A polyetherimide dielectric film containing an indane ring structure and a preparation method and application thereof

Abstract

The present application relates to the technical field of dielectric material, and more particularly to a kind of polyetherimide dielectric film containing indane ring structure and its preparation method and application.The polyetherimide dielectric film containing indane ring structure provided by the present application is obtained by polymerization reaction and imidization reaction from diamine monomer and dianhydride monomer containing segment shown in formula I.The polyetherimide dielectric film provided by the present application has higher room temperature and high-temperature breakdown field strength, and also has good high-temperature energy storage performance, and the preparation method is simple, suitable for industrial application.Formula I.

Description

Technical Field

[0001] This invention relates to the field of dielectric materials technology, and in particular to a polyetherimide dielectric film containing an indene ring structure, its preparation method, and its application. Background Technology

[0002] Polymer dielectric capacitors are key components in modern electronic and power systems. However, currently commercially available capacitors have low energy density and their performance deteriorates sharply under extreme environments such as high temperatures, severely limiting their application in aerospace, new energy vehicles, and other fields. While widely used biaxially oriented polypropylene (BOPP) film has low dielectric loss, its dielectric constant is only about 2.2, resulting in limited energy density. Polyvinylidene fluoride (PVDF), although possessing a higher dielectric constant (about 8-10), suffers from high dielectric loss and early polarization saturation, with discharge efficiency typically below 30% and energy density rarely exceeding 2 J / cm². 3 Polyetherimide (PEI) is produced by polycondensation of specific diamine monomers and anhydride monomers containing ether bonds to form polyetheramic acid, followed by high-temperature dehydration and cyclization. Due to its high insulation properties, excellent thermal stability, and tunable molecular structure, it has become a highly promising high-temperature dielectric material.

[0003] However, the breakdown field strength of existing polyetherimides remains low, failing to meet the requirements of applications under extreme conditions. Current methods to improve the breakdown field strength of polyetherimides mainly involve adding fillers and designing multilayer structures. For example, by adding nickel-based metal-organic framework nanosheets (Ni-MOFs), a Ni-MOFs / PEI dielectric nanocomposite containing 2 wt% Ni-MOFs exhibits a breakdown field strength of 640 kV / mm and 6.37 J / cm² at 150 °C. 3 The discharge energy density is high. However, the introduction of fillers can easily lead to interface defects and electric field concentration, causing early breakdown; at the same time, the poor compatibility between inorganic fillers and the polymer matrix reduces the flexibility and processing performance of the material, resulting in unstable dielectric material performance. For example, through a sandwich structure design, such as using linear polyetherimide (PEI) dielectric as the outer layer and poly(vinylidene fluoride-trifluoroethylene-chlorofluoroethylene) (P(VDF-TrFE-CFE)) composite material as the middle layer, the three-layer composite material achieved 18.9 J / cm² at 625 MV / m. 3 While multilayer structures can synergistically regulate the electric field distribution, their complex manufacturing process and high cost make them difficult to scale up for application. Therefore, there is an urgent need to provide a high breakdown field strength dielectric material with stable performance and a simple manufacturing process to meet industrial requirements. Summary of the Invention

[0004] This invention provides a polyetherimide dielectric film containing an indene ring structure, its preparation method, and its application. The polyetherimide dielectric film provided by this invention has a high high-temperature breakdown field strength and good high-temperature energy storage performance. Moreover, the preparation method is simple and suitable for industrial applications.

[0005] This invention provides a polyetherimide dielectric film containing an indene ring structure, obtained by polymerization and imidization of a diamine monomer and a dianhydride monomer containing the chain segment shown in Formula I. Formula I.

[0006] Optionally, the diamine monomer containing the segment shown in Formula I includes at least one of 1-(4-aminophenyl)-1,3,3-trimethyl-2,3-dihydro-1H-indene-5-amine and 3-(4-aminophenyl)-1,1,3-trimethyl-2,3-dihydro-1H-indene-5-amine.

[0007] Optionally, the dianhydride monomer includes at least one of 4,4'-(4,4'-isopropyldiphenoxy)diphthalic anhydride and 4,4'-(hexafluoroisopropyl)diphthalic anhydride.

