A high dielectric polyimide / graphene composite film and preparation method thereof

Abstract

The present invention proposes a high dielectric polyimide / graphene composite film and a preparation method thereof, wherein the preparation method of the composite film comprises: subjecting hydroxylated graphene and an iron-containing MOF material to an esterification reaction to obtain functionalized graphene; after forming a dispersed solution of the functionalized graphene, mixing it with a polyamic acid solution to obtain a blended solution; after casting the blended solution into a film, performing a thermal imidization reaction to obtain the composite film. In the present invention, functionalized graphene is introduced by subjecting hydroxylated graphene and an iron-containing MOF material to an esterification reaction, and a porous structure is formed on the surface of the functionalized graphene. This not only overcomes the strong π-π interaction between graphene sheets, allowing it to be stably dispersed in a polyimide matrix, but also enhances the interaction between graphene and the polyimide matrix. In addition to being conducive to increasing dielectric properties, it also overcomes the defect of damaging the mechanical properties of the composite film due to the addition of fillers.

Description

Technical Field

[0001] The present invention relates to the technical field of dielectric films, and in particular to a high-dielectric polyimide / graphene composite film and a preparation method thereof. Background Art

[0002] High dielectric thin film materials are one of the core materials for power and electronic devices, and are mainly used in embedded thin film capacitors. As the size of ultra-large-scale integrated circuits gradually shrinks, embedded capacitors are needed to achieve overall packaging, reduce circuit size, and increase integration. At present, the high dielectric dielectrics used in capacitors are mostly inorganic ceramic materials. Although they have extremely high dielectric constants, the processing and molding process requires high-temperature baking above 700°C, which is a complex process. The resulting material has poor flexibility and is prone to cracking. Moreover, the substrates of embedded capacitors are mostly organic polymer materials, which are difficult to withstand such high processing temperatures. This determines that high-dielectric ceramic inorganic materials are not suitable for embedded capacitors. Therefore, the development of composite materials with good flexibility, polymers as the matrix, and containing ultra-high dielectric constant components is an important direction for dielectric film materials for high-performance capacitors.

[0003] In recent years, research on polymer-based high-dielectric constant composite thin films has focused on incorporating inorganic ceramic powders with ultra-high dielectric constants, such as titanates and niobates, into polymer matrices. For example, Weng Ling et al. fabricated nano-barium titanate / polyimide high-dielectric constant composite films using in-situ polymerization and high-speed sand milling. When the powder volume fraction reached 50%, the composite film's dielectric constant increased 10-fold compared to the pure film (Weng Ling et al., Preparation and Properties of Nano-Barium Titanate-Doped Polyimide-Based High-Dielectric Constant Composite Films, Polymer Science and Engineering, 2012, 2:113-116). However, this method suffers from limitations in the inherent properties of the materials and the mechanisms involved in increasing the dielectric constant. Consequently, high-dielectric constant composite film materials require a high content of ceramic filler, significantly reducing the polymer-based composite film's flexibility and potentially impairing its mechanical properties.

[0004] Graphene, a single-atom-thick, two-dimensional carbon nanomaterial, possesses exceptional optical, electrical, thermal, and mechanical properties. It can significantly improve the mechanical, thermal, and dielectric properties of polymer-based composite thin films. As a new class of flexible, strong, lightweight, and high-performance dielectric materials, graphene / polymer composite thin films show promising application prospects in a wide range of fields, including thin-film capacitors, ultra-large-scale integrated circuits, and electrode materials. However, graphene alone struggles to form strong interactions directly at polymer interfaces, making it difficult to achieve the desired enhancement effects in polymer composite thin films. Furthermore, strong π-π interactions between graphene sheets lead to a strong tendency for the sheets to aggregate, resulting in poor dielectric and mechanical properties of graphene-enhanced polymer thin films. Summary of the Invention

[0005] Based on the technical problems existing in the background technology, the present invention proposes a high dielectric polyimide / graphene composite film and a preparation method thereof. By introducing functionalized graphene through esterification reaction of hydroxylated graphene and iron-containing MOF material, a porous structure is formed on the surface of the functionalized graphene. This not only overcomes the strong π-π interaction between graphene sheets, allowing them to be stably dispersed in the polyimide matrix, but also enhances the interaction between graphene and the polyimide matrix. In addition to being beneficial to increasing the dielectric properties, it also overcomes the defect that the mechanical properties of the composite film are damaged due to the addition of fillers.

