A flexible polyimide film and a method for manufacturing the same
By preparing a polymer containing ether diamine, fluorine-containing monomers, and modified boron nitride, the problems of brittleness and insufficient thermal conductivity of traditional polyimide films were solved, and high flexibility, insulation, and excellent heat dissipation performance of flexible polyimide films were achieved, making them suitable for thermal management of high-power electronic devices.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- DILUTE CONDUCTIVITY TECHNOLOGY (ZHONGSHAN) CO LTD
- Filing Date
- 2026-03-16
- Publication Date
- 2026-05-29
AI Technical Summary
Traditional rigid polyimide films are brittle and cannot withstand bending and curling. They also have insufficient thermal conductivity, which cannot meet the requirements of flexible electronic devices and high-power devices.
Flexible polyimide films are formed by polymerizing ether-containing diamine monomers, fluorine-containing monomers, and modified boron nitride. The ether bonds and fluorine monomers are used to improve flexibility and insulation, while the modified boron nitride enhances thermal conductivity.
It achieves high mechanical flexibility, excellent insulation and superior heat dissipation performance of flexible polyimide film, making it suitable for thermal management of high-power electronic devices.
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Abstract
Description
Technical Field
[0001] This invention relates to the field of polyimide film technology, specifically to a flexible polyimide film and its preparation method. Background Technology
[0002] Polyimide, a polymer material possessing ultra-high heat resistance, chemical corrosion resistance, and mechanical properties, has become a key research focus in the field of high-power electronic packaging, particularly in the context of the rapid evolution of the electronics and information industry towards miniaturization, integration, and flexibility. Its composite with phase change materials (PCMs), which exhibit high latent heat and precise temperature control, has resulted in phase change insulating films. In the thermal management and insulating packaging scenarios of high-power electronic devices such as DDR memory and SSD chips, polyimide films not only provide structural support and electrical isolation but also serve as functional carriers for composite PCMs and thermally conductive fillers, constructing integrated thermal management solutions. This is crucial for achieving device miniaturization and high reliability.
[0003] While traditional rigid polyimide films possess excellent heat resistance and mechanical strength, their densely packed aromatic ring conjugated structure makes them brittle and unable to withstand bending, curling, and other deformation stresses, failing to meet the requirements of flexible electronic devices. Simultaneously, insufficient thermal conductivity remains a key bottleneck restricting the application of polyimide films in high-end thermal management scenarios. Typical flexible polyimide films are characterized by alternating rigid aromatic rings and flexible segments in their molecular chains, resulting in dense intermolecular packing but lacking effective thermal conduction pathways. Their inherent thermal conductivity is low, far from meeting the heat dissipation requirements of high-power devices. Therefore, developing a high-performance thermally conductive flexible polyimide film has become a core research direction for overcoming the bottlenecks of traditional thermal management materials and promoting the development of the high-power flexible electronics industry. Summary of the Invention
[0004] The purpose of this invention is to provide a flexible polyimide film and its preparation method to solve the problems existing in the prior art.
[0005] To solve the above-mentioned technical problems, the present invention provides the following solution: A flexible polyimide film is prepared by reacting 4,4'-(oxybis(methylene))bis(chlorobenzene) and 4-nitrophenol to obtain a dinitro intermediate; reducing the dinitro intermediate with Raney nickel to obtain an ether-containing diamine monomer; preparing a fluorinated monomer by Suzuki coupling reaction of 5-bromo-1,3-phenylenediamine and 3,5-bis(trifluoromethyl)phenylboronic acid; hydrolyzing γ-aminopropyltriethoxysilane and grafting it onto the surface of boron nitride to obtain modified boron nitride; and then polymerizing the ether-containing diamine monomer, the fluorinated monomer, the modified boron nitride, and pyromellitic dianhydride in situ. The 4,4'-(oxybis(methylene))bis(chlorobenzene) is prepared by condensation of p-chlorobenzaldehyde.
[0006] A method for preparing a flexible polyimide film, the method comprising the following steps: (1) Mix the dinitro intermediate, Raney nickel, and ethanol / dioxane solution with a volume ratio of 10:9 at a mass ratio of 1:(0.1~0.2):(6~8). Under nitrogen protection, heat to 75~85℃ and stir for 9~11h. Filter and add the filtrate to ice-cold deionized water at a volume of 4~6 times that of the ethanol / dioxane solution. Filter and wash with deionized water 2~4 times. Dry under vacuum at 55~65℃ for 9~11h to obtain the ether-containing diamine monomer. (2) Mix 5-bromo-1,3-phenylenediamine, catalyst, anhydrous potassium carbonate, toluene, and deionized water in a mass ratio of 1:(0.04~0.06):(1.5~1.7):(6~8):(3~4) until homogeneous. Stir at room temperature for 10~20 min. Add 3,5-bis(trifluoromethyl)phenylboronic acid in equimolar amounts of 5-bromo-1,3-phenylenediamine. Heat to 105~115℃ and reflux for 4~6 h. Cool to room temperature, filter, extract with toluene, remove toluene by rotary evaporation of the organic layer, and vacuum dry at 75~85℃ for 10~12 h to obtain a fluorinated monomer. (3) Mix boron nitride and silane hydrolysate at a mass ratio of 1:(4~6), heat to 65~75℃, reflux and stir for 9~11h, cool to room temperature, centrifuge for 5~15min, wash with anhydrous ethanol 2~4 times, and vacuum dry at 55~65℃ for 11~13h to obtain modified boron nitride. (4) Cast the PAA solution onto a clean glass plate, dry it at 75~85℃ for 3~5h, heat it to 95~115℃ for 1~2h, heat it to 190~210℃ for 1~2h, heat it to 290~310℃ for 1~2h, cool it to room temperature, immerse it in deionized water, peel it off, and obtain a flexible polyimide film.