[0008] Optionally, when the dianhydride monomer comprises 4,4'-(4,4'-isopropyldiphenoxy)diphthalic anhydride and 4,4'-(hexafluoroisopropyl)diphthalic anhydride, the molar ratio of the 4,4'-(4,4'-isopropyldiphenoxy)diphthalic anhydride and 4,4'-(hexafluoroisopropyl)diphthalic anhydride is 1:0-4.

[0009] Optionally, the thickness of the polyetherimide dielectric film containing the indene ring structure is 9-25 μm.

[0010] The present invention also provides a method for preparing a polyetherimide dielectric thin film containing an indene ring structure as described in any of the above technical solutions, comprising the following steps: A diamine monomer containing the chain segment shown in Formula I, a dianhydride monomer, and a solvent are mixed and subjected to a polymerization reaction to obtain a polyamic acid solution. Formula I After the polyamic acid solution is subjected to degassing and film formation in sequence, an imidization reaction is carried out to obtain a polyether imide dielectric film containing an indene ring structure.

[0011] Optionally, the solvent includes at least one of N-methylpyrrolidone, N,N-dimethylacetamide, N,N-dimethylformamide, and resorcinol.

[0012] Optionally, the total mass of the diamine monomer and dianhydride monomer containing the chain segment shown in Formula I accounts for 10-20 wt% of the mass of the mixture of the diamine monomer, dianhydride monomer and solvent containing the chain segment shown in Formula I.

[0013] Optionally, the polymerization reaction is carried out at room temperature for 24-30 hours.

[0014] Optionally, the imidization reaction is carried out under a gradient temperature program, wherein the gradient temperature program is as follows: holding at 80-90℃ for 0.5-0.8 h, holding at 105-115℃ for 0.5-0.8 h, holding at 150-170℃ for 0.8-1.2 h, holding at 190-210℃ for 0.8-1.2 h, holding at 215-225℃ for 0.8-1.2 h, holding at 250-270℃ for 0.8-1.2 h, and holding at 290-300℃ for 0.8-1.2 h.

[0015] The present invention also provides the application of the polyetherimide dielectric film containing the indene ring structure as described in any one of the above technical solutions, or the polyetherimide dielectric film containing the indene ring structure prepared by any one of the above technical solutions, in dielectric capacitors.

[0016] Compared with the prior art, the present invention has the following beneficial effects: The polyetherimide dielectric film containing an indene ring structure provided by this invention is obtained by polymerization and imidization of a diamine monomer and a dianhydride monomer containing the chain segment shown in Formula I. The structure shown in Formula I contains an indene ring structure and three methyl groups, forming a large and rigid side group. This structure creates significant steric hindrance in the polymer chain, effectively suppressing the free rotation and tight stacking of the molecular chains, greatly increasing the tortuosity of the charge migration path within the material, suppressing the formation and propagation of electrical trees, and thus significantly improving the breakdown field strength. Furthermore, the electron-rich indene ring itself can act as a powerful charge trapping site. Compared to linear 1,4-phenylenediamine, this structure introduces deeper trap levels in the polymer band structure. Under an applied high electric field, these deep traps can effectively trap and bind injected charge carriers (electrons or holes), preventing them from further migrating and accumulating to form destructive conductive channels, thereby delaying the occurrence of electrical breakdown. As described in the embodiments, the polyetherimide dielectric film containing an indene ring structure provided by the present invention exhibits breakdown field strengths of 645.98-678.35 kV / mm at 150°C and 606.52-651.82 kV / mm at 200°C, which are significantly higher than those of polyetherimide dielectric films without an indene ring structure. Furthermore, it possesses a glass transition temperature above 250°C (251.15-291.59°C) and high high-temperature energy storage performance (discharge energy density reaching 2.93-4.38 J / cm² at 200°C and 90% energy storage efficiency). 3 All of them can operate stably at 200℃. Attached Figure Description

[0017] The above and other objects, features, and advantages of the invention will be apparent from the following description of preferred embodiments illustrating the gist of the invention and its use, and the accompanying drawings, in which: Figure 1 The structures of polyetherimide in the films obtained in Examples 1, 3 and Comparative Example 1 are shown.