[0006] The present invention provides a method for preparing a high dielectric polyimide / graphene composite film, comprising the following steps:

[0007] S1, esterifying the hydroxylated graphene and the iron-containing MOF material to obtain functionalized graphene;

[0008] S2, adding the functionalized graphene to an organic solvent to form a dispersed solution, and mixing the dispersed solution with a polyamic acid solution formed by polycondensation of a diamine monomer and a dianhydride monomer to obtain a blended solution;

[0009] S3, casting the blend solution into a film, and then performing a thermal imidization reaction to obtain the high dielectric polyimide / graphene composite film.

[0010] In the present invention, functionalized graphene is obtained by esterification reaction between hydroxylated graphene and iron-containing MOF material, thereby coating the graphene surface with a layer of iron-containing MOF material; on the one hand, the iron-containing MOF material has an octahedral hollow structure, so that a porous structure can be formed on the graphene surface, which not only overcomes the strong π-π interaction between graphene sheets, but also increases the interaction area between graphene and polyimide, thereby improving the dielectric properties of the obtained composite film and suppressing dielectric loss; on the other hand, the carboxyl group of the iron-containing MOF material can form hydrogen bonds or chemical bonding reactions with polyamic acid, thereby further promoting the uniform dispersion of graphene in the polyimide matrix, avoiding the defect of poor mechanical properties of the obtained composite film due to the addition of fillers.

[0011] Preferably, in step S1, the hydroxylated graphene is obtained by covalently bonding graphene oxide with a polyol and then performing a reduction reaction;

[0012] Preferably, the polyol is at least one of ethylene glycol, propylene glycol or diethylene glycol.

[0013] Preferably, in step S1, the iron-containing MOF material is MIL-101(Fe);

[0014] Preferably, the MIL-101(Fe) is obtained by carrying out a coordination reaction between ferric chloride hexahydrate and terephthalic acid.

[0015] Preferably, in step S1, the mass ratio of the hydroxylated graphene to the iron-containing MOF material is 1:0.5-1.5.

[0016] Preferably, in step S2, the organic solvent is at least one of N,N-dimethylacetamide, N,N-dimethylformamide, N-methylpyrrolidone or dimethyl sulfoxide.

[0017] Preferably, in step S2, the diamine monomer is at least one of p-phenylenediamine, 4,4'-diaminodiphenyl ether or 3,3'-diaminobenzophenone;

[0018] The dianhydride monomer is at least one of pyromellitic anhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride, 3,3',4,4'-diphenyl ether tetracarboxylic dianhydride, 3,3',4,4'-benzophenone tetracarboxylic dianhydride or 3,3',4,4'-diphenyl sulfone tetracarboxylic dianhydride;

[0019] Preferably, the molar ratio of the diamine monomer to the dianhydride monomer is 0.95-1.05:1.

[0020] Preferably, in step S2, the amount of the functionalized graphene is 1-10 wt% of the mass of the polyamic acid.

[0021] Preferably, in step S3, the substrate used for the film casting is a glass plate or a silicon wafer with a smooth surface and uniform thickness.

[0022] Preferably, in step S3, the thermal imidization reaction comprises: heating to 80° C., keeping warm for 2-3 hours, then heating to 120° C., keeping warm for 1-2 hours, then heating to 200° C., keeping warm for 1-2 hours, then heating to 300° C., keeping warm for 1-2 hours;

[0023] Preferably, the heating rate is 5-10°C / min.

[0024] The present invention also provides a high dielectric polyimide / graphene composite film, which is prepared by the above preparation method.

[0025] In the preparation method of the high-dielectric polyimide / graphene composite film described in the present invention, hydroxylated graphene and an iron-containing MOF material are subjected to an esterification reaction, thereby coating the iron-containing MOF material on the graphene surface to form graphene with a porous surface structure. When the graphene is introduced into a polyimide matrix, not only the strong π-π interaction between graphene sheets is overcome, but also the dispersion effect of the graphene in the polyimide matrix is ​​enhanced. In addition to being beneficial to improving the dielectric properties, the defect of damaging the mechanical properties of the resulting composite film due to the addition of graphene is also overcome. DETAILED DESCRIPTION

[0026] Hereinafter, the technical solutions of the present invention will be described in detail through specific embodiments. However, it should be clearly stated that these embodiments are provided for illustration only and are not to be construed as limiting the scope of the present invention.

