Heat-resistant fluoride-free low-dielectric polyarylene ether nitrile copolymer film and preparation method thereof

Abstract

The invention belongs to the technical field of high polymer material synthesis processes, and provides a heat-resistant fluorine-free low-dielectric polyarylene ether nitrile copolymer film and a preparation method thereof. The preparation method comprises the following steps: firstly, initiating a polymerization reaction by adopting a nucleophilic substitution reaction under a precise temperature control condition to obtain polyarylene ether nitrile, then heating and dissolving the polyarylene ether nitrile in N-methyl pyrrolidone, forming a uniform thin film by adopting a casting film forming technology, and finally, finishing the forming of the thin film through a gradient heating procedure to prepare the polyarylene ether nitrile copolymer thin film. The molecular engineering strategy adopted by the invention does not depend on the addition of fluorine element to reduce the dielectric constant, also avoids the inevitable mechanical property loss when the crosslinking strategy is adopted, and effectively overcomes the technical bottleneck that the sustainability and durability are difficult to consider in the research and development process of the high-performance polymer; an ideal material solution with excellent thermal stability and low dielectric property is provided for the fields of electronic packaging, high-frequency circuits and the like.

Description

Technical Field

[0001] The invention belongs to the technical field of polymer material synthesis technology, and particularly relates to a method for preparing a heat-resistant fluorine-free low-dielectric polyarylene ether nitrile copolymer film. Background Art

[0002] Driven by the rapid advancement of modern technology, electronic devices are continuously evolving towards miniaturization, integration, and high speed. From smartphones and portable computers to sophisticated aerospace electronics, devices are shrinking in size, while the density of internal components is increasing exponentially, significantly increasing the amount of heat generated per unit area. In such harsh thermal environments, the heat resistance of materials becomes a key factor in determining the reliability of electronic devices. Furthermore, low dielectric constant properties are of vital strategic importance to modern electronic systems. During signal transmission, the performance of dielectric materials directly impacts the efficiency of electrical signal propagation. Low-k dielectric materials can effectively reduce signal transmission loss and latency, significantly improving data transmission speed and signal integrity. Furthermore, low-k dielectric materials can significantly minimize crosstalk between signals and, by reducing electromagnetic coupling, ensure stable signal transmission in complex communication networks. As technological research and development advance, the requirements for material dielectric properties and heat resistance will continue to rise, driving innovation in electronic materials towards ultra-low dielectric constants and high heat resistance.

[0003] Poly(arylene ether nitrile) is a class of high-performance polymer materials, whose backbones are composed of alternating aromatic rings, ether bonds, and cyano groups. This gives them high heat resistance, mechanical strength, and chemical stability, making them an indispensable key material in modern materials science. Molecular structure design can effectively control the molecular structure and morphology of poly(arylene ether nitrile), enabling control of the microstructure of the polymer. However, despite significant progress in improving the heat resistance and reducing the dielectric constant of poly(arylene ether nitrile), several challenges and limitations remain. These challenges not only affect the overall performance of the material but also pose potential risks to the environment and safety. The introduction of fluorine atoms is an effective method for reducing the dielectric constant of poly(arylene ether nitrile), but fluorinated compounds are difficult to degrade in the environment and may pose long-term risks to ecosystems and human health. Regarding improving heat resistance, cross-linking modification can improve thermal stability but can also lead to brittleness and reduced impact strength or fracture toughness. The introduction of nanofillers can also lead to poor interfacial compatibility or performance degradation over long-term use. Summary of the Invention

[0004] In view of this, in order to solve the problems in the prior art, the present invention provides a heat-resistant fluorine-free low-dielectric poly (arylene ether nitrile) copolymer film and a preparation method thereof.