[0007] As an optimization, the preparation process of the dinitro intermediate in step (1) is as follows: 4,4'-(oxybis(methylene))bis(chlorobenzene), 4-nitrophenol and anhydrous potassium carbonate are weighed in a molar ratio of 1:(2~2.1):(2.1~2.2); 4-nitrophenol and anhydrous potassium carbonate are dissolved in a mixed solvent of N,N-dimethylformamide and toluene in a volume ratio of 1:(0.09~0.11) equal to 5~7 times the mass of 4-nitrophenol. Stir at 95-105℃ for 50-70 min, add 4,4'-(oxybis(methylene))bis(chlorobenzene) at a uniform rate over 20-30 min, heat to 105-115℃, stir and react for 11-13 h, cool to room temperature, pour into 4-6 times the volume of N,N-dimethylformamide in ice-cold deionized water, filter, wash 2-4 times with deionized water, and dry at 65-75℃ for 12-14 h to obtain the dinitro intermediate.
[0008] As an optimization, the preparation process of 4,4'-(oxybis(methylene))bis(chlorobenzene) is as follows: p-chlorobenzaldehyde, triethylsilane, and dichloromethane are mixed evenly at a mass ratio of 1:(0.75~0.85):(5~7), stirred at room temperature for 10~20 min, and then trifluoromethanesulfonic acid (0.07~0.09 times the mass of p-chlorobenzaldehyde) is added uniformly over 20~30 min. The mixture is stirred and reacted at room temperature for 23~25 h, then deionized water (0.4~0.6 times the volume of dichloromethane) is added, followed by extraction with dichloromethane (8~10 times the mass of p-chlorobenzaldehyde). The lower organic phase is dried with anhydrous MgSO4, filtered, and the dichloromethane solvent is removed by rotary evaporation. The mixture is then freeze-dried at -50~-40℃ for 6~8 h to obtain 4,4'-(oxybis(methylene))bis(chlorobenzene).
[0009] As an optimization, the catalyst in step (2) is tetra(triphenylphosphine)palladium.
[0010] As an optimization, the boron nitride in step (3) has a specification of 2μm and is purchased from Beijing Deco Island Gold Technology Co., Ltd.
[0011] As an optimization, the preparation process of the silane hydrolysate in step (3) is as follows: γ-aminopropyltriethoxysilane, anhydrous ethanol and deionized water are mixed evenly in a mass ratio of 1:(14~16):(1.4~1.6), the pH is adjusted to 4~5 with glacial acetic acid, and the mixture is stirred and reacted at room temperature for 10~20 min to obtain the silane hydrolysate.
[0012] As an optimization, the preparation process of the PAA solution in step (4) is as follows: dissolve the ether-containing diamine monomer and the fluorine-containing monomer in a molar ratio of 1:(0.9~1.1) in N,N-dimethylacetamide at 10~12 times the mass of the ether-containing diamine monomer, add modified boron nitride, ultrasonically disperse at room temperature for 10~20 min, add pyromellitic dianhydride at 1.9~2.1 times the molar number of the ether-containing diamine monomer, stir and react for 5~7 h under nitrogen protection to obtain the PAA solution.
[0013] As an optimization, the amount of modified boron nitride added is 0.02 to 0.04 times the mass of the ether diamine monomer.
[0014] Compared with the prior art, the beneficial effects achieved by the present invention are: In preparing a flexible polyimide film, this invention involves condensing p-chlorobenzaldehyde to obtain 4,4'-(oxybis(methylene))bis(chlorobenzene); reacting 4,4'-(oxybis(methylene))bis(chlorobenzene) with 4-nitrophenol to obtain a dinitro intermediate; reducing the dinitro intermediate with Raney nickel to obtain an ether-containing diamine monomer; preparing a fluorinated monomer by Suzuki coupling reaction of 5-bromo-1,3-phenylenediamine and 3,5-bis(trifluoromethyl)phenylboronic acid; hydrolyzing γ-aminopropyltriethoxysilane and grafting it onto the surface of boron nitride to obtain modified boron nitride; and in-situ polymerization of the ether-containing diamine monomer, the fluorinated monomer, the modified boron nitride, and pyromellitic dianhydride to obtain a flexible polyimide film.
