A method for improving the energy storage density of polythiourea thin films by block copolymerization

Abstract

The application provides a method for improving the energy storage density of a polythiourea film by block copolymerization, thiocyanate is added to a polar solvent, stirring is performed to dissolve the thiocyanate, and a dissolution solution is obtained; an excess of aromatic ring diamine is added to the dissolution solution in multiple times, and reaction is performed under an inert gas atmosphere to obtain an amino-terminated polythiourea precursor; dianhydride and m-phenylenediamine are added to the amino-terminated polythiourea precursor, and the reaction is continued to obtain a block copolymer solution; 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; the carrier is soaked in deionized water to remove the film, and the obtained polythiourea-based block copolymer film is dried under vacuum to complete the improvement of the energy storage density of the polythiourea film. The polythiourea film obtained by the method has high breakdown strength, the energy storage density is improved, and the cost is low, so the polythiourea film has a good application prospect in the field of film capacitors.

Description

Technical Field

[0001] This invention relates to the field of polymer dielectric films, and more specifically to a method for improving the energy storage density of polythiourea films through block copolymerization. Background Technology

[0002] Dielectric capacitors are widely used in distributed energy, flexible DC transmission systems, and new energy vehicles. The most common dielectric film material on the market is biaxially oriented polypropylene (BOPP), which has a dielectric constant of approximately 2.2 and an energy storage density of less than 2 J / cm³. 3 This cannot meet the demands of equipment miniaturization. Therefore, it is necessary to develop polymer dielectric materials with high energy storage density. With the miniaturization of power equipment and electronic devices, simultaneously improving the breakdown field strength and dielectric constant of polymers has become a key issue in developing new energy storage dielectrics, ultimately achieving increased energy storage density. Therefore, it is necessary to modify polymer dielectric films to improve their energy storage performance. Summary of the Invention

[0003] The purpose of this invention is to provide a method for improving the energy storage density of polythiourea films through block copolymerization, thereby overcoming the problems existing in the prior art. The polythiourea films obtained by this invention have high breakdown strength and achieve improved energy storage density, and are low in cost, showing great application prospects in the field of film capacitors.

[0004] This invention is achieved through the following technical solution: A method for improving the energy storage density of polythiourea films through block copolymerization includes the following steps: (1) Add thiocyanate to a polar solvent and stir to dissolve it, thus obtaining a solution; (2) Add excess aromatic cyclic diamine to the solution in multiple portions and react under an inert gas atmosphere to obtain the terminal amino polythiourea precursor; (3) Add dianhydride and m-phenylenediamine to the amino-terminated polythiourea precursor and continue the reaction to obtain a block copolymer solution; (4) The block copolymer solution is uniformly coated on the carrier, heated to remove the polar solvent, and then heated in a stepwise manner at a preset rate, and held at different temperatures for a preset time to complete the imidization. (5) The carrier is immersed in deionized water to remove the membrane, and the obtained polythiourea-based block copolymer film is dried under vacuum conditions to complete the improvement of the energy storage density of polythiourea film.

[0005] Furthermore, the ratio between the thiocyanate and the polar solvent is 2 mmol: 6 mL; The thiocyanate used is 1,4-phenyl diisothiocyanate.

[0006] Furthermore, the polar solvent is DMAc; Thiocyanate is added to a polar solvent and stirred until it dissolves and the solution becomes clear, thus obtaining a solution.

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

[0008] Further, in step (3), the molar ratio between dianhydride and m-phenylenediamine is 1:1, and the molar ratio between dianhydride or m-phenylenediamine and thiocyanate is (1-4):2; the reaction continues for 16 h; The dianhydride used is 4,4'-(4,4'-isopropyldiphenoxy)phthalic anhydride.

[0009] Furthermore, the heating to remove the polar solvent in step (4) specifically involves maintaining the temperature at 80 °C for 3 hours to remove the polar solvent.

[0010] Furthermore, in step (4), the temperature is increased in steps at a preset rate and held for a preset time at different temperatures. Specifically, the temperature is increased in steps at a rate of 3 ℃ / min and held for 1 h at 80 ℃, 100 ℃, and 120 ℃ respectively.

[0011] Further, in step (5), the carrier is immersed in deionized water at 80 °C to remove the membrane.

[0012] Furthermore, the vacuum drying temperature in step (5) is 80 °C.

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

[0014] Compared with the prior art, the present invention has the following beneficial technical effects: This invention uses a segmented amino polythiourea obtained by reacting thiocyanate with a slightly excess of aromatic cyclic diamine as a precursor. Dihydric anhydride and m-phenylenediamine are added to obtain polyetherimide segments, thus preparing a polythiourea-based block polyetherimide copolymer. Through block copolymerization, an interfacial region is formed between the polythiourea and polyetherimide molecular chains. This interfacial region enhances dipole polarization, and the increased interchain spacing promotes dipole reversal, increasing the dielectric constant of the polythiourea-based block polyetherimide copolymer. Simultaneously, a deep trap energy level is introduced, resulting in higher breakdown strength and ultimately improved energy storage density. Furthermore, it is inexpensive and has excellent application prospects in the field of thin-film capacitors.

