Polyimide material and preparation method thereof

Abstract

The invention relates to a polyimide material and a preparation method thereof, and the preparation method comprises the following steps: mixing a polyamine monomer, a diamine monomer and a dianhydride monomer in an organic solvent, and carrying out a prepolymerization reaction to obtain a polyamide acid solution; the number of amino groups in the multi-amino monomer is more than 3; and coating the polyamide acid solution on a substrate to form a film, carrying out surface drying, heating and curing to obtain the polyimide material with the glass transition temperature Tg of 350 DEG C or above. According to the preparation method, a multi-amino monomer is selected as a core component, the core component, a diamine monomer (containing two amino groups) and a dianhydride monomer are subjected to a ternary polymerization reaction to form a polyimide molecular structure with a fishing net-like special structure and an ultrahigh crosslinking density, and the ultrahigh crosslinking density is improved through three mechanisms of steric hindrance limitation, free volume compression and energy barrier improvement. And the movement of a polyimide chain segment can be obviously inhibited, so that the glass-transition temperature of the polyimide material is greatly increased to 350 DEG C or above.

Description

Technical Field

[0001] This invention relates to the field of polyimide materials, and particularly to a polyimide material and its preparation method. Background Technology

[0002] Polyimide (PI) has become an indispensable core material in the microelectronics industry due to its excellent high-temperature resistance, low dielectric constant, high insulation, and dimensional stability. PI's applications in microelectronics mainly include serving as an interlayer dielectric material for integrated circuit packaging and interconnection, a substrate material for flexible displays and electronics, and an interface material in high-frequency communication and thermal management. In integrated circuit packaging and interconnection, PI films are often used as insulating layers in multilayer interconnect structures of chips. With a dielectric constant as low as 3.4@1MHz, they can significantly reduce signal crosstalk and loss, improving the performance of high-frequency circuits. Simultaneously, when used as a buffer / passivation layer in chip packaging structures, polyimide covers the chip surface, reducing the risk of warpage caused by thermal expansion mismatch through stress buffering, while also shielding against alpha particle radiation to prevent soft errors. In the fabrication of flexible displays (such as OLED displays) and electronic substrate materials, transparent PI films replace rigid glass, withstanding thin-film transistor (TFT) process temperatures >300℃, supporting foldable screens. Meanwhile, in the OLED thin-film encapsulation (TFE) process, PI and inorganic films are alternately stacked to form a flexible water and oxygen barrier layer, which can significantly extend the lifespan of OLED devices. In the preparation of substrates for high-frequency communication and thermal management, the low dielectric loss (Df<0.005) of PI is suitable for millimeter-wave transmission and is used for flexible antenna circuits. At the same time, modified high thermal conductivity PI films (such as graphene composites) are used for chip heat dissipation, with a thermal conductivity of up to 20 W / (m·K) (9), which is very suitable for thermal interface materials in high-frequency communication and thermal management.

[0003] Glass transition temperature (T) g The glass transition temperature (TVT) is the temperature at which an amorphous polymer transitions from a glassy (brittle) to a rubbery (elastic) state. It is one of the most important performance indicators of polyimide (PI), and currently, the glass transition temperature of polyimide is typically below 300°C. In PI applications, T... g Excessively low glass transition temperatures (T0) can significantly weaken a PI's core performance advantages, potentially leading to systemic failures, especially in high-temperature, high-precision, or high-reliability applications. The impact of low T0 on PI performance primarily includes deterioration in thermal stability and mechanical properties, performance defects in critical applications, and challenges in processing and testing. Regarding thermal stability and mechanical property degradation, a low T0... g Temperatures below 250°C cause intensified chain segment movement in materials at high temperatures (e.g., above 200°C), leading to softening and deformation. For example, aerospace engine components need to withstand long-term temperatures above 250°C. g Materials can become structurally unstable due to creep. Meanwhile, low T... gKey components made from polyimide materials suffer from poor dimensional stability, making them prone to warping or delamination between the chip and substrate due to thermal stress in microelectronic packaging. g The performance defects caused by low performance in microelectronics applications mainly include: (1) Microelectronic packaging failure. In microelectronic packaging, due to the low T of polyimide material... g This often leads to poor compatibility with reflow soldering processes. For example, chip packaging requires reflow soldering at temperatures above 260°C, while low-T... g At this temperature, polyimide materials lose their glassy state, molecular chain segment motion intensifies, and the dielectric constant (Dk) and loss factor (Df) fluctuate more, leading to dielectric layer collapse, increased signal transmission loss, and short circuits, thereby affecting the integrity of high-frequency signals. (2) Shortened lifetime of flexible electronics. In the high-temperature process of flexible OLEDs (such as TFT layer deposition, >300°C), low T g Substrates made of polyimide materials are prone to shrinkage and deformation due to insufficient process tolerance, leading to pixel misalignment or film peeling, and severely reducing long-term reliability. For example, OLED foldable screens need to withstand tens of thousands of bends, and low T... g Polyimide has enhanced molecular chain flexibility but weakened fatigue resistance, and repeated screen folding will accelerate crack propagation. (3) Limited application in extreme environments. In aerospace components, rocket nozzle heat shields are often made of polyimide materials, which have a low T0 g Under aerodynamic thermal shock, the heat insulation layer of rocket nozzles is prone to undergo a glass-rubber transition, resulting in the loss of heat insulation performance.

