Fluorine-containing polyamide acid and polyimide film based on sequence regulation and control and preparation method of fluorine-containing polyamide acid and polyimide film

Abstract

The invention provides a fluorine-containing polyamide acid based on sequence regulation, a polyimide film and a preparation method thereof, and relates to the field of materials. The preparation method comprises the following steps: carrying out a first polycondensation reaction on first diamine and first dianhydride to obtain a fluorine-free polyamide acid short chain; carrying out second polycondensation reaction on the fluorine-free polyamide acid short chain and second diamine and / or second dianhydride; or second diamine and second dianhydride are subjected to a third polycondensation reaction to obtain a fluorine-containing polyamide acid short chain, and then the fluorine-free polyamide acid short chain and one or more of the fluorine-containing polyamide acid short chain, the second diamine and the second dianhydride are subjected to a fourth polycondensation reaction. According to the preparation method, the ratio of first diamine to first dianhydride is controlled, the length of a fluorine-free polyamide acid short chain is adjusted, and then fluorine-containing second diamine and fluorine-containing second dianhydride are matched, so that the content of a fluorine-containing monomer in a polymer and a dispersion or aggregation distribution mode are regulated and controlled; finally, the design of the polyamide acid and polyimide film with target mechanical properties and optical properties is realized.

Description

Technical Field

[0001] The present application relates to the field of materials, and in particular to a fluorine-containing polyamic acid and polyimide film based on sequence regulation and a preparation method thereof. Background Art

[0002] Adding a certain proportion of fluorinated monomers to the synthetic polyimide can effectively improve the optical properties of the material; however, too high a proportion of fluorinated monomers will cause a significant decrease in the mechanical properties of the polyimide: on the one hand, fluorinated monomers will weaken the CTC effect between polyimide molecular chains, reduce the accumulation of molecular chains, reduce visible light absorption, and increase light transmittance; on the other hand, fluorinated monomers will weaken the molecular conjugation effect, destroy the rigid structure in the molecular chain, and lead to a decrease in mechanical properties. In the past, the regulation of performance was mostly focused on changing the feeding ratio of monomers, which was a rough method with poor results, obvious performance loss, and a loss of one thing for another.

[0003] Developing a method that can comprehensively optimize the performance of polyimide while keeping the overall monomer ratio roughly unchanged has become a new direction for performance regulation. Summary of the invention

[0004] The purpose of the present application is to provide a fluorinated polyamic acid, polyimide film and a preparation method thereof based on sequence regulation to solve the above-mentioned problems.

[0005] To achieve the above objectives, this application adopts the following technical solutions:

[0006] A method for preparing fluorinated polyamic acid based on sequence regulation, comprising:

[0007] Carrying out a first polycondensation reaction on the first diamine and the first dianhydride to form a fluorine-free polyamic acid short chain terminated with dianhydride or diamine;

[0008] The fluorine-free polyamic acid short chain is subjected to a second polycondensation reaction with a second diamine and / or a second dianhydride to obtain the fluorine-containing polyamic acid based on sequence regulation; or, the second diamine and the second dianhydride are subjected to a third polycondensation reaction to obtain a fluorine-containing polyamic acid short chain, and then the fluorine-free polyamic acid short chain is subjected to a fourth polycondensation reaction with one or more of the fluorine-containing polyamic acid short chain, the second diamine, and the second dianhydride to obtain the fluorine-containing polyamic acid based on sequence regulation;

[0009] Wherein, at least one of the second diamine and the second dianhydride participating in the second polycondensation reaction contains fluorine.

[0010] Preferably, the preparation method of fluorinated polyamic acid based on sequence regulation satisfies at least one of the following conditions:

[0011] A. the first diamine comprises a fluorine-free substituted aromatic diamine monomer or an aliphatic diamine monomer;

[0012] B. the first dianhydride comprises a fluorine-free substituted aromatic dianhydride monomer or an aliphatic dianhydride monomer;

[0013] C. the second diamine comprises an aromatic trifluoromethyl diamine monomer;

[0014] D. The second dianhydride includes an aromatic hexafluorodianhydride monomer.

[0015] Preferably, the preparation method of fluorinated polyamic acid based on sequence regulation satisfies at least one of the following conditions:

[0016] E. The first diamine includes one or more of 1,4-diaminobenzene, 4,4'-diaminobiphenyl, 4,4-diaminodiphenyl ether, 4,4'-diaminobenzophenone, 4,4'-diaminodiphenyl ether diphenyl sulfone, 4,4'-diaminodiphenyl ether bisphenol A, 2,2'-dimethyl-4,4'-diaminobiphenyl, 4,4'-diaminodicyclohexylmethane, and 1,4-cyclohexanediamine;

[0017] F. The first dianhydride comprises one or more of cyclobutanetetracarboxylic dianhydride, 1,2,3,4-cyclopentanetetracarboxylic dianhydride, cis-1,2,3,4-cyclopentanetetracarboxylic dianhydride, 1,2,4,5-cyclohexanetetracarboxylic dianhydride, bicyclo (2.2.2) oct-7-ene-2,3,5,6-tetracarboxylic dianhydride, 2,3,3',4'-diphenyl ether tetracarboxylic dianhydride, 4-(2,5-dioxotetrahydrofuran-3-yl)-1,2,3,4-tetrahydronaphthalene-1,2-dicarboxylic dianhydride, 4,4'-phenylenedioxydiphthalic anhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride, 1,2,4,5-pyromellitic dianhydride, and 3,3',4,4'-benzophenonetetracarboxylic dianhydride;

[0018] G. The second diamine includes one or more of 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl, 2,2'-bis(trifluoromethyl)-4,4'-diaminophenyl ether, 2,2-bis(3-aminophenyl)hexafluoropropane, and 4,4'-[1,4-phenylbis(oxy)]bis[3-(trifluoromethyl)aniline];

[0019] H. The second dianhydride includes one or more of 2,2'-bis(3,4-dicarboxylic acid)hexafluoropropane dianhydride and 9,9-bis(trifluoromethyl)xanthenetetracarboxylic acid dianhydride.