[0018] Figure 2 The Fourier transform infrared spectra of the films obtained in Examples 1-4 and Comparative Example 1 are shown.

[0019] Figure 3 The X-ray diffraction patterns of the thin films obtained in Examples 1-4 and Comparative Example 1 are shown.

[0020] Figure 4 Differential scanning calorimetry (DSC) curves of the thin films obtained in Examples 1-4 and Comparative Example 1 are shown.

[0021] Figure 5 The room temperature fluorescence emission spectra of the films obtained in Examples 1, 3 and Comparative Example 1 are shown.

[0022] Figure 6 The dielectric temperature spectrum test results of the films obtained in Examples 1-4 and Comparative Example 1 are shown.

[0023] Figure 7 The images show the Weber distribution of the films obtained in Examples 1-4 and Comparative Example 1 at 150°C and 200°C.

[0024] Figure 8 The results of energy storage performance tests of the films obtained in Examples 1-4 and Comparative Example 1 at 200°C and 250°C are shown. Detailed Implementation

[0025] The present invention will be described below through specific embodiments. Those skilled in the art will understand that the specific embodiments described below are for illustrative purposes only and do not limit the scope of the invention in any way. Furthermore, in the following embodiments, unless otherwise specified, the reagents and equipment used are commercially available. If specific processing conditions and methods are not explicitly described in the following embodiments, conditions and methods known in the art can be used for processing.

[0026] This invention provides a polyetherimide dielectric film containing an indene ring structure, obtained by polymerization and imidization of a diamine monomer and a dianhydride monomer containing the chain segment shown in Formula I. Formula I.

[0027] This invention introduces an indene ring structure and three methyl groups into polyetherimide to form a large and rigid side group. This structure creates a large steric hindrance in the polymer chain, effectively suppressing the free rotation and tight stacking of the molecular chain, greatly increasing the tortuosity of the charge migration path inside the material, suppressing the formation and propagation of electrical trees, and thus significantly improving the breakdown field strength.

[0028] In some embodiments of the present invention, the diamine monomer containing the segment shown in Formula I includes at least one of 1-(4-aminophenyl)-1,3,3-trimethyl-2,3-dihydro-1H-indene-5-amine and 3-(4-aminophenyl)-1,1,3-trimethyl-2,3-dihydro-1H-indene-5-amine.

[0029] In some embodiments of the present invention, the dianhydride monomer includes at least one of 4,4'-(4,4'-isopropyldiphenoxy)phthalic anhydride and 4,4'-(hexafluoroisopropyl)phthalic anhydride.

[0030] In some embodiments of the present invention, when the dianhydride monomer comprises 4,4'-(4,4'-isopropyldiphenoxy)phthalic anhydride and 4,4'-(hexafluoroisopropyl)phthalic anhydride, the molar ratio of the 4,4'-(4,4'-isopropyldiphenoxy)phthalic anhydride and 4,4'-(hexafluoroisopropyl)phthalic anhydride is 1:0-4, specifically 1:0.3, 1:1, 1:3, 1:4, etc. In this invention, the introduction of the fluorine-containing dianhydride monomer increases dipole interaction, aiming to utilize its strong electronegativity to bind charge transport and increase free volume, effectively suppressing the migration of charge carriers and the accumulation of space charge under high electric fields, thereby significantly reducing losses and improving efficiency. The fluorinated dianhydride monomers within the above-mentioned ratio range can not only reduce losses and improve efficiency, but also ensure that the resulting film has good film-forming properties. However, excessive fluorinated dianhydride monomers will cause the moldability of the resulting polyetherimide dielectric film to deteriorate and its brittleness to increase, making it impossible to obtain an applicable dielectric film.

[0031] In some embodiments of the present invention, the molar ratio of the diamine monomer to the dianhydride monomer is 1-1.02:1, specifically 1:1, 1.01:1, 1.02:1, etc.

