A conductive polymer containing a naphthalimide structure and a preparation method thereof

Abstract

The present invention provides a conductive polymer containing a naphthalimide structure, a preparation method thereof, and an application thereof as an organic electrode material in a supercapacitor. The novel polymer film prepared by the present invention can be used in the field of supercapacitor energy storage. The conductive polymer film electrode material prepared from the monomer has the ability of bidirectional energy storage with both p-doping and n-doping, and the film exhibits a wide voltage window of +1.6 V in the positive direction and -2 V in the negative direction, making it a potential electrode material for future supercapacitors.

Description

Technical Field

[0001] The present invention relates to a novel structural molecule containing a naphthalimide structure, specifically to a conductive polymer containing a naphthalimide structure, and the electro-polymerization of the same into a film for use as an electrode material in energy storage fields such as supercapacitors. Background Art

[0002] With the extensive application of flexible and wearable electronic products, efficient, clean, and environmentally friendly electrochemical energy storage devices have attracted people's attention. Supercapacitors can achieve rapid charge and discharge due to their high power density, and are now widely used in fields such as new energy, flexible electronics, and aerospace. Especially in recent years, with the development of wearable and portable consumer electronics, higher requirements are put forward for energy storage devices. A supercapacitor is a high-power charge and discharge energy storage device between traditional capacitors and secondary batteries. Supercapacitors with conductive polymers as electrode materials can adjust their electrochemical properties by designing a reasonable molecular structure, and exhibit advantages such as flexibility and visualization, making them one of the most promising substances in supercapacitor electrode materials. However, the low energy density of supercapacitors limits their continuous development.

[0003] Conductive polymer electrode materials are pseudocapacitive electrode materials that store energy through doping. Currently, most of the studied are relatively stable p-type (oxidized) doped conductive polymers, such as polyaniline, polypyrrole, poly(3,4-ethylenedioxythiophene) (PEDOT), etc. However, the voltage range is limited to the positive direction, while bipolar conductive polymers can be both p-doped and n-doped, greatly broadening the voltage range of supercapacitors and promising high-energy density energy storage devices. However, currently, there are few bipolar conductive polymers developed, and the synthesis of new bipolar conductive polymers is crucial for wide-voltage and high-energy density supercapacitors. At the same time, this type of material does not contain metal elements such as lithium and manganese, avoiding the problem of metal element recovery, and is an efficient and clean electrochemical energy storage material.

[0004] Therefore, the present invention relates to a novel monomer containing a naphthalimide structure and a preparation method of a bipolar conductive polymer film. The donor selects 3,4-ethylenedioxythiophene (EDOT) with high conductivity, and the acceptor selects 1,8-naphthalimide with good redox performance as the n-doping unit. Summary of the Invention

[0005] The object of the present invention is to design and synthesize a novel compound containing a naphthalimide structure, and electro-polymerize it into a film for use as an electrode material in energy storage fields such as supercapacitors.

[0006] The object of the present invention is achieved by the following technical solutions:

[0007] In the first aspect, the present invention provides a monomer containing a naphthalimide structure shown in formula (I):

[0008]

[0009] In a second aspect, the present invention also provides a method for preparing the monomer containing a naphthalimide structure represented by formula (I), and the method is as follows:

[0010] Under a protective atmosphere (nitrogen in one embodiment of the present invention), 1,8-naphthalic anhydride and aminomethyl EDOT are added to propionic acid, and the reaction is carried out at 110-140 °C for 12-24 hours (preferably at 130 °C for 16 hours). The obtained reaction solution is post-treated to obtain the monomer containing a naphthalimide structure represented by formula (I); the molar ratio of 1,8-naphthalic anhydride to aminomethyl EDOT is 1:2-3 (1:2.5 in one embodiment of the present invention). Further, the volume of the propionic acid is 8-10 mL / g based on the mass of the aminomethyl EDOT.