[0020] Preferably, the preparation method of fluorinated polyamic acid based on sequence regulation satisfies at least one of the following conditions:

[0021] I. the ratio of the total molar amount of the first dianhydride and the second dianhydride to the total molar amount of the first diamine and the second diamine is 1:(0.85-1.15);

[0022] J. When preparing the fluorine-free polyamic acid short chain terminated with dianhydride, the molar ratio of the first dianhydride to the first diamine is 1:(0.5-0.95);

[0023] K. When preparing the fluorine-free polyamic acid short chain terminated with diamine, the molar ratio of the first dianhydride to the first diamine is 1:(1.05-2).

[0024] Preferably, the preparation method of fluorinated polyamic acid based on sequence regulation satisfies at least one of the following conditions:

[0025] (1) The organic solvents used in the first polycondensation reaction and the second polycondensation reaction independently include one or more of N-methylpyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide, and dimethyl sulfoxide;

[0026] (2) After the first polycondensation reaction is completed, the solid content of the system is 5%-20%;

[0027] (3) After the second polycondensation reaction is completed, the solid content of the system is 10%-25%;

[0028] (4) The temperature of the first polycondensation reaction and the second polycondensation reaction are independently -5°C to 25°C, and the time is independently 4-48 hours;

[0029] (5) Before use, the first diamine, the first dianhydride, the second diamine and the second dianhydride are vacuum dried at 50-200° C. for 12-24 h with a vacuum degree of 0.1-1000 Pa.

[0030] The present application also provides a fluorinated polyamic acid based on sequence regulation, which is prepared using the preparation method of the fluorinated polyamic acid based on sequence regulation.

[0031] The present application also provides a polyimide film, the raw materials of which include the fluorine-containing polyamic acid based on sequence regulation.

[0032] Preferably, the polyimide film has a thickness of 5-150 μm.

[0033] The present application also provides a method for preparing the polyimide film, comprising:

[0034] The polyimide film is prepared by subjecting the sequence-regulated fluorine-containing polyamic acid to a thermal cyclization reaction.

[0035] Preferably, the temperature raising program of the thermal cyclization reaction comprises:

[0036] The temperature was raised in a step-by-step manner starting from room temperature at a heating rate of 1-10°C per minute. The target temperature platforms were set to 80-100°C, 120-150°C, 180-200°C, and 250-350°C, respectively. The residence time of each temperature platform was set to 0.5-3h, and the cooling rate was controlled to 1-5°C per minute.

[0037] Compared with the prior art, the beneficial effects of this application include:

[0038] The preparation method of fluorinated polyamic acid based on sequence regulation provided in the present application first prepares a fluorinated short chain of polyamic acid, and then forms a long chain by reacting with fluorinated diamines and dianhydrides; in this process, by controlling the overall unchanged ratio of diamine dianhydride monomers and fluorinated monomers therein, the length of the fluorinated short chain of polyamic acid can be adjusted to achieve the effect of aggregation or dispersion by embedding the fluorinated monomers in the polyamic acid long chain at a certain distance. Based on the study of the aggregation or dispersion effect and mechanical and optical properties, it is found that when the fluorinated monomers are aggregated under a fixed ratio of fluorinated monomers, the optical properties of polyimide are significantly improved; and when the fluorinated monomers are dispersed, the mechanical properties of polyimide are significantly improved. Under this method, according to the needs of the optical and mechanical properties of the material, the target material can be obtained more conveniently through the design of fluorinated dispersion or fluorinated aggregation. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope of the present application.

[0040] Figure 1 A schematic diagram of the control strategy of the preparation method of fluorinated polyamic acid based on sequence control provided in this application;

[0041] Figure 2 is a comparison chart of the tensile strength of the polyimide films obtained in various embodiments and comparative examples;

[0042] Figure 3 A comparison chart of the elongation at break of the polyimide films obtained in each embodiment and comparative example;

[0043] Figure 4 is a comparison chart of the modulus of the polyimide films obtained in various embodiments and comparative examples;

[0044] Figure 5 It is a comparison chart of the light transmittance of the polyimide films obtained in various embodiments and comparative examples;

[0045] Figure 6 It is a color comparison diagram of the polyimide films obtained in various embodiments and comparative examples;

[0046] Figure 7 This is a simulated diagram of the distribution of fluorinated monomers (10%) in the chain segments during the synthesis based on sequence regulation;

[0047] Figure 8 This is a simulation diagram of the distribution of fluorinated monomer (10%) in the chain segments during random copolymerization. DETAILED DESCRIPTION

[0048] In order to better explain the technical solution provided by this application, before the embodiments, the technical solution is first described as a whole, as follows:

[0049] A method for preparing fluorinated polyamic acid based on sequence regulation, comprising:

[0050] Carrying out a first polycondensation reaction on the first diamine and the first dianhydride to form a fluorine-free polyamic acid short chain terminated with dianhydride or diamine;

[0051] The fluorine-free polyamic acid short chain is subjected to a second polycondensation reaction with a second diamine and / or a second dianhydride to obtain the fluorine-containing polyamic acid based on sequence regulation; or, the second diamine and the second dianhydride are subjected to a third polycondensation reaction to obtain a fluorine-containing polyamic acid short chain, and then the fluorine-free polyamic acid short chain is subjected to a fourth polycondensation reaction with one or more of the fluorine-containing polyamic acid short chain, the second diamine, and the second dianhydride to obtain the fluorine-containing polyamic acid based on sequence regulation;

[0052] Wherein, at least one of the second diamine and the second dianhydride participating in the second polycondensation reaction contains fluorine.