[0004] Meanwhile, low T g During the use of polyimide materials, the free volume usually increases, solvent molecules can penetrate more easily, and the chemical resistance is weakened, which may cause the lining of chemical equipment to be swollen and corroded by concentrated acid / alkali.

[0005] In summary, to ensure the reliability, lifespan, and performance of polyimide materials in the microelectronics field, it is necessary to develop materials with ultra-high glass transition temperatures (T0). g Polyimide materials are urgently needed. Summary of the Invention

[0006] The purpose of this invention is to overcome the above-mentioned technical deficiencies and provide a polyimide material and its preparation method, thereby solving the technical problem of the low glass transition temperature of polyimide materials in the prior art.

[0007] To achieve the above-mentioned technical objectives, the technical solution provided by this invention is as follows: In a first aspect, the present invention provides a method for preparing a polyimide material, comprising the following steps: mixing a polyamine monomer, a diamine monomer, and a dianhydride monomer in an organic solvent, and obtaining a polyamic acid solution through a prepolymerization reaction; wherein the polyamine monomer has more than three amine groups; coating the polyamic acid solution onto a substrate to form a film, and curing it at a temperature after surface drying to obtain a polyimide material with a glass transition temperature (Tg) of 350°C or higher.

[0008] Secondly, the present invention provides a polyimide material prepared by the above-described preparation method.

[0009] Compared with the prior art, the beneficial effects of the present invention include: This invention selects polyamine monomers as the core components and forms a special "fishing net"-like structure of ultra-high crosslinking density polyimide molecular structure through a ternary copolymerization reaction with diamine monomers (containing two amino groups) and dianhydride monomers. This ultra-high crosslinking density can significantly inhibit the movement of polyimide chain segments through a triple mechanism of steric hindrance restriction, free volume compression, and energy barrier enhancement, thereby greatly increasing the glass transition temperature of polyimide materials to above 350°C. Attached Figure Description

[0010] Figure 1 The polyimide films T prepared in Examples 1-5 and Comparative Example 1 of this invention are g Test curve; Figure 2 The polyimide film T prepared in Examples 3 and 6-7 of this invention g Test curve. Detailed Implementation

[0011] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0012] To address the current deficiency of low glass transition temperature in polyimide materials, this invention provides an ultra-high glass transition temperature polyimide material with a special structure and its preparation method. This ultra-high glass transition temperature (T0) g The preparation of polyimide materials is based on the preparation of ultra-high cross-linking density polyimide materials prepared by polyamine (three or four) monomers and dianhydride monomers. By designing and selecting polyamine (three or four) monomers as core components, they form a "fishing net"-like cross-linked polyimide structure through ternary copolymerization with diamine monomers (containing two amine groups) and dianhydride monomers. This increases the cross-linking density, restricts molecular chain movement, and thus effectively increases its glass transition temperature.

[0013] In a first aspect, the present invention provides a method for preparing a polyimide material, comprising the following steps: A polyamine monomer, a diamine monomer, and a dianhydride monomer are mixed in an organic solvent and subjected to a prepolymerization reaction to obtain a polyamic acid solution; the polyamine monomer contains more than three amine groups; A polyamic acid solution is coated onto a substrate to form a film, which is then surface-dried and cured by heating to obtain a polyimide material with a glass transition temperature (Tg) above 350℃.

