Fluorine Atom-Modified Bipolar Conductive Polymer and Preparation Method Thereof

Abstract

The present invention discloses a fluorine atom-modified bipolar conductive polymer and a preparation method thereof. By modifying the ends of the bipolar conductive polymer with different numbers of fluorine atoms, a series of novel bipolar structure molecules and conductive polymers are synthesized, and the energy levels and electrostatic potential can be adjusted at the molecular level. Compared with the unmodified molecular structure, it has a lower energy gap and intermolecular interaction, so it can bring better electrochemical performance, especially an obvious improvement in capacitance, which is extremely important for high-performance supercapacitors.

Description

Technical Field

[0001] The present invention relates to a series of bipolar conductive polymers modified with fluorine atoms, a preparation method thereof, and their application as electrode materials in energy storage fields such as supercapacitors. Background Art

[0002] With the extreme consumption of non-renewable energy, energy storage and reuse will be the most important pillar industry in the future. Supercapacitors are widely used in fields such as automobiles, military, aerospace, and electronic displays due to their high power density. The electrode materials of supercapacitors mainly include three types: carbon materials, metal oxides, and conductive polymers. The present invention relates to organic conductive polymer materials. Conductive polymer-based electrode materials can adjust their electrochemical properties by designing a reasonable molecular structure, and conductive polymers exhibit advantages such as flexibility and visualization, making them one of the most promising substances in supercapacitor electrode materials.

[0003] Conductive polymer electrode materials are pseudo-capacitive electrode materials that occur through doping, and have advantages such as good conductivity, modifiable structure, and easy processing, and have been widely studied. However, most of the current research focuses on relatively stable p-type (oxidative) doped conductive polymers, such as polyaniline, polypyrrole, etc. Therefore, the voltage range is limited to the positive direction, while bipolar conductive polymers can be both p-doped and n-doped. As pseudo-capacitive electrode materials, they can significantly increase the working voltage of devices and obtain energy storage devices with high energy density.

[0004] However, there is less research on the molecular design of n-doping, and there is currently less research on how to adjust the electrochemical properties of n-doping by designing the molecular structure. The present invention designs and synthesizes structural monomers of bipolar conductive polymers substituted with different numbers of fluorine atoms. For p-doping on the main structure, highly conductive 3,4-ethylenedioxythiophene (EDOT) is selected as the main chain, and phthalimide is selected as the main structure for n-doping. They are electrochemically polymerized into films and applied as novel bipolar conductive polymers in the field of supercapacitors. Summary of the Invention

[0005] In view of the above situation, one of the purposes of the present invention is to provide a synthesis strategy for a series of bipolar conductive polymers modified with fluorine atoms

[0006] Another purpose of the present invention is to synthesize a series of compounds with the structure of bipolar conductive polymers modified with fluorine atoms and apply them as electrode materials in energy storage fields such as supercapacitors.

[0007] The purpose of the present invention is achieved through the following technical solutions:

[0008] In the first aspect, the present invention provides a monomer represented by Formula 1,

[0009]

[0010] Among them, y refers to the number of fluorine atoms on the benzene ring, which is an integer between 1 and 4.

[0011] In the embodiments of the present invention, the monomer shown in Formula 1 is one of the following compounds:

[0012]

[0013] In a second aspect, the present invention provides a method for preparing the monomer shown in Formula 1 above, and the method is as follows:

[0014] Under a protective atmosphere, aminomethyl EDOT shown in Formula 2 and the compound shown in Formula 3 are added to propionic acid, and the reaction is carried out at 110-130 °C for 12-22 hours. The obtained reaction solution is post-treated to obtain the monomer shown in Formula 1; the molar ratio of aminomethyl EDOT shown in Formula 2 to the compound shown in Formula 3 is 2-3:1;

[0015]

[0016] In an embodiment of the present invention, the protective atmosphere is nitrogen, or it can also be an inert gas.

[0017] Furthermore, the volume of the propionic acid is 6-8 mL / g based on the mass of aminomethyl EDOT shown in Formula 2.

[0018] Furthermore, the post-treatment is as follows: the reaction solution is cooled to room temperature, poured into distilled water, and waited for the solid phase to precipitate. Then it is vacuum filtered, and the obtained filter cake is washed with distilled water and dried. Silica gel column chromatography is carried out with a mixed solution of dichloromethane and petroleum ether with a volume ratio of 2:1, and the eluent containing the target product is collected. The mixed solvent is removed by rotary evaporation under reduced pressure to obtain the monomer shown in Formula 1.