[0053] The method provided by this application, sequence regulation such as Figure 1 shown.

[0054] Both the first reaction and the second reaction are carried out under a protective atmosphere, for example, a nitrogen atmosphere.

[0055] In an optional embodiment, the preparation method of fluorinated polyamic acid based on sequence regulation satisfies at least one of the following conditions:

[0056] A. the first diamine comprises a fluorine-free substituted aromatic diamine monomer or an aliphatic diamine monomer;

[0057] B. the first dianhydride comprises a fluorine-free substituted aromatic dianhydride monomer or an aliphatic dianhydride monomer;

[0058] C. the second diamine comprises an aromatic trifluoromethyl diamine monomer;

[0059] D. The second dianhydride includes an aromatic hexafluorodianhydride monomer.

[0060] In an optional embodiment, the preparation method of fluorinated polyamic acid based on sequence regulation satisfies at least one of the following conditions:

[0061] E. The first diamine includes one or more of 1,4-diaminobenzene, 4,4'-diaminobiphenyl, 4,4-diaminodiphenyl ether, 4,4'-diaminobenzophenone, 4,4'-diaminodiphenyl ether diphenyl sulfone, 4,4'-diaminodiphenyl ether bisphenol A, 2,2'-dimethyl-4,4'-diaminobiphenyl, 4,4'-diaminodicyclohexylmethane, and 1,4-cyclohexanediamine;

[0062] F. The first dianhydride comprises one or more of cyclobutanetetracarboxylic dianhydride, 1,2,3,4-cyclopentanetetracarboxylic dianhydride, cis-1,2,3,4-cyclopentanetetracarboxylic dianhydride, 1,2,4,5-cyclohexanetetracarboxylic dianhydride, bicyclo (2.2.2) oct-7-ene-2,3,5,6-tetracarboxylic dianhydride, 2,3,3',4'-diphenyl ether tetracarboxylic dianhydride, 4-(2,5-dioxotetrahydrofuran-3-yl)-1,2,3,4-tetrahydronaphthalene-1,2-dicarboxylic dianhydride, 4,4'-phenylenedioxydiphthalic anhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride, 1,2,4,5-pyromellitic dianhydride, and 3,3',4,4'-benzophenonetetracarboxylic dianhydride;

[0063] G. The second diamine includes one or more of 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl, 2,2'-bis(trifluoromethyl)-4,4'-diaminophenyl ether, 2,2-bis(3-aminophenyl)hexafluoropropane, and 4,4'-[1,4-phenylbis(oxy)]bis[3-(trifluoromethyl)aniline];

[0064] H. The second dianhydride includes one or more of 2,2'-bis(3,4-dicarboxylic acid)hexafluoropropane dianhydride and 9,9-bis(trifluoromethyl)xanthenetetracarboxylic acid dianhydride.

[0065] In an optional embodiment, the preparation method of fluorinated polyamic acid based on sequence regulation satisfies at least one of the following conditions:

[0066] I. the ratio of the total molar amount of the first dianhydride and the second dianhydride to the total molar amount of the first diamine and the second diamine is 1:(0.85-1.15);

[0067] Optionally, the ratio of the total molar amount of the first dianhydride and the second dianhydride to the total molar amount of the first diamine and the second diamine can be 1:0.85, 1:0.90, 1:0.95, 1:1, 1:1.05, 1:1.10, 1:1.15 or any value between 1:(0.85-1.15);

[0068] J. When preparing the fluorine-free polyamic acid short chain terminated with dianhydride, the molar ratio of the first dianhydride to the first diamine is 1:(0.5-0.95);

[0069] Optionally, when preparing the fluorine-free polyamic acid short chain terminated with dianhydride, the molar ratio of the first dianhydride to the first diamine can be 1:0.50, 1:0.55, 1:0.60, 1:0.65, 1:0.70, 1:0.75, 1:0.80, 1:0.85, 1:0.90, 1:0.95 or any value between 1:(0.5-0.95);

[0070] K. When preparing the fluorine-free polyamic acid short chain terminated with diamine, the molar ratio of the first dianhydride to the first diamine is 1:(1.05-2).

[0071] Optionally, when preparing the fluorine-free polyamic acid short chain terminated with diamine, the molar ratio of the first dianhydride to the first diamine can be 1:1.05, 1:1.10, 1:1.15, 1:2 or any value between 1:(1.05-2).

