have many pinholes, and has a problem of lack of homogeneity such as nonuniform conductivity due to the pinholes. "Means for Solving the Problems" Accordingly, the present invention provides a cyclic voltammogram of an electrolytic bath when an o-aminobenzothiol represented by the following formula (I) is subjected to electric field polymerization by a potential scanning method or a constant potential method. A film-shaped polymer was obtained by electrolytic polymerization using a potential higher than the rising potential of the oxidation peak on the low potential side as an electrolytic set potential, and this polymer was placed in a solution containing no o-aminobenzothiols. By sweeping and activating, it has sufficient conductivity and flexibility as an electronic material,
Moreover, a pinhole-free and homogeneous thin film or film polymer was obtained. [In the formula, both R ₁ and R ₂ are organic groups represented by CnH ₂ n + ₁ (where n is 1, 2, or 3)]. The poly (O-aminobenzothiols) of the present invention obtained by this electrolytic polymerization are deposited on the working electrode as a pinhole-free and highly flexible film or thin film, and the polymer film is removed by an appropriate peeling means. It can be used as a simple substance, and can be sufficiently used in the deposited state. The obtained polymer has an electric conductivity of 10 ^-5 to 10 ^-8 S / cm depending on the degree of the activation treatment after the polymerization. Next, the electrolytic polymerization in the present invention will be described. Electropolymerization is performed in a two-electrode system using a working electrode and a counter electrode or in a three-electrode system using a working electrode, a counter electrode and a reference electrode, and an electrolysis set potential based on a rising potential of a maximum oxidation peak of a cyclic voltammogram described later. Is determined, a three-electrode type having a reference electrode is preferable, but the present invention is not limited to this. Working electrodes include metals such as gold, platinum, and stainless steel, graphite, In ₂ O ₃ , S
A conductive metal oxide such as nO ₂ or a semiconductor such as Si or GaAs is used. Unused platinum, graphite or the like is used for the counter electrode, and a sodium chloride saturated calomel electrode (SSCE), a saturated calomel electrode (SCE) or the like is used for the reference electrode. In the electrolytic bath, O-aminobenzothiols and water that dissolves them and does not react with the supporting electrolyte, acetonitrile, propylene carbonate, methanol, ethanol, and other solvents and LiCl, chlorides such as NaCl, LiClO ₄ ,
(C ₄ H _{9) 4} perchlorate NClO ₄ such as (C ₄ H _{9) 4} tetrafluoroborate of NBF _4, etc., sulfates such as Na ₂ SO _4, CF ₃ COONa, etc. tetrafluoro acid A material composed of a supporting electrolyte such as a salt, an acid substance such as H ₂ SO ₄ , HCl and HClO _{4 and} an alkaline substance such as NaOH and KOH is used. The supporting electrolyte concentration is 0.1 to
The concentration of the O-aminobenzothiols monomer is preferably 0.01 to 0.5 mol / degree. As the electrolysis mode for polymerizing the O-aminobenzothiol monomer, a potential scanning method or a constant potential method is preferable. In the potential scanning method, a forward and backward triangular liquid potential is alternately applied between a potential E ₁ and a potential E ₂ higher than the potential E ₁ . The constant potential method is to apply a constant potential E _3. In the present invention, in these electrolytic polymerization methods, it is important to appropriately determine the electrolytic set voltage. First, a cyclic voltammogram of an electrolytic bath system to be subjected to electrolytic polymerization is measured by cyclic voltammetry. Cyclic voltammetry sweeps the potential proportional to time from the initial voltage E _{0 at which} no Faraday current flows, reverses the potential sweep direction at the reversal potential E _λ , and the same potential sweep speed (usually 10 ^{−3 to 1} V /
Sweeping seconds) intended to return to the initial potential E _0, the current obtained by the triangular potential sweep - referred to as a cyclic voltammogram potential curve. In addition, the cyclic voltammogram in the present invention refers to one obtained by a single sweep method in which one potential sweep is performed. Fig. 2 shows an example of a cyclic voltammogram of Fig. 1.