[0019] In a third aspect, the present invention provides a fluorine atom-modified bipolar conductive polymer shown in Formula 4,

[0020]

[0021] Preferably, the fluorine atom-modified bipolar conductive polymer shown in Formula 4 is one of the following:

[0022]

[0023] Particularly preferably, the fluorine atom-modified bipolar conductive polymer shown in Formula 4 is the polymer shown in Formula (VII).

[0024] Fourthly, the present invention provides a method for preparing the bipolar conductive polymer modified with fluorine atoms as shown in the above formula 4. The method is as follows: Dissolve the monomer shown in formula 1 and tetrabutylammonium hexafluorophosphate in a mixed organic solvent of acetonitrile and dichloromethane. Using a three-electrode system, with ITO as the working electrode, a platinum wire as the counter electrode, and Ag / Ag⁺ as the reference electrode, construct an electrochemical polymerization system. Adopt cyclic voltammetry with -0.3 to 1.6 V, set the polymerization sweep rate to 90 to 120 mV / s (preferably 100 mV / s), and set the number of polymerization cycles to 8 to 15 cycles (preferably 10 cycles) to obtain the bipolar conductive polymer modified with fluorine atoms as shown in the above formula 4. In the electrochemical polymerization system, the concentration of the monomer shown in formula 1 is 5 mmol / L, and the concentration of the tetrabutylammonium hexafluorophosphate is 0.05 mol / L;

[0025]

[0026] Among them, y refers to the number of fluorine atoms on the benzene ring, which is an integer between 1 and 4.

[0027] Furthermore, in the mixed organic solvent of acetonitrile and dichloromethane, the volume ratio of dichloromethane to acetonitrile is 2:3.

[0028] Fifthly, the present invention also provides an application of the bipolar conductive polymer modified with fluorine atoms as shown in the above formula 4 in the preparation of a supercapacitor (as an electrode material).

[0029] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0030] The beneficial effects of the present invention are mainly reflected in: By modifying the ends of the bipolar conductive polymer with different numbers of fluorine atoms, a series of novel bipolar structure molecules and conductive polymers are synthesized, which can adjust the energy level and electrostatic potential at the molecular level. Compared with the unmodified molecular structure, it has a lower energy gap and intermolecular interaction, so it can bring better electrochemical performance, especially a significant improvement in capacitance, which is extremely important for high-performance supercapacitors. Description of the Drawings

[0031] Figure 1 : ¹H NMR characterization of the monomer in Example 1 of the present invention;

[0032] Figure 2 : ¹H NMR characterization of the monomer in Example 2 of the present invention;

[0033] Figure 3 : ¹H NMR characterization of the monomer in Example 3 of the present invention;

[0034] Figure 4 : ¹H NMR characterization of the monomer in Example 4 of the present invention;

[0035] Figure 5: Infrared Characterization of the Film in Example 5 of the Present Invention;

[0036] Figure 6 : Negative Capacitance of the Film in Example 5 of the Present Invention;

[0037] Figure 7 : Infrared Characterization of the Film in Example 6 of the Present Invention;

[0038] Figure 8 : Negative Capacitance of the Film in Example 6 of the Present Invention;

[0039] Figure 9 : Infrared Characterization of the Film in Example 7 of the Present Invention;

[0040] Figure 10 : Negative Capacitance of the Film in Example 7 of the Present Invention;

[0041] Figure 11 : Infrared Characterization of the Film in Example 8 of the Present Invention;

[0042] Figure 12 : Negative Capacitance of the Film in Example 8 of the Present Invention;

[0043] Figure 13 : Molecular Structure of the Monomer in Comparative Example 9 of the Present Invention;

[0044] Figure 14 : Negative Capacitance of the Film in Comparative Example 9 of the Present Invention; Detailed Embodiments

[0045] The technical solutions of the present invention will be further described below with specific examples, but the protection scope of the present invention is not limited thereto.

[0046] Synthesis of Bipolar Structure Monomer (Ⅰ) in Example 1

[0047] Under a nitrogen atmosphere, 3-fluorophthalic anhydride (0.55 g, 3.3 mmol) as a reactant was added to a reaction flask, and then 12 ml of propionic acid solvent and aminomethyl EDOT reactant (1.70 g, 10.0 mmol) were added to the reaction system. The reaction system was carried out at 120 °C for 16 hours. After the reaction was completed and cooled, the reaction solution was poured into 120 mL of distilled water. After the solid phase precipitated, the solid phase was filtered out by vacuum filtration, washed repeatedly with distilled water, and then placed in an oven for drying at 60 °C. After the solid phase was dried, column chromatography purification was carried out using silica gel with a mesh size of 300 - 400 as the stationary phase and a mixed solution of dichloromethane / petroleum ether with a volume ratio of 2:1 as the mobile phase. The eluate containing the target product was collected, and the mixed solvent was removed by rotary evaporation under reduced pressure to obtain 1 g of the target white solid product. The nuclear magnetic resonance hydrogen spectrum characterization of the monomer molecule is as Figure 11H NMR (400 MHz, Chloroform-d) δ 7.72 (s, 2H), 7.41 (s, 1H), 6.33 (s, 2H), 4.51 (s, 1H), 4.25 (s, 1H), 4.05 (s, 2H), 3.88 (s, 1H).