[0015] First, 4,4'-(oxybis(methylene))bis(chlorobenzene) is prepared by condensation of p-chlorobenzaldehyde. Then, 4,4'-(oxybis(methylene))bis(chlorobenzene) and 4-nitrophenol are reacted to prepare a dinitro intermediate. The dinitro intermediate is then reduced with Raney nickel to obtain an ether-containing diamine monomer. The ether-containing diamine structure contains multiple ether bonds and methylene flexible segments. The ether bonds have high rotational freedom, which can break the conjugation of rigid aromatic rings and reduce the rotational energy barrier within the molecular chain. Simultaneously, the moderate polarity of the ether bonds can prevent the formation of excessively strong hydrogen bonds or π-π stacking between molecules, making the molecular chain easier to slide, resulting in improved flexibility. The methylene groups can weaken the intermolecular packing density and enhance the chain segment mobility, thereby endowing the flexible polyimide film with excellent mechanical flexibility.
[0016] Secondly, fluorinated monomers were prepared by Suzuki coupling reaction of 5-bromo-1,3-phenylenediamine and 3,5-bis(trifluoromethyl)phenylboronic acid. The trifluoromethyl group in the fluorinated monomer has strong electronegativity and low polarizability, which can reduce the electron cloud density and charge transfer tendency between molecules. The nonpolar characteristics of trifluoromethyl group make the inter-chain forces mainly weak van der Waals forces, reducing the overall polarization of the material, thereby reducing the dielectric constant and loss. At the same time, when combined with thermally conductive fillers such as amino-modified boron nitride, the fluorinated segments can improve the interfacial compatibility between the matrix and the filler, avoid the filler agglomeration to form local conductive paths, enhance the insulation continuity, and thus endow the flexible polyimide film with excellent insulation properties.
[0017] Finally, γ-aminopropyltriethoxysilane was hydrolyzed and grafted onto the surface of boron nitride to obtain modified boron nitride. A flexible polyimide film was prepared by in-situ polymerization of an ether-containing diamine monomer, a fluorine-containing monomer, modified boron nitride, and pyromellitic dianhydride, with modified boron nitride added as a filler. The layered structure of boron nitride exhibits excellent in-plane thermal conductivity, but the unmodified boron nitride has poor interfacial compatibility with the polyimide matrix, easily forming interfacial defects and air gaps, resulting in high interfacial thermal resistance. After amino modification, the -NH2 on the surface of boron nitride can be uniformly dispersed through hydrogen bonds or covalent bonds, avoiding agglomeration and forming a continuous thermal conductive path, thus endowing the flexible polyimide film with excellent heat dissipation performance. Simultaneously, boron nitride itself has a thermal decomposition temperature >1000℃, which can act as a thermal stabilizer to inhibit the molecular chain degradation of polyimide at high temperatures, maintain the continuity of the thermal conductive network, and ensure reliable heat dissipation under long-term thermal cycling. Detailed Implementation
[0018] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.
[0019] Example 1: A method for preparing a flexible polyimide film, the method comprising the following steps: (1) Mix p-chlorobenzaldehyde, triethylsilane, and dichloromethane in a mass ratio of 1:0.75:5 and stir at room temperature for 20 min. Add trifluoromethanesulfonic acid at a constant rate of 0.07 times the mass of p-chlorobenzaldehyde within 30 min. Stir and react at room temperature for 225 h. Add deionized water at a volume of 0.4 times the volume of dichloromethane and extract with dichloromethane at a volume of 8 times the mass of p-chlorobenzaldehyde. Dry the lower organic phase with anhydrous MgSO4, filter, remove the dichloromethane solvent by rotary evaporation, and freeze-dry at -50℃ for 8 h to obtain 4,4'-(oxybis(methylene))bis(chlorobenzaldehyde). Weigh 4,4'-(oxybis(methylene))bis(chlorobenzaldehyde), 4-nitrophenol, and anhydrous potassium carbonate in a molar ratio of 1:2:2.1. Dissolve 4-nitrophenol and anhydrous potassium carbonate in a volume ratio of 1:0.5 times the mass of 4-nitrophenol. In a mixed solvent of N,N-dimethylformamide and toluene, the mixture was stirred at 95°C for 70 min. 4,4'-(oxybis(methylene))bis(chlorobenzene) was added uniformly over 30 min. The mixture was heated to 105°C and stirred for 13 h. After cooling to room temperature, the mixture was poured into ice-cold deionized water at a volume of 4 times that of N,N-dimethylformamide, filtered, washed twice with deionized water, and dried at 65°C for 14 h to obtain a dinitro intermediate. The dinitro intermediate, Raney nickel, and an ethanol / dioxane solution with a volume ratio of 10:9 were mixed uniformly at a mass ratio of 1:0.1:6. Under nitrogen protection, the mixture was heated to 75°C and stirred for 11 h. After filtration, the filtrate was added to ice-cold deionized water at a volume of 4 times that of the ethanol / dioxane solution, filtered, washed twice with deionized water, and dried under vacuum at 55°C for 11 h to obtain an ether-containing diamine monomer. (2) Mix 5-bromo-1,3-phenylenediamine, tetra(triphenylphosphine)palladium, anhydrous potassium carbonate, toluene, and