[0027] Example 1

[0028] A method for preparing a high dielectric polyimide / graphene composite film comprises the following steps:

[0029] (1) 1 g of graphite powder was prepared into graphene oxide by the classic Hummers method, and the obtained graphene oxide was added into 20 mL of N, N-dimethylformamide (DMF) and ultrasonically dispersed uniformly. Then 0.2 g of ethylene glycol was added thereto, and the mixture was heated to 80 ° C and stirred for 4 h. Then 1 g of hydrazine hydrate was added, and the mixture was heated to 90 ° C and stirred for 3 h. After filtering, washing, and drying, hydroxylated graphene was obtained. 1.3 g (5 mmol) of ferric chloride hexahydrate and 0.34 g (2 mmol) of terephthalic acid were added into 30 mL of N, N-dimethylformamide (DMF) and ultrasonically dispersed uniformly. The obtained mixed solution was transferred to a high-pressure hydrothermal reactor with a polytetrafluoroethylene liner, heated to 110°C for reaction for 20 hours, cooled, centrifuged, and washed alternately with N,N-dimethylformamide (DMF) and methanol (CH3OH). After vacuum drying, MIL-101(Fe) was obtained. 0.5g of the hydroxylated graphene and 0.5g of the MIL-101(Fe) were added to 10mL of N,N-dimethylformamide (DMF) and mixed evenly. After 3 drops of concentrated sulfuric acid were added as a catalyst, the temperature was raised to 80°C and stirred for reaction for 4 hours. After filtering, washing, and drying, functionalized graphene was obtained.

[0030] (2) Under nitrogen (N2) protection, 1.6 g (15 mmol) of p-phenylenediamine was added to 40 mL of N, N-dimethylformamide (DMF), stirred and ultrasonically dispersed, and then 3.3 g (15 mmol) of pyromellitic anhydride was added. After stirring and reacting at room temperature for 6 h, a polyamic acid solution was obtained; 0.15 g of the functionalized graphene was added to 20 mL of N, N-dimethylformamide (DMF) and ultrasonically dispersed to obtain a dispersed solution; the dispersed solution was added to the polyamic acid solution and stirred to obtain a blended solution;

[0031] (3) The blended solution is uniformly coated on a glass substrate, and after film casting, the obtained coating film is first heated to 80°C, kept warm for 3 hours, then heated to 120°C, kept warm for 2 hours, continued to heat to 200°C, kept warm for 1 hour, then heated to 300°C, kept warm for 1 hour, and then naturally cooled to room temperature and placed in water for demolding. After taking out, vacuum drying is obtained to obtain the high dielectric polyimide / graphene composite film, the film thickness of which is 20 μm.

[0032] Example 2

[0033] A method for preparing a high dielectric polyimide / graphene composite film comprises the following steps:

[0034] (1) 1 g of graphite powder was prepared into graphene oxide by the classic Hummers method, and the obtained graphene oxide was added into 20 mL of N, N-dimethylformamide (DMF) and ultrasonically dispersed uniformly. Then 0.2 g of ethylene glycol was added thereto, and the mixture was heated to 80 ° C and stirred for 4 h. Then 1 g of hydrazine hydrate was added, and the mixture was heated to 90 ° C and stirred for 3 h. After filtering, washing, and drying, hydroxylated graphene was obtained. 1.3 g (5 mmol) of ferric chloride hexahydrate and 0.34 g (2 mmol) of terephthalic acid were added into 30 mL of N, N-dimethylformamide (DMF) and ultrasonically dispersed uniformly. The obtained mixed solution was transferred to a high-pressure hydrothermal reactor with a polytetrafluoroethylene liner, heated to 110°C for reaction for 20 hours, cooled, centrifuged, and washed alternately with N,N-dimethylformamide (DMF) and methanol (CH3OH). After vacuum drying, MIL-101(Fe) was obtained. 0.5g of the hydroxylated graphene and 0.5g of the MIL-101(Fe) were added to 10mL of N,N-dimethylformamide (DMF) and mixed evenly. After 3 drops of concentrated sulfuric acid were added as a catalyst, the temperature was raised to 80°C and stirred for reaction for 4 hours. After filtering, washing, and drying, functionalized graphene was obtained.