[0032] In some embodiments of the present invention, the thickness of the polyetherimide dielectric film containing the indene ring structure is 9-25 μm, specifically 10 μm, 11 μm, 20 μm, 25 μm, etc.

[0033] The present invention also provides a method for preparing a polyetherimide dielectric thin film containing an indene ring structure as described in any of the above technical solutions, comprising the following steps: A diamine monomer containing the chain segment shown in Formula I, a dianhydride monomer, and a solvent are mixed and subjected to a polymerization reaction to obtain a polyamic acid solution. Formula I After the polyamic acid solution is subjected to degassing and film formation in sequence, an imidization reaction is carried out to obtain a polyether imide dielectric film containing an indene ring structure.

[0034] This invention first involves mixing a diamine monomer containing the chain segment shown in Formula I, a dianhydride monomer, and a solvent, and then performing a polymerization reaction to obtain a polyamic acid solution. In this invention, the diamine monomer and the dianhydride monomer undergo a polymerization reaction to generate a polyamic acid solution.

[0035] The present invention does not have a particular limitation on the mixing method, as long as the three are mixed evenly. It can be that one monomer is dissolved in the solvent first and then the other monomer is added, or both are added to the solvent at the same time, or the dianhydride monomer and the diamine monomer are dissolved in the solvent separately and then one solution is added to the other solution; in the embodiments of the present invention, the mixing is to dissolve the diamine monomer and the dianhydride monomer in the solvent separately to obtain a diamine monomer solution and a dianhydride monomer solution, and then add the diamine monomer solution dropwise to the dianhydride monomer solution.

[0036] In some embodiments of the present invention, the solvent includes at least one of N-methylpyrrolidone, N,N-dimethylacetamide, N,N-dimethylformamide, and resorcinol.

[0037] In some embodiments of the present invention, the total mass of the diamine monomer and dianhydride monomer containing the segment shown in Formula I accounts for 10-20 wt% of the mass of the mixture containing the diamine monomer, dianhydride monomer, and solvent, specifically 11 wt%, 13 wt%, 15 wt%, 18 wt%, 20 wt%, etc. In the present invention, the above percentages can further ensure that the resulting polyamic acid solution has a suitable viscosity to facilitate film formation.

[0038] In some embodiments of the present invention, the polymerization reaction is carried out at room temperature for a duration of 24-30 hours, specifically 24 hours, 26 hours, 28 hours, 30 hours, etc. After the polymerization reaction, a viscous polyamic acid solution is obtained.

[0039] After obtaining the polyamic acid solution, the present invention performs degassing and film formation sequentially on the polyamic acid solution, followed by an imidization reaction to obtain a polyether imide dielectric film containing an indene ring structure.

[0040] The present invention does not have any particular limitation on the degassing and film formation methods. Conventional liquid degassing (such as vacuum degassing) and film formation methods (such as coating on a substrate) can be used.

[0041] In some embodiments of the present invention, the film formation involves coating a degassed polyamic acid solution onto a substrate in an atmosphere of 65-75°C (specifically, 65°C, 70°C, 75°C, etc.), and then holding the solution at 65-75°C (specifically, 65°C, 70°C, 75°C, etc.) for 10-15 minutes. This process promotes film leveling and solvent evaporation, thereby forming a shaped film.