deionized water in a mass ratio of 1:0.04:1.5:6:3 until homogeneous. Stir at room temperature for 20 min. Add 3,5-bis(trifluoromethyl)phenylboronic acid in equimolar amounts of 5-bromo-1,3-phenylenediamine. Heat to 105 °C and reflux for 6 h. Cool to room temperature, filter, extract with toluene, remove toluene by rotary evaporation of the organic layer, and dry under vacuum at 75 °C for 12 h to obtain a fluorinated monomer. (3) Mix γ-aminopropyltriethoxysilane, anhydrous ethanol and deionized water in a mass ratio of 1:14:1.4, adjust the pH to 4 with glacial acetic acid, stir and react at room temperature for 20 min to obtain silane hydrolysate; mix boron nitride and silane hydrolysate in a mass ratio of 1:4, heat to 65℃, reflux and stir for 11 h, cool to room temperature, centrifuge for 15 min, wash twice with anhydrous ethanol, and vacuum dry at 55℃ for 13 h to obtain modified boron nitride; (4) Dissolve the ether-containing diamine monomer and the fluorine-containing monomer in a molar ratio of 1:0.9 in N,N-dimethylacetamide at 10 times the mass of the ether-containing diamine monomer, add modified boron nitride at 0.02 times the mass of the ether-containing diamine monomer, ultrasonically disperse at room temperature for 20 min, add pyromellitic dianhydride at 1.9 times the molar number of the ether-containing diamine monomer, stir and react for 7 h under nitrogen protection to obtain PAA solution; cast the PAA solution onto a clean glass plate, dry at 75℃ for 5 h, heat to 95℃ for 2 h, heat to 190℃ for 2 h, heat to 290℃ for 2 h, cool to room temperature, immerse in deionized water, peel off, and obtain flexible polyimide film.
[0020] Example 2: A method for preparing a flexible polyimide film, the method comprising the following steps: (1) Mix p-chlorobenzaldehyde, triethylsilane, and dichloromethane at a mass ratio of 1:0.8:6 until homogeneous. Stir at room temperature for 15 min. Add trifluoromethanesulfonic acid at a constant rate of 0.08 times the mass of p-chlorobenzaldehyde within 25 min. Stir and react at room temperature for 24 h. Add deionized water at a volume of 0.5 times the volume of dichloromethane. Extract with dichloromethane at a volume of 9 times the mass of p-chlorobenzaldehyde. Dry the lower organic phase with anhydrous MgSO4, filter, remove the dichloromethane solvent by rotary evaporation, and freeze-dry at -45℃ for 7 h to obtain 4,4'-(oxybis(methylene))bis(chlorobenzaldehyde). Weigh 4,4'-(oxybis(methylene))bis(chlorobenzaldehyde), 4-nitrophenol, and anhydrous potassium carbonate at a molar ratio of 1:2.05:2.05. Dissolve 4-nitrophenol and anhydrous potassium carbonate in a volume ratio of 1:0.6 times the mass of 4-nitrophenol. In a mixed solvent of N,N-dimethylformamide and toluene, the mixture was stirred at 100°C for 60 min. 4,4'-(oxybis(methylene))bis(chlorobenzene) was added uniformly over 25 min. The mixture was heated to 110°C and stirred for 12 h. After cooling to room temperature, the mixture was poured into ice-cold deionized water at a volume of 5 times that of N,N-dimethylformamide, filtered, washed three times with deionized water, and dried at 70°C for 13 h to obtain a dinitro intermediate. The dinitro intermediate, Raney nickel, and an ethanol / dioxane solution with a volume ratio of 10:9 were mixed uniformly at a mass ratio of 1:0.15:7. Under nitrogen protection, the mixture was heated to 80°C and stirred for 10 h. After filtration, the filtrate was added to ice-cold deionized water at a volume of 5 times that of the ethanol / dioxane solution, filtered, washed three times with deionized water, and dried under vacuum at 60°C for 10 h to obtain an ether-containing diamine monomer. (2) Mix 5-bromo-1,3-phenylenediamine, tetra(triphenylphosphine)palladium, anhydrous potassium carbonate, toluene, and deionized water in a mass ratio of 1:0.05:1.6:7:3.5 until homogeneous. Stir at room temperature for 15 min. Add 3,5-bis(trifluoromethyl)phenylboronic acid in equimolar amounts of 5-bromo-1,3-phenylenediamine. Heat to 110 °C and reflux for 5 h. Cool to room temperature, filter, extract with toluene, remove toluene by rotary evaporation of the organic layer, and dry under vacuum at 80 °C for 11 h to obtain a fluorinated monomer. (3) Mix γ-aminopropyltriethoxysilane, anhydrous ethanol and deionized water in a mass ratio of 1:15:1.5, adjust the pH to 4.5 with glacial acetic acid, stir and react at room temperature for 15 min to obtain silane hydrolysate; mix boron nitride and silane hydrolysate in a mass ratio of 1:5, heat to 70℃, reflux and stir for 10 h, cool to room temperature, centrifuge for 10 min, wash 3 times with anhydrous ethanol, and vacuum dry at 60℃ for 12 h to obtain modified boron nitride; (4) Dissolve the ether-containing diamine monomer and the fluorine-containing monomer in a molar ratio of 1:1 in N,N-dimethylacetamide at 11 times the mass of the ether-containing diamine monomer, add modified boron nitride at 0.03 times the mass of the ether-containing diamine monomer, ultrasonically disperse at room temperature for 15 min, add pyromellitic dianhydride at 2 times the molar number of the ether-containing diamine monomer, stir and react for 6 h under nitrogen protection to obtain PAA solution; cast the PAA solution onto a clean glass plate, dry at 75℃ for 4 h, heat to 105℃ for 1.5 h, heat to 200℃ for 1.5 h, heat to 300℃ for 1.5 h, cool to room temperature, immerse in deionized water, peel off, and obtain flexible polyimide film.
