Method for improving energy storage density of polythiourea film through block copolymerization

Abstract

The invention provides a method for improving the energy storage density of a polythiourea film through block copolymerization, which comprises the following steps: adding thiocyanate into a polar solvent, and stirring to dissolve the thiocyanate to obtain a dissolved solution; adding excessive aromatic ring diamine into the dissolved solution for multiple times, and reacting in an inert gas atmosphere to obtain an amino-terminated polythiourea precursor; adding dianhydride and m-phenylenediamine into the amino-terminated polythiourea precursor, and continuously reacting to obtain a segmented copolymer solution; uniformly coating a carrier with the segmented copolymer solution, heating to remove the polar solvent, then heating at a preset rate step by step, and respectively keeping preset time at different temperatures to complete imidization; the carrier is placed in deionized water to be soaked and demolded, the obtained polythiourea-based segmented copolymer film is dried under the vacuum condition, and the energy storage density of the polythiourea film is improved. The obtained polythiourea film has high breakdown strength, the energy storage density is improved, the cost is low, and the polythiourea film has good application prospects in the field of film capacitors.

Description

TECHNICAL FIELD

[0001] The application relates to the field of polymer dielectric films, and particularly relates to a method for improving the energy storage density of a polythiourea film through block copolymerization. BACKGROUND

[0002] Dielectric capacitors are widely used in distributed energy, flexible DC power transmission systems, new energy vehicles and other fields. The common dielectric film material on the market is biaxially oriented polypropylene (BOPP), and the dielectric constant thereof is about 2.2, and the energy storage density is less than 2 J / cm 3 , which cannot meet the needs of the development of device miniaturization. Therefore, it is necessary to develop a polymer dielectric material with high energy storage density. With the development of power equipment and electronic devices, how to simultaneously improve the breakdown field strength and the dielectric constant of the polymer has become a key problem for developing a new type of energy storage dielectric, and finally the energy storage density is improved. Therefore, the polymer dielectric film needs to be modified to improve the energy storage performance. SUMMARY

[0003] The application aims to provide a method for improving the energy storage density of a polythiourea film through block copolymerization, so as to overcome the problems existing in the prior art. The polythiourea film obtained by the application has high breakdown strength, realizes the improvement of the energy storage density, is low in cost, and has a good application prospect in the field of film capacitors.

[0004] The application is realized through the following technical scheme: A method for improving the energy storage density of a polythiourea film through block copolymerization comprises the following steps: (1) sulfur isothiocyanate is added to a polar solvent, and stirring is performed to dissolve the sulfur isothiocyanate, so as to obtain a dissolved solution; (2) an excess of aromatic ring diamine is added to the dissolved solution in multiple times, and reaction is performed under an inert gas atmosphere, so as to obtain an amino-terminated polythiourea precursor; (3) dianhydride and m-phenylenediamine are added to the amino-terminated polythiourea precursor, and the reaction is continued, so as to obtain a block copolymer solution; (4) the block copolymer solution is uniformly coated on a carrier, heating is performed to remove the polar solvent, then the temperature is increased in steps at a preset rate, and imidization is completed at different temperatures for a preset time; (5) the carrier is soaked in deionized water for demolding, and the obtained polythiourea-based block copolymer film is dried under vacuum conditions, so as to complete the improvement of the energy storage density of the polythiourea film.

[0005] Further, the ratio between the sulfur isothiocyanate and the polar solvent is 2 mmol:6 mL; The sulfur isothiocyanate is 1,4-benzenediisothiocyanate.

[0006] Further, the polar solvent is DMAc. The thiocyanate is added into the polar solvent, and stirred to dissolve until the solution is clear, to obtain a solution.

[0007] Further, in step (2), the molar ratio between the aromatic ring diamine and the thiocyanate is 2.04:2, and the reaction time is 8 h. The aromatic ring diamine is 3,3'-diaminodiphenyl methane.

