A method for synthesizing a PEDOT polymer

Abstract

The present invention belongs to the field of polymer materials technology and provides a method for synthesizing a PEDOT polymer. The method uses EDOT (3,4-ethylenedioxythiophene) as a starting material, employs a two-electrode system with conductive glass, glassy carbon, platinum sheet, nickel foam, or cobalt foam as a working electrode or counter electrode, respectively, and uses dimethyl carbonate as an electrolyte solution. Electrochemical polymerization is performed under stirring to obtain a highly conductive and soluble PEDOT polymer. The method is simple to operate, has a high yield, and is suitable for industrial application.

Description

Technical Field

[0001] The invention belongs to the technical field of polymer materials, and particularly relates to a method for synthesizing and preparing a PEDOT polymer. Background Art

[0002] Poly (3,4-ethylenedioxythiophene) (PEDOT) is a conductive polymer formed by chemical polymerization or electrochemical polymerization of 3,4-ethylenedioxythiophene (EDOT). Due to the poor solubility of pure PEDOT and the unsatisfactory results of industrial production, organic or inorganic acids are often used as dopants in the market to improve this drawback. The chemical structure of PEDOT gives it the characteristics of small energy gap, high conductivity, good environmental stability, high mechanical strength and high visible light transmittance in the doped state. It is widely used in organic thin-film solar cell materials, OLED materials, electrochromic materials, transparent electrode materials and other fields, and is particularly suitable for modifying synthetic electrode materials.

[0003] In recent years, reports have shown that polystyrene sulfonic acid-doped PEDOT is used to obtain poly(3,4-ethylenedioxythiophene):polystyrene sulfonic acid polymers, namely PEDOT:PSS polymers. These polymers not only possess most of the advantages of pure PEDOT, but also greatly improve their solubility in aqueous solutions and organic solvents. The only drawback is that the production process of PEDOT:PSS polymers is complex, the production time is long, and there are many by-products. Summary of the Invention

[0004] To address the above technical problems, the present invention proposes a method for synthesizing and preparing PEDOT polymers. This method uses camphorsulfonic acid as a dopant, which not only improves conductivity by increasing the density of charge carriers but also enhances polymer solubility by weakening interactions between polymer chains. The method for synthesizing and preparing PEDOT polymers provided by the present invention features a simple process, high yield, and is suitable for industrial production.

[0005] The reaction principle is:

[0006]

[0007] The synthetic preparation method of the present invention comprises the following steps:

[0008] (1) Preparation of electrolyte solution: Dissolve a certain amount of dopant in carbonate solution, heat and stir at 40°C until the dopant is dissolved, and then add EDOT and catalyst.

[0009] (2) Using any one of platinum sheet, glassy carbon, nickel foam, cobalt foam, and conductive glass ITO as a counter electrode and any one of platinum sheet, glassy carbon, nickel foam, and cobalt foam as a working electrode, the pretreated electrodes are immersed in a prepared electrolyte solution, and an electrochemical polymerization reaction is carried out under stirring conditions to obtain a product.

[0010] Preferably, the carbonate solution in (1) is dimethyl carbonate;

[0011] Preferably, the catalyst in (1) is hexamethylphosphoric triamide;

[0012] Preferably, the dopant in (1) is camphorsulfonic acid;

[0013] Preferably, the concentration of EDOT in (1) is 0.1-0.2 mol / L, the concentration of hexamethylphosphoric acid triamide is 0.01-0.5 mol / L, and the concentration of camphorsulfonic acid is 0.1-0.2 mol / L;

[0014] Preferably, the electrochemical polymerization current density in (2) is 5-15 mA / cm 2 ;

[0015] Preferably, the electrochemical polymerization time in (2) is 2-4 h;

[0016] Preferably, the platinum sheet in (2) is pretreated as either a counter electrode or a working electrode by ultrasonic cleaning in a 1 mol / L hydrochloric acid solution for 5 min, then repeatedly rinsed with deionized water and ethanol, and dried;

[0017] Preferably, (2) glassy carbon is used as the working electrode, and its pretreatment method is: polishing with 0.05 μm Al2O3 powder, rinsing with deionized water and anhydrous ethanol, and drying;

[0018] Preferably, the nickel foam or cobalt foam in (2) is pretreated as either a counter electrode or a working electrode by ultrasonic cleaning in an acetone solution for 10 minutes, rinsing with deionized water, ultrasonic cleaning in a 1 mol / L hydrochloric acid solution for 10 minutes, and finally repeatedly rinsing with deionized water and ethanol, and drying.