[0014] Preferably, the polyamine monomer includes a triamine monomer or a tetraamine monomer.

[0015] Further preferably, the triamine monomer includes, but is not limited to, one or more of tris(4-aminophenyl)methane, tris(4-aminophenyl)methanol, 2,4,6-tris(4-aminophenyl)pyridine (CAS: 83266-97-1), tris(4-aminophenyl)amine, and 2,4,6-tris(4-aminophenyl)-1,3,5-triazine (CAS: 14544-47-9); the specific structural formula is shown below:

[0016] Further preferably, the tetraamine monomer includes, but is not limited to, one or more of 1,2,4,5-phenyltetramine, tetra(4-aminophenyl)methane, 5,10,15,20-tetra(4-aminophenyl)porphyrin, 4,4,4,4-[phenyl-1,2,4,5-tetrayltetra(acetylene-2,1-diyl)]tetraphenylamine, and tetra-(4-aminophenyl)-ethylene; the specific structural formulas are shown below:

[0017] Preferably, the diamine monomer (containing two amino groups) includes one or more of the following: 1,6-hexanediamine (HMDA), 4,4′-diaminodiphenyl ether (ODA), diethyltoluenediamine (DETDA), 4,4'-diaminodiphenylmethane (MDA), 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl (TFDB), p-phenylenediamine (PPD), m-phenylenediamine (MPD), 3,3'-dimethyl-4,4'-diaminodiphenylmethane (DMMDA), 2,6-diaminotoluene (2,6-TDA), isophoronediamine (IPDA), 3,3-dimethyl-4,4-diaminodicyclohexylmethane (DMDC), 1,3-cyclohexanediamine (CHM), triethylenediamine (TEDA), and methylcyclopentanediamine (TAC-900).

[0018] The diamine monomers of this invention include one or more of aliphatic diamines, aromatic diamines, alicyclic diamines, heterocyclic diamines, and other functional diamines. They are widely available and low in cost. Among them, aliphatic diamines are mostly linear or branched structures, which have high reactivity and are often used in polymer synthesis. Aromatic diamines contain benzene ring structures, which can impart heat resistance and mechanical strength to materials. Heterocyclic diamines have nitrogen-heterocyclic structures, which have outstanding catalytic activity.

[0019] More preferably, the diamine monomer comprises compounds or combinations thereof represented by any of the following structural formulas:

[0020] Preferably, the dianhydride monomer includes one or more of aromatic dianhydrides, alicyclic dianhydrides, and functional dianhydrides.

[0021] In this invention, a wide range of dianhydride monomers can be selected. Aromatic dianhydrides contain benzene ring structures, which endow the material with high thermal stability and mechanical strength, and are often used in high-performance polymers. Alicyclic dianhydrides contain saturated ring structures, which take into account both weather resistance and processability, and are suitable for preparing light-colored products. Functional dianhydrides contain special groups and are mainly used to expand the performance boundaries of materials.

[0022] More preferably, the aromatic dianhydride includes one or more of pyromellitic dianhydride (PMDA), 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA), and diphenyl ether tetracarboxylic dianhydride (ODPA).

[0023] More preferably, the alicyclic dianhydride includes one or more of 1,2,4,5-cyclohexanetetracarboxylic dianhydride (HPMDA), cyclobutanetetracarboxylic dianhydride (CBDA), and 1,2,3,4-cyclopentanetetracarboxylic dianhydride (CPDA).

[0024] Further preferred, the functional dianhydride includes one or more of bisphenol A diether dianhydride (BPADA) and hexafluorodianhydride (6FDA).

[0025] More preferably, the dianhydride monomer comprises one or more compounds shown in the following structural formulas:

[0026] Preferably, the molar ratio of polyamine monomer, diamine monomer and dianhydride monomer is (0.5-2):20:22.

[0027] Preferably, the organic solvent includes one or more of N,N-dimethylacetamide (DMAC), N-methylpyrrolidone (NMP), N,N-dimethylformamide (DMF), and dimethyl sulfoxide (DMSO).

[0028] Preferably, the solid content of the mixture obtained by mixing the polyamine monomer, the diamine monomer, and the dianhydride monomer in an organic solvent is 15-25%.

[0029] Preferably, the prepolymerization reaction is carried out at 20–28°C with stirring for 10–14 hours.

[0030] Preferably, the surface drying is carried out at 75-85℃ for 0.5-1.5 hours.