[0005] It should be noted that the bulky fluorene rings in the bisphenol fluorene structure increase steric hindrance, restricting chain segment motion, thereby increasing the glass transition temperature of the poly(arylene ether nitrile). Furthermore, the benzene rings on the side chains of the bisphenol AP structure reduce the packing density of the molecular chains, reducing the number of dielectric molecules per unit volume, thereby lowering the dielectric constant of the poly(arylene ether nitrile), thereby replacing the method of lowering the dielectric constant by introducing fluorine atoms. Accordingly, the present invention proposes a poly(arylene ether nitrile) copolymer film obtained from bisphenol fluorene and bisphenol AP via a simple nucleophilic substitution reaction and casting method. The introduction of the highly heat-resistant bisphenol monomer bisphenol fluorene and the low-dielectric bisphenol monomer bisphenol AP enables the resulting copolymer film to be environmentally friendly while possessing coordinated thermal, mechanical, and electrical properties, providing key material support for high-tech fields such as electronic communications.

[0006] In order to achieve the above technical objectives, the present invention provides a method for preparing a heat-resistant fluorine-free low-dielectric poly (arylene ether nitrile) copolymer film, comprising the following steps:

[0007] S1: Synthesis of poly(arylene ether nitrile) copolymers with different molar ratios:

[0008] 1.1 In a three-necked flask equipped with a mechanical stirrer, a water separator, a thermometer, and a condenser reflux apparatus, bisphenol AP, bisphenol fluorene, and 2,6-dichlorobenzonitrile in a predetermined ratio are added as reactants, and potassium carbonate is added as a catalyst to obtain a mixture powder; in the mixture powder, the molar ratio of the total molar amount of bisphenol AP and bisphenol fluorene to 2,6-dichlorobenzonitrile and potassium carbonate is (0.12-0.2):(0.121-0.202):(0.168-0.28), preferably 1:1.008:1.4;

[0009] 1.2 Add the mixture powder obtained in step 1.1 to a mixed solution of N-methylpyrrolidone (NMP) and toluene, wherein the volume ratio of N-methylpyrrolidone (NMP) to toluene is (2.96-3):1, preferably 3:1;

[0010] 1.3 The mixed solution obtained in step 1.2 was heated to (144°C-150°C) in an electric heating mantle and reacted at a constant temperature for 3 hours; the water separator was opened and a certain amount of toluene was released, and after the temperature was raised to 180°C, it was slowly heated to 190°C within 2 hours; finally, the obtained reaction solution was poured into pure water and stirred to precipitate the poly(arylene ether nitrile) solid material;

[0011] 1.4 The solid material obtained in step 1.3 was crushed, soaked in a 0.2 mol / L hydrochloric acid solution for 24 hours, filtered, and washed with pure water 3 to 5 times until the solution was neutral; the washed powder was placed in a vacuum oven and dried for 24 hours to obtain the polyarylene ether nitrile copolymer;

[0012] The ratio of the molar number m of bisphenol AP to the molar number n of bisphenol fluorene in the polyarylethernitrile copolymer is m:n=0~100:100~0, where m+n=100, and the preferred molar ratios are 0:100, 20:80, 40:60, 50:50, 60:40, 80:20, and 100:0, respectively.

[0013] S2: The poly(arylene ether nitrile) copolymer obtained in S1 was mixed with solvent N-methylpyrrolidone at a ratio of 2 g: 20 mL, and mechanically stirred for 2 h to obtain a copolymer hot solution;

[0014] S3. The copolymer hot solution obtained in S2 is formed into a film by a casting method, and then the solvent is removed by gradient heating to obtain a copolymer film; wherein the gradient heating process is: keeping warm at 80°C, 100°C, 120°C, and 160°C for 1 hour respectively, and then keeping warm at 200°C for 2 hours.

[0015] The present invention also claims protection for a heat-resistant, fluorine-free, low-dielectric poly(arylene ether nitrile) copolymer film prepared by the above method.