[0048] Synthesis of Bipolar Structure Monomer (II)

[0049] Under nitrogen protection, 4-fluorophthalic anhydride (0.55 g, 3.3 mmol) was dissolved in propionic acid solvent (12 ml), and aminomethyl EDOT (1.70 g, 10.0 mmol) was added thereto. The reaction was carried out at 130 °C for 18 h. After the reaction was completed, the product was poured into 120 ml of distilled water, washed repeatedly with distilled water, and then placed in an oven at 60 °C for drying. After the solid phase was dried, column chromatography purification was carried out. Using 300-400 mesh silica gel as the stationary phase, a mixed solution of dichloromethane / petroleum ether with a volume ratio of 2:1 was used as the mobile phase for elution. The eluate of the target product was collected, and the mixed solvent was removed by rotary evaporation under reduced pressure to obtain 1 g of the target white solid product. The 1H NMR characterization of the synthesized monomer molecule is as Figure 2 1H NMR (400 MHz, CDCl3) δ 7.88 (s, 1H), 7.55 (s, 1H), 7.42 (s, 1H), 6.34 (s, 2H), 4.48 (s, 1H), 4.24 (s, 1H), 4.05 (s, 2H), 3.90 (s, 1H).

[0050] Synthesis of Bipolar Structure Monomer (III)

[0051] Under nitrogen protection, 4,5-difluorophthalic anhydride (0.6 g, 3.3 mmol) was added to a flask containing propionic acid solvent (12 ml), and aminomethyl EDOT (1.7 g, 10.0 mmol) was added thereto. The reaction was carried out at 130 °C for 16 h. After the system reaction was completed and cooled to room temperature, the reaction solution was poured into a beaker containing 120 ml of distilled water. After the solid was precipitated, the solid phase was filtered out by vacuum filtration, washed repeatedly with distilled water to remove the solvent, and then placed in an oven at 60 °C for drying. After the solid phase was dried, column chromatography purification was carried out using 300-400 mesh silica gel as the stationary phase and a mixed solution of dichloromethane / petroleum ether with a volume ratio of 2:1 as the mobile phase. The eluate of the target product was collected, and the mixed solvent was removed by rotary evaporation under reduced pressure to obtain 1 g of the target white solid product. The 1H NMR characterization of the monomer molecule is as Figure 3As shown, it is proved that the monomer was successfully synthesized. 1H NMR (400 MHz, CDCl3) δ 7.66 (s, 2H), 6.30 (s, 2H), 4.44 (s, 1H), 4.19 (s, 1H), 4.00 (s, 2H), 3.85 (s, 1H).

[0052] Synthesis of bipolar structure monomer (IV)

[0053] Under the protection of a nitrogen atmosphere, 3,4,5,6-tetrafluorophthalic anhydride (0.73 g, 3.3 mmol) was dissolved in propionic acid solvent (12 ml), and aminomethyl EDOT (1.70 g, 10.0 mmol) was added thereto. The reaction was carried out at 120 °C for 18 hours. The reaction solution was poured into a beaker containing 130 ml of distilled water. After the solid was precipitated, the solid phase was filtered out by vacuum filtration, and the propionic acid solvent was removed by repeated washing with distilled water. After washing, the solid phase was placed in an oven and dried at 60 °C. After the solid phase was dried, the crude product was purified. Using 300-400 mesh silica gel as the stationary phase and a dichloromethane / petroleum ether mixed solution with a volume ratio of 5:1 as the mobile phase for column chromatography purification, the eluate of the target product was collected, and the mixed solvent was removed by rotary evaporation under reduced pressure to obtain 1.1 g of the target yellow solid product. The nuclear magnetic hydrogen spectrum characterization of the monomer molecule proved that the monomer molecule was successfully synthesized, as Figure 4 shown by 1H NMR (400 MHz, Chloroform-d) δ 6.31 (s, 2H), 4.49 (s, 1H), 4.25 (s, 1H), 4.04 (s, 2H), 3.88 (s, 1H).