[0021] Example 3: A method for preparing a flexible polyimide film, the method comprising the following steps: (1) Mix p-chlorobenzaldehyde, triethylsilane, and dichloromethane at a mass ratio of 1:0.85:7, stir at room temperature for 10 min, add trifluoromethanesulfonic acid at a constant rate of 0.09 times the mass of p-chlorobenzaldehyde within 20 min, stir at room temperature for 23 h, add deionized water at a volume of 0.6 times the volume of dichloromethane, add dichloromethane at a volume of 10 times the mass of p-chlorobenzaldehyde for extraction, take the lower organic phase, dry with anhydrous MgSO4, filter, remove dichloromethane solvent by rotary evaporation, freeze-dry at -40℃ for 6 h to obtain 4,4'-(oxybis(methylene))bis(chlorobenzaldehyde); weigh 4,4'-(oxybis(methylene))bis(chlorobenzaldehyde), 4-nitrophenol, and anhydrous potassium carbonate at a molar ratio of 1:2.1:2.2; dissolve 4-nitrophenol and anhydrous potassium carbonate in a volume ratio of 1:7 times the mass of 4-nitrophenol. In a mixed solvent of 0.11 N,N-dimethylformamide and toluene, the mixture was stirred at 105°C for 50 min. 4,4'-(oxybis(methylene))bis(chlorobenzene) was added uniformly over 20 min. The mixture was heated to 115°C and stirred for 11 h. After cooling to room temperature, the mixture was poured into ice-cold deionized water at a volume of 6 times that of N,N-dimethylformamide, filtered, washed four times with deionized water, and dried at 75°C for 12 h to obtain a dinitro intermediate. The dinitro intermediate, Raney nickel, and an ethanol / dioxane solution with a volume ratio of 10:9 were mixed uniformly at a mass ratio of 1:0.2:8. Under nitrogen protection, the mixture was heated to 85°C and stirred for 9 h. After filtration, the filtrate was added to ice-cold deionized water at a volume of 6 times that of the ethanol / dioxane solution, filtered, washed four times with deionized water, and dried under vacuum at 65°C for 9 h to obtain an ether-containing diamine monomer. (2) Mix 5-bromo-1,3-phenylenediamine, tetra(triphenylphosphine)palladium, anhydrous potassium carbonate, toluene, and deionized water in a mass ratio of 1:0.06:1.7:8:4. Stir at room temperature for 10 min. Add 3,5-bis(trifluoromethyl)phenylboronic acid in equimolar amounts of 5-bromo-1,3-phenylenediamine. Heat to 115 °C and reflux for 4 h. Cool to room temperature, filter, extract with toluene, remove toluene by rotary evaporation of the organic layer, and dry under vacuum at 85 °C for 10 h to obtain a fluorinated monomer. (3) Mix γ-aminopropyltriethoxysilane, anhydrous ethanol and deionized water in a mass ratio of 1:16:1.6, adjust the pH to 5 with glacial acetic acid, stir and react at room temperature for 10 min to obtain silane hydrolysate; mix boron nitride and silane hydrolysate in a mass ratio of 1:4, heat to 75℃, reflux and stir for 9 h, cool to room temperature, centrifuge for 5 min, wash 4 times with anhydrous ethanol, and vacuum dry at 65℃ for 11 h to obtain modified boron nitride; (4) Dissolve the ether-containing diamine monomer and the fluorine-containing monomer in a molar ratio of 1:1.1 in N,N-dimethylacetamide at 12 times the mass of the ether-containing diamine monomer, add modified boron nitride at 0.04 times the mass of the ether-containing diamine monomer, ultrasonically disperse at room temperature for 10 min, add pyromellitic dianhydride at 2.1 times the molar number of the ether-containing diamine monomer, stir and react for 5 h under nitrogen protection to obtain PAA solution; cast the PAA solution onto a clean glass plate, dry at 85℃ for 3 h, heat to 115℃ for 1 h, heat to 210℃ for 1 h, heat to 310℃ for 1 h, cool to room temperature, immerse in deionized water, peel off, and obtain flexible polyimide film.