[0042] In some embodiments of the present invention, the imidization reaction is carried out under a gradient temperature program, wherein the gradient temperature program is as follows: holding at 80-90℃ (specifically, 80℃, 85℃, 90℃, etc.) for 0.5-0.8 h (specifically, 0.5 h, 0.8 h, etc.), holding at 105-115℃ (specifically, 105℃, 110℃, 115℃, etc.) for 0.5-0.8 h (specifically, 0.5 h, 0.8 h, etc.), holding at 150-170℃ (specifically, 150℃, 160℃, 170℃, etc.) for 0.8-1.2 h (specifically, 0.8 h, 1.0 h, 1.2 h, etc.), and holding at 190-210℃ (specifically, 190℃, 200℃, 210℃, etc.) for 0.8-1.2 h (specifically, 0.8 h, 1.0 h, 1.2 h, etc.). The temperature is maintained at 215-225℃ (specifically 215℃, 220℃, 225℃, etc.) for 0.8-1.2 h (specifically 0.8 h, 1.0 h, 1.2 h, etc.), at 250-270℃ (specifically 250℃, 260℃, 270℃, etc.) for 0.8-1.2 h (specifically 0.8 h, 1.0 h, 1.2 h, etc.), and at 290-300℃ (specifically 290℃, 300℃, etc.) for 0.8-1.2 h (specifically 0.8 h, 1.0 h, 1.2 h, etc.). Preferably, the gradient temperature program is maintained at 80℃ for 0.5 h, at 110℃ for 0.5 h, at 160℃ for 1 h, at 200℃ for 1 h, and at 220℃ for 1 h. The temperature is maintained at 260℃ for 1 hour and at 300℃ for 1 hour. This invention does not have special requirements for the heating rate at each stage.

[0043] In some embodiments of the present invention, in order to apply the film, after the imidization reaction is completed to obtain the polyimide dielectric film, the polyimide dielectric film is naturally cooled to room temperature and then peeled off from the substrate for application; the present invention does not have a special limitation on the peeling method, and a conventional peeling method can be used, such as soaking in warm water (e.g., 60°C) for peeling, then drying before application.

[0044] The present invention also provides the application of polyetherimide dielectric films containing indene ring structures as described in any one of the above technical solutions, or polyetherimide dielectric films containing indene ring structures prepared by any one of the above technical solutions, in dielectric capacitors, especially in dielectric capacitors used in high-temperature (100-200°C, or even 100-250°C) environments.

[0045] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings and embodiments. The embodiments of this application are only examples, and all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0046] Example 1 (1) At room temperature, 0.4 mmol of diamine monomer (1-(4-aminophenyl)-1,3,3-trimethyl-2,3-dihydro-1H-indene-5-amine) was dissolved in 1.0 mL of N-methylpyrrolidone to obtain a diamine solution; 0.4 mmol of dianhydride monomer (4,4'-(4,4'-isopropyldiphenoxy)phthalic anhydride) was dissolved in 1.26 mL of N-methylpyrrolidone to obtain a dianhydride solution, wherein the total mass of the diamine monomer and the dianhydride monomer accounted for 13 wt% of the total mass of the diamine solution and the dianhydride solution.

[0047] (2) The diamine solution was added dropwise to the dianhydride solution, and then the polymerization reaction was carried out under stirring for 24 h to obtain a polyamic acid solution.

[0048] (3) After degassing the polyamic acid solution under vacuum, the degassed polyamic acid solution was coated onto a glass plate in an oven at 70°C. The plate was then dried at 70°C for 10 min, and then the temperature was successively increased to 80°C and held for 0.5 h, then at 110°C for 0.5 h, then at 160°C for 1 h, then at 200°C for 1 h, then at 220°C for 1 h, then at 260°C for 1 h, and finally at 300°C for 1 h. This resulted in a 10 μm thick polyetherimide dielectric film containing an indene ring structure on the glass plate, denoted as IPEI (structure as shown). Figure 1 (As shown).

[0049] Example 2 (1) 0.4 mmol of diamine monomer (1-(4-aminophenyl)-1,3,3-trimethyl-2,3-dihydro-1H-indene-5-amine) was dissolved in 1.0 mL of N-methylpyrrolidone to obtain a diamine solution; 0.4 mmol of dianhydride monomer (4,4'-(4,4'-isopropyldiphenoxy) diaphthalic anhydride and 4,4'-(hexafluoroisopropyl) diaphthalic anhydride, with a molar ratio of 3:1) was dissolved in 0.92 mL of N-methylpyrrolidone to obtain a dianhydride solution, wherein the total mass of the diamine monomer and the dianhydride monomer accounted for 13 wt% of the total mass of the diamine solution and the dianhydride solution.

[0050] (2)-(3) Prepare a polyetherimide dielectric film with an indene ring structure according to the method of steps (2)-(3) in Example 1. The thickness is 11 μm and it is denoted as 25HF-PI.