[0031] Preferably, the specific process of temperature rise and curing includes: sequentially raising the temperature to 90-110℃, 140-160℃, 190-210℃ and 240-260℃, and maintaining each temperature step for 20-40 minutes.

[0032] Secondly, the present invention provides an ultra-high glass transition temperature polyimide material prepared by the above-mentioned preparation method.

[0033] Preferably, the glass transition temperature of the polyimide material is 351–399°C.

[0034] The main mechanism of action and advantages of this invention are as follows: (1) When the selected core component polyamine monomer is a tetraamine monomer containing four amino groups, the cross-linked polyimide structure obtained by copolymerization with diamine monomer (containing two amino groups) and dianhydride monomer is shown in Formula I below.

[0035]

[0036] Where A is a tetraamine monomer containing four amino groups, B is a dianhydride monomer containing two anhydride groups, and C is a diamine monomer (containing two amino groups), and a, b, c, and d are all integers not less than 1. Meanwhile, the structure shown in Formula I is only for the prepared material with ultra-high T g Local structure of polyimide material molecules.

[0037] (2) When the selected core component polyamine monomer is a triamine monomer containing three amino groups, the cross-linked polyimide structure obtained by copolymerization with diamine monomer (containing two amino groups) and dianhydride monomer is shown in Formula II.

[0038]

[0039] Where X is a triamine monomer containing three amino groups, Y is a dianhydride monomer containing two acid anhydride groups, and Z is a diamine monomer (containing two amino groups), and x, y, and z are all integers not less than 1. Meanwhile, the structure shown in Formula II is only for the prepared material with ultra-high T g Local structure of polyimide material molecules.

[0040] (3) The present invention introduces ultra-high crosslinking density into the polyimide (PI) molecular structure, which can significantly improve its glass transition temperature (T). g The main reasons can be explained by three core mechanisms: restricted molecular chain motion (steric hindrance), reduced free volume (thermodynamic constraint), and enhanced intermolecular forces (increased energy barrier). (301) The cross-linking reaction forms covalent bonds between polyimide molecular chains, constructing a three-dimensional network structure. The cross-linking points form a rigid network, which significantly restricts the free rotation and conformational change capabilities of the molecular chain segments. Simultaneously, at ultra-high cross-linking densities in polyimide, the average chain length between adjacent cross-linking points decreases significantly, and the thermal energy barrier of short chain segments is higher, requiring higher temperatures to excite chain segment motion, thus significantly increasing the thermal efficiency of polyimide materials. g ; (302) Polyimide materials in T g The glass transition that occurs nearby is essentially due to the molecular free volume reaching the critical point of minimum free volume required for chain segment movement. By forming an ultra-high crosslink density in polyimide materials, the crosslink network forces the molecular chains to pack tightly, reducing the voids (free volume) inside the material. This makes it more difficult for the chain segments to reach the space required for movement, thereby significantly improving the glass transition temperature (Tg) of polyimide materials. g Purpose; (303) Crosslinking bonds in polyimide materials (such as carbon-carbon bonds or ether bonds between imide rings) require higher energy to break or twist, which can significantly increase the activation energy of chain segment motion. In highly crosslinked polyimides (such as structures containing phenylacetylene or tetrafluorostyrene side groups), the crosslinking points hinder the micro Brownian motion of local chain segments, causing the secondary transformation temperature to shift to higher temperatures, indirectly increasing the primary transformation temperature T of the polyimide material. g .

[0041] In summary, ultra-high crosslinking density significantly inhibits polyimide chain segment movement through a triple mechanism of steric hindrance confinement, free volume compression, and energy barrier enhancement, thereby greatly improving the Tt of polyimide materials. g This addresses the problems that polyimide materials can cause in the microelectronics industry, such as packaging failure, short lifespan of flexible electronics, or loss of thermal insulation performance.

[0042] The present invention will be further described in detail below through specific embodiments.

[0043] Example 1 A method for preparing a polyimide material includes the following steps: According to the raw material ratio shown in Table 1, 1,2,4,5-phenyltetramine, 4,4′-diaminodiphenyl ether (ODA), and pyromellitic dianhydride (PMDA) were added to a clean three-necked flask. Under nitrogen protection, an appropriate amount of DMAC solvent was added, and the solid content was controlled at 20%. The mixture was stirred at room temperature for 12 hours to obtain a polyamic acid solution of a certain viscosity. This polyamic acid solution was spin-coated onto a glass substrate to form a film, which was then surface-dried at 80°C for 1 hour. The temperature was then stepped up to 100°C, 150°C, 200°C, and 250°C, and each temperature step was maintained for 30 minutes to obtain a polyimide film material. The molar ratio of 1,2,4,5-phenyltetramine, 4,4′-diaminodiphenyl ether (ODA), and pyromellitic dianhydride (PMDA) was controlled to be 1:20:22.

