End group boric acid cross-linked fluoropolyamide imide film as well as preparation method and application thereof

Abstract

The invention provides a boric acid-terminated cross-linked fluoropolyamide-imide film as well as a preparation method and application thereof, and belongs to the technical field of high polymer materials. The preparation method comprises the following steps: carrying out a reaction on fluorine-containing imide structure-containing diacyl chloride and fluorine-containing diamine to prepare an acyl chloride-terminated fluoropolyamideimide oligomer, then carrying out a reaction on the acyl chloride-terminated fluoropolyamideimide oligomer and 3-aminophenylboronic acid to prepare a phenylboronic acid-terminated fluoropolyamideimide oligomer, and finally carrying out high-temperature heat treatment dehydration condensation to form the end-group boric acid cross-linked fluoropolyamideimide. The polyamide-imide film prepared on the basis of the method shows high light transmittance, low thermal expansion coefficient, high tensile strength and excellent comprehensive performance. Based on the dynamic nature of the borate bond, the film also has reprocessing performance.

Description

Technical Field

[0001] The invention relates to the technical field of polymer materials, and in particular to a terminal boric acid cross-linked fluoropolyamide-imide film and a preparation method and application thereof. Background Art

[0002] As display technology develops towards flexible and foldable, high-performance transparent polymer films show great potential as a substitute for hard glass substrates and cover materials. Polyimide films have attracted great attention due to their excellent thermal properties, mechanical properties and stability. However, traditional polyimide is golden yellow due to the presence of inter-chain and intra-chain charge transfer complexes, which seriously limits its application in the field of optoelectronic displays.

[0003] In order to improve the transmittance of polyimide films, there are three main strategies: the first is to introduce strong electronegative fluorine atoms to inhibit charge transfer; the second is to introduce large side groups or twisted structures to increase chain spacing and simple conjugation; the third is to introduce alicyclic structures to reduce π electrons. The above three methods can effectively make polyimide transparent, but in practical applications, in addition to high transparency, transparent polyimide also requires a low linear thermal expansion coefficient to avoid warping, dislocation and debonding caused by mismatched thermal expansion coefficients when compounded with other inorganic / metallic materials during the preparation process. The above three strategies often weaken the mechanical properties and thermal dimensional stability of transparent polyimide.

[0004] In addition to the five-membered nitrogen heterocyclic structure of polyimide, polyamide-imide also has an amide bond. The introduction of amide bonds is conducive to the formation of hydrogen bonds between molecular chains, which can effectively enhance the mechanical properties of polymers and reduce the thermal expansion coefficient of polymers. At present, the preparation methods of polyamide-imide can be divided into the following three categories: 1) polycondensation of diamine / dianhydride containing amide groups to prepare polyamide-imide; 2) co-condensation of diacid chloride monomers with diamine and dianhydride monomers; 3) dehydration polycondensation of diacids containing imide structures and diamines. In order to ensure excellent thermal and mechanical properties, the molecular weight of polyamide-imide needs to be large enough. The above three methods are all condensation reactions. According to the polymer polymerization theory, in order to ensure high molecular weight, the purity of the monomers involved in the polymerization and the accuracy of the molar ratio of each monomer must be strictly controlled. At the same time, small molecules such as water in the reaction process need to be removed in time through high temperature and high pressure. The above limitations make the control of the polymerization process extremely complicated and difficult to scale up the polymerization.

[0005] Therefore, it is necessary to develop a transparent polyamide-imide film which has an easier polymerization process, excellent mechanical properties and a low thermal expansion coefficient. Summary of the invention

[0006] The present invention aims at the problem that the polymerization process is complicated and difficult to control in the prior art for preparing transparent polyamide-imide with high mechanical properties and low thermal expansion coefficient, and provides a terminal boric acid cross-linked fluoropolyamide-imide film and a preparation method thereof. The method for preparing polyamide-imide can not only avoid the strict control of the monomer feed ratio in polymerization, and the problems of reduced solubility and high system viscosity caused by high polymer molecular weight, but also the prepared film has a low thermal expansion coefficient, high tensile strength and transparency.

[0007] The invention provides a terminal boric acid cross-linked fluoropolyamideimide. The synthesis process of the terminal boric acid cross-linked fluoropolyamideimide is as follows: a fluorine-containing amide-containing diacyl chloride is reacted with a fluorine-containing diamine to obtain an acyl chloride-terminated fluoropolyamideimide oligomer, which is then reacted with 3-aminophenylboric acid to prepare a fluoropolyamideimide oligomer with a terminal phenylboric acid, and finally a high-temperature heat treatment is performed to dehydrate and condense to form the terminal boric acid cross-linked fluoropolyamideimide.