[0035] (2) Under nitrogen (N2) protection, 1.6 g (15 mmol) of p-phenylenediamine was added to 40 mL of N, N-dimethylformamide (DMF), stirred and ultrasonically dispersed, and then 4.4 g (15 mmol) of 3,3',4,4'-biphenyltetracarboxylic dianhydride was added. After stirring and reacting at room temperature for 6 hours, a polyamic acid solution was obtained; 0.15 g of the functionalized graphene was added to 20 mL of N, N-dimethylformamide (DMF) and ultrasonically dispersed to obtain a dispersed solution; the dispersed solution was added to the polyamic acid solution and stirred to obtain a blended solution;

[0036] (3) The blended solution is uniformly coated on a glass substrate, and after film casting, the obtained coating film is first heated to 80°C, kept warm for 3 hours, then heated to 120°C, kept warm for 2 hours, continued to heat to 200°C, kept warm for 1 hour, then heated to 300°C, kept warm for 1 hour, and then naturally cooled to room temperature and placed in water for demolding. After taking out, vacuum drying is obtained to obtain the high dielectric polyimide / graphene composite film, the film thickness of which is 20 μm.

[0037] Example 3

[0038] A method for preparing a high dielectric polyimide / graphene composite film comprises the following steps:

[0039] (1) 1 g of graphite powder was prepared into graphene oxide by the classic Hummers method, and the obtained graphene oxide was added into 20 mL of N, N-dimethylformamide (DMF) and ultrasonically dispersed uniformly. Then 0.2 g of ethylene glycol was added thereto, and the mixture was heated to 80 ° C and stirred for 4 h. Then 1 g of hydrazine hydrate was added, and the mixture was heated to 90 ° C and stirred for 3 h. After filtering, washing, and drying, hydroxylated graphene was obtained. 1.3 g (5 mmol) of ferric chloride hexahydrate and 0.34 g (2 mmol) of terephthalic acid were added into 30 mL of N, N-dimethylformamide (DMF) and ultrasonically dispersed uniformly. The obtained mixed solution was transferred to a high-pressure hydrothermal reactor with a polytetrafluoroethylene liner, heated to 110°C for reaction for 20 hours, cooled, centrifuged, and washed alternately with N,N-dimethylformamide (DMF) and methanol (CH3OH). After vacuum drying, MIL-101(Fe) was obtained. 0.5g of the hydroxylated graphene and 0.5g of the MIL-101(Fe) were added to 10mL of N,N-dimethylformamide (DMF) and mixed evenly. After 3 drops of concentrated sulfuric acid were added as a catalyst, the temperature was raised to 80°C and stirred for reaction for 4 hours. After filtering, washing, and drying, functionalized graphene was obtained.

[0040] (2) Under nitrogen (N2) protection, 3.0 g (15 mmol) of 4,4'-diaminodiphenyl ether was added to 40 mL of N,N-dimethylformamide (DMF), stirred and ultrasonically dispersed, and then 3.3 g (15 mmol) of pyromellitic anhydride was added. After stirring and reacting at room temperature for 6 h, a polyamic acid solution was obtained; 0.15 g of the functionalized graphene was added to 20 mL of N,N-dimethylformamide (DMF) and ultrasonically dispersed to obtain a dispersed solution; the dispersed solution was added to the polyamic acid solution and stirred to obtain a blended solution;

[0041] (3) The blended solution is uniformly coated on a glass substrate, and after film casting, the obtained coating film is first heated to 80°C, kept warm for 3 hours, then heated to 120°C, kept warm for 2 hours, continued to heat to 200°C, kept warm for 1 hour, then heated to 300°C, kept warm for 1 hour, and then naturally cooled to room temperature and placed in water for demolding. After taking out, vacuum drying is obtained to obtain the high dielectric polyimide / graphene composite film, the film thickness of which is 20 μm.