[0044] Table 1. Proportions of raw materials in Example 1

[0045] Example 2 A method for preparing a polyimide material includes the following steps: According to the raw material ratio shown in Table 2, tetra(4-aminophenyl)methane, 4,4′-diaminodiphenyl ether (ODA), and pyromellitic dianhydride (PMDA) were added to a clean three-necked flask. Under nitrogen protection, an appropriate amount of DMAC solvent was added, and the solid content was controlled at 20%. The mixture was stirred at room temperature for 12 hours to obtain a polyamic acid solution of a certain viscosity. This polyamic acid solution was spin-coated onto a glass substrate to form a film, which was then surface-dried at 80°C for 1 hour. The temperature was then stepped up to 100°C, 150°C, 200°C, and 250°C, and each step was maintained for 30 minutes to obtain a polyimide film material. The molar ratio of tetra(4-aminophenyl)methane, 4,4′-diaminodiphenyl ether (ODA), and pyromellitic dianhydride (PMDA) was controlled to be 1:20:22.

[0046] Table 2. Proportions of raw materials in Example 2

[0047] Example 3 A method for preparing a polyimide material includes the following steps: According to the raw material ratio shown in Table 3, tetra-(4-aminophenyl)-ethylene, 4,4′-diaminodiphenyl ether (ODA), and pyromellitic dianhydride (PMDA) were added to a clean three-necked flask. Under nitrogen protection, an appropriate amount of DMAC solvent was added, and the solid content was controlled at 20%. The mixture was stirred at room temperature for 12 hours to obtain a polyamic acid solution of a certain viscosity. The polyamic acid solution was spin-coated onto a glass substrate to form a film, which was then surface-dried at 80°C for 1 hour. The temperature was then stepped up to 100°C, 150°C, 200°C, and 250°C, and each step was maintained for 30 minutes to obtain a polyimide film material. The molar ratio of tetra-(4-aminophenyl)-ethylene, 4,4′-diaminodiphenyl ether (ODA), and pyromellitic dianhydride (PMDA) was controlled to be 1:20:22.

[0048] Table 3. Proportions of raw materials in Example 3

[0049] Example 4 A method for preparing a polyimide material includes the following steps: Tris(4-aminophenyl)methane, 4,4′-diaminodiphenyl ether (ODA), and pyromellitic dianhydride (PMDA) were added to a clean three-necked flask according to the raw material ratio shown in Table 4. Under nitrogen protection, an appropriate amount of DMAC solvent was added, controlling the solid content to 20%. The mixture was stirred at room temperature for 12 hours to obtain a polyamic acid solution of a certain viscosity. This polyamic acid solution was spin-coated onto a glass substrate to form a film, which was then surface-dried at 80°C for 1 hour. The temperature was then stepped up to 100°C, 150°C, 200°C, and 250°C, with each temperature step maintained for 30 minutes to obtain a polyimide film material. The molar ratio of tris(4-aminophenyl)methane, 4,4′-diaminodiphenyl ether (ODA), and pyromellitic dianhydride (PMDA) was controlled to be 1:20:22.

[0050] Table 4. Proportions of raw materials in Example 4

[0051] Example 5 A method for preparing a polyimide material includes the following steps: Tris(4-aminophenyl)methanol, 4,4′-diaminodiphenyl ether (ODA), and pyromellitic dianhydride (PMDA) were added to a clean three-necked flask according to the raw material ratio shown in Table 1. Under nitrogen protection, an appropriate amount of DMAC solvent was added, controlling the solid content to 20%. The mixture was stirred at room temperature for 12 hours to obtain a polyamic acid solution of a certain viscosity. This polyamic acid solution was spin-coated onto a glass substrate to form a film, which was then surface-dried at 80°C for 1 hour. The temperature was then stepped up to 100°C, 150°C, 200°C, and 250°C, with each temperature step maintained for 30 minutes to obtain a polyimide film material. The molar ratio of tris(4-aminophenyl)methanol, 4,4′-diaminodiphenyl ether (ODA), and pyromellitic dianhydride (PMDA) was controlled to be 1:20:22.