[0019] Preferably, the pretreatment method of the glassy carbon or conductive glass ITO used as the counter electrode in (2) is as follows: immersing the electrode in a sodium hydroxide solution (0.1 mol / L) for about 20 min, repeatedly washing with deionized water until neutral, rinsing with anhydrous ethanol after washing, and drying;

[0020] Preferably, the contact area between the counter electrode and the working electrode used in (2) and the electrolyte solution is 10 mm×20 mm (the volume of the electrolyte solution is 80 mL).

[0021] The present invention relates to a method for synthesizing PEDOT polymers. Using 3,4-ethylenedioxythiophene as a raw material, suitable electrodes are selected for electrochemical polymerization of poly(3,4-ethylenedioxythiophene). Compared with other existing methods, this method has the following advantages:

[0022] (1) Rapid reaction, only 2-4 hours is required, which greatly shortens the polymerization reaction time and improves production efficiency;

[0023] (2) The production process is simple to operate. It only requires the preparation of electrolyte solution and pretreatment of working electrode and counter electrode before the electrochemical polymerization reaction can be carried out, and the yield can reach 78.9%;

[0024] (3) Low cost, easy industrial production, and easy waste disposal. For example, the byproducts of the electrochemical polymerization reaction in Example 1 are only oxygen and hydrogen, which have no side effects on humans. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is the cyclic voltammetry test diagram in Example 1;

[0026] Figure 2 This is the molecular weight distribution diagram in Example 1. DETAILED DESCRIPTION

[0027] In order to enable those skilled in the art to better understand the present invention, the present invention will be further described in conjunction with specific embodiments.

[0028] Example 1

[0029] (1) Preparation of electrolyte solution:

[0030] Weigh 1.74 g of camphorsulfonic acid and dissolve it in 75 mL of dimethyl carbonate solution. Stir at 40°C until the camphorsulfonic acid is completely dissolved. Then, add 1.07 g of EDOT and 0.134 g of hexamethylphosphoric triamide to obtain an electrolyte solution with a volume of 80 mL.

[0031] (2) Electrode pretreatment:

[0032] A platinum sheet was used as the counter electrode, and a glassy carbon electrode was used as the working electrode. Both electrodes were pretreated accordingly. Platinum sheet electrode pretreatment: ultrasonically clean the sheet in 1 mol / L hydrochloric acid for 5 minutes, then rinse repeatedly with deionized water and ethanol, and dry. Glassy carbon electrode pretreatment: Polish the sheet with 0.05 μm Al2O3 powder, then rinse with deionized water and anhydrous ethanol, and dry.

[0033] (3) Electrochemical polymerization reaction and electrochemical testing:

[0034] Using an electrochemical workstation (Shanghai Chenhua Instrument Co., Ltd., DZ202201), the pretreated platinum electrode and glassy carbon electrode in (2) were placed in the electrolyte solution in (1). The contact area between the two electrodes and the electrolyte solution was 10 mm × 20 mm. Electrochemical polymerization was then carried out under stirring conditions with a current density of 15 mA / cm 2 , the reaction time was 2 h, and PEDOT polymer was obtained.

[0035] During the polymerization process, bubbles were observed to be generated at the platinum electrode, bubbles were generated at the glassy carbon electrode, a uniform blue-black substance was generated, and a black product was present in the solution. Cyclic voltammetry tests were performed on the polymerization process.

[0036] Cyclic voltammetry test: Scan at a scan rate of 50mV / s (activate first, then start the test after stabilization). Figure 1 , oxidation peak and reduction peak current can be observed, indicating that an oxidation reaction occurs on the working electrode, i.e., the glassy carbon electrode, and the bubbles generated are oxygen. Correspondingly, a reduction reaction occurs on the counter electrode, i.e., the platinum electrode, and electrons are obtained to generate hydrogen. EDOT is polymerized on the platinum electrode, and the polymerization product is a blue-black substance.

[0037] The blue-black substance on the platinum electrode and the black product in the electrolyte solution were washed with ethanol and dried at 55° C. for 12 h to obtain the final product. The final product was weighed to have a mass of 0.844 g and a yield of 78.9%.