[0015] Furthermore, in this invention, setting different polyetherimide block ratios can change the size of the interface region, thereby affecting the dielectric constant and breakdown field strength of the polythiourea-based block polyetherimide copolymer. By comparing the changes in dielectric constant and breakdown field strength, the optimal ratio can be selected to maximize the energy storage density. Attached Figure Description

[0016] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly described below. The following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained from these drawings without creative effort.

[0017] Figure 1 Infrared schematic diagrams of the films of Example 1, Example 2, Example 3 and Comparative Example 1; Figure 2 The X-ray diffraction test results are for the thin films of Example 1, Example 2, Example 3 and Comparative Example 1; Figure 3 The dielectric constant test results are for the thin films of Examples 1, 2, 3 and Comparative Example 1; Figure 4 The results are the DC breakdown field strength test results of the films in Examples 1, 2, 3 and Comparative Example 1. Detailed Implementation

[0018] The present invention will now be described in detail: A method for improving the energy storage density of polythiourea films through block copolymerization includes the following steps: (1) Weigh thiocyanate (1,4-phenyl diisothiocyanate) using a high-precision balance, add it to a polar solvent, and stir magnetically until the solution is clear. The ratio of thiocyanate to polar solution is 2 mmol to 6 mL. (2) Add a slightly excess of aromatic cyclic diamine (3,3'-diaminodiphenylmethane) in multiple portions. The molar ratio between the aromatic cyclic diamine and thiocyanate is 2.04:2. React for 8 h under an inert gas atmosphere to obtain the terminal amino polythiourea precursor. (3) Add dianhydride (4,4'-(4,4'-isopropyldiphenoxy) phthalic anhydride) and m-phenylenediamine to the amino-terminated polythiourea precursor. The molar ratio between dianhydride and m-phenylenediamine is 1:1, and the molar ratio between dianhydride or m-phenylenediamine and thiocyanate is (1-4):2. Continue the reaction 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 multiple portions and reacted for 8 h under an inert gas atmosphere to synthesize the terminal amino polythiourea precursor; (3) Add 2 mmol of 4,4'-(4,4'-isopropyldiphenoxy) phthalic anhydride and 2 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 -PEI1.

[0022] Example 3 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 1 mmol of 4,4'-(4,4'-isopropyldiphenoxy) phthalic anhydride and 1 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 12 μm polythiourea block copolymer film, denoted as PTU2- b -PEI1.

[0023] Comparative Example 1 The polythiourea film was synthesized using 2 mmol of thiocyanate (1,4-phenylenediisothiocyanate) and an equal molar mass of 3,3'-diaminodiphenylmethane in 6 ml of DMAc solution. The solution was uniformly coated onto a clean glass slide and heated stepwise at 80, 100, and 120 °C for 1 h each. The film was then removed by immersion in deionized water at 80 °C and dried in a vacuum oven at 80 °C to remove moisture, yielding a 10 μm polythiourea film, denoted as PTU.

[0024] Performance testing: (1) Fourier transform infrared spectroscopy was used to test the polythiourea-based block copolymer films prepared in Examples 1, 2, 3 and Comparative Example 1. The test was conducted in reflectance mode, and the test range was 4000-500 cm⁻¹. -1 The test results are as follows Figure 1 As shown.

[0025] (2) X-ray diffraction tests were performed on the polythiourea-based block copolymers prepared in Examples 1, 2, 3, and Comparative Example 1. The radiation was generated using a Cu target with a wavelength of 0.1542 nm and a test angle of 5-35°. The test results are as follows: Figure 2 As shown.

[0026] (3) Broadband dielectric spectroscopy was performed on the polythiourea-based block copolymer films prepared in Examples 1, 2, 3 and Comparative Example 1. The test frequency range was 10 Hz. -1 -10 6 Hz. Test results are as follows Figure 3 As shown.

[0027] (4) The films prepared in the above examples and comparative examples were placed in a DC breakdown test apparatus for testing. A column-plate copper electrode with a diameter of 3 mm was used, and the voltage rise rate was 1 MV / m. At room temperature, each sample was tested 10 times, and the results were analyzed using a two-parameter Weibull distribution. Figure 4 As shown.