[0052] Table 5. Proportions of raw materials in Example 5

[0053] Comparative Example 1 A method for preparing a polyimide material includes the following steps: According to the raw material ratio shown in Table 6, 4,4′-diaminodiphenyl ether (ODA) and pyromellitic dianhydride (PMDA) were added to a clean three-necked flask. Under nitrogen protection, an appropriate amount of DMAC solvent was added, and the solid content was controlled at 20%. The mixture was stirred at room temperature for 12 hours to obtain a polyamic acid solution of a certain viscosity. This polyamic acid solution was spin-coated onto a glass substrate to form a film, which was then surface-dried at 80°C for 1 hour. The temperature was then stepped up to 100°C, 150°C, 200°C, and 250°C, and each step was maintained for 30 minutes to obtain a polyimide film material. The molar ratio of 4,4′-diaminodiphenyl ether (ODA) to pyromellitic dianhydride (PMDA) was controlled to be 1:1.

[0054] Table 6. Proportions of raw materials in Comparative Example 1

[0055] The Tg of the polyimide films prepared in Examples 1-5 and Comparative Example 1 was tested using dynamic thermomechanical analysis (DMA), and the main raw materials and their Tg values ​​were also analyzed. g The test results were statistically analyzed and detailed in Table 7, showing the polyimide films T prepared in Examples 1-5 and Comparative Example 1. g Test curves as follows Figure 1 As shown.

[0056] Table 7. Main raw material types and T in Examples 1-5 and Comparative Example 1 g Test Result Statistics

[0057] From Table 7 and Figure 1The results show that the Tg of the polyimide films obtained in Examples 1-5 of this invention is significantly improved compared to Comparative Example 1, reaching 351-399℃; especially in Example 3, when tetra-(4-aminophenyl)-ethylene was selected as the polyamine monomer, 4,4′-diaminodiphenyl ether (ODA) as the diamine monomer, and pyromellitic dianhydride (PMDA) as the dianhydride monomer, and the equivalent ratio of the three was 1:20:22, the Tg of the prepared polyimide film was significantly improved. g It can reach a maximum of 399℃.

[0058] To investigate the equivalent ratios of tetra-(4-aminophenyl)-ethylene as a polyamine monomer, 4,4′-diaminodiphenyl ether (ODA) as a diamine monomer, and pyromellitic dianhydride (PMDA) as a dianhydride monomer, the polyimide film sample T was obtained. g To further verify the effects of these factors, the present invention conducted the following experiments.

[0059] Example 6 The only difference from Example 3 is that the mass of tetra-(4-aminophenyl)-ethylene was adjusted to 0.98 g to control the molar ratio of tetra-(4-aminophenyl)-ethylene, 4,4′-diaminodiphenyl ether (ODA), and pyromellitic dianhydride (PMDA) to 0.5:20:22; and the amount of N,N-dimethylacetamide (DMAC) was adjusted to 179.96 g. All other steps and conditions were the same as in Example 3.

[0060] Example 7 The only difference from Example 3 is that the mass of tetra-(4-aminophenyl)-ethylene was adjusted to 3.92 g to control the molar ratio of tetra-(4-aminophenyl)-ethylene, 4,4′-diaminodiphenyl ether (ODA), and pyromellitic dianhydride (PMDA) to be 2:20:22.

[0061] The main raw material ratios and T of polyimide films prepared in Examples 3 and 6-7 g The test results were statistically analyzed and detailed in Table 8. g Test curves as follows Figure 2 As shown.

[0062] Table 8. Main raw material ratios and T in Examples 3 and 6-7 g Test Result Statistics

[0063] From Table 8 and Figure 2It is known that when tetra-(4-aminophenyl)-ethylene is used as the polyamine monomer, both excessive and insufficient dosage will affect the Tg of the obtained polyimide. Therefore, the present invention preferably uses a molar ratio of polyamine monomer, diamine monomer, and dianhydride monomer of (0.5-2):20:22, more preferably (0.9-1.1):20:22, and even more preferably 1:20:22. Under these conditions, the polyimide film prepared will have a Tg of... g It can reach a maximum of 399℃.