[0038] Yield calculation formula:

[0039]

[0040] (4) Characterization of the final product:

[0041] At 25°C, using No. 7021 as a blank control, without taking any product, only N,N-dimethylformamide (DMF) was tested using an NDJ-8S digital viscometer;

[0042] Samples numbered 7022, 7023, 7024, and 7025 from the same batch of products were taken. The above numbers refer to 0.05 g, 0.1 g, 0.2 g, and 0.3 g of the final product obtained in (3), respectively. These samples were dissolved in 80 mL of N,N-dimethylformamide (DMF) and tested using an NDJ-8S digital viscometer. The data are shown in Table 1.

[0043] Table 1 Viscosity data of different final product qualities

[0044]

[0045]

[0046] In this digital viscometer, to ensure accuracy, the range percentage reading should be controlled between 10% and 90%, with 50% being the best.

[0047] As shown in Table 1, the viscosity of sample No. 7024 is 15.20 mPa·s when the viscosity meter range percentage is 60%, which is the best performance. Sample No. 7024 was selected for gel permeation chromatography (GPC) test to determine the molecular weight of 7024. The test results are as follows Figure 2 , Table 2, Table 3.

[0048] Depend on Figure 2 It can be seen that the peak shape is narrow, the high molecular weight is less, the molecular weight distribution is more concentrated, and the polydispersity index is 1.365857.

[0049] Table 2 Molecular weight results of gel chromatography

[0050]

[0051] Table 3 Peak results of gel chromatography

[0052]

[0053] The number-average molecular weight is the average molecular weight of all polymer chains, while the weight-average molecular weight takes into account the greater proportion of chains with larger molecular weight in the total mass, and therefore better reflects the impact of high-molecular-weight chains on all polymer chains. As shown in Table 2, the number-average molecular weight of 7024 is 7902 g / mol, and the weight-average molecular weight is 10793 g / mol. Since the weight-average molecular weight is greater than the number-average molecular weight, it indicates that chains with larger molecular weight are present in the polymer, and these chains account for a significant proportion of the total mass. Therefore, it can be concluded that in the present invention, a polymerization reaction was carried out using EDOT as the raw material to obtain a PEDOT polymer.

[0054] Example 2

[0055] Regarding the second embodiment of the present invention, descriptions of parts that are the same as those of the first embodiment are omitted and are denoted by the same reference numerals.

[0056] (1) The preparation method of the electrolyte in Example 2 is the same as that in Example 1.

[0057] (2) Electrode pretreatment:

[0058] Use nickel foam as the counter electrode and glassy carbon as the working electrode. Place the nickel foam electrode in an acetone solution for ultrasonic cleaning for 10 minutes, rinse with deionized water, place it in a 1 mol / L hydrochloric acid solution for ultrasonic cleaning for 10 minutes, and finally rinse repeatedly with deionized water and ethanol and dry. The pretreatment method of the glassy carbon electrode is the same as in Example 1. The current density is set to 15 mA / cm 2, electrochemical polymerization was carried out under stirring conditions, and the reaction time was 2h.

[0059] During the polymerization process, bubbles were observed on the nickel foam electrode and a small amount of bubbles and a blue-black substance were observed on the glassy carbon electrode. The blue-black substance on the glassy carbon electrode was rinsed with ethanol and dried at 55°C for 12 hours. 0.738 g of product (7026) was weighed, yielding 69%.

[0060] 0.2 g of the product (7026) was subjected to gel permeation chromatography (GPC) to determine the molecular weight of the product. Table 4 shows the molecular weight results of the gel permeation chromatography of the sample of Example 2.

[0061] Table 4 Molecular weight results of gel chromatography

[0062]

[0063] As shown in Table 4, the number average molecular weight of 7026 is 7814 g / mol, and the weight average molecular weight is 10311 g / mol. Since the weight average molecular weight is greater than the number average molecular weight, it indicates that chains with larger molecular weight exist in the polymer, and these chains account for a large proportion of the total mass. Therefore, it can be concluded that in the present invention, a polymerization reaction occurs using EDOT as a raw material to obtain a PEDOT polymer.

[0064] Example 3

[0065] Regarding the third embodiment of the present invention, descriptions of parts that are the same as those of the first embodiment are omitted and are denoted by the same reference numerals.

[0066] The preparation method of the electrolyte solution in Example 3 is the same as that in Example 1, with nickel foam as the working electrode and platinum sheet as the counter electrode. The pretreatment method of the nickel foam electrode in Example 3 is the same as that in Example 2, and the pretreatment method of the platinum sheet electrode is the same as that in Example 1.

[0067] The current density was set to 15 mA / cm 2 , electrochemical polymerization was carried out under stirring conditions, and the reaction time was 2h.