[0008] The present invention also provides a method for preparing a terminal boric acid cross-linked fluoropolyamide-imide film, which comprises the following steps:

[0009] (1) Under a nitrogen environment, a fluorine-containing diamine is dissolved in an anhydrous organic solvent, and a fluorine-containing diacid chloride containing an imide structure is added in an ice bath to react to form a fluorinated polyamide-imide terminated with an acyl chloride, and 3-aminophenylboronic acid is added to continue the reaction to form a fluorinated polyamide-imide with a terminal group of phenylboronic acid; a precipitant is added to the reaction solution to precipitate, and the resin is obtained after washing and drying;

[0010] (2) The resin is dissolved in an anhydrous organic solvent to form a solution, and after forming a film using a film-forming process, a terminal boric acid cross-linked fluoropolyamide-imide film is formed by dehydration condensation through heat treatment.

[0011] Optionally, the structural formula of the fluorinated diamine is at least one of the following or a combination of the following structures:

[0012]

[0013] Optionally, the structural formula of the fluorine-containing and imide-containing diacyl chloride is at least one of the following or a combination of the following structures:

[0014]

[0015] Optionally, the preparation method of the fluorine-containing imide-containing diacyl chloride is: and trimellitic anhydride are added to acetic acid and refluxed at 115°C for 24 hours. The reaction solution is then added to a large amount of ethanol or methanol, the precipitate is collected, and vacuum dried to obtain a diacid monomer containing an imide structure. The diacid monomer containing an imide structure is then reacted with thionyl chloride at 80°C for 4 hours, and the excess thionyl chloride is removed by rotary evaporation to obtain a diacid chloride monomer containing an imide structure.

[0016] Optionally, the molar ratio of the fluorine-containing diamine to the fluorine-containing diacid chloride having an imide structure is 0.8-0.9:1.

[0017] Optionally, the organic solvent includes at least one of N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, dimethyl sulfoxide and cyclopentanone.

[0018] Optionally, the molar ratio of the 3-aminophenylboronic acid to the fluorine-containing and imide-containing diacyl chloride is 0.4-0.8:1.

[0019] Optionally, the heat treatment includes programmed temperature drying and post-programmed temperature heating, the programmed temperature drying comprises the following steps: 50℃-60℃ / 1-2h, 80℃-90℃ / 1-2h, 120℃-130℃ / 1-2h, 150℃-160℃ / 1-2h; the post-programmed temperature heating comprises the following steps: 180℃-190℃ / 1-2h, 210℃-220℃ / 1-2h, 250℃-260℃ / 1-2h, ensuring that the solvent is completely removed and boric acid cross-linked.

[0020] Optionally, the precipitant includes ethanol, water, methanol, etc.

[0021] Optionally, the film forming process includes coating, drying, heat treatment, etc.

[0022] Further, the steps of the preparation method are as follows:

[0023] (1) Under a nitrogen environment, a fluorinated diamine is dissolved by stirring with an anhydrous organic solvent, and a fluorinated diacyl chloride containing an imide structure is added in batches in an ice bath. After the addition is completed, the reaction is first carried out in an ice bath for 2-4 hours, and then at room temperature for 4-12 hours, and then 3-aminophenylboric acid is added, and the reaction is continued at room temperature for 12-24 hours to form a fluoropolyamideimide with a terminal group of phenylboric acid. During the reaction, the solid content is controlled to be 10-20%; after the reaction is completed, it is slowly poured into a mixed solvent of ethanol and water under vigorous stirring to precipitate a white fibrous resin, and vacuum dried;

[0024] (2) The dried resin is dissolved in an anhydrous organic solvent to prepare a solution with a solid content of 10-20 wt%; then poured onto a substrate, coated by a doctor blade, then dried by program heating, and finally placed in a vacuum oven, and then continued to program heating to completely remove the solvent and crosslink. Finally, after the temperature is naturally cooled to room temperature, it is taken out to obtain a terminal boric acid crosslinked fluoropolyamideimide film.

[0025] The thickness of the prepared films ranged from 20 to 50 μm.

[0026] The obtained terminal boric acid cross-linked fluoropolyamideimide film, optionally, the terminal boric acid cross-linked fluoropolyamideimide has the structure shown below:

[0027]

[0028] R1 is the residue of the above-mentioned fluorine-containing imide-containing diacyl chloride, and R2 is the residue of the above-mentioned fluorine-containing diamine.

[0029] The synthetic route of the above-mentioned terminal boric acid cross-linked fluoropolyamide-imide is as follows:

[0030]

[0031] R1 can be selected as R2 can be selected as

[0032] The above-mentioned terminal boric acid cross-linked fluoropolyamide-imide film is used as a transparent layer material for optical devices, and the optical devices include but are not limited to display devices, photoelectric detection devices, etc.