[0028] from Figure 1 It can be seen that the polythiourea-based block copolymer at 1658 cm⁻¹ -1 The C=O stretching vibration peak of etheramic acid and 1550 cm⁻¹ -1 The disappearance of the NH bending vibration peaks indicates that the imine structure in the copolymer has disappeared, suggesting complete amidation of the polyether imide. Aromatic polythiourea exists in two configurations: trans / trans and cis / trans, corresponding to 3300 cm⁻¹, respectively. -1 and 3000 cm -1 -NH stretching vibration.

[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 located at 18.08°, 18.76°, 19.27° and 20.18°, respectively. The molecular chain spacing of Example 1, Example 2, Example 3 and Comparative Example 1 is calculated to be 0.49, 0.47, 0.46 and 0.44 nm, respectively, indicating an increase in molecular chain spacing.

[0030] from Figure 3 It can be seen that the dielectric constants of Example 1, Example 2, Example 3 and Comparative Example 1 are 6.5, 5.7, 5.2 and 4.8, respectively. Among them, the dielectric constants of Example 1, Example 2 and Example 3 are significantly improved compared with Comparative Example 1, by 35.4, 18.8 and 8.3%, respectively.

[0031] from Figure 4 As can be seen, at room temperature, the DC breakdown field strength of Comparative Example 1 is 603.3 MV / m, while the DC breakdown field strengths of Example 1, Example 2 and Example 3 are 650.0, 632.0 and 664.3 MV / m, respectively, which are significantly improved compared to Comparative Example 1, by 7.7%, 4.8% and 10.1%, respectively.

[0032] Therefore, the polythiourea-based block copolymer film of the present invention simultaneously improves the dielectric constant and breakdown field strength, and its application in energy storage capacitors can further enhance the energy storage performance of the capacitors.

[0033] Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Anyone skilled in the art can make various modifications and alterations without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention should be determined by the claims.

Claims

1. A method for improving the energy storage density of polythiourea films through block copolymerization, characterized in that, Includes the following steps: (1) Add thiocyanate to a polar solvent and stir to dissolve it to obtain a solution, wherein the thiocyanate is 1,4-phenyl diisothiocyanate; (2) Add an excess of aromatic cyclic diamine to the solution in multiple portions and react under an inert gas atmosphere to obtain a terminal amino polythiourea precursor, wherein the aromatic cyclic diamine is 3,3'-diaminodiphenylmethane. (3) Add dianhydride and m-phenylenediamine to the amino-terminated polythiourea precursor and continue the reaction to obtain a block copolymer solution, wherein the molar ratio between dianhydride and m-phenylenediamine is 1:1 and the molar ratio between dianhydride or m-phenylenediamine and thiocyanate is (1-4):2; the reaction time is 16 h. The dianhydride used is 4,4'-(4,4'-isopropyldiphenoxy)diphthalic anhydride; (4) The block copolymer solution is uniformly coated on the carrier, heated to remove the polar solvent, and then heated in a stepwise manner at a preset rate, and held at different temperatures for a preset time to complete the imidization. (5) The carrier is immersed in deionized water to remove the film, and the resulting polythiourea block copolymer film is dried under vacuum conditions.

2. The method for improving the energy storage density of polythiourea films through block copolymerization according to claim 1, characterized in that, The ratio of thiocyanate to polar solvent is 2 mmol: 6 mL.

3. The method for improving the energy storage density of polythiourea films through block copolymerization according to claim 1, characterized in that, The polar solvent is DMAc; Thiocyanate is added to a polar solvent and stirred until it dissolves and the solution becomes clear, thus obtaining a solution.

4. A method for improving the energy storage density of polythiourea films through block copolymerization according to claim 1, characterized in that, In step (2), the molar ratio between the aromatic cyclic diamine and the thiocyanate is 2.04:2, and the reaction time is 8 h.

5. A method for improving the energy storage density of polythiourea films through block copolymerization according to claim 1, characterized in that, In step (4), heating to remove the polar solvent specifically involves maintaining the temperature at 80 °C for 3 h to remove the polar solvent.

6. A method for improving the energy storage density of polythiourea films through block copolymerization according to claim 1, characterized in that, In step (4), the temperature is increased in a stepwise manner at a preset rate, and the temperature is maintained for a preset time at different temperatures. Specifically, the temperature is increased in a stepwise manner at a rate of 3 ℃ / min, and the temperature is maintained for 1 h at 80 ℃, 100 ℃, and 120 ℃ respectively.

7. A method for improving the energy storage density of polythiourea films by block copolymerization according to claim 1, characterized in that, In step (5), the carrier is immersed in deionized water at 80 °C to remove the membrane.

8. A method for improving the energy storage density of polythiourea thin films by block copolymerization according to claim 1, characterized in that, The vacuum drying temperature in step (5) is 80 °C.

9. A method for improving the energy storage density of polythiourea thin films by block copolymerization according to claim 1, characterized in that, The thickness of the polythiourea-based block copolymer film is 10-12 μm.

Images