[0068] During the polymerization process, bubbles were observed on the platinum electrode and black material was generated on the nickel foam electrode. The black material on the nickel foam electrode was rinsed with ethanol and dried at 55°C for 12 h to obtain 0.621 g of product (7027) with a yield of 58%.

[0069] 0.2 g of the product (7027) was subjected to gel permeation chromatography (GPC) to determine the molecular weight of the product. Table 5 shows the molecular weight results of the gel permeation chromatography of the sample of Example 3.

[0070] Table 5 Molecular weight results of gel chromatography

[0071]

[0072] As shown in Table 5, the number average molecular weight of 7027 is 7401 g / mol, and the weight average molecular weight is 11705 g / mol. Since the weight average molecular weight is greater than the number average molecular weight, it indicates that chains with larger molecular weight exist in the polymer, and these chains account for a large proportion of the total mass. Therefore, it can be concluded that in the present invention, a polymerization reaction occurs using EDOT as a raw material to obtain a PEDOT polymer.

[0073] Example 4

[0074] Regarding the fourth embodiment of the present invention, descriptions of parts that are the same as those of the first embodiment are omitted and are denoted by the same reference numerals.

[0075] The preparation method of the electrolyte solution in Example 4 is the same as that in Example 1. Nickel foam is used as the working electrode, and the pretreatment method is the same as that in Example 2. The conductive glass ITO is used as the counter electrode. The electrode is immersed in a sodium hydroxide solution (0.1 mol / L) for about 20 minutes, and repeatedly washed with deionized water until neutral. After washing, it is rinsed with anhydrous ethanol and dried. The current density is set to 15 mA / cm 2 , electrochemical polymerization was carried out under stirring conditions, and the reaction time was 2h.

[0076] During the polymerization process, bubbles and blackening were observed on the nickel foam electrode, and a nonuniform layer of black material was observed on the conductive glass ITO electrode. Under stirring, some of the black product fell into the electrolyte. The blue-black material on the glassy carbon electrode was rinsed with ethanol and dried at 55°C for 12 hours to obtain 0.667 g of product (7028), with a yield of 62.3%.

[0077] 0.2 g of the product (7028) was subjected to gel permeation chromatography (GPC) to determine the molecular weight of the product. Table 6 shows the molecular weight results of the gel permeation chromatography of the sample of Example 4.

[0078] Table 6 Molecular weight results of gel chromatography

[0079]

[0080] As shown in Table 6, the number average molecular weight of 7028 is 7501 g / mol, and the weight average molecular weight is 11305 g / mol. Since the weight average molecular weight is greater than the number average molecular weight, it indicates that chains with larger molecular weight exist in the polymer, and these chains account for a large proportion of the total mass. Therefore, it can be concluded that in the present invention, a polymerization reaction occurs using EDOT as a raw material to obtain a PEDOT polymer.

[0081] Examples 5 to 8

[0082] Regarding Examples 5 to 8 of the present invention, descriptions of parts that are the same as those of Example 1 are omitted and are denoted by the same reference numerals.

[0083] By changing only the current density and reaction time in the electrochemical polymerization, the corresponding final products were obtained. The gel chromatography molecular weight results of the final products were tested, and the relevant data obtained are shown in Table 7 below.

[0084] Table 7 Electrochemical polymerization reaction and gel chromatography measurement results of Examples 5 to 8

[0085]

[0086] In summary, the present invention provides a method for synthesizing and preparing a PEDOT polymer, using 3,4-ethylenedioxythiophene as a raw material, camphorsulfonic acid as a dopant, and selecting suitable electrodes and pretreatment methods to perform electrochemical polymerization to obtain the PEDOT polymer. The synthesis process is simple, has a high yield, and is suitable for industrial production.

[0087] The above are only preferred embodiments of the present invention, and are not intended to limit the scope of the present invention. All equivalent changes and modifications made within the scope of the present invention should still fall within the scope of the present invention.

[0088] Comparative Example 1

[0089] The inventors conducted a large number of experiments in the process of obtaining the technical solution of the present invention. Regarding the selection of electrodes, the inventors initially selected conductive glass ITO as the working electrode and a platinum sheet electrode as the counter electrode, and conducted experiments after performing corresponding pretreatment. The details are as follows:

[0090] 1.74 g of camphorsulfonic acid was weighed and dissolved in 75 mL of dimethyl carbonate solution. The mixture was stirred at 40° C. until the camphorsulfonic acid was completely dissolved. Then, 2.13 g of EDOT and 0.134 g of hexamethylphosphoric triamide were added.