This cyclic voltammogram shows 2-amino-6-
Methyl benzothiol is 50 mmol /, Na ₂ SO ₄ and
For an electrolytic bath in which the concentration of SO ₄ ^2- ion was 0.5 mol / H ₂ SO ₄ and the pH was 1.0, initial potential E ₀ −0.4 V (vs. SCE), reversal potential E _λ +1.0 V (vs. SCE), potential sweep It was obtained at a speed of 50 mV / sec. Such a cyclic voltammogram shows the state of polymerization of a monomer versus (O-aminobenzothiols) on the working electrode during electrolysis. In the graph of FIG. 1, an oxidation reaction occurs above the horizontal axis. It can be seen that two or more oxidation peaks appear due to the oxidation of the monomer. Then, the rising potential (indicated by B in FIG. 1) of the oxidation peak on the low potential side (indicated by A in FIG. 1) in this cyclic voltammogram is determined from the graph. In the present invention, a potential higher than the rising potential is set as the electrolytic set potential. If the electrolysis mode is the constant potential method, the electrolysis may be performed while the above-mentioned electrolysis set voltage is kept constant.
Further, if the electrolysis mode potential scanning method, a high potential E ₂ and the electrolytic set potential, it is desirable to perform to set the low potential E ₁ for example, -0.4V or less. In addition, in the combination of the potential scanning method and the constant potential method, it is sufficient that the above condition is satisfied.
The combination pattern and the number of combinations are free. Further, the rising potential of the oxidation peak on the low potential side in the cyclic voltammogram is determined by the monomer of the electrolytic bath, the solvent,
Since it varies depending on the type and concentration of the supporting electrolyte, it is necessary to measure the cyclic voltammogram of the electrolytic bath every time the composition of the electrolytic bath changes, and to find the rising potential. In the case of the potential scanning method, the potential sweeping speed is arbitrary, but is preferably about 10 mV / sec to about 1000 mV / sec, and the number of scans is also arbitrary.However, since the thickness of the polymer depends on the number of scans, Usually, it is often determined by the film thickness. By carrying out electrolytic polymerization under such conditions, a thin film or film polymer obtained by polymerizing O-aminobenzothiols is deposited on the surface of the working electrode. Further, the polymer thus obtained is subjected to an activation treatment for improving electric conductivity. In this activation treatment, a potential sweep is performed on the polymer immersed in a solution containing no monomer under the same conditions as in the measurement of the cyclic voltammogram described above. It is possible to significantly improve. Examples of the solution used for such an activation treatment include chlorides such as LiCl and NaCl, LiClO ₄ , (C
₄ H _{9) 4} perchlorate NClO ₄ such, (C ₄ H ₉₎ tetrafluoroborate of ₄ NBF _4, etc., sulfates such as Na ₂ SO _4, tetrafluoro acid salt such as CF ₃ COONa, H ₂ SO _4, HCl, acid substances such as HClO _4, N
aOH, supporting electrolyte such as alkaline substances such as KOH 0.1 to 1.0
An aqueous acidic solution containing at a concentration of about mol / about or methanol or propylene carbonate containing the above supporting electrolyte;
An acidic non-aqueous solution such as benzonitrile is preferably used. The sweep potential in the activation treatment may be higher than the set potential at the time of polymerization at least on the high potential side. Although the number of sweeps is arbitrary, it is preferable to perform the cycle until the peak current value of the cyclic voltammogram is stabilized.