[0016] Compared with the prior art, the present invention has the following beneficial effects:

[0017] 1) The present invention first uses a nucleophilic substitution reaction to initiate a polymerization reaction under precise temperature control conditions to obtain polyarylene ether nitrile, then heats and dissolves the polyarylene ether nitrile in N-methylpyrrolidone, uses a cast film forming technique to form a uniform film, and finally completes the film forming by a gradient temperature ramp program to obtain a polyarylene ether nitrile copolymer film. The molecular engineering strategy adopted in the present invention does not need to rely on reducing the dielectric constant by adding fluorine elements, and also avoids the inevitable loss of mechanical properties when adopting a cross-linking strategy. It effectively overcomes the technical bottleneck of the difficulty in balancing sustainability and durability in the development of high-performance polymers, and provides an ideal material solution with excellent thermal stability and low dielectric properties for fields such as electronic packaging and high-frequency circuits.

[0018] 2) The molecular engineering method disclosed in the present invention avoids the reliance on traditional cross-linking strategies that require the addition of fluorine to reduce the dielectric constant and compromise mechanical properties, thereby solving the key issues of sustainability and durability that are prevalent in the development of high-performance polymers. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are merely embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying any creative work.

[0020] Figure 1This is a synthetic route for poly(arylene ether nitrile) copolymers.

[0021] Figure 2 It is the glass transition temperature of the poly(arylene ether nitrile) of Examples 1-5 and Comparative Examples 1-2 of the present invention.

[0022] Figure 3 5% decomposition temperature and residual carbon rate of poly(arylene ether nitrile) in Examples 1-5 of the present invention and Comparative Examples 1-2.

[0023] Figure 4 The dielectric constant and dielectric loss of poly(arylene ether nitrile) of Examples 1-5 and Comparative Examples 1-2 at 1 kHz are shown.

[0024] Figure 5 The mechanical properties of poly(arylene ether nitrile) of Examples 1-5 and Comparative Examples 1-2 of the present invention are shown. DETAILED DESCRIPTION

[0025] The following is a clear and complete description of the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0026] The term "embodiment" is used herein specifically to describe any embodiment as "exemplary," and should not be construed as superior or preferable to other embodiments. Performance indicators in the embodiments of this application were tested using conventional testing methods in the art, unless otherwise specified. It should be understood that the terms used in this application are intended solely to describe specific implementations and are not intended to limit the disclosure herein.

[0027] Unless otherwise specified, the technical and scientific terms used herein have the same meanings as commonly understood by ordinary technicians in the technical field to which this application belongs; other experimental methods and technical means not specifically specified in this application refer to experimental methods and technical means commonly used by ordinary technicians in this field.

[0028] In order to better illustrate the content of this application, numerous specific details are provided in the specific examples below. It should be understood by those skilled in the art that this application can be implemented without certain specific details. In the examples, some methods, means, instruments, equipment, etc. well known to those skilled in the art are not described in detail in order to highlight the main purpose of this application.

[0029] Under the premise of no conflict, the technical features disclosed in the embodiments of this application can be combined arbitrarily, and the resulting technical solutions belong to the contents disclosed in the embodiments of this application.

[0030] The invention discloses a method for preparing a heat-resistant fluorine-free low-dielectric polyarylene ether nitrile copolymer film.

[0031] For a better understanding of the present invention, the present invention is further specifically described below through the following examples, but it should not be understood as limiting the present invention. Some non-essential improvements and adjustments made by those skilled in the art based on the above invention content are also considered to fall within the scope of protection of the present invention.

[0032] Example 1

[0033] S1: 11.6142 g of bisphenol AP, 56.0656 g of bisphenol fluorene, 34.6729 g of 2,6-dichlorobenzonitrile, and 38.6974 g of potassium carbonate were added to a three-necked flask equipped with a stirring rod, a thermometer, a condenser, and a water separator to obtain a mixed powder; 159 mL of N-methylpyrrolidone and 53 mL of toluene were poured into the three-necked flask containing the mixed powder to obtain a mixed solution.