[0054] Example 5 Electrochemical polymerization of bipolar molecule (I):

[0055] Taking bipolar structure molecule (I) (0.02 g, 0.05 mmol) as the monomer and tetrabutylammonium hexafluorophosphate (0.19 g, 0.5 mmol) as the supporting electrolyte, they were dissolved in 10 ml of a dichloromethane:acetonitrile mixed solvent, where the volume ratio of dichloromethane:acetonitrile was 2:3. A three-electrode system was adopted, with ITO as the working electrode, a platinum wire as the counter electrode, and Ag / Ag+ as the reference electrode. Cyclic voltammetry was used at -0.3 to 1.6 V, the polymerization sweep rate was set at 100 mV / s, and the number of polymerization cycles was set at 10. The polymer was characterized by infrared spectroscopy. From Figure 5 it can be seen that the absorption peaks at 3100 cm -1 , 1800 cm -1 and 920 cm -1 do not exist. These peaks correspond to the C-H vibrations at the 2,5 positions of the thiophene ring, indicating that the monomer was successfully polymerized. The negative capacitance of the electrode material in this example is as Figure 6 shown. When the current density is from 10 A / cm 3Increase to 25 A / cm 3 It can be seen that its negative capacitance decreases from 27.5 F / cm 3 to 18 F / cm 3 .

[0056] Electrochemical Polymerization of Bipolar Molecule (II) in Example 6

[0057] Take bipolar structure molecule (II) (0.02 g, 0.05 mmol) as the monomer and tetrabutylammonium hexafluorophosphate (0.19 g, 0.5 mmol) as the supporting electrolyte, dissolve them in 10 ml of dichloromethane:acetonitrile mixed solvent, where the volume ratio of dichloromethane:acetonitrile is 2:3. Adopt a three-electrode system, use ITO as the working electrode, a platinum wire as the counter electrode, and Ag / Ag+ as the reference electrode. Use cyclic voltammetry from -0.3 V to 1.6 V, set the polymerization sweep rate at 100 mV / s, set the number of polymerization cycles at 10. The polymer film is characterized by infrared spectroscopy. From Figure 7 it can be seen that the absorption peaks at 3100 cm -1 , 1800 cm -1 and 920 cm -1 do not exist, indicating that the monomer has been successfully polymerized. The negative capacitance of the electrode material in this example is as Figure 8 shown. It can be seen that when the current density increases from 5 A / cm 3 to 50 A / cm 3 its negative capacitance decreases from 110 F / cm 3 to 32 F / cm 3 .

[0058] Electrochemical Polymerization of Bipolar Molecule (III) in Example 7

[0059] Take bipolar structure molecule (III) (0.017 g, 0.05 mmol) as the monomer and tetrabutylammonium hexafluorophosphate (0.19 g, 0.5 mmol) as the supporting electrolyte, dissolve them in 10 ml of dichloromethane:acetonitrile mixed solvent, where the volume ratio of dichloromethane:acetonitrile is 2:3. Adopt a three-electrode system, use ITO as the working electrode, a platinum wire as the counter electrode, and Ag / Ag+ as the reference electrode. Use cyclic voltammetry from -0.3 V to 1.6 V, set the polymerization sweep rate at 100 mV / s, set the number of polymerization cycles at 10. The polymer film is characterized by infrared spectroscopy. From Figure 9 it can be seen that the absorption peaks at 3100 cm -1 , 1800 cm -1 and 920 cm -1 do not exist, indicating that the monomer has been successfully polymerized. The negative capacitance of the electrode material in this example is as Figure 10 shown. When the current density increases from 5 A / cm 3 to 50 A / cm 3It can be seen that its negative capacitance decreases from 63 F / cm 3 to 43 F / cm 3 .

[0060] Example 8 Electrochemical Polymerization of Bipolar Molecule (IV)

[0061] Taking the bipolar structure molecule (IV) (0.02 g, 0.05 mmol) as the monomer and tetrabutylammonium hexafluorophosphate (0.19 g, 0.5 mmol) as the supporting electrolyte, they were dissolved in 10 ml of a dichloromethane:acetonitrile mixed solvent, where the volume ratio of dichloromethane:acetonitrile was 2:3. Using a three-electrode system, with ITO as the working electrode, a platinum wire as the counter electrode, and Ag / Ag+ as the reference electrode, cyclic voltammetry was carried out at -0.3 to 1.6 V, the polymerization scan rate was set at 100 mV / s, and the number of polymerization cycles was set at 10. The polymer film was characterized by infrared spectroscopy. From Figure 11 it can be seen that the absorption peaks at 3100 cm -1 , 1800 cm -1 and 920 cm -1 do not exist, indicating that the monomer was successfully polymerized. The negative capacitance of the electrode material in this example is as Figure 12 shown. When the current density increases from 5 A / cm 3 to 25 A / cm 3 it can be seen that its negative capacitance decreases from 40 F / cm 3 to 15 F / cm 3 .