[0091] A conductive ITO glass electrode was used as the working electrode, and a platinum electrode was used as the counter electrode. The conductive ITO glass electrode was immersed in a 0.1 mol / L sodium hydroxide solution for approximately 20 minutes, then repeatedly rinsed with deionized water until neutral. After rinsing, it was rinsed with anhydrous ethanol and dried. The platinum electrode was ultrasonically cleaned in a 1 mol / L hydrochloric acid solution for 5 minutes, then repeatedly rinsed with deionized water and ethanol, and dried.

[0092] Under stirring conditions, the current density was 15 mA / cm 2 Electrochemical polymerization was carried out with a polymerization time of 2 h. The above electrodes were all pretreated.

[0093] During the polymerization process, it was observed that there was no obvious phenomenon on the conductive glass ITO electrode, very few bubbles were generated on the platinum electrode, and no film was generated.

[0094] Comparative Example 2

[0095] Regarding Comparative Example 2 of the present invention, description of the parts that are the same as those of Comparative Example 1 will be omitted.

[0096] Conductive glass ITO was used as the working electrode, and the counter electrode was replaced with a glassy carbon electrode as the counter electrode, and the treatment method was the same as that in Comparative Example 1. The treatment method was carried out under stirring conditions with a current density of 15 mA / cm 2 Electrochemical polymerization was carried out with a polymerization time of 2 h. The above electrodes were all pretreated.

[0097] During the polymerization process, it can be observed that there is no obvious phenomenon on the conductive glass ITO electrode and no film is generated on the glassy carbon electrode.

[0098] From the above experiments, it can be seen that the selection of electrodes is one of the key points of the present invention. If conductive glass is used as the working electrode, the experiment will fail and the PEDOT polymer cannot be obtained.

Claims

1. A method for synthesizing a PEDOT polymer, characterized in that: The following steps are involved: (1) Preparation of electrolyte solution: Add the dopant to the carbonate solution, heat and stir at 40°C until the dopant is dissolved, then add 3,4-ethylenedioxythiophene and the catalyst to obtain the electrolyte solution; The doping agent is camphorsulfonic acid, and its concentration is 0.1-0.2 mol / L; The catalyst is hexamethylphosphoric triamide; (2) Pre-treating the working electrode and the counter electrode separately, and then immersing them in the electrolyte solution in (1) at the same time, stirring, and electrochemical polymerization reaction to obtain PEDOT polymer; The working electrode is selected from any one of glassy carbon and nickel foam; the counter electrode is selected from any one of platinum sheet, nickel foam and conductive glass ITO; The electrochemical polymerization current density is 5-15 mA / cm 2 .

2. The method for synthesizing a PEDOT polymer according to claim 1, characterized in that: The carbonate solution in (1) is dimethyl carbonate.

3. The method for synthesizing a PEDOT polymer according to claim 1, characterized in that: In the above (1), the concentration of 3,4-ethylenedioxythiophene is 0.1-0.2 mol / L, and the concentration of the catalyst is 0.01-0.5 mol / L.

4. The method for synthesizing a PEDOT polymer according to claim 1, wherein: The electrochemical polymerization time in (2) is 2-4 h.

5. The method for synthesizing a PEDOT polymer according to claim 1, characterized in that: The platinum sheet is pretreated by placing it in a 1 mol / L hydrochloric acid solution for ultrasonic cleaning for 5 minutes, then repeatedly rinsing with deionized water and ethanol, and drying; The pretreatment method of the glassy carbon as a working electrode is as follows: polishing with 0.05 μm Al2O3 powder, rinsing with deionized water and anhydrous ethanol, and drying; The pretreatment method of the nickel foam is as follows: ultrasonic cleaning in acetone solution for 10 minutes, rinsing with deionized water, ultrasonic cleaning in 1 mol / L hydrochloric acid solution for 10 minutes, and finally repeatedly rinsing with deionized water and ethanol, and drying; The pretreatment method for the glassy carbon or conductive glass ITO as the counter electrode is as follows: immersing the electrode in a 0.1 mol / L sodium hydroxide solution, taking it out after 15-25 minutes, repeatedly washing it with deionized water until it is neutral, rinsing it with anhydrous ethanol after washing, and drying it.

6. The method for synthesizing a PEDOT polymer according to claim 1, characterized in that: The contact areas of the counter electrode and the working electrode with the electrolyte solution are both 10 mm×20 mm, and the volume of the electrolyte solution is 80 mL.

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