[0072] In an optional embodiment, the preparation method of fluorinated polyamic acid based on sequence regulation satisfies at least one of the following conditions:

[0073] (1) The organic solvents used in the first polycondensation reaction and the second polycondensation reaction independently include one or more of N-methylpyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide, and dimethyl sulfoxide; preferably N,N-dimethylacetamide;

[0074] The organic solvent needs to be dehydrated before use;

[0075] (2) After the first polycondensation reaction is completed, the solid content of the system is 5%-20%, preferably 15%-20%;

[0076] Optionally, after the first polycondensation reaction is completed, the solid content of the system can be 5%, 10%, 15%, 20% or any value between 5% and 20%;

[0077] (3) After the second polycondensation reaction is completed, the solid content of the system is 10%-25%, preferably 10%-15%;

[0078] Optionally, after the second polycondensation reaction is completed, the solid content of the system can be 10%, 15%, 20%, 25% or any value between 10% and 25%;

[0079] (4) The temperature of the first polycondensation reaction and the second polycondensation reaction are independently -5°C to 25°C, and the time is independently 4-48 hours;

[0080] Optionally, the temperature of the first polycondensation reaction and the second polycondensation reaction can be independently -5°C, 0°C, 5°C, 10°C, 15°C, 20°C, 25°C or any value between -5°C and 25°C, and the time can be independently 4h, 6h, 10h, 16h, 20h, 24h, 30h, 36h, 40h, 42h, 48h or any value between 4-48h;

[0081] (5) Before use, the first diamine, the first dianhydride, the second diamine and the second dianhydride are vacuum dried at 50-200° C. for 12-24 h with a vacuum degree of 0.1-1000 Pa.

[0082] Optionally, before use, the first diamine, the first dianhydride, the second diamine and the second dianhydride are vacuum dried for 12 h, 18 h, 24 h or any time between 12 and 24 h at 50°C, 100°C, 150°C, 200°C or any temperature between 50-200°C, and the vacuum degree can be 0.1 Pa, 1 Pa, 10 Pa, 100 Pa, 500 Pa, 1000 Pa or any value between 0.1 and 1000 Pa.

[0083] The present application also provides a fluorinated polyamic acid based on sequence regulation, which is prepared using the preparation method of the fluorinated polyamic acid based on sequence regulation.

[0084] The present application also provides a polyimide film, the raw material of which includes the fluorine-containing polyamic acid based on sequence regulation.

[0085] In an optional embodiment, the polyimide film has a thickness of 5-150 μm.

[0086] Optionally, the thickness of the polyimide film can be 5 μm, 10 μm, 20 μm, 30 μm, 40 μm, 50 μm, 60 μm, 70 μm, 80 μm, 90 μm, 100 μm, 110 μm, 120 μm, 130 μm, 140 μm, 150 μm or any value between 5 and 150 μm.

[0087] The present application also provides a method for preparing the polyimide film, comprising:

[0088] The polyimide film is prepared by subjecting the sequence-regulated fluorine-containing polyamic acid to a thermal cyclization reaction.

[0089] In an alternative embodiment, the temperature raising program of the thermal cyclization reaction comprises:

[0090] The temperature is raised in a step-by-step manner starting from room temperature at a heating rate of 1-10°C per minute (which may be 1°C per minute, 2°C per minute, 3°C per minute, 4°C per minute, 5°C per minute, 6°C per minute, 7°C per minute, 8°C per minute, 9°C per minute, 10°C per minute or any value between 1-10°C per minute). The target temperature platforms are set to 80-100°C, 120-150°C, 180-200°C, and 250-350°C in sequence. The residence time of each temperature platform is set to 0.5-3h, and the cooling rate is controlled to 1-5°C per minute.

[0091] The embodiments of the present application will be described in detail below in conjunction with specific examples, but it will be appreciated by those skilled in the art that the following examples are only used to illustrate the present application and should not be considered as limiting the scope of the present application. If specific conditions are not specified in the examples, they are carried out according to normal conditions or the conditions recommended by the manufacturer. If the manufacturer is not specified for the reagents or instruments used, they are all conventional products that can be purchased commercially.

[0092] Example 1

[0093] This embodiment provides a fluorinated polyamic acid, and the preparation method thereof is as follows:

[0094] Under nitrogen atmosphere, 10 mmol of 4,4'-diaminodiphenyl ether was added to a round-bottom flask, 35 ml of N,N-dimethylacetamide was added thereto, and the mixture was placed in a constant temperature water bath at 25°C. After the diamine was completely dissolved, 8 mmol of 3,3',4,4'-biphenyltetracarboxylic dianhydride was slowly added, and the mixture was reacted for 3 h in the dark to obtain a diamine-terminated polyamic acid short-chain solution;

[0095] 2 mmol of 2,2'-bis(3,4-dicarboxylic acid)hexafluoropropane dianhydride was added to the solution, and the mixture was reacted for 8 hours in the dark to obtain a fluorinated polyamic acid solution.

[0096] This embodiment also provides a polyimide film, and the preparation method thereof is as follows:

[0097] Take 5g of the above-mentioned fluorinated polyamic acid solution and evenly apply it (specifically, the spin coating is performed by controlling a certain rotation speed of a spin coater to form a film, which is also a way to control the thickness; the same effect can be achieved by a scraper, a coater, etc.) on a clean and smooth silicon wafer or glass plate, and carry out imidization in a vacuum oven. Set the heating program: insulation time 80℃ / 2h, 120℃ / 2h, 200℃ / 2h, 300℃ / 2h, heating rate 5℃ / min, to obtain a polyimide film with a thickness of 50μm.