[0034] S2: The mixed solution was heated and stirred on a heating mantle, and the temperature was raised to 145°C and kept at this temperature for 3 hours. After that, the toluene vapor in the system was released and the temperature was raised to 180°C. The temperature was slowly raised to 190°C within 2 hours. The obtained reaction solution was poured into pure water and stirred to precipitate the poly(arylene ether nitrile) solid material;

[0035] S3: The poly(arylene ether nitrile) solid material was crushed, immersed in a 0.2 mol / L hydrochloric acid solution for 24 h, filtered, and washed several times with pure water until neutral; the washed powder was dried in a vacuum oven for 24 h to obtain a purified sample, i.e., the poly(arylene ether nitrile) copolymer.

[0036] S4: The obtained polyarylene ether nitrile copolymer is mixed with solvent N-methylpyrrolidone in a ratio of 2g:20mL, and mechanically stirred for 2 hours to obtain a copolymer hot solution; the copolymer hot solution is formed into a film by a casting method, and the film is kept at 80°C, 100°C, 120°C, and 160°C for 1 hour, respectively, and then kept at 200°C for 2 hours to obtain a polyarylene ether nitrile copolymer film.

[0037] Example 2

[0038] S1: 23.2285 g of bisphenol AP, 42.0492 g of bisphenol fluorene, 34.6729 g of 2,6-dichlorobenzonitrile, and 38.6974 g of potassium carbonate were added to a three-necked flask equipped with a stirring rod, a thermometer, a condenser, and a water separator to obtain a mixed powder; 156 mL of N-methylpyrrolidone and 52 mL of toluene were poured into the three-necked flask containing the mixed powder to obtain a mixed solution.

[0039] S2: The mixed solution was heated and stirred on a heating mantle, and the temperature was raised to 148°C and kept at this temperature for 3 hours. After that, the toluene vapor in the system was released and the temperature was raised to 180°C. The temperature was slowly raised to 190°C within 2 hours. The obtained reaction solution was poured into pure water and stirred to precipitate the poly(arylene ether nitrile) solid material.

[0040] S3: The poly(arylene ether nitrile) solid material was crushed, immersed in a 0.2 mol / L hydrochloric acid solution for 24 h, filtered, and washed several times with pure water until neutral; the washed powder was dried in a vacuum oven for 24 h to obtain a purified sample, i.e., the poly(arylene ether nitrile) copolymer.

[0041] S4: The obtained polyarylene ether nitrile copolymer is mixed with solvent N-methylpyrrolidone in a ratio of 2g:20mL, and mechanically stirred for 2 hours to obtain a copolymer hot solution; the copolymer hot solution is formed into a film by a casting method, and the film is kept at 80°C, 100°C, 120°C, and 160°C for 1 hour, respectively, and then kept at 200°C for 2 hours to obtain a polyarylene ether nitrile copolymer film.

[0042] Example 3

[0043] S1: 29.0356 g of bisphenol AP, 35.041 g of bisphenol fluorene, 34.6729 g of 2,6-dichlorobenzonitrile, and 38.6974 g of potassium carbonate were added to a three-necked flask equipped with a stirring rod, a thermometer, a condenser, and a water separator to obtain a mixed powder; 152 mL of N-methylpyrrolidone and 51 mL of toluene were poured into the three-necked flask containing the mixed powder to obtain a mixed solution.

[0044] S2: The mixed solution was heated and stirred on a heating mantle, and the temperature was raised to 152°C and kept at this temperature for 3 hours. After that, the toluene vapor in the system was released and the temperature was raised to 180°C. The temperature was slowly raised to 190°C within 2 hours. The obtained reaction solution was poured into pure water and stirred to precipitate the poly(arylene ether nitrile) solid material.

[0045] S3: The poly(arylene ether nitrile) solid material was crushed, immersed in a 0.2 mol / L hydrochloric acid solution for 24 h, filtered, and washed several times with pure water until neutral; the washed powder was dried in a vacuum oven for 24 h to obtain a purified sample, i.e., the poly(arylene ether nitrile) copolymer.

[0046] S4: The obtained polyarylene ether nitrile copolymer is mixed with solvent N-methylpyrrolidone in a ratio of 2g:20mL, and mechanically stirred for 2 hours to obtain a copolymer hot solution; the copolymer hot solution is formed into a film by a casting method, and the film is kept at 80°C, 100°C, 120°C, and 160°C for 1 hour, respectively, and then kept at 200°C for 2 hours to obtain a polyarylene ether nitrile copolymer film.