[0042] Example 4

[0043] A method for preparing a high dielectric polyimide / graphene composite film comprises the following steps:

[0044] (1) 1 g of graphite powder was prepared into graphene oxide by the classic Hummers method, and the obtained graphene oxide was added into 20 mL of N, N-dimethylformamide (DMF) and ultrasonically dispersed uniformly. Then 0.2 g of ethylene glycol was added thereto, and the mixture was heated to 80 ° C and stirred for 4 h. Then 1 g of hydrazine hydrate was added, and the mixture was heated to 90 ° C and stirred for 3 h. After filtering, washing, and drying, hydroxylated graphene was obtained. 1.3 g (5 mmol) of ferric chloride hexahydrate and 0.34 g (2 mmol) of terephthalic acid were added into 30 mL of N, N-dimethylformamide (DMF) and ultrasonically dispersed uniformly. The obtained mixed solution was transferred to a high-pressure hydrothermal reactor with a polytetrafluoroethylene liner, heated to 110°C for reaction for 20 hours, cooled, centrifuged, and washed alternately with N,N-dimethylformamide (DMF) and methanol (CH3OH). After vacuum drying, MIL-101(Fe) was obtained. 0.5g of the hydroxylated graphene and 0.5g of the MIL-101(Fe) were added to 10mL of N,N-dimethylformamide (DMF) and mixed evenly. After 3 drops of concentrated sulfuric acid were added as a catalyst, the temperature was raised to 80°C and stirred for reaction for 4 hours. After filtering, washing, and drying, functionalized graphene was obtained.

[0045] (2) Under nitrogen (N2) protection, 3.0 g (15 mmol) of 4,4'-diaminodiphenyl ether was added to 40 mL of N,N-dimethylformamide (DMF), stirred and ultrasonically dispersed uniformly, and then 4.8 g (15 mmol) of 3,3',4,4'-benzophenone tetracarboxylic dianhydride was added. After stirring and reacting at room temperature for 6 hours, a polyamic acid solution was obtained; 0.15 g of the functionalized graphene was added to 20 mL of N,N-dimethylformamide (DMF) and ultrasonically dispersed uniformly to obtain a dispersed solution; the dispersed solution was added to the polyamic acid solution and stirred and mixed uniformly to obtain a blended solution;

[0046] (3) The blended solution is uniformly coated on a glass substrate, and after film casting, the obtained coating film is first heated to 80°C, kept warm for 3 hours, then heated to 120°C, kept warm for 2 hours, continued to heat to 200°C, kept warm for 1 hour, then heated to 300°C, kept warm for 1 hour, and then naturally cooled to room temperature and placed in water for demolding. After taking out, vacuum drying is obtained to obtain the high dielectric polyimide / graphene composite film, the film thickness of which is 20 μm.

[0047] Example 5

[0048] A method for preparing a high dielectric polyimide / graphene composite film comprises the following steps:

[0049] (1) 1 g of graphite powder was prepared into graphene oxide by the classic Hummers method, and the obtained graphene oxide was added into 20 mL of N, N-dimethylformamide (DMF) and ultrasonically dispersed uniformly. Then 0.2 g of ethylene glycol was added thereto, and the mixture was heated to 80 ° C and stirred for 4 h. Then 1 g of hydrazine hydrate was added, and the mixture was heated to 90 ° C and stirred for 3 h. After filtering, washing, and drying, hydroxylated graphene was obtained. 1.3 g (5 mmol) of ferric chloride hexahydrate and 0.34 g (2 mmol) of terephthalic acid were added into 30 mL of N, N-dimethylformamide (DMF) and ultrasonically dispersed uniformly. The obtained mixed solution was transferred to a high-pressure hydrothermal reactor with a polytetrafluoroethylene liner, heated to 110°C for reaction for 20 hours, cooled, centrifuged, and washed alternately with N,N-dimethylformamide (DMF) and methanol (CH3OH). After vacuum drying, MIL-101(Fe) was obtained. 0.5g of the hydroxylated graphene and 0.5g of the MIL-101(Fe) were added to 10mL of N,N-dimethylformamide (DMF) and mixed evenly. After 3 drops of concentrated sulfuric acid were added as a catalyst, the temperature was raised to 80°C and stirred for reaction for 4 hours. After filtering, washing, and drying, functionalized graphene was obtained.