[0051] Example 3 A polyetherimide dielectric film containing an indene ring structure was prepared according to the method of Example 2, the only difference being the use of 4,4'-(4,4'-isopropyldiphenoxy)phthalic anhydride and 4,4'-(hexafluoroisopropyl)phthalic anhydride in a molar ratio of 1:1. The total mass of the diamine monomer and the dianhydride monomer accounted for 15 wt% of the total mass of the diamine solution and the dianhydride solution. The resulting polyetherimide dielectric film containing an indene ring structure had a thickness of 11 μm and was designated as 50HF-PI (structure as shown in Example 2). Figure 1 (As shown).

[0052] Example 4 A polyetherimide dielectric film containing an indene ring structure was prepared according to the method of Example 2, the only difference being the use of 4,4'-(4,4'-isopropyldiphenoxy) phthalic anhydride and 4,4'-(hexafluoroisopropyl) phthalic anhydride, with a molar ratio of 1:3. The total mass of the diamine monomer and the dianhydride monomer accounted for 15 wt% of the total mass of the diamine solution and the dianhydride solution. The resulting polyetherimide dielectric film containing an indene ring structure had a thickness of 11 μm and was designated as 75HF-PI.

[0053] Comparative Example 1 Polyetherimide dielectric films were prepared according to the method of Example 1, except that 1,4-phenylenediamine was used as the diamine monomer. The resulting polyetherimide dielectric film had a thickness of 10 μm and was denoted as PEI (structure as shown in Example 1). Figure 1 (As shown).

[0054] The film properties obtained from micro-tests are obtained by naturally cooling the polyetherimide dielectric film to room temperature after the imidization reaction is completed, then peeling the film off in warm water, and then drying it at 80°C for 24 h before application or performance testing.

[0055] The Fourier transform infrared spectra of the thin films obtained in Examples 1-4 and Comparative Example 1 were tested, and the results are as follows: Figure 2 As shown. Figure 2 1780 cm -1 The characteristic peak is attributed to the C=O group, 1380 cm⁻¹ -1 The characteristic peaks are attributed to the C=N group, by Figure 2 It can be seen that the films obtained in Examples 1-4 and Comparative Example 1 all contain imide ring structures, and the imidization is complete.

[0056] The X-ray diffraction patterns of the thin films obtained in Examples 1-4 and Comparative Example 1 were tested, and the results were as follows: Figure 3 As shown. In Figure 3In the peak that appears around 25°, it is a characteristic peak of π-π packing. From PEI to 75HF-PI, the peak position gradually weakens, indicating that π-π packing weakens and the molecular chain packing changes from tight π-π packing to more open inter-chain ordered packing, thereby increasing the molecular chain spacing, hindering charge transport, and increasing the breakdown field strength.

[0057] The differential scanning calorimetry (DSC) curves of the thin films obtained in Examples 1-4 and Comparative Example 1 were tested using a differential scanning calorimeter. The results are as follows: Figure 4 As shown. By Figure 4 It can be concluded that the glass transition temperatures of the polyetherimide dielectric films obtained in Examples 1-4 are 251.15℃, 264.48℃, 275.43℃ and 291.59℃, respectively, which are all significantly higher than those of the film obtained in Comparative Example 1 (239.26℃), indicating that they can all work stably under higher temperature conditions. The three fluorine-containing components can even work stably at 250℃. In addition, the glass transition temperatures of the films obtained in Examples 2-4 are significantly higher than those of the film obtained in Example 1, indicating that the introduction of fluorine further improves the thermodynamic stability of the film.

[0058] The fluorescence emission spectra of the films obtained in Examples 1, 3 and Comparative Example 1 at room temperature were tested, and the results are as follows: Figure 5 As shown. By Figure 5 It can be seen that, compared with the PEI obtained in Comparative Example 1, the peak positions of the films obtained in Examples 1 and 3 have shifted to the left (i.e., blue shift occurred), and the fluorescence intensity has increased, and the peak shape is sharper. This indicates that the π-π stacking in the polyetherimide film provided by the present invention is weakened, and the intra-chain / inter-chain electron transfer is suppressed. It can be seen that the twisted non-planar indene structure introduces steric hindrance, which weakens charge transport and is beneficial to increasing the breakdown field strength.