[0022] Comparative Example 1: The preparation method of the flexible polyimide film in Comparative Example 1 differs from that in Example 2 in that step (1) is omitted, and step (4) is changed to: dissolving 4,4'-diaminodiphenyl ether and fluorinated monomers in a molar ratio of 1:1 in N,N-dimethylacetamide at 11 times the mass of 4,4'-diaminodiphenyl ether, adding modified boron nitride at 0.03 times the mass of 4,4'-diaminodiphenyl ether, ultrasonically dispersing for 15 min at room temperature, adding pyromellitic dianhydride at 2 times the molar mass of 4,4'-diaminodiphenyl ether, stirring and reacting for 6 h under nitrogen protection to obtain a PAA solution; casting the PAA solution onto a clean glass plate, drying at 75°C for 4 h, heating to 105°C for 1.5 h, heating to 200°C for 1.5 h, heating to 300°C for 1.5 h, cooling to room temperature, immersing in deionized water, and peeling to obtain a flexible polyimide film. The remaining steps are the same as in Example 2.
[0023] Comparative Example 2: The preparation method of the flexible polyimide film in Comparative Example 2 differs from that in Example 2 in that step (2) is omitted, and step (4) is changed to: dissolving ether-containing diamine monomer and 4,4'-diaminodiphenyl ether in a molar ratio of 1:1 in N,N-dimethylacetamide at 11 times the mass of the ether-containing diamine monomer, adding modified boron nitride at 0.03 times the mass of the ether-containing diamine monomer, ultrasonically dispersing at room temperature for 15 min, adding pyromellitic dianhydride at 2 times the molar mass of the ether-containing diamine monomer, stirring and reacting for 6 h under nitrogen protection to obtain a PAA solution; casting the PAA solution onto a clean glass plate, drying at 75°C for 4 h, heating to 105°C for 1.5 h, heating to 200°C for 1.5 h, heating to 300°C for 1.5 h, cooling to room temperature, immersing in deionized water, and peeling to obtain a flexible polyimide film. The remaining steps are the same as in Example 2.
[0024] Comparative Example 3: The preparation method of the flexible polyimide film in Comparative Example 3 differs from that in Example 2 in that step (3) is omitted, and step (4) is changed as follows: An ether-containing diamine monomer and a fluorine-containing monomer in a molar ratio of 1:1 are dissolved in N,N-dimethylacetamide at 11 times the mass of the ether-containing diamine monomer. Boron nitride at 0.03 times the mass of the ether-containing diamine monomer is added, and the mixture is ultrasonically dispersed at room temperature for 15 min. Pyromellitic dianhydride at 2 times the molar mass of the ether-containing diamine monomer is added, and the mixture is stirred and reacted for 6 h under nitrogen protection to obtain a PAA solution. The PAA solution is cast onto a clean glass plate, dried at 75°C for 4 h, then heated to 105°C for 1.5 h, then heated to 200°C for 1.5 h, then heated to 300°C for 1.5 h, cooled to room temperature, immersed in deionized water, and peeled off to obtain a flexible polyimide film. The remaining steps are the same as in Example 2.
[0025] Comparative Example 4: The preparation method of the flexible polyimide film in Comparative Example 4 differs from that in Example 2 in that step (3) is omitted, and step (4) is changed as follows: An ether-containing diamine monomer and a fluorine-containing monomer in a molar ratio of 1:1 are dissolved in N,N-dimethylacetamide at 11 times the mass of the ether-containing diamine monomer. The mixture is stirred at room temperature for 15 min, and then pyromellitic dianhydride at 2 times the molar mass of the ether-containing diamine monomer is added. Under nitrogen protection, the mixture is stirred and reacted for 6 h to obtain a PAA solution. The PAA solution is cast onto a clean glass plate, dried at 75°C for 4 h, then heated to 105°C for 1.5 h, then heated to 200°C for 1.5 h, then heated to 300°C for 1.5 h, cooled to room temperature, immersed in deionized water, and peeled off to obtain a flexible polyimide film. The remaining steps are the same as in Example 2.
[0026] Test Example 1 Mechanical property testing Test method: Standard strips of 20mm × 5mm were cut from the flexible polyimide films of the examples and comparative examples, and the tensile strength was tested using an Instron 5966 electronic universal testing machine at a tensile rate of 10mm / min. The results are shown in Table 1.
[0027] Table 1 A comparison of the experimental data from Examples 1-3 and Comparative Examples 1-4 in Table 1 reveals that the flexible polyimide film prepared by this invention possesses excellent mechanical properties.
[0028] By comparison, the tensile strength of Examples 1-3 is greater than that of Comparative Example 1, indicating that the condensation of p-chlorobenzaldehyde yields 4,4'-(oxybis(methylene))bis(chlorobenzene); the reaction of 4,4'-(oxybis(methylene))bis(chlorobenzene) and 4-nitrophenol yields a dinitro intermediate; and the reduction of the dinitro intermediate with Raney nickel yields an ether-containing diamine monomer. The ether-containing diamine structure contains multiple ether bonds and methylene flexible segments. The ether bonds have high rotational freedom, which can break the conjugation of rigid aromatic rings and reduce the rotational energy barrier within the molecular chain. At the same time, the polarity of the ether bonds is moderate, which can avoid the formation of excessively strong hydrogen bonds or π-π stacking between molecules, making the molecular chain easier to slide, which macroscopically manifests as improved flexibility. The methylene groups can weaken the intermolecular packing density and improve the chain segment mobility, thereby giving the flexible polyimide film excellent mechanical flexibility.