[0008] Further, in step (3), the molar ratio between the dianhydride and the m-phenylenediamine is 1:1, and the molar ratio between the dianhydride or the m-phenylenediamine and the thiocyanate is (1-4):2; the time for continuous reaction is 16 h. The dianhydride is 4,4'-(4,4'-isopropyl diphenyl oxy) diphthalic anhydride.

[0009] Further, in step (4), the polar solvent is removed by heating, specifically: the polar solvent is removed at 80 ℃ for 3 h.

[0010] Further, in step (4), the temperature is increased in steps at a preset rate, and each temperature is maintained for a preset time, specifically: the temperature is increased in steps at a rate of 3 ℃ / min, and each temperature of 80 ℃, 100 ℃ and 120 ℃ is maintained for 1 h.

[0011] Further, in step (5), the carrier is soaked in deionized water at 80 ℃ for demolding.

[0012] Further, in step (5), the temperature for vacuum drying is 80 ℃.

[0013] Further, the thickness of the polythiourea-based block copolymer film is 10-12 um.

[0014] Compared with the prior art, the present application has the following beneficial technical effects: The present application uses thiocyanate and slightly excessive aromatic ring diamine to obtain a diamino polythiourea as a precursor, adds dianhydride and m-phenylenediamine to obtain a polyetherimide chain segment, and prepares a polythiourea-based block polyetherimide copolymer. Through block copolymerization, an interface region is formed between the polythiourea and the polyetherimide molecular chain, which can enhance the dipole polarization, increase the molecular chain spacing, promote the dipole turning, increase the dielectric constant of the polythiourea-based block polyetherimide copolymer, introduce deep trap levels, and have high breakdown strength, so as to finally improve the energy storage density. Moreover, the cost is low, and the present application has good application prospect in the field of thin film capacitors.

[0015] Further, the different polyetherimide block ratios in the present application can change the size of the interface region, thereby affecting the dielectric constant and the breakdown field strength of the polythiourea-based block polyetherimide copolymer. By comparing the changes in the dielectric constant and the breakdown field strength, the optimal ratio can be selected, and the energy storage density is maximized. BRIEF DESCRIPTION OF DRAWINGS

[0016] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings needed in the embodiments will be briefly introduced below. The following drawings only show some embodiments of the present application, and therefore should not be considered as limiting the scope. For those skilled in the art, other related drawings can also be obtained without creative labor.

[0017] Figure 1 Infrared spectra of the films of Example 1, Example 2, Example 3 and Comparative Example 1; Figure 2 X-ray diffraction test results of the films of Example 1, Example 2, Example 3 and Comparative Example 1; Figure 3 Dielectric constant test results of the films of Example 1, Example 2, Example 3 and Comparative Example 1; Figure 4 DC breakdown field strength test results of the films of Example 1, Example 2, Example 3 and Comparative Example 1. DETAILED DESCRIPTION

[0018] The present application will be described in detail below: A method for improving the energy storage density of a polythiourea film by block copolymerization, comprising the following steps: (1) A high-precision balance is used to weigh thiocyanate (1,4-benzene diisothiocyanate), which is added to a polar solvent, and magnetic stirring is used to dissolve it until the solution is clear, wherein the molar ratio of thiocyanate to polar solution is 2 mmol:6 mL; (2) A slightly excessive amount of aromatic ring diamine (3,3'-diaminodiphenylmethane) is added in multiple portions, and the molar ratio between the aromatic ring diamine and the thiocyanate is 2.04:2. The reaction is carried out under an inert gas atmosphere for 8 h to obtain an amino-terminated polythiourea precursor; (3) The amino-terminated polythiourea precursor is added with dianhydride (4,4'-(4,4'-isopropyl diphenyl oxy) diphthalic anhydride) and m-phenylenediamine, and the molar ratio between the dianhydride and the m-phenylenediamine is 1:1, and the molar ratio between the dianhydride or the m-phenylenediamine and the thiocyanate is (1-4):2. The reaction is continued for 16 h; (4) The block copolymer solution was uniformly coated on a clean glass slide and placed in an oven at 80 °C for 3 h to remove the polar solvent. The temperature was then increased stepwise at a rate of 3 °C / min and held at 80 °C, 100 °C and 120 °C for 1 h each to complete the imidization. (5) Soak the glass slide in deionized water at 80 °C to remove the film, and place the polythiourea block copolymer film (thickness of 10-12 μm) in a vacuum oven to dry to remove moisture.