[0098] Example 2

[0099] This embodiment provides a fluorinated polyamic acid, and the preparation method thereof is as follows:

[0100] Under nitrogen atmosphere, 10 mmol of 4,4'-diaminodiphenyl ether was added to a round-bottom flask, 35 ml of N,N-dimethylacetamide was added thereto, and the mixture was placed in a constant temperature water bath at 25°C. After the diamine was completely dissolved, 7 mmol of 3,3',4,4'-biphenyltetracarboxylic dianhydride was slowly added, and the mixture was reacted for 3 h in the dark to obtain a diamine-terminated polyamic acid short chain solution;

[0101] 2 mmol of 2,2'-bis(3,4-dicarboxylic acid)hexafluoropropane dianhydride and 1 mmol of 3,3',4,4'-biphenyltetracarboxylic dianhydride were added to the solution, and the mixture was reacted for 8 hours in the dark to obtain a fluorinated polyamic acid solution.

[0102] This embodiment also provides a polyimide film, and the preparation method thereof is as follows:

[0103] Take 5g of the above-mentioned fluorinated polyamic acid solution and evenly coat it on a clean and smooth silicon wafer or glass plate, and carry out imidization in a vacuum oven. According to the heating program with a holding time of 80℃ / 2h, 120℃ / 2h, 200℃ / 2h, 300℃ / 2h and a heating rate of 5℃ / min, a polyimide film with a thickness of 50μm is obtained.

[0104] Example 3

[0105] This embodiment provides a fluorinated polyamic acid, and the preparation method thereof is as follows:

[0106] Under nitrogen atmosphere, 10 mmol of 4,4'-diaminodiphenyl ether was added to a round-bottom flask, 35 ml of N,N-dimethylacetamide was added thereto, and the mixture was placed in a constant temperature water bath at 25°C. After the diamine was completely dissolved, 6 mmol of 3,3',4,4'-biphenyltetracarboxylic dianhydride was slowly added, and the mixture was reacted for 3 h in the dark to obtain a diamine-terminated polyamic acid short chain solution;

[0107] 2 mmol of 2,2'-bis(3,4-dicarboxylic acid)hexafluoropropane dianhydride and 2 mmol of 3,3',4,4'-biphenyltetracarboxylic dianhydride were added to the solution, and the mixture was reacted for 8 hours in the dark to obtain a fluorinated polyamic acid solution.

[0108] This embodiment also provides a polyimide film, and the preparation method thereof is as follows:

[0109] Take 5g of the above-mentioned fluorinated polyamic acid solution and evenly coat it on a clean and smooth silicon wafer or glass plate, and carry out imidization in a vacuum oven. According to the heating program with a holding time of 80℃ / 2h, 120℃ / 2h, 200℃ / 2h, 300℃ / 2h and a heating rate of 5℃ / min, a polyimide film with a thickness of 50μm is obtained.

[0110] Example 4

[0111] This embodiment provides a fluorinated polyamic acid, and the preparation method thereof is as follows:

[0112] Under nitrogen atmosphere, 10 mmol of 4,4'-diaminodiphenyl ether was added to a round-bottom flask, 35 ml of N,N-dimethylacetamide was added thereto, and the mixture was placed in a constant temperature water bath at 25°C. After the diamine was completely dissolved, 5 mmol of 3,3',4,4'-biphenyltetracarboxylic dianhydride was slowly added, and the mixture was reacted for 3 h in the dark to obtain a diamine-terminated polyamic acid short chain solution;

[0113] 2 mmol of 2,2'-bis(3,4-dicarboxylic acid)hexafluoropropane dianhydride and 3 mmol of 3,3',4,4'-biphenyltetracarboxylic dianhydride were added to the solution, and the mixture was reacted for 8 hours in the dark to obtain a fluorinated polyamic acid solution.

[0114] This embodiment also provides a polyimide film, and the preparation method thereof is as follows:

[0115] Take 5g of the above-mentioned fluorinated polyamic acid solution and evenly coat it on a clean and smooth silicon wafer or glass plate, and carry out imidization in a vacuum oven. According to the heating program with a holding time of 80℃ / 2h, 120℃ / 2h, 200℃ / 2h, 300℃ / 2h and a heating rate of 5℃ / min, a polyimide film with a thickness of 50μm is obtained.

[0116] Examples 1-4 are synthesis cases where the fluorinated monomers are increasingly aggregated, among which Example 1 is the most dispersed example of the fluorinated monomers.

[0117] Example 5

[0118] This embodiment provides a fluorine-containing polyamic acid (copolymerization of dianhydride-terminated fluorine-free segments and diamine-terminated fluorine-containing segments), the preparation method of which is as follows:

[0119] Under nitrogen atmosphere, 6 mmol of 4,4'-diaminodiphenyl ether was added to a round-bottom flask, and 20 ml of N,N-dimethylacetamide was added thereto. The flask was placed in a constant temperature water bath at 25°C. After the diamine was completely dissolved, 8 mmol of 3,3',4,4'-biphenyltetracarboxylic dianhydride was slowly added. The mixture was reacted for 3 h in the dark to obtain a dianhydride-terminated polyamic acid short-chain solution.

[0120] Under nitrogen atmosphere, 4 mmol of 4,4'-diaminodiphenyl ether was added to a round-bottom flask, 20 ml of N,N-dimethylacetamide was added thereto, and the mixture was placed in a constant temperature water bath at 25°C. After the diamine was completely dissolved, 2 mmol of 2,2'-bis(3,4-dicarboxylic acid)hexafluoropropane dianhydride was slowly added, and the mixture was reacted for 3 h in the dark to obtain a diamine-terminated fluorinated polyamic acid short-chain solution;

[0121] The diamine-terminated fluorinated polyimide short-chain solution was added to the dianhydride-terminated polyamic acid short-chain solution, and the mixture was reacted in the dark for 8 hours to obtain a fluorinated polyamic acid solution.