[0029] Test Example 2 Insulation performance test Test method: The flexible polyimide films of the examples and comparative examples were cut into circular samples with a diameter of 4 cm. A layer of aluminum foil with a diameter of 2.5 cm was electroplated on both sides of the sample. The dielectric constant of the sample was tested using a Concept80 broadband dielectric spectrum analyzer. The AC voltage used for the test was 1 V. The results are shown in Table 2.
[0030] Table 2 A comparison of the experimental data from Examples 1-3 and Comparative Examples 1-4 in Table 2 reveals that the flexible polyimide film prepared by this invention has excellent insulation properties.
[0031] By comparison, the dielectric constants of Examples 1-3 are lower than those of Comparative Example 2, indicating that fluorinated monomers are prepared by the Suzuki coupling reaction of 5-bromo-1,3-phenylenediamine and 3,5-bis(trifluoromethyl)phenylboronic acid. The trifluoromethyl group in the fluorinated monomer has strong electronegativity and low polarizability, which can reduce the electron cloud density and charge transfer tendency between molecules. The nonpolar characteristics of trifluoromethyl group make the inter-chain forces mainly weak van der Waals forces, reducing the overall polarization of the material, thereby reducing the dielectric constant and loss. At the same time, when combined with thermally conductive fillers such as amino-modified boron nitride, the fluorinated segments can improve the interfacial compatibility between the matrix and the filler, avoid the filler agglomeration to form local conductive paths, strengthen the insulation continuity, and thus endow the flexible polyimide film with excellent insulation properties.
[0032] Test Example 3 Thermal conductivity test Test method: The flexible polyimide films of the examples and comparative examples were cut into standard samples of 10×2cm. The thermal diffusivity of the standard samples was measured using a Netzsch LFA447 flash thermal conductivity meter. The results are shown in Table 3.
[0033] Table 3 A comparison of the experimental data from Examples 1-3 and Comparative Examples 1-4 in Table 3 reveals that the flexible polyimide film prepared by this invention has good thermal conductivity.
[0034] By comparison, the thermal diffusivity of Examples 1-3 is greater than that of Comparative Examples 3-4, indicating that modified boron nitride is prepared by hydrolyzing γ-aminopropyltriethoxysilane and grafting it onto the surface of boron nitride; a flexible polyimide film is prepared by in-situ polymerization of an ether-containing diamine monomer, a fluorine-containing monomer, modified boron nitride, and pyromellitic dianhydride, and modified boron nitride filler is added to the polyimide film; the layered structure of boron nitride has excellent in-plane thermal conductivity, but the interface between unmodified boron nitride and the polyimide matrix is... Poor surface compatibility easily leads to interface defects and air gaps, resulting in high interfacial thermal resistance. After amino modification, the -NH2 on the surface of boron nitride can be uniformly dispersed through hydrogen bonds or covalent bonds, avoiding agglomeration and forming a continuous thermally conductive path, thereby endowing the flexible polyimide film with excellent heat dissipation performance. At the same time, the thermal decomposition temperature of boron nitride itself is >1000℃, which can act as a thermal stabilizer to inhibit the molecular chain degradation of polyimide at high temperatures, maintain the continuity of the thermally conductive network, and ensure the reliability of heat dissipation under long-term thermal cycling.
[0035] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.
Claims
1. A flexible polyimide film, characterized in that, The flexible polyimide film is prepared by reacting 4,4'-(oxybis(methylene))bis(chlorobenzene) and 4-nitrophenol to obtain a dinitro intermediate; reducing the dinitro intermediate with Raney nickel to obtain an ether-containing diamine monomer; reacting 5-bromo-1,3-phenylenediamine and 3,5-bis(trifluoromethyl)phenylboronic acid to obtain a fluorinated monomer; hydrolyzing γ-aminopropyltriethoxysilane and grafting it onto the surface of boron nitride to obtain modified boron nitride; and then polymerizing the ether-containing diamine monomer, the fluorinated monomer, the modified boron nitride, and pyromellitic dianhydride in situ. The 4,4'-(oxybis(methylene))bis(chlorobenzene) is prepared by condensation of p-chlorobenzaldehyde.