[0019] The embodiments of the present invention will be described in detail below with reference to the examples. These embodiments represent preferred solutions of the present invention and should not be construed as limiting the scope of the invention. Unless otherwise specified, the methods and experimental equipment used in the following embodiments are conventional methods and instruments.

[0020] Example 1 A method for improving the energy storage density of polythiourea films through block copolymerization includes the following steps: (1) Weigh 2 mmol of thiocyanate (1,4-phenyl diisothiocyanate) using a high-precision balance, add it to 6 mL of polar solvent DMAc, and stir magnetically to dissolve it; (2) 2.04 mmol of 3,3'-diaminodiphenylmethane was added in multiple portions and reacted for 8 h under an inert gas atmosphere to synthesize the terminal amino polythiourea precursor; (3) Add 4 mmol of 4,4'-(4,4'-isopropyldiphenoxy) phthalic anhydride and 4 mmol of m-phenylenediamine respectively, and continue the reaction for 16 h; (4) The block copolymer solution was uniformly coated on a clean glass slide, placed in an oven, and kept at 80 °C for 3 h to remove the polar solvent. The temperature was then increased stepwise at a rate of 3 °C / min, and kept at 80, 100, and 120 °C for 1 h to complete the imidization. (5) The glass slide was immersed in deionized water at 80 °C to remove the film, and the polythiourea block copolymer film was placed in a vacuum oven at 80 °C to dry to remove moisture, resulting in a 10 μm polythiourea block copolymer film, denoted as PTU1- b -PEI2.

[0021] Example 2 A method for improving the energy storage density of polythiourea films through block copolymerization includes the following steps: (1) Weigh 2 mmol of thiocyanate (1,4-phenyl diisothiocyanate) using a high-precision balance, add it to 6 mL of polar solvent DMAc, and stir magnetically to dissolve it; (2) 2.04 mmol of 3,3'-diaminodiphenylmethane was added in several portions, and the reaction was carried out for 8 h under an inert gas atmosphere to synthesize an amino-terminated polythiourea precursor; (3) 2 mmol of 4,4'-(4,4'-isopropyl diphenyloxy) diphthalic anhydride and 2 mmol of m-phenylenediamine were added, respectively, and the reaction was continued for 16 h; (4) The block copolymer solution was uniformly coated on a clean glass sheet, which was placed in an oven, and the polar solvent was removed at 80 °C for 3 h, and the temperature was increased at a rate of 3 °C / min in steps, and imidization was completed at 80, 100, and 120 °C for 1 h, respectively; (5) The glass sheet was immersed in deionized water at 80 °C to remove the film, and the polythiourea-based block copolymer film was placed in a vacuum oven at 80 °C to remove water, and a 10 um polythiourea-based block copolymer film was obtained, denoted as PTU1- b -PEI1.