[0122] This embodiment also provides a polyimide film, and the preparation method thereof is as follows:

[0123] Take 5g of the above-mentioned fluorinated polyamic acid solution and evenly coat it on a clean and smooth silicon wafer or glass plate, and carry out imidization in a vacuum oven. According to the heating program with a holding time of 80℃ / 2h, 120℃ / 2h, 200℃ / 2h, 300℃ / 2h and a heating rate of 5℃ / min, a polyimide film with a thickness of 50μm is obtained.

[0124] Example 6

[0125] This embodiment provides a fluorine-containing polyamic acid (copolymerization of a diamine-terminated fluorine-free segment and a dianhydride-terminated fluorine-containing segment), and the preparation method thereof is as follows:

[0126] Under nitrogen atmosphere, 8 mmol of 4,4'-diaminodiphenyl ether was added to a round-bottom flask, 20 ml of N,N-dimethylacetamide was added thereto, and the mixture was placed in a constant temperature water bath at 25°C. After the diamine was completely dissolved, 6 mmol of 3,3',4,4'-biphenyltetracarboxylic dianhydride was slowly added, and the mixture was reacted for 3 h in the dark to obtain a diamine-terminated polyamic acid short chain solution;

[0127] Under nitrogen atmosphere, 2 mmol of 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl was added to a round-bottom flask, 20 ml of N,N-dimethylacetamide was added thereto, and the mixture was placed in a constant temperature water bath at 25°C. After the diamine was completely dissolved, 4 mmol of 3,3',4,4'-biphenyltetracarboxylic dianhydride was slowly added, and the mixture was reacted for 3 h in the dark to obtain a dianhydride-terminated fluorinated polyamic acid short-chain solution;

[0128] The dianhydride-terminated fluorinated polyimide short-chain solution was added to the diamine-terminated polyamic acid short-chain solution, and the mixture was reacted in the dark for 8 hours to obtain a fluorinated polyamic acid solution.

[0129] This embodiment also provides a polyimide film, and the preparation method thereof is as follows:

[0130] Take 5g of the above-mentioned fluorinated polyamic acid solution and evenly coat it on a clean and smooth silicon wafer or glass plate, and carry out imidization in a vacuum oven. According to the heating program with a holding time of 80℃ / 2h, 120℃ / 2h, 200℃ / 2h, 300℃ / 2h and a heating rate of 5℃ / min, a polyimide film with a thickness of 50μm is obtained.

[0131] Comparative Example 1

[0132] Under nitrogen atmosphere, 10 mmol of 4,4'-diaminodiphenyl ether was added to a round-bottom flask, 35 ml of N,N-dimethylacetamide was added thereto, and the mixture was placed in a constant temperature water bath at 25°C. After the diamine was completely dissolved, 10 mmol of 3,3',4,4'-biphenyltetracarboxylic dianhydride was slowly added, and the mixture was reacted for 3 hours in the dark to obtain a polyamic acid solution;

[0133] Take 5g of polyamic acid solution and evenly coat it on a clean and smooth silicon wafer or glass plate, and carry out imidization in a vacuum oven. According to the heating program of keeping time at 80℃ / 2h, 120℃ / 2h, 200℃ / 2h, 300℃ / 2h and heating rate at 5℃ / min, a polyimide film with a thickness of 50μm is obtained.

[0134] This comparative example is a random copolymerization of fluorine-free monomers. Comparison with Examples 1-4 shows that the addition of fluorine-containing monomers has a weakening effect on mechanical properties: at a fixed fluorine monomer content, the aggregation of fluorine-containing monomers will reduce the tensile strength, while the dispersion will enhance it; while the elongation at break and the modulus are the opposite; in fact, it is a relationship between the local easier to break and the overall easier to deform.

[0135] Comparative Example 2

[0136] Under nitrogen atmosphere, 10 mmol of 4,4'-diaminodiphenyl ether was added to a round-bottom flask, 35 ml of N,N-dimethylacetamide was added thereto, and the mixture was placed in a constant temperature water bath at 25°C. After the diamine was completely dissolved, 8 mmol of 3,3',4,4'-biphenyltetracarboxylic dianhydride and 2 mmol of 2,2'-bis(3,4-dicarboxylic acid)hexafluoropropane dianhydride were slowly added, and the mixture was reacted for 8 hours in the dark to obtain a fluorinated polyamic acid solution;

[0137] Take 5g of fluorinated polyamic acid solution and evenly coat it on a clean and smooth silicon wafer or glass plate, and carry out imidization in a vacuum oven. Set the heating program: holding time 80℃ / 2h, 120℃ / 2h, 200℃ / 2h, 300℃ / 2h, heating rate 5℃ / min, to obtain a polyimide film with a thickness of 50μm.

[0138] This comparative example is a random copolymerization of 10% fluorine-containing monomers. Comparative Example 1-4 shows that this is a case where the fluorine-containing monomers have the highest aggregation degree (fluorine-containing monomers have high activity and react first).