2. A method for preparing a flexible polyimide film, characterized in that, The preparation method of the flexible polyimide film includes the following preparation steps: (1) Mix the dinitro intermediate, Raney nickel, and ethanol / dioxane solution with a volume ratio of 10:9 at a mass ratio of 1:(0.1~0.2):(6~8). Under nitrogen protection, heat to 75~85℃ and stir for 9~11h. Filter and add the filtrate to ice-cold deionized water at a volume of 4~6 times that of the ethanol / dioxane solution. Filter and wash with deionized water 2~4 times. Dry under vacuum at 55~65℃ for 9~11h to obtain the ether-containing diamine monomer. (2) Mix 5-bromo-1,3-phenylenediamine, catalyst, anhydrous potassium carbonate, toluene, and deionized water in a mass ratio of 1:(0.04~0.06):(1.5~1.7):(6~8):(3~4) until homogeneous. Stir at room temperature for 10~20 min. Add 3,5-bis(trifluoromethyl)phenylboronic acid in equimolar amounts of 5-bromo-1,3-phenylenediamine. Heat to 105~115℃ and reflux for 4~6 h. Cool to room temperature, filter, extract with toluene, remove toluene by rotary evaporation of the organic layer, and vacuum dry at 75~85℃ for 10~12 h to obtain a fluorinated monomer. (3) Mix boron nitride and silane hydrolysate at a mass ratio of 1:(4~6), heat to 65~75℃, reflux and stir for 9~11h, cool to room temperature, centrifuge for 5~15min, wash with anhydrous ethanol 2~4 times, and vacuum dry at 55~65℃ for 11~13h to obtain modified boron nitride. (4) Cast the PAA solution onto a clean glass plate, dry it at 75~85℃ for 3~5h, heat it to 95~115℃ for 1~2h, heat it to 190~210℃ for 1~2h, heat it to 290~310℃ for 1~2h, cool it to room temperature, immerse it in deionized water, peel it off, and obtain a flexible polyimide film.
3. The method for preparing the flexible polyimide film according to claim 2, characterized in that, The preparation process of the dinitro intermediate in step (1) is as follows: Weigh 4,4'-(oxybis(methylene))bis(chlorobenzene), 4-nitrophenol, and anhydrous potassium carbonate in a molar ratio of 1:(2~2.1):(2.1~2.2); dissolve 4-nitrophenol and anhydrous potassium carbonate in a mixed solvent of N,N-dimethylformamide and toluene in a volume ratio of 1:(0.09~0.11), which is 5~7 times the mass of 4-nitrophenol; and then... Stir at 5-105℃ for 50-70 min, add 4,4'-(oxybis(methylene))bis(chlorobenzene) at a uniform rate over 20-30 min, raise the temperature to 105-115℃, stir and react for 11-13 h, cool to room temperature, pour into 4-6 times the volume of N,N-dimethylformamide in ice-cold deionized water, filter, wash 2-4 times with deionized water, and dry at 65-75℃ for 12-14 h to obtain the dinitro intermediate.
4. The method for preparing the flexible polyimide film according to claim 3, characterized in that, The preparation process of 4,4'-(oxybis(methylene))bis(chlorobenzene) is as follows: p-chlorobenzaldehyde, triethylsilane, and dichloromethane are mixed evenly at a mass ratio of 1:(0.75~0.85):(5~7), stirred at room temperature for 10~20 min, and then trifluoromethanesulfonic acid (0.07~0.09 times the mass of p-chlorobenzaldehyde) is added uniformly over 20~30 min. The mixture is stirred and reacted at room temperature for 23~25 h, then deionized water (0.4~0.6 times the volume of dichloromethane) is added, followed by extraction with dichloromethane (8~10 times the mass of p-chlorobenzaldehyde). The lower organic phase is dried with anhydrous MgSO4, filtered, and the dichloromethane solvent is removed by rotary evaporation. The mixture is then freeze-dried at -50~-40℃ for 6~8 h to obtain 4,4'-(oxybis(methylene))bis(chlorobenzene).
5. The method for preparing the flexible polyimide film according to claim 2, characterized in that, The catalyst in step (2) is tetra(triphenylphosphine)palladium.
6. The method for preparing the flexible polyimide film according to claim 2, characterized in that, The boron nitride in step (3) has a specification of 2 μm.
7. The method for preparing the flexible polyimide film according to claim 2, characterized in that, The preparation process of the silane hydrolysate in step (3) is as follows: γ-aminopropyltriethoxysilane, anhydrous ethanol and deionized water are mixed evenly in a mass ratio of 1:(14~16):(1.4~1.6), the pH is adjusted to 4~5 with glacial acetic acid, and the mixture is stirred at room temperature for 10~20 min to obtain the silane hydrolysate.
8. The method for preparing the flexible polyimide film according to claim 2, characterized in that, The preparation process of the PAA solution in step (4) is as follows: dissolve the ether-containing diamine monomer and the fluorine-containing monomer in a molar ratio of 1:(0.9~1.1) in N,N-dimethylacetamide at 10~12 times the mass of the ether-containing diamine monomer, add modified boron nitride, ultrasonically disperse at room temperature for 10~20 min, add pyromellitic dianhydride at 1.9~2.1 times the molar number of the ether-containing diamine monomer, stir and react for 5~7 h under nitrogen protection to obtain the PAA solution.
9. The method for preparing the flexible polyimide film according to claim 8, characterized in that, The amount of modified boron nitride added is 0.02 to 0.04 times the mass of the ether diamine monomer.