[0059] The electrical properties of the thin films obtained in Examples 1-4 and Comparative Example 1 were tested using the following method: Metal photomasks with a circular aperture diameter of 3 mm were prepared. The prepared thin film was sandwiched between two metal photomasks, and gold electrodes were symmetrically sputtered onto the upper and lower surfaces at a sputtering current of 30 mA for 300 s. Dielectric spectrum, dielectric temperature spectrum, breakdown field strength, and energy storage performance were tested using an impedance analyzer and a ferroelectric workstation.

[0060] The dielectric temperature spectra of the films obtained in Examples 1-4 and Comparative Example 1 were tested, and the results are as follows: Figure 6 As shown. By Figure 6It can be seen that the room temperature dielectric constants (1kHz) of the films obtained in Examples 1-4 and Comparative Example 1 are 3.097, 3.027, 2.971, 2.952 and 3.101, respectively, and the dielectric constants (1kHz) at 200℃ are 2.907, 2.833, 2.832, 2.824 and 2.920, respectively. This indicates that the dielectric film provided by the present invention has a relatively stable dielectric constant as the temperature increases, and maintains a high level. The introduction of the indene ring structure and fluorine-containing groups does not have a significant negative impact on the dielectric constant, and also has a small loss tangent value.

[0061] The breakdown field strength of the films obtained in Examples 1-4 and Comparative Example 1 at 150°C and 200°C was tested, and the results are as follows: Figure 7 As shown, (a) is the Weber distribution at 150℃, and (b) is the Weber distribution at 200℃. Figure 7 It can be seen that the breakdown field strengths of the films obtained in Examples 1-4 and Comparative Example 1 at 150°C are 645.98 kV / mm, 650.88 kV / mm, 678.35 kV / mm, 666.56 kV / mm, and 524.11 kV / mm, respectively, and the breakdown field strengths at 200°C are 606.52 kV / mm, 618.22 kV / mm, 651.82 kV / mm, 647.23 kV / mm, and 518.73 kV / mm, respectively. It is evident that the film provided by the present invention exhibits at least a 23.25% increase in breakdown field strength compared to the film obtained in Comparative Example 1 at 150°C, and at least a 16.92% increase at 200°C compared to the film obtained in Comparative Example 1, indicating that the introduction of the indene ring structure improves the breakdown field strength.

[0062] The energy storage performance of the thin films obtained in Examples 1-4 and Comparative Example 1 at 200°C and 250°C was tested, and the results are as follows: Figure 8 As shown, (a) represents the energy storage performance test results of the films obtained in Examples 1-4 and Comparative Example 1 at 200°C, and (b) represents the energy storage performance test results of the films obtained in Examples 2-4 at 250°C. Figure 8 As can be seen from (a) in the figure, the discharge energy densities of the films obtained in Examples 1-4 and Comparative Example 1 at 200°C with a storage efficiency of 90% are 3.35 J / cm². 3 2.93 J / cm 3 4.38 J / cm 3 3.49 J / cm 3 1.66 J / cm 3 The maximum discharge energy density is 4.53 J / cm³. 3 5.09 J / cm 3 5.92 J / cm3 5.41 J / cm 3 2.65 J / cm 3 As can be seen, compared to Comparative Example 1, the high-temperature energy storage performance of the films obtained in Examples 1-4 is significantly improved, especially the film obtained in Example 3, which shows a 163.8% increase in discharge energy density at a storage efficiency of 90%. Figure 8 As can be seen from (b) in the figure, the discharge energy density of the thin films obtained in Examples 2-4 at 250°C with a storage efficiency of 90% is 1.74 J / cm³. 3 2.81 J / cm 3 3.65 J / cm 3 The maximum discharge energy densities were 3.41, 3.98, and 4.84 J / cm³, respectively. 3 As can be seen, the polyetherimide dielectric film containing both indene ring structure and fluorine-containing groups provided by the present invention still has a high discharge energy density at 250°C and can operate stably at 250°C.