[0022] Example 3 A method for improving the energy storage density of a polythiourea film by block copolymerization, comprising the following steps: (1) 2 mmol of thiocyanate (1,4-benzenediisothiocyanate) was weighed using a high-precision balance, and was added to 6 mL of a polar solvent DMAc, and was dissolved by magnetic stirring; (2) 2.04 mmol of 3,3'-diaminodiphenylmethane was added in several portions, and the reaction was carried out for 8 h under an inert gas atmosphere to synthesize an amino-terminated polythiourea precursor; (3) 1 mmol of 4,4'-(4,4'-isopropyl diphenyloxy) diphthalic anhydride and 1 mmol of m-phenylenediamine were added, respectively, and the reaction was continued for 16 h; (4) The block copolymer solution was uniformly coated on a clean glass sheet, which was placed in an oven, and the polar solvent was removed at 80 °C for 3 h, and the temperature was increased at a rate of 3 °C / min in steps, and imidization was completed at 80, 100, and 120 °C for 1 h, respectively; (5) The glass sheet was immersed in deionized water at 80 °C to remove the film, and the polythiourea-based block copolymer film was placed in a vacuum oven at 80 °C to remove water, and a 12 um polythiourea-based block copolymer film was obtained, denoted as PTU2- b -PEI1.

[0023] Comparative Example 1 Synthesis of polythiourea thin film: 2 mmol of thiocyanate (1,4-benzene diisothiocyanate) was dissolved in 6 ml of DMAc with the same molar mass of 3,3'-diaminodiphenylmethane, and the solution was uniformly coated on a clean glass sheet and subjected to stepwise temperature elevation, and kept at 80, 100, and 120 °C for 1 h, respectively. The film was removed by immersion in deionized water at 80 °C, and the polythiourea film was placed in a vacuum oven at 80 °C to dry to remove water, to obtain a 10-μm-thick polythiourea film, denoted as PTU.

[0024] Performance test: (1) Fourier infrared spectroscopy was used to test the polythiourea-based block copolymer thin films prepared in Example 1, Example 2, Example 3, and Comparative Example 1. The test selected the reflection mode, and the test range was 4000-500 cm -1 . The test results are shown in Figure 1 .

[0025] (2) X-ray diffraction was used to test the polythiourea-based block copolymers prepared in Example 1, Example 2, Example 3, and Comparative Example 1. Cu target radiation was used, with a wavelength of 0.1542 nm, and the test angle was 5-35°. The test results are shown in Figure 2 .

[0026] (3) Broadband dielectric spectroscopy was used to test the polythiourea-based block copolymer thin films prepared in Example 1, Example 2, Example 3, and Comparative Example 1. The test frequency range was 10 -1 -10 6 Hz. The test results are shown in Figure 3 .

[0027] (4) The thin films prepared in the above examples and comparative examples were placed in a direct current breakdown test device for testing. Columnar copper electrodes with a diameter of 3 mm were used, and the voltage was raised at a rate of 1 MV / m. Each sample was tested 10 times at room temperature, and the results were analyzed by a two-parameter Weibull distribution, as shown in Figure 4 .

[0028] As can be seen from Figure 1 , the ether amide acid C=O stretching vibration peak at 1658 cm -1 and the N-H bending vibration peak at 1550 cm -1 both disappeared, indicating that the imide acid structure in the copolymer had disappeared, which indicated that the polyetherimide amide was completely amided. The thiourea of the aromatic polythiourea exists in two configurations, trans / trans configuration and cis / trans configuration, corresponding to -N-H stretching vibration at 3300 cm -1 and 3000 cm -1 , respectively.

[0029] From Figure 2 It can be seen that the diffraction peak positions of example 1, example 2, example 3 and comparative example 1 are respectively located at 18.08 °, 18.76 °, 19.27 ° and 20.18 ° 18.08 ° and 20.18 °, and the calculated molecular chain spacing of example 1, example 2, example 3 and comparative example 1 is respectively 0.49, 0.47, 0.46 and 0.44 nm, and the molecular chain spacing increases.

[0030] From Figure 3 It can be seen that the dielectric constant of example 1, example 2, example 3 and comparative example 1 is respectively 6.5, 5.7, 5.2, 4.8, wherein the dielectric constant of example 1, example 2, example 3 is greatly improved compared with comparative example 1, which is increased by 35.4, 18.8, 8.3%.