[0047] Example 4

[0048] S1: 34.8427 g of bisphenol AP, 28.0328 g of bisphenol fluorene, 34.6729 g of 2,6-dichlorobenzonitrile, and 38.6974 g of potassium carbonate were added to a three-necked flask equipped with a stirring rod, a thermometer, a condenser, and a water separator to obtain a mixed powder; 105 mL of N-methylpyrrolidone and 35 mL of toluene were poured into the three-necked flask containing the mixed powder to obtain a mixed solution.

[0049] S2: The mixed solution was heated and stirred on a heating mantle, and the temperature was raised to 148°C and kept at this temperature for 3 hours. After that, the toluene vapor in the system was released and the temperature was raised to 180°C. The temperature was slowly raised to 190°C within 2 hours. The obtained reaction solution was poured into pure water and stirred to precipitate the poly(arylene ether nitrile) solid material.

[0050] S3: The poly(arylene ether nitrile) solid material was crushed, immersed in a 0.2 mol / L hydrochloric acid solution for 24 h, filtered, and washed several times with pure water until neutral; the washed powder was dried in a vacuum oven for 24 h to obtain a purified sample, i.e., the poly(arylene ether nitrile) copolymer.

[0051] S4: The obtained polyarylene ether nitrile copolymer is mixed with solvent N-methylpyrrolidone in a ratio of 2g:20mL, and mechanically stirred for 2 hours to obtain a copolymer hot solution; the copolymer hot solution is formed into a film by a casting method, and the film is kept at 80°C, 100°C, 120°C, and 160°C for 1 hour, respectively, and then kept at 200°C for 2 hours to obtain a polyarylene ether nitrile copolymer film.

[0052] Example 5

[0053] S1: 37.1655 g of bisphenol AP, 11.2131 g of bisphenol fluorene, 27.7383 g of 2,6-dichlorobenzonitrile, and 30.959 g of potassium carbonate were added to a three-necked flask equipped with a stirring rod, a thermometer, a condenser, and a water separator to obtain a mixed powder; 99 mL of N-methylpyrrolidone and 33 mL of toluene were poured into the three-necked flask containing the mixed powder to obtain a mixed solution.

[0054] S2: The mixed solution was heated and stirred on a heating mantle, and the temperature was raised to 150°C for constant temperature reaction for 3 hours. After that, the toluene vapor in the system was released and the temperature was raised to 180°C. The temperature was slowly raised to 190°C within 2 hours. The obtained reaction solution was poured into pure water and stirred to precipitate the poly(arylene ether nitrile) solid material;

[0055] S3: The poly(arylene ether nitrile) solid material was crushed, immersed in a 0.2 mol / L hydrochloric acid solution for 24 h, filtered, and washed several times with pure water until neutral; the washed powder was dried in a vacuum oven for 24 h to obtain a purified sample, i.e., the poly(arylene ether nitrile) copolymer.

[0056] S4: The obtained polyarylene ether nitrile copolymer is mixed with solvent N-methylpyrrolidone in a ratio of 2g:20mL, and mechanically stirred for 2 hours to obtain a copolymer hot solution; the copolymer hot solution is formed into a film by a casting method, and the film is kept at 80°C, 100°C, 120°C, and 160°C for 1 hour, respectively, and then kept at 200°C for 2 hours to obtain a polyarylene ether nitrile copolymer film.

[0057] In order to further demonstrate the beneficial effects of the present invention and to better understand the present invention, the following comparative examples are provided to further illustrate the technical features disclosed in the present invention, but they should not be construed as limiting the present invention. Other improvements made by those skilled in the art based on the above invention without inventive work are also considered to fall within the scope of protection of the present invention.