[0011]

[0012] Specifically, the post-treatment is as follows: the reaction solution is cooled to room temperature, poured into deionized water, filtered after the solid settles, the obtained filter cake is washed with deionized water, dried, and eluted and purified by silica gel column with a mixed solution of dichloromethane and petroleum ether with a volume ratio of 4-5:1 as the mobile phase, and the eluate containing the target product is collected, and the solvent is removed by reduced pressure distillation to obtain the monomer containing a naphthalimide structure represented by formula (I).

[0013] The monomer of the present invention is characterized by nuclear magnetic resonance hydrogen spectrum (1H NMR), and a new molecular structure is confirmed: 1H NMR (400 MHz, Chloroform-d) δ 8.64 (s, 2H), 8.26 (s, 2H), 7.81 (s, 2H), 6.35 (s, 2H), 4.68 (s, 1H), 4.63 (s, 1H), 4.40 (s, 1H), 4.30 (s, 1H), 4.15 (s, 1H).

[0014] In a third aspect, the present invention provides a conductive polymer prepared from a monomer containing a naphthalimide structure (the structure of formula (I) can be used as a monomer for electrochemical polymerization to form a film), and the conductive polymer is prepared by the following method:

[0015] The monomer containing a naphthalimide structure represented by formula (I) and tetrabutylammonium hexafluorophosphate (supporting electrolyte) are dissolved in a mixed solvent of dichloromethane and acetonitrile to form an electrochemical reaction system. Using a three-electrode system, that is, a polymerization substrate ITO as the working electrode, a silver electrode as the reference electrode, and a platinum wire as the counter electrode, electrochemical polymerization is carried out to obtain the conductive polymer.

[0016]

[0017] In one embodiment of the present invention, in the electro-chemical reaction system, the concentration of the monomer containing naphthalimide structure shown in formula (I) is 5 mmol / L, and the concentration of tetrabutylammonium hexafluorophosphate is 0.05 mol / L.

[0018] The present invention recommends that the electrochemical polymerization adopt cyclic voltammetry; the parameters of the cyclic voltammetry are as follows: carried out in a voltage range of -0.3 to 1.6 V, the polymerization sweep rate is set to 100 to 150 mV / s, and the polymerization number of cycles is set to 10 cycles.

[0019] In one embodiment of the present invention, the parameters of the cyclic voltammetry are as follows: the voltage range is -0.3 to 1.6 V, the polymerization sweep rate is set to 100 mV / s, and the number of electro-polymerization cycles is 10 cycles.

[0020] The conductivity of pure dichloromethane solvent is too low, which is not conducive to polymerization. Acetonitrile is a poor solvent, and pure acetonitrile will cause incomplete dissolution of the monomer, affecting the polymerization process. Therefore, while ensuring dissolution, conductivity should also be pursued. Therefore, a mixed solvent is set, and its ratio is based on the proportion of dichloromethane in which the monomer is completely dissolved. The present invention recommends that in the mixed solvent of dichloromethane and acetonitrile, the volume ratio of dichloromethane to acetonitrile is 2:3.

[0021] Fourthly, the present invention provides an application of the above-mentioned conductive polymer (as an electrode material) in the preparation of supercapacitors.

[0022] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0023] Compared with the prior art, the beneficial effects of the present invention are mainly reflected in: using naphthalimide with better conjugation as the n-doping material in the bipolar conductive polymer, the enhanced conjugation is beneficial to charge migration. Therefore, the prepared thin film of electrochemically polymerized with a new molecular structure has better electrochemical performance and higher rate performance than the bipolar conductive polymer prepared from phthalimide. The rate performance is a key index for supercapacitors with fast charge and discharge. Description of the Drawings

[0024] Figure 1 : 1H NMR characterization of the monomer in Example 1 of the present invention;

[0025] Figure 2 : Infrared characterization of the polymer in Example 2 of the present invention;