[0031] From Figure 4 It can be seen that at room temperature, the direct current breakdown field strength of comparative example 1 is 603.3 MV / m, while the direct current breakdown field strength of example 1, example 2 and example 3 is respectively 650.0, 632.0 and 664.3 MV / m, which is greatly improved compared with comparative example 1, which is increased by 7.7%, 4.8%, 10.1% compared with comparative example 1.

[0032] Therefore, the polysulfourea-based block copolymer film of the present application simultaneously realizes the improvement of dielectric constant and breakdown field strength, and when applied to energy storage capacitors, it can further improve the energy storage performance of the capacitors.

[0033] Although the present application has been disclosed with the above preferred embodiments, it is not intended to limit the present application, and any person skilled in the art can make various modifications and modifications without departing from the spirit and scope of the present application, therefore the protection scope of the present application should be defined by the claims.

Claims

1. A method for increasing the energy storage density of polythiourea thin films by block copolymerization, characterized by, The method comprises the following steps: (1) adding thiocyanate into a polar solvent and stirring to dissolve the thiocyanate to obtain a solution; (2) adding an excess of aromatic ring diamine into the solution in multiple times and reacting under an inert gas atmosphere to obtain an amino-terminated polysulfourea precursor; (3) adding a dianhydride and m-phenylenediamine into the amino-terminated polysulfourea precursor and continuing to react to obtain a block copolymer solution; (4) uniformly coating the block copolymer solution on a carrier, removing the polar solvent by heating, and then performing stepwise temperature increase at a preset rate, and completing imidization at different temperatures for a preset time; (5) soaking the carrier in deionized water to remove the film, and drying the obtained polysulfourea-based block copolymer film under vacuum to complete the improvement of the energy storage density of the polysulfourea film.

2. The method for improving the energy storage density of polythiourea thin films by block copolymerization according to claim 1, characterized in that, The ratio between the thiocyanate and the polar solvent is 2 mmol:6 mL; The thiocyanate is 1,4-benzene diisothiocyanate.

3. The method of increasing the energy density of polythiourea thin films by block copolymerization according to claim 1, characterized in that, The polar solvent is DMAc. The thiocyanate is added into the polar solvent and stirred to dissolve the thiocyanate until the solution is clear to obtain a solution.

4. The method for improving the energy density of polythiourea thin film by block copolymerization according to claim 1, characterized in that, In step (2), the molar ratio between the aromatic ring diamine and the thiocyanate is 2.04:2, and the reaction time is 8 h. The aromatic ring diamine is 3,3'-diaminodiphenylmethane.

5. The method of increasing the energy density of polythiourea thin films by block copolymerization according to claim 1, characterized in that, In step (3), the molar ratio between the dianhydride and the m-phenylenediamine is 1:1, and the molar ratio between the dianhydride or the m-phenylenediamine and the thiocyanate is (1-4):2; the time for continuing to react is 16 h. The dianhydride is 4,4'-(4,4'-isopropyl diphenyloxy) diphthalic anhydride.

6. The method of increasing the energy density of polythiourea thin films by block copolymerization according to claim 1, characterized in that, In step (4), the polar solvent is removed by heating at 80 ℃ for 3 h.

7. The method of increasing the energy density of polythiourea thin films by block copolymerization according to claim 1, characterized in that, In step (4), the stepwise temperature increase is performed at a rate of 3 ℃ / min, and the film is kept at 80 ℃, 100 ℃ and 120 ℃ for 1 h, respectively.

8. The method of increasing the energy density of polythiourea thin films by block copolymerization according to claim 1, wherein, In step (5), the carrier is soaked in deionized water at 80 ℃ to remove the film.

9. The method of increasing the energy density of polythiourea thin films by block copolymerization according to claim 1, wherein, In step (5), the temperature for vacuum drying is 80 ℃.

10. The method of increasing the energy density of polythiourea thin films by block copolymerization according to claim 1, wherein The thickness of the polysulfourea-based block copolymer film is 10-12 um.

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