[0058] Comparative Example 1

[0059] S1: Add 42.0492 g of bisphenol fluorene, 34.6729 g of 2,6-dichlorobenzonitrile, and 38.6974 g of potassium carbonate to a three-necked flask equipped with a stirring rod, a thermometer, a condenser, and a water separator to obtain a mixed powder; pour 97 mL of N-methylpyrrolidone and 32 mL of toluene into the three-necked flask containing the mixed powder to obtain a mixed solution.

[0060] S2: The mixed solution was heated and stirred on a heating mantle, and the temperature was raised to 150°C for constant temperature reaction for 3 hours. After that, the toluene vapor in the system was released and the temperature was raised to 180°C. The temperature was slowly raised to 190°C within 2 hours. The obtained reaction solution was poured into pure water and stirred to precipitate the poly(arylene ether nitrile) solid material;

[0061] S3: The poly(arylene ether nitrile) solid material was crushed, immersed in a 0.2 mol / L hydrochloric acid solution for 24 h, filtered, and washed several times with pure water until neutral; the washed powder was dried in a vacuum oven for 24 h to obtain a purified sample, i.e., the poly(arylene ether nitrile) copolymer.

[0062] S4: The obtained polyarylene ether nitrile copolymer is mixed with solvent N-methylpyrrolidone in a ratio of 2g:20mL, and mechanically stirred for 2 hours to obtain a copolymer hot solution; the copolymer hot solution is formed into a film by a casting method, and the film is kept at 80°C, 100°C, 120°C, and 160°C for 1 hour, respectively, and then kept at 200°C for 2 hours to obtain a polyarylene ether nitrile film.

[0063] Comparative Example 2

[0064] S1: 34.84 g of bisphenol AP, 34.6729 g of 2,6-dichlorobenzonitrile, and 38.6974 g of potassium carbonate were added to a three-necked flask equipped with a stirring rod, a thermometer, a condenser, and a water separator to obtain a mixed powder; 86 mL of N-methylpyrrolidone and 29 mL of toluene were poured into the three-necked flask containing the mixed powder to obtain a mixed solution.

[0065] S2: The mixed solution was heated and stirred on a heating mantle, and the temperature was raised to 144°C and kept at this temperature for 3 hours. After that, the toluene vapor in the system was released and the temperature was raised to 180°C. The temperature was slowly raised to 190°C within 2 hours. The obtained reaction solution was poured into pure water and stirred to precipitate the poly(arylene ether nitrile) solid material.

[0066] S3: The poly(arylene ether nitrile) solid material was crushed, immersed in a 0.2 mol / L hydrochloric acid solution for 24 h, filtered, and washed several times with pure water until neutral; the washed powder was dried in a vacuum oven for 24 h to obtain a purified sample, i.e., the poly(arylene ether nitrile) copolymer.

[0067] S4: The obtained polyarylene ether nitrile copolymer is mixed with solvent N-methylpyrrolidone in a ratio of 2g:20mL, and mechanically stirred for 2 hours to obtain a copolymer hot solution; the copolymer hot solution is formed into a film by a casting method, and the film is kept at 80°C, 100°C, 120°C, and 160°C for 1 hour, respectively, and then kept at 200°C for 2 hours to obtain a polyarylene ether nitrile film.

[0068] The performance test of the poly(arylene ether nitrile) films obtained in Examples 1 to 5 and Comparative Examples 1 to 2 was conducted to verify the superior effect of the technology of the present invention compared with the prior art. The specific experimental content and experimental analysis are as follows:

[0069] like Figure 1 Shown is the structural formula of the synthesized poly(arylene ether nitrile) copolymer.

[0070] like Figure 2 As shown, compared with Comparative Example 2, the glass transition temperature of the poly(arylene ether nitrile) copolymer increases from 202° C. in Example 5 to 254° C. in Example 1, showing excellent heat resistance.

[0071] like Figure 3 As shown, compared with Comparative Example 2, the 5% decomposition temperature of the poly(arylene ether nitrile) copolymer increases from 512.86° C. in Example 5 to 517.82° C. in Example 1, and the thermal stability is improved.