[0139] Comparative Example 3

[0140] Under nitrogen atmosphere, 10 mmol of 4,4'-diaminodiphenyl ether was added to a round-bottom flask, 35 ml of N,N-dimethylacetamide was added thereto, and the mixture was placed in a constant temperature water bath at 25°C. After the diamine was completely dissolved, 2 mmol of 3,3',4,4'-biphenyltetracarboxylic dianhydride and 8 mmol of 2,2'-bis(3,4-dicarboxylic acid)hexafluoropropane dianhydride were slowly added, and the mixture was reacted for 8 hours in the dark to obtain a fluorinated polyamic acid solution;

[0141] Take 5g of fluorinated polyamic acid solution and evenly coat it on a clean and smooth silicon wafer or glass plate, and carry out imidization in a vacuum oven. Set the heating program: holding time 80℃ / 2h, 120℃ / 2h, 200℃ / 2h, 300℃ / 2h, heating rate 5℃ / min, to obtain a polyimide film with a thickness of 50μm.

[0142] This comparative example is a random copolymerization of 40% fluorine-containing monomers. Comparing Examples 1-4, it is demonstrated that the optical properties of the 10% fluorine-containing monomers regulated by aggregation are equal to those of the 40% fluorine-containing monomers randomly copolymerized, but the mechanical properties of the 10% fluorine-containing monomers are better.

[0143] The mechanical and optical properties of polyamic acid cyclized polyimide film were characterized. The main test contents included tensile strength, elongation at break, modulus and transmittance.

[0144] Figure 2 The tensile strength of each embodiment is compared: It can be seen from Examples 1 to 4 and Comparative Example 1 that adding 10% fluorinated monomer (molar ratio) will significantly reduce the tensile strength of the material; this is because the fluorinated monomer weakens the rigid structure of the long chain, and the chain segments are more likely to break at the fluorinated monomer, and the more the fluorinated monomer is aggregated, the greater the possibility of breakage; therefore, under a fixed fluorinated monomer ratio, through sequence regulation, dispersing the fluorinated monomer into the chain segments can effectively reduce the loss of tensile strength, and the higher the dispersion of the fluorinated monomer, the less the loss of tensile strength. Figure 3The elongation at break of each embodiment is compared: It can be seen from Examples 1 to 4 and Comparative Example 1 that the addition of 10% fluorinated monomer (molar ratio) will significantly reduce the elongation at break of the material. Contrary to the change in tensile strength, at a fixed fluorinated monomer ratio, the higher the degree of dispersion of the fluorinated monomer, the greater the loss of elongation at break performance, because the length of the chain segment not containing the fluorinated monomer becomes shorter and the overall resistance to deformation becomes weaker. Figure 4 For the comparison of the modulus of each embodiment, it can be seen from Examples 1 to 4 and Comparative Example 1 that the addition of 10% fluorinated monomer (molar ratio) will significantly reduce the elongation at break of the material. Similarly, at a fixed fluorinated monomer ratio, the higher the dispersion of the fluorinated monomer, the greater the modulus loss, because the length of the chain segment that does not contain the fluorinated monomer becomes shorter, and the overall resistance to deformation becomes weaker. In general, at a fixed fluorinated monomer ratio, the higher the dispersion of the fluorinated monomer, the higher the tensile strength, and the lower the elongation at break and the modulus; the lower the dispersion of the fluorinated monomer, the lower the tensile strength, and the higher the elongation at break and the modulus. This synthesis strategy provides a method for targeted regulation of the mechanical properties of fluorinated monomer polyimide films.

[0145] Figure 5 For the transmittance comparison of each embodiment, adding 10% fluorine-containing monomer (molar ratio) can effectively improve the transmittance of the material and reduce coloration; and under the same fluorine-containing monomer ratio, the fluorine-containing monomer can be aggregated on the chain by sequence regulation. The higher the aggregation degree of the fluorine-containing monomer, the higher the transmittance, the smaller the visible light absorption area, and the better the optical performance. Figure 6 For the color performance of each example, by comparing Examples 1 to 4 with Comparative Example 2, it can be intuitively reflected that the aggregation of fluorinated monomers can effectively reduce coloration; and by comparing Example 4 with Comparative Example 3, it can be seen that thanks to the sequence regulation to form a fluorinated aggregated structure, the 10% fluorinated monomer can be similar to the 40% fluorinated monomer material in chromaticity, and the 10% fluorinated monomer material has better mechanical properties due to the lower fluorine content. In general, this synthesis strategy provides another method to improve the optical properties of polyimide in addition to increasing the proportion of fluorinated monomers.

[0146] Figure 7 , Figure 8 The following are the distribution simulation diagrams of fluorinated monomers in the fluorinated polyamic acid segments synthesized by sequence regulation and random copolymerization, respectively. The green and blue balls represent non-fluorinated monomers, and the red balls represent fluorinated monomers. The reaction model was established through polycondensation kinetics on the Predici software to infer the binding sites and distribution of fluorinated monomers. Since the segment structure of polyamic acid is difficult to measure accurately, the chain length control cannot be accurately verified, but the chain length depends on the feed ratio of dianhydride and diamine and obeys the normal distribution. Therefore, the simulation is only used for side auxiliary verification, and the main argument is still the performance difference of polyimide film.