Usually it is about 100 times. Further, the sweep speed is also arbitrary, but is usually set in the range of 50 mV / sec to 1000 mV / sec. By such an activation treatment, the activity of the polymer can be improved, and the conductivity can be freely adjusted in the range of 10 ^-5 to 10 ^-8 S / cm. “Example” Hereinafter, an example will be described specifically. (Example 1) 50 mM 2 in an aqueous solution of 0.5 M Na ₂ SO ₄ —H ₂ SO ₄ (pH = 1.0)
- dissolving the amino-6-methylbenzoyl thiol, after the O ₂ in the solution was eliminated by N _2, a counter electrode platinum wire reference electrode saturated calomel electrode (SCE), act ITO film (30Ω / □) electrode As a result of scanning electrolysis. In this solution system, the rising potential of the oxidation peak on the low potential side observed in the cyclic voltammogram during polymerization was 250 mV (vs. SCE). The scanning speed was 50 mV / sec, and the potential was scanned from -400 mV to +400 mV. The amount of electric charge during polymerization was measured with a coulomb meter, the conductivity was measured with a two-terminal method, and the film thickness was measured with a surface roughness meter. As a result of polymerization under the above polymerization conditions, the film thickness reached 0.2 μm after 100 scans. Then 0.2 without monomer
An activation treatment was performed in a M NaClO ₄ (pH 1.0) aqueous solution by scanning 100 times between −400 mV ← → + 800 mV at a sweep speed of 200 mV / sec. The conductivity of the resulting film is 5 × 10 ^-7
S / cm, pinhole-free, and the film had a smooth and flexible appearance. (Example 2) The polymerization was conducted under the same conditions as in Example 1 except that the scanning potential range was from -400 mV to +1000 mV (vs. SCE). In this case, the film pressure reached 0.5 μm with 100 scans. Thereafter, when the same activation treatment as in Example 1 was performed, the obtained film had an electric conductivity of 10 ⁻⁶ S / cm, was free from pinholes, and had a smooth and flexible appearance. (Example 3) In the same solution system as in Example 1, constant potential electrolysis was performed at 100 mV (vs. SCE). Formation of a film was observed on the surface of the ITO film, and the film thickness was 0.2 μm after a polymerization time of 3 hours, and the conductivity thereof was 8 × 10 ⁻⁶ S / cm after the activation treatment. (Example 4) The polymerization potential was set to 500 mV (vs. SCE), and polymerization was carried out in the same manner as in Example 3. After a polymerization time of 4 hours, the film thickness was 0.1 μm, and after the activation treatment described above, the electric conductivity was 9 × 10 ⁻⁶ S / cm. (Example 5) In the same solution system as in Example 1, the potential scanning was performed from -400 to +500.
It was performed 50 times with mV (vs. SCE), and then the potential was kept at +500 mV to carry out potentiostatic electrolysis. Under this condition, the energization amount is 0.03
0.1 μm thickness at C / cm ² , conductivity after the above treatment is 8.5 × 10
It was ^-6 S / cm. (Example 6) After keeping the same solution system as in Example 1 at +500 mV for 300 seconds,-
Scanning electrolysis was performed 100 times from 400 mV to +500 mV (vs. SCE). At this time, the film thickness was 0.4 μm, and the conductivity was 2 × 10 ⁻⁶ S / cm after the activation treatment described above. Example 7 50 mM 2-amino-6-ethylbenzothiol was dissolved in an aqueous solution of 0.5 M NaClO ₄ —HClO ₄ (pH = 3), and O ₂ in the solution was sufficiently replaced with N ₂ . Platinum wire as counter electrode, saturated calomel electrode (SCE) as reference electrode, ITO film (30Ω / □)
Scanning electrolysis was performed as a working electrode. In this solution system, the rising potential of the oxidation peak on the low potential side observed in the cyclic voltammogram during polymerization was 200 mV (vs. SCE). The scanning speed is 50 mV / sec, and the potential is from -400 mV to +600 mV (vs. SC
Scanned to E). When polymerized under these polymerization conditions, the film thickness is 0.1 μm after 100 scans, and the conductivity is 5 × 10 5 after the above treatment.