[0072] like Figure 4 As shown, compared with Comparative Example 1, the dielectric constant of the poly(arylene ether nitrile) copolymer at 1 kHz is reduced to between 3.41 and 3.55, which is attributed to the introduction of the low dielectric bisphenol monomer bisphenol AP.

[0073] like Figure 5 As shown, the tensile strength and tensile modulus of the poly(arylene ether nitrile) copolymer are maintained above 65 MPa and 1800 MPa, respectively. The film has both high tensile strength and appropriate tensile modulus, ensuring its load-bearing capacity and deformation adaptability.

[0074] The above description of the disclosed embodiments is intended to enable one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be readily apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention is not limited to the embodiments shown herein but is intended to conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing a heat-resistant, fluorine-free, low-dielectric poly(arylene ether nitrile) copolymer film, characterized in that: The following steps are involved: S1: Synthesis of poly(arylene ether nitrile) copolymers with different molar ratios; S2: The poly(arylene ether nitrile) copolymer obtained in S1 was mixed with N-methylpyrrolidone and stirred on a heating mantle equipped with a mechanical stirrer for 2 h to obtain a hot solution of the copolymer; S3: The copolymer hot solution obtained in S2 is formed into a film by a casting method, and then the solvent is removed by gradient temperature increase to obtain a copolymer film.

2. The preparation method according to claim 1, characterized in that In S1, the ratio of the molar number m of bisphenol AP to the molar number n of bisphenol fluorene in the polyarylene ether nitrile copolymer is m:n=0-100:100-0, wherein m+n=100.

3. The preparation method according to claim 1 or 2, characterized in that In S1, the steps for synthesizing the poly(arylene ether nitrile) copolymer are as follows: 1.1 In a three-necked flask equipped with a mechanical stirrer, a water separator, a thermometer, and a condenser reflux apparatus, bisphenol AP, bisphenol fluorene, and 2,6-dichlorobenzonitrile in a predetermined ratio were added as reactants, and potassium carbonate was added as a catalyst to obtain a mixture powder; 1.2 Add the mixture powder obtained in step 1.1 to a mixed solvent of N-methylpyrrolidone and toluene to obtain a mixed solution; 1.3 The mixed solution obtained in step 1.2 is heated and reacted at a constant temperature, followed by dehydration. The obtained reaction solution is poured into pure water and stirred to precipitate a poly(arylene ether nitrile) solid material; 1.4 The poly(arylene ether nitrile) solid material obtained in step 1.3 is crushed, immersed in a hydrochloric acid solution, filtered and repeatedly washed with pure water until neutral; the washed powder is dried to obtain the poly(arylene ether nitrile) copolymer.

4. The preparation method according to claim 3, characterized in that In step 1.1, the molar ratio of the total molar amount of bisphenol AP and bisphenol fluorene to 2,6-dichlorobenzonitrile and potassium carbonate is (0.12-0.2):(0.121-0.202):(0.168-0.28).

5. The preparation method according to claim 3, characterized in that In step 1.2, the volume ratio of N-methylpyrrolidone and toluene in the mixed solvent is (2.96-3):

1.

6. The preparation method according to claim 3, characterized in that In step 1.3, the reaction temperature is raised to 144°C to 150°C, and the reaction time is 3 hours; and the dehydration operation is as follows: after the dehydration temperature is raised to 180°C, it is slowly raised to 190°C within 2 hours.

7. The preparation method according to claim 3, characterized in that In step 1.4, the concentration of the hydrochloric acid solution is 0.2 mol / L, and the soaking time is 24 h.

8. The preparation method according to claim 1, characterized in that In S2, the ratio of the poly(arylene ether nitrile) copolymer to N-methylpyrrolidone is 2 g:20 mL.

9. The preparation method according to claim 1, characterized in that In S3, the gradient heating process is: keeping warm at 80°C, 100°C, 120°C, and 160°C for 1 hour respectively, and then keeping warm at 200°C for 2 hours.

10. A heat-resistant, fluorine-free, low-dielectric poly(arylene ether nitrile) copolymer film prepared by the method of claim 1.

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