[0064] In summary, this invention designs and selects polyamine monomers (three or four groups) as core components, and forms a "fishing net"-like polyimide molecular structure with ultra-high crosslinking density through a ternary copolymerization reaction with diamine monomers (containing two amino groups) and dianhydride monomers. This ultra-high crosslinking density significantly inhibits the movement of polyimide chain segments through a triple mechanism of steric hindrance restriction, free volume compression, and energy barrier enhancement, thereby greatly increasing the glass transition temperature (T0) of the polyimide material. g ).

[0065] The specific embodiments of the present invention described above do not constitute a limitation on the scope of protection of the present invention. Any other corresponding changes and modifications made in accordance with the technical concept of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A method for preparing a polyimide material, characterized in that, Includes the following steps: A polyamine monomer, a diamine monomer, and a dianhydride monomer are mixed in an organic solvent and subjected to a prepolymerization reaction to obtain a polyamic acid solution; the polyamine monomer contains more than three amine groups; A polyamic acid solution is coated onto a substrate to form a film, which is then surface-dried and cured by heating to obtain a polyimide material with a glass transition temperature (Tg) above 350℃.

2. The method for preparing the polyimide material according to claim 1, characterized in that, The polyamine monomer includes a triamine monomer or a tetraamine monomer.

3. The method for preparing the polyimide material according to claim 2, characterized in that, The triamine monomer includes, but is not limited to, one or more of tris(4-aminophenyl)methane, tris(4-aminophenyl)methanol, 2,4,6-tris(4-aminophenyl)pyridine, tris(4-aminophenyl)amine, and 2,4,6-tris(4-aminophenyl)-1,3,5-triazine; The tetraamine monomers include, but are not limited to, one or more of 1,2,4,5-phenyltetramine, tetra(4-aminophenyl)methane, 5,10,15,20-tetra(4-aminophenyl)porphyrin, 4,4,4,4-[benzene-1,2,4,5-tetramethyltetra(ethynyl-2,1-diyl)]tetraphenylamine, and tetra-(4-aminophenyl)-ethylene.

4. The method for preparing the polyimide material according to claim 1, characterized in that, The diamine monomer includes one or more of the following: 1,6-hexanediamine, 4,4′-diaminodiphenyl ether, diethyltoluenediamine, 4,4'-diaminodiphenylmethane, 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl, p-phenylenediamine, m-phenylenediamine, 3,3'-dimethyl-4,4'-diaminodiphenylmethane, 2,6-diaminotoluene, isophoronediamine, 3,3-dimethyl-4,4-diaminodicyclohexylmethane, 1,3-cyclohexanediamine, triethylenediamine, and methylcyclopentanediamine.

5. The method for preparing the polyimide material according to claim 1, characterized in that, The dianhydride monomer includes one or more of aromatic dianhydrides, alicyclic dianhydrides, and functional dianhydrides; The aromatic dianhydride includes one or more of pyromellitic dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride, and diphenyl ether tetracarboxylic dianhydride. The alicyclic dianhydride includes one or more of 1,2,4,5-cyclohexanetetracarboxylic dianhydride, cyclobutanetetracarboxylic dianhydride, and 1,2,3,4-cyclopentanetetracarboxylic dianhydride. The functional dianhydride includes one or more of bisphenol A type diether dianhydride and hexafluorodianhydride.

6. The method for preparing the polyimide material according to claim 1, characterized in that, The molar ratio of the polyamine monomer, diamine monomer, and dianhydride monomer is (0.5-2):20:

22.

7. The method for preparing the polyimide material according to claim 1, characterized in that, The organic solvent includes one or more of N,N-dimethylacetamide, N-methylpyrrolidone, N,N-dimethylformamide, and dimethyl sulfoxide; The solid content of the mixture obtained by mixing the polyamine monomer, diamine monomer, and dianhydride monomer in an organic solvent is 15-25%.

8. The method for preparing the polyimide material according to claim 1, characterized in that, The prepolymerization reaction is carried out by stirring at 20–28°C for 10–14 hours.

9. The method for preparing the polyimide material according to claim 1, characterized in that, The surface drying process involves drying at 75–85°C for 0.5–1.5 hours. The specific process of heating and curing includes: stepwise heating to 90-110℃, 140-160℃, 190-210℃ and 240-260℃, with each step temperature maintained for 20-40 minutes.

10. The polyimide material prepared by the preparation method according to any one of claims 1-9.

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