[0050] (2) Under nitrogen (N2) protection, 1.6 g (15 mmol) of p-phenylenediamine was added to 40 mL of N, N-dimethylformamide (DMF), stirred and ultrasonically dispersed, and then 3.3 g (15 mmol) of pyromellitic anhydride was added. After stirring and reacting at room temperature for 6 h, a polyamic acid solution was obtained; 0.3 g of the functionalized graphene was added to 20 mL of N, N-dimethylformamide (DMF) and ultrasonically dispersed to obtain a dispersed solution; the dispersed solution was added to the polyamic acid solution and stirred to obtain a blended solution;

[0051] (3) The blended solution is uniformly coated on a glass substrate, and after film casting, the obtained coating film is first heated to 80°C, kept warm for 3 hours, then heated to 120°C, kept warm for 2 hours, continued to heat to 200°C, kept warm for 1 hour, then heated to 300°C, kept warm for 1 hour, and then naturally cooled to room temperature and placed in water for demolding. After taking out, vacuum drying is obtained to obtain the high dielectric polyimide / graphene composite film, the film thickness of which is 20 μm.

[0052] Comparative Example 1

[0053] A method for preparing a polyimide / graphene composite film comprises the following steps:

[0054] (1) Under nitrogen (N2) protection, 1.6 g (15 mmol) of p-phenylenediamine was added to 40 mL of N, N-dimethylformamide (DMF), stirred and ultrasonically dispersed, and then 3.3 g (15 mmol) of pyromellitic anhydride was added. After stirring and reacting at room temperature for 6 h, a polyamic acid solution was obtained; 0.15 g of graphite powder was added to 20 mL of N, N-dimethylformamide (DMF) and ultrasonically dispersed to obtain a dispersed solution; the dispersed solution was added to the polyamic acid solution and stirred to obtain a blended solution;

[0055] (2) The blended solution is uniformly coated on a glass substrate, and after film casting, the obtained coating film is first heated to 80°C, kept warm for 3 hours, then heated to 120°C, kept warm for 2 hours, continued to heat to 200°C, kept warm for 1 hour, then heated to 300°C, kept warm for 1 hour, and naturally cooled to room temperature and placed in water for demolding. After taking out, vacuum drying is obtained to obtain the polyimide / graphene composite film, the film thickness of which is 20 μm.

[0056] Comparative Example 2

[0057] A method for preparing a polyimide / graphene composite film comprises the following steps:

[0058] (1) 1 g of graphite powder was prepared into graphene oxide by the classic Hummers method, and the obtained graphene oxide was added into 20 mL of N, N-dimethylformamide (DMF) and ultrasonically dispersed uniformly. Then, 1 g of hydrazine hydrate was added thereto, and the mixture was heated to 90°C and stirred for 3 h. After filtering, washing, and drying, graphene was obtained.

[0059] (2) Under nitrogen (N2) protection, 1.6 g (15 mmol) of p-phenylenediamine was added to 40 mL of N, N-dimethylformamide (DMF), stirred and ultrasonically dispersed, and then 3.3 g (15 mmol) of pyromellitic anhydride was added. After stirring and reacting at room temperature for 6 hours, a polyamic acid solution was obtained; 0.15 g of the graphene was added to 20 mL of N, N-dimethylformamide (DMF) and ultrasonically dispersed to obtain a dispersed solution; the dispersed solution was added to the polyamic acid solution and stirred to obtain a blended solution;

[0060] (3) The blended solution is uniformly coated on a glass substrate, and after film casting, the obtained coating film is first heated to 80°C, kept warm for 3 hours, then heated to 120°C, kept warm for 2 hours, continued to heat to 200°C, kept warm for 1 hour, then heated to 300°C, kept warm for 1 hour, and naturally cooled to room temperature and placed in water for demolding. After taking out, vacuum drying is obtained to obtain the polyimide / graphene composite film, the film thickness of which is 20 μm.

[0061] After both sides of the polyimide / graphene composite films obtained in Examples 1-5 and Comparative Examples 1-2 were sputter-coated with aluminum, they were tested using an Agilent 4294A precision impedance analyzer to calculate the dielectric constant (ε) and dielectric loss (tan δ) at room temperature at a frequency of 100 Hz. The polyimide / graphene composite films obtained in Examples 1-5 and Comparative Examples 1-2 were then tested using a universal material testing machine in accordance with GB / T1040.3-2006 to obtain their mechanical properties.