[0026] Figure 3 : Cyclic voltammograms of the thin film in Example 2 of the present invention at different forward sweep rates;

[0027] Figure 4 : Cyclic voltammograms of the thin film in Example 2 of the present invention at different reverse sweep rates;

[0028] Figure 5 : Impedance diagram of the film of embodiment 2 of the present invention;

[0029] Figure 6 : The monomer molecular structure of the comparative example of the present invention;

[0030] Figure 7 : Rate test of polymer film of comparative example of the present invention;

[0031] Figure 8 : Rate capability test of the polymer film of Example 2 of the present invention. DETAILED DESCRIPTION

[0032] The technical solution of the present invention is further described below with reference to specific embodiments, but the protection scope of the present invention is not limited thereto.

[0033] Example 1 Synthesis of Naphthalimide-Containing Monomer Molecule

[0034] Under the protection of nitrogen atmosphere, 1,8-naphthalene dicarboxylic anhydride (0.8g, 4mmol) was added to a round-bottom flask, and then propionic acid solvent (15ml) and aminomethyl EDOT (1.7g, 10mmol) were added thereto, and the reaction was carried out at 130°C for 16 hours. When the reaction was completed and cooled to room temperature (20-25°C), the reaction solution was poured into a beaker containing 120ml of deionized water, and the liquid was filtered out after the solid was precipitated. The solid phase was washed with deionized water and then placed in an oven for drying. The dried solid was purified by column chromatography, with 300-400 mesh silica gel as the stationary phase and a mixture of dichloromethane / petroleum ether in a volume ratio of 5:1 as the mobile phase for elution and purification. The eluate of the target product was collected, and the dichloromethane / petroleum ether mixed solvent was removed by reduced pressure distillation to finally obtain 1.5g of the target solid product. Monomer nuclear magnetic hydrogen spectrum characterization is as follows Figure 1 Shown is 1HNMR (400MHz, Chloroform-d) δ 8.64 (s, 2H), 8.26 (s, 2H), 7.81 (s, 2H), 6. 35(s,2H),4.68(s,1H),4.63(s,1H),4.40(s,1H),4.30(s,1H),4.15(s,1H).

[0035] Example 2 Preparation of a Naphthalimide-Containing Conductive Polymer Film:

[0036] A molecule containing a naphthalimide structure (0.02 g, 0.05 mmol) was used as a monomer, and tetrabutylammonium hexafluorophosphate (0.19 g, 0.5 mmol) was used as a supporting electrolyte. The two were dissolved in 10 ml of a dichloromethane:acetonitrile mixed solvent, with a volume ratio of 2:3 between the two. Polymerization was carried out using a traditional three-electrode system, i.e., ITO was used as the substrate, and a glassy carbon electrode and a Ag / Ag + , the voltage range was -0.3 to 1.6 V, the polymerization sweep rate was set at 100 mV / s, and the polymer film was obtained after 10 cycles of electro-polymerization. The prepared polymer film was characterized by infrared spectroscopy. From Figure 2 it can be seen that the absorption peaks at 3115 cm -1 1847 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.

[0037] The prepared conductive polymer film was electrochemically tested in a three-electrode system. Lithium perchlorate (0.1 mol / L) was used as the supporting electrolyte, and acetonitrile was used as the solvent. The cyclic voltammograms of the polymer film at different forward sweep rates are as Figure 3 shown. From low sweep rate to high sweep rate, the symmetry of the redox potential is good, showing good stability, and the sine voltage reaches 1.6 V. The cyclic voltammograms of the film at different negative sweep rates are as Figure 4 shown, and it has obvious redox peaks. The impedance diagram of the polymer film is as Figure 5 shown. The high-frequency region is almost perpendicular to the abscissa, indicating that the diffusion resistance of the polymer film is small.