[0147] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit it. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A method for preparing fluorinated polyamic acid based on sequence regulation, characterized in that: include: Carrying out a first polycondensation reaction on the first diamine and the first dianhydride to form a fluorine-free polyamic acid short chain terminated with dianhydride or diamine; The fluorine-free polyamic acid short chain is subjected to a second polycondensation reaction with a second diamine and / or a second dianhydride to obtain the fluorine-containing polyamic acid based on sequence regulation; or, the second diamine and the second dianhydride are subjected to a third polycondensation reaction to obtain a fluorine-containing polyamic acid short chain, and then the fluorine-free polyamic acid short chain is subjected to a fourth polycondensation reaction with one or more of the fluorine-containing polyamic acid short chain, the second diamine, and the second dianhydride to obtain the fluorine-containing polyamic acid based on sequence regulation; Wherein, at least one of the second diamine and the second dianhydride participating in the second polycondensation reaction contains fluorine.

2. The method for preparing fluorinated polyamic acid based on sequence regulation according to claim 1, characterized in that: At least one of the following conditions is met: A. the first diamine comprises a fluorine-free substituted aromatic diamine monomer or an aliphatic diamine monomer; B. the first dianhydride comprises a fluorine-free substituted aromatic dianhydride monomer or an aliphatic dianhydride monomer; C. the second diamine comprises an aromatic trifluoromethyl diamine monomer; D. The second dianhydride includes an aromatic hexafluorodianhydride monomer.

3. The method for preparing fluorinated polyamic acid based on sequence regulation according to claim 2, characterized in that: At least one of the following conditions is met: E. The first diamine includes one or more of 1,4-diaminobenzene, 4,4'-diaminobiphenyl, 4,4-diaminodiphenyl ether, 4,4'-diaminobenzophenone, 4,4'-diaminodiphenyl ether diphenyl sulfone, 4,4'-diaminodiphenyl ether bisphenol A, 2,2'-dimethyl-4,4'-diaminobiphenyl, 4,4'-diaminodicyclohexylmethane, and 1,4-cyclohexanediamine; F. The first dianhydride comprises one or more of cyclobutanetetracarboxylic dianhydride, 1,2,3,4-cyclopentanetetracarboxylic dianhydride, cis-1,2,3,4-cyclopentanetetracarboxylic dianhydride, 1,2,4,5-cyclohexanetetracarboxylic dianhydride, bicyclo (2.2.2) oct-7-ene-2,3,5,6-tetracarboxylic dianhydride, 2,3,3',4'-diphenyl ether tetracarboxylic dianhydride, 4-(2,5-dioxotetrahydrofuran-3-yl)-1,2,3,4-tetrahydronaphthalene-1,2-dicarboxylic dianhydride, 4,4'-phenylenedioxydiphthalic anhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride, 1,2,4,5-pyromellitic dianhydride, and 3,3',4,4'-benzophenonetetracarboxylic dianhydride; G. The second diamine includes one or more of 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl, 2,2'-bis(trifluoromethyl)-4,4'-diaminophenyl ether, 2,2-bis(3-aminophenyl)hexafluoropropane, and 4,4'-[1,4-phenylbis(oxy)]bis[3-(trifluoromethyl)aniline]; H. The second dianhydride includes one or more of 2,2'-bis(3,4-dicarboxylic acid)hexafluoropropane dianhydride and 9,9-bis(trifluoromethyl)xanthenetetracarboxylic acid dianhydride.

4. The method for preparing fluorinated polyamic acid based on sequence regulation according to claim 3, characterized in that: At least one of the following conditions is met: I. the ratio of the total molar amount of the first dianhydride and the second dianhydride to the total molar amount of the first diamine and the second diamine is 1:(0.85-1.15); J. When preparing the fluorine-free polyamic acid short chain terminated with dianhydride, the molar ratio of the first dianhydride to the first diamine is 1:(0.5-0.95); K. When preparing the fluorine-free polyamic acid short chain terminated with diamine, the molar ratio of the first dianhydride to the first diamine is 1:(1.05-2).

5. The method for preparing fluorinated polyamic acid based on sequence regulation according to any one of claims 1 to 4, characterized in that: At least one of the following conditions is met: (1) The organic solvents used in the first polycondensation reaction and the second polycondensation reaction independently include one or more of N-methylpyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide, and dimethyl sulfoxide; (2) After the first polycondensation reaction is completed, the solid content of the system is 5%-20%; (3) After the second polycondensation reaction is completed, the solid content of the system is 10%-25%; (4) The temperature of the first polycondensation reaction and the second polycondensation reaction are independently -5°C to 25°C, and the time is independently 4-48 hours; (5) Before use, the first diamine, the first dianhydride, the second diamine and the second dianhydride are vacuum dried at 50-200° C. for 12-24 h with a vacuum degree of 0.1-1000 Pa.

6. A fluorinated polyamic acid based on sequence regulation, characterized in that: The polyamide is prepared by the method for preparing fluorinated polyamic acid based on sequence regulation as described in any one of claims 1 to 5.

7. A polyimide film, characterized in that: The raw materials include the fluorine-containing polyamic acid based on sequence regulation as described in claim 6.

8. The polyimide film according to claim 7, characterized in that: The thickness of the polyimide film is 5-150 μm.

9. A method for preparing a polyimide film according to claim 7 or 8, characterized in that: include: The polyimide film is prepared by subjecting the sequence-regulated fluorine-containing polyamic acid to a thermal cyclization reaction.

10. The method for preparing a polyimide film according to claim 9, characterized in that: The temperature raising program of the thermal cyclization reaction comprises: The temperature was raised in a step-by-step manner starting from room temperature at a heating rate of 1-10°C per minute. The target temperature platforms were set to 80-100°C, 120-150°C, 180-200°C, and 250-350°C, respectively. The residence time of each temperature platform was set to 0.5-3h, and the cooling rate was controlled to 1-5°C per minute.

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