[0062] Table 1 Performance test results of polyimide / graphene composite films obtained in Examples and Comparative Examples

[0063] Dielectric constant Dielectric loss (%) Tensile strength (MPa) Example 1 49.78 0.0061 131 Example 2 37.56 0.0099 120 Example 3 41.34 0.0076 125 Example 4 32.65 0.0092 123 Example 5 77.13 0.031 140 Comparative Example 1 25.18 1.07 96 Comparative Example 2 12.35 0.28 101

[0064] Based on the comparison of the performance test results of the polyimide / graphene composite films described in the examples and comparative examples in the above table, it can be seen that after introducing functionalized graphene into the polyimide matrix, not only the dielectric constant is increased to a considerable extent, but the dielectric loss can also be maintained at a low level. At the same time, the defect of damaging the mechanical properties of the resulting composite film due to the addition of graphene is overcome.

[0065] The above description is only a preferred specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with the technical field, within the technical scope disclosed by the present invention, who makes equivalent replacements or changes based on the technical solution and inventive concept of the present invention, should be covered by the scope of protection of the present invention.

Claims

1. A method for preparing a high dielectric polyimide / graphene composite film, characterized in that: The steps include: S1, esterifying the hydroxylated graphene and the iron-containing MOF material to obtain functionalized graphene; S2, adding the functionalized graphene to an organic solvent to form a dispersed solution, and mixing the dispersed solution with a polyamic acid solution formed by polycondensation of a diamine monomer and a dianhydride monomer to obtain a blended solution; S3, casting the blend solution into a film, and then performing a thermal imidization reaction to obtain the high dielectric polyimide / graphene composite film; The hydroxylated graphene is obtained by covalently bonding graphene oxide with a polyol and then performing a reduction reaction; The polyol is at least one of ethylene glycol, propylene glycol or diethylene glycol; The iron-containing MOF material is MIL-101 (Fe); The MIL-101 (Fe) is obtained by reacting ferric chloride hexahydrate with terephthalic acid. In step S1, the mass ratio of the hydroxylated graphene to the iron-containing MOF material is 1:0.5-1.5; In step S2, the amount of the functionalized graphene is 1-10 wt % of the mass of the polyamic acid.

2. The method for preparing a high dielectric polyimide / graphene composite film according to claim 1, wherein: In step S2, the organic solvent is at least one of N,N-dimethylacetamide, N,N-dimethylformamide, N-methylpyrrolidone or dimethyl sulfoxide.

3. The method for preparing a high dielectric polyimide / graphene composite film according to claim 1 or 2, characterized in that: In step S2, the diamine monomer is at least one of p-phenylenediamine, 4,4'-diaminodiphenyl ether or 3,3'-diaminobenzophenone; The dianhydride monomer is at least one of pyromellitic anhydride, 3,3',4,4'-biphenyltetracarboxylic anhydride, 3,3',4,4'-diphenyl ether tetracarboxylic anhydride, 3,3',4,4'-benzophenone tetracarboxylic anhydride or 3,3',4,4'-diphenyl sulfone tetracarboxylic anhydride.

4. The method for preparing a high dielectric polyimide / graphene composite film according to claim 1 or 2, wherein: In step S2, the molar ratio of the diamine monomer to the dianhydride monomer is 0.95-1.05:

1.

5. The method for preparing a high dielectric polyimide / graphene composite film according to claim 1 or 2, wherein: In step S3, the substrate for film casting is a glass plate or a silicon wafer with a smooth surface and uniform thickness.

6. The method for preparing a high dielectric polyimide / graphene composite film according to claim 1 or 2, wherein: In step S3, the thermal imidization reaction includes: heating to 80°C, keeping warm for 2-3 hours, then heating to 120°C, keeping warm for 1-2 hours, continuing to heat to 200°C, keeping warm for 1-2 hours, and then heating to 300°C, keeping warm for 1-2 hours.

7. The method for preparing a high dielectric polyimide / graphene composite film according to claim 6, wherein: The heating rate is 5-10°C / min.

8. A high dielectric polyimide / graphene composite film, characterized in that: The compound is prepared by the preparation method according to any one of claims 1 to 7.