[0063] Although preferred embodiments of the invention have been shown and described, it is conceivable that those skilled in the art can devise various modifications to the invention within the spirit and scope of the appended claims.

Claims

1. A polyetherimide dielectric film containing an indene ring structure, obtained by polymerization and imidization of a diamine monomer and a dianhydride monomer containing the chain segment shown in Formula I. Equation I; The diamine monomer containing the chain segment shown in Formula I includes at least one of 1-(4-aminophenyl)-1,3,3-trimethyl-2,3-dihydro-1H-indene-5-amine and 3-(4-aminophenyl)-1,1,3-trimethyl-2,3-dihydro-1H-indene-5-amine. The dianhydride monomers include 4,4'-(4,4'-isopropyldiphenoxy) dianhydride and 4,4'-(hexafluoroisopropyl) dianhydride, wherein the molar ratio of 4,4'-(4,4'-isopropyldiphenoxy) dianhydride to 4,4'-(hexafluoroisopropyl) dianhydride is 1:1-4. The method for preparing the polyetherimide dielectric film containing the indene ring structure includes the following steps: A diamine monomer containing the chain segment shown in Formula I, a dianhydride monomer, and a solvent are mixed and subjected to a polymerization reaction to obtain a polyamic acid solution. Equation I; After the polyamic acid solution is subjected to degassing and film formation in sequence, an imidization reaction is carried out to obtain a polyether imide dielectric film containing an indene ring structure. The total mass of the diamine monomer and dianhydride monomer containing the chain segment shown in Formula I accounts for 15-20 wt% of the mass of the mixture of the diamine monomer, dianhydride monomer, and solvent containing the chain segment shown in Formula I. The polymerization reaction is carried out at room temperature for 24-30 hours. The imidization reaction was carried out under a gradient temperature program, which consisted of holding at 80-90℃ for 0.5-0.8 h, at 105-115℃ for 0.5-0.8 h, at 150-170℃ for 0.8-1.2 h, at 190-210℃ for 0.8-1.2 h, at 215-225℃ for 0.8-1.2 h, at 250-270℃ for 0.8-1.2 h, and at 290-300℃ for 0.8-1.2 h.

2. The polyetherimide dielectric film containing an indene ring structure according to claim 1, characterized in that, The thickness of the polyetherimide dielectric film containing the indene ring structure is 9-25 μm.

3. A method for preparing a polyetherimide dielectric film containing an indene ring structure as described in any one of claims 1-2, comprising the following steps: A diamine monomer containing the chain segment shown in Formula I, a dianhydride monomer, and a solvent are mixed and subjected to a polymerization reaction to obtain a polyamic acid solution. Equation I; After the polyamic acid solution is subjected to degassing and film formation in sequence, an imidization reaction is carried out to obtain a polyether imide dielectric film containing an indene ring structure.

4. The preparation method according to claim 3, characterized in that, The solvent includes at least one selected from N-methylpyrrolidone, N,N-dimethylacetamide, N,N-dimethylformamide, and resorcinol. The total mass of the diamine monomer and dianhydride monomer containing the chain segment shown in Formula I accounts for 15-20 wt% of the mass of the mixture of the diamine monomer, dianhydride monomer and solvent containing the chain segment shown in Formula I.

5. The preparation method according to claim 3 or 4, characterized in that, The polymerization reaction is carried out at room temperature for 24-30 hours.

6. The preparation method according to claim 3, characterized in that, The imidization reaction was carried out under a gradient temperature program, which consisted of holding at 80-90℃ for 0.5-0.8 h, at 105-115℃ for 0.5-0.8 h, at 150-170℃ for 0.8-1.2 h, at 190-210℃ for 0.8-1.2 h, at 215-225℃ for 0.8-1.2 h, at 250-270℃ for 0.8-1.2 h, and at 290-300℃ for 0.8-1.2 h.

7. The application of the polyetherimide dielectric film containing an indene ring structure according to any one of claims 1-2 or the polyetherimide dielectric film containing an indene ring structure obtained by the preparation method according to any one of claims 3-6 in a dielectric capacitor.

Images