It was ^-6 S / cm. The resulting film was pinhole free, smooth and flexible. (Example 8) In the same solution system as in Example 7, constant potential electrolysis was performed while maintaining the potential at +600 mV (vs. SCE). When the polymerization current is 0.05 C / cm ² , the film thickness is
The film had a thickness of 0.1 μm, an electric conductivity of 9 × 10 ⁻⁶ S / cm after the treatment, was pinhole-free, and had a smooth and flexible appearance. (Example 9) An aqueous solution was prepared under the same conditions as in Example 1 using 2-amino-3-methylbenzothiol as a monomer. The rising potential of the oxidation peak on the low potential side observed in the cyclic voltammogram during polymerization in this solution system was 250 mV (vs. SCE). The scanning speed is 50mV / sec, and the potential is + 600mV to +
When scanning up to 650mV, the film thickness is 0.1μ with 100 scans
m was obtained. Conductivity is 5 × 10 after the above treatment
^{At -7} S / cm, it was a pinhole-free, smooth and flexible film. (Example 10) Using 2-amino-6-methylbenzothiol as a monomer, an aqueous solution was prepared under the same conditions as in Example 1. The rising potential of the oxidation peak on the low potential side of the cyclic voltammogram in this solution system was 300 mV (vs. SCE). When the scanning speed was 50 mV / sec and the potential was scanned from -400 mV to +600 mV, a film having a thickness of 0.1 μm was obtained after 100 scans. The conductivity was 5 × 10 ^-7 S / cm after the treatment, and it was a pinhole-free, smooth and flexible film. (Comparative Example 1) Potential scanning was performed using a solution system under the same conditions as in Example 1 with the scanning range being from -400 mV to +200 mV (vs SCE). Other conditions are the same. It was observed that current flowed with potential scanning, but no increase in peak current was observed and film formation was not observed even when the number of scans was increased. (Comparative Example 2) The potential was set to +200 mV (vs. SCE) in the same solution system as in Example 1.
Time kept. Six hours later, when the ITO film was taken out of the solution and examined, no film formation was observed. (Comparative Example 3) In the same solution system as in Example 1, the potential scan was performed from -200 mV to +2.
The test was performed 10 times at 00 mV (vs. SCE), and then the potential was kept at +200 mV for 6 hours. After 6 hours, when the ITO film was taken out and examined, no film formation was observed. Comparative Example 4 In the same solution system as in Example 7, −400 mV to +150 mV (vs. SC)
Potential scanning was performed 100 times in the range of E). Thereafter, when the ITO film was taken out of the solution and examined, no film formation was observed. [Effects of the Invention] As described above, according to the present invention, a polymer of o-aminobenzothiols having good conductivity and flexibility, and being pinhole-free and homogeneous in a thin film or film is provided. Is obtained, and it can be used as it is as an electronic material utilizing its good conductivity. In particular, in the present invention, the polymer obtained by electrolytic polymerization is subjected to activation treatment, so that the conductivity of the polymer is further improved. In addition, the effect that the value of the electric conductivity of the polymer can be controlled by the degree of the activation treatment can be obtained.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagram showing an example of a cyclic voltammogram for setting an electrolytic set voltage in the present invention.

Claims (1)

(57) [Claims] General formula [Wherein, R ₁ and R ₂ are both CnH _{2 + 1} (where n =
1, 2, and 3. ). The working electrode and the counter electrode are immersed in an electrolytic bath containing o-aminobenzothiols represented by the formula, and a film-like polymer of o-aminobenzothiols is deposited on the working electrode by a potential scanning method or a constant potential method. In this case, electrolytic polymerization is performed using a potential higher than the rising potential of the oxidation peak on the low potential side of the cyclic voltammogram of the electrolytic bath as an electrolytic set potential, and then the obtained polymer contains the o-aminobenzothiols. A method for producing a conductive organic polymer, wherein the activation treatment is performed by sweeping the potential in a solution that does not have a potential.