[0062] Example 9 Conductive Polymer Electrode Material Without Fluorine Atom Modification as a Comparative Example

[0063] Taking the electrode material composed of the monomer without fluorine atom modification structure as a comparative example, its monomer molecular structure is as Figure 13 shown. Other operations are the same as in Example 5. The only difference is that in the electrochemical polymerization process, the selected monomer is Figure 13 the molecule (0.015 g, 0.05 mmol) to replace the bipolar structure monomer (I) in Example 5. The negative capacitance of the electrode material composed of this monomer is as Figure 14 shown. It can be seen that the capacitance value without fluorine atom modification is lower. When the current density increases from 5 A / cm 3 to 15 A / cm 3 , its negative capacitance decreases from 26 F / cm 3 to only 3 F / cm 3 . After fluorine atom modification, the capacitance is significantly improved. Moreover, the bipolar conductive polymer with two fluorine atom substitution structures (III) not only has a higher negative capacitance value but also has the highest rate performance among a series of fluorine atom substitutions.

Claims

1. A monomer represented by Formula 1, wherein, y refers to the number of fluorine atoms on the benzene ring, which is an integer between 1 and 4.

2. The monomer represented by Formula 1 according to claim 1, characterized in that The monomer shown in Formula 1 is one of the following compounds:

3. A method for preparing the monomer represented by Formula 1 according to claim 1, characterized in that: The method is as follows: Under a protective atmosphere, the aminomethyl EDOT shown in Formula 2 and the compound shown in Formula 3 are added to propionic acid, and the reaction is carried out at 110-130 °C for 12-22 hours. The obtained reaction solution is post-treated to obtain the monomer shown in Formula 1; the molar ratio of the aminomethyl EDOT shown in Formula 2 to the compound shown in Formula 3 is 2-3:1; 4. The method for preparing the monomer represented by Formula 1 according to claim 3, characterized in that: The protective atmosphere is nitrogen; The volume of the propionic acid is 6-8 mL / g based on the mass of the aminomethyl EDOT shown in Formula 2.

5. The method for preparing the monomer represented by Formula 1 according to claim 3, characterized in that: The post-treatment is as follows: The reaction solution is cooled to room temperature, poured into distilled water, and when the solid phase precipitates, it is vacuum filtered. The obtained filter cake is washed with distilled water and dried. Silica gel column chromatography is carried out with a mixed solution of dichloromethane and petroleum ether with a volume ratio of 2:1, and the eluate containing the target product is collected. The mixed solvent is removed by rotary evaporation under reduced pressure to obtain the monomer shown in Formula 1.

6. A fluorine atom-modified bipolar conductive polymer represented by Formula 2, wherein, y refers to the number of fluorine atoms on the benzene ring, which is an integer between 1 and 4.

7. The fluorine atom-modified bipolar conductive polymer represented by Formula 2 according to claim 6, characterized in that The fluorine atom-modified bipolar conductive polymer shown in Formula 4 is one of the following:

8. A method for preparing the fluorine atom-modified bipolar conductive polymer represented by Formula 2 according to claim 6, characterized in that The method is as follows: The monomer shown in Formula 1 and tetrabutylammonium hexafluorophosphate are dissolved in a mixed organic solvent of acetonitrile and dichloromethane. Using a three-electrode system, with ITO as the working electrode, a platinum wire as the counter electrode, and Ag / Ag+ as the reference electrode, an electrochemical polymerization system is constructed. Cyclic voltammetry is carried out at -0.3-1.6 V, the polymerization sweep rate is set at 90-120 mV / s, and the number of polymerization cycles is set at 8-15 cycles to obtain the fluorine atom-modified bipolar conductive polymer shown in Formula 4; in the electrochemical polymerization system, the concentration of the monomer shown in Formula 1 is 5 mmol / L, and the concentration of the tetrabutylammonium hexafluorophosphate is 0.05 mol / L; Among them, y refers to the number of fluorine atoms on the benzene ring, which is an integer between 1 and 4.

9. The method for preparing the fluorine atom-modified bipolar conductive polymer represented by Formula 2 according to claim 6, characterized in that: In the mixed organic solvent of acetonitrile and dichloromethane, the volume ratio of dichloromethane to acetonitrile is 2:

3.

10. Use of the fluorine atom-modified bipolar conductive polymer represented by Formula 2 according to claim 6 in the preparation of a supercapacitor.

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