[0038] Preparation of a conductive polymer film containing phthalimide for comparison as a comparative example

[0039] The same conditions as in Example 2 were selected, and the monomer structure is as Figure 6 shown. Among them, 0.015 g, 0.05 mmol of the monomer was selected. After polymerizing into the electrode material, electrochemical tests were carried out to obtain the rate performance of the comparative example and Example 2. The capacities at different current densities of the comparative example are as Figure 7 shown. It can be seen that when the current density increases from 1 A / cm 3 to 15 A / cm 3 , the capacity remains at 12%, while the rate performance of Example 2 with extended conjugation is as Figure 8 shown. When the current density increases from 5 A / cm 3 to a high current density of 50 A / cm 3 , the capacity decreases from 10 F / cm 3 to 5 F / cm 3, the magnification is maintained at 50%, so it can be seen that the structure of Example 2 obtained has excellent magnification performance and is more conducive to being used in the field of bipolar conductive polymer supercapacitors.

Claims

1. Monomer with naphthalimide structure shown in formula (I): (I).

2. Preparation method of the monomer with naphthalimide structure shown in formula (I) as claimed in claim 1, characterized in that The method is as follows: Under a protective atmosphere, 1,8-naphthalic anhydride and aminomethyl EDOT are added to propionic acid, and the reaction is carried out at 110-140 °C for 12-24 hours. The obtained reaction solution is post-treated to obtain the monomer containing a naphthalimide structure shown in the formula (I); the molar ratio of 1,8-naphthalic anhydride to aminomethyl EDOT is 1:2-3.

3. Preparation method of the monomer with naphthalimide structure shown in formula (I) as claimed in claim 2, characterized in that: The volume of the propionic acid is 8-10 mL / g based on the mass of the aminomethyl EDOT.

4. Preparation method of the monomer with naphthalimide structure shown in formula (I) as claimed in claim 2, characterized in that: The protective atmosphere is a nitrogen atmosphere.

5. Preparation method of the monomer with naphthalimide structure shown in formula (I) as claimed in claim 2, characterized in that The post-treatment is as follows: The reaction solution is cooled to room temperature, poured into deionized water, filtered after the solid settles, the obtained filter cake is washed with deionized water, dried, and eluted and purified by silica gel column with a mixed solution of dichloromethane and petroleum ether with a volume ratio of 4-5:1 as the mobile phase. The eluate containing the target product is collected, and the solvent is removed by vacuum distillation to obtain the monomer containing a naphthalimide structure shown in the formula (I).

6. Conductive polymer prepared from the monomer with naphthalimide structure as claimed in claim 1 is shown in formula (IV), characterized in that The conductive polymer is prepared by the following method: The monomer containing a naphthalimide structure shown in the formula (I) and tetrabutylammonium hexafluorophosphate are dissolved in a mixed solvent of dichloromethane and acetonitrile to form an electrochemical reaction system. Using a three-electrode system, that is, a polymerized substrate ITO as the working electrode, a silver electrode as the reference electrode, and a platinum wire as the counter electrode, electrochemical polymerization is carried out to obtain the conductive polymer.

7. Conductive polymer as claimed in claim 6, characterized in that: In the electrochemical reaction system, the concentration of the monomer containing a naphthalimide structure shown in the formula (I) is 5 mmol / L, and the concentration of tetrabutylammonium hexafluorophosphate is 0.05 mol / L.

8. Conductive polymer as claimed in claim 6, characterized in that: The electrochemical polymerization uses cyclic voltammetry; the parameters of the cyclic voltammetry are: carried out in a voltage range of -0.3-1.6 V, the polymerization scan rate is set to 100-150 mV / s, and the number of polymerization cycles is set to 10.

9. Conductive polymer as claimed in claim 6, characterized in that: In the mixed solvent of dichloromethane and acetonitrile, the volume ratio of dichloromethane to acetonitrile is 2:

3.

10. Application of the conductive polymer as claimed in claim 6 in preparing supercapacitors.

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