[0033] Compared with the prior art, the present invention has the following beneficial effects:

[0034] (1) The preparation process of the fluoropolyamide-imide in the present invention adopts the reaction of fluorine-containing and imide-containing diacyl chloride with fluorine-containing diamine. The polymerization conditions are mild, and the polymerization of the two is not equimolar. Instead, 3-aminophenylboronic acid is added for end-capping treatment, thereby avoiding the problem of reduced solubility and poor fluidity caused by high molecular weight.

[0035] (2) The present invention ensures transparency by introducing fluorine-containing groups, introduces amide structures through polymerization reactions to enhance the interaction between molecular chains and reduce the thermal expansion coefficient, and caps the film with 3-aminophenylboronic acid and then thermally crosslinks, thereby avoiding the influence of low molecular weight on the mechanical properties of the film.

[0036] (3) The present invention uses phenylboronic acid for end-capping and reheat crosslinking, which avoids the problem of system gelation and difficulty in polymerization and film formation caused by the introduction of traditional multi-functional monomers. At the same time, due to the dynamic nature of the boric acid ester bond, the cross-linked fluoropolyamide-imide film also has the ability to be reprocessed.

[0037] (4) The fluoropolyamideimide of the present invention has high transparency, low thermal expansion and good mechanical properties, and is suitable for use as a transparent layer material for optical devices.

[0038] Other features and advantages of the present invention will be set forth in the following description, and in part will be apparent from the description, or may be learned by practicing the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 This is the thermal expansion curve of the terminal boric acid cross-linked fluoropolyamideimide film prepared in Example 1;

[0040] Figure 2 The stress-strain curve of the terminal boric acid cross-linked fluoropolyamide-imide film prepared in Example 1;

[0041] Figure 3 This is a visible light transmission curve of the terminal boric acid cross-linked fluoropolyamide-imide film prepared in Example 1;

[0042] Figure 4 This is a schematic diagram of the reprocessing of the terminal boric acid cross-linked fluoropolyamideimide film prepared in Example 1. DETAILED DESCRIPTION

[0043] In order to explain the present invention more clearly, the present invention is further described below in conjunction with preferred embodiments. It should be understood by those skilled in the art that the following specific description is illustrative rather than restrictive, and should not be used to limit the scope of protection of the present invention.

[0044] Example 1

[0045] The preparation method of 2,2'-(2,2'-bis(trifluoromethyl)-[1,1'-biphenyl]-4,4'-diyl)bis(1,3-dioxoisoindoline-5-yl chloride) is as follows: 10mmol 4,4'-diamino-2,2'-bistrifluoromethylbiphenyl and 20mmol trimellitic anhydride are added to 60mL glacial acetic acid and refluxed at 115°C for 24 hours. After the system temperature drops to room temperature, it is poured into ethanol, the precipitate is collected, filtered, and repeatedly rinsed with ethanol for 3 times, and finally dried in a vacuum oven at 150°C for 24 hours.

[0046] Under nitrogen, add 4,4'-diamino-2,2'-bis(trifluoromethyl)biphenyl (0.8mmol) to a thoroughly dried three-necked flask, add anhydrous DMAc (9mL), stir magnetically to dissolve, place the flask in an ice bath for 20 minutes, and then add 2,2'-(2,2'-bis(trifluoromethyl)-[1,1'-biphenyl]-4,4'-diyl)bis(1,3-dioxoisoindolin-5-yl chloride) (1mmol) in several portions to ensure the uniformity of the reaction. After the addition is complete, react in an ice bath for 2h and at room temperature for 4h. Then add 3-aminophenylboronic acid (0.4mmol) and react at room temperature for 12h. After the reaction is complete, slowly pour it into a mixed solvent of ethanol and water (1:1) under vigorous stirring to precipitate a white fibrous resin, which is dried at 100℃ for 24h.

[0047] The dried resin was dissolved in DMAc to prepare a 10wt% solution. Then it was slowly poured onto a flat glass plate and coated at a height of 1000 to form a film. Then it was dried at a temperature program of 50℃ / 2h, 80℃ / 1h, 120℃ / 1h, and 150℃ / 1h. Then it was transferred to a vacuum oven preheated to 150℃, and then the solvent was completely removed and cross-linked at 180℃ / 1h, 210℃ / 1h, and 250℃ / 1h. Finally, after it was naturally cooled to room temperature, it was taken out to obtain a terminal boric acid cross-linked fluoropolyamideimide film sample.

[0048] Example 2

[0049] Under nitrogen, add 2,2-bis(4-aminophenyl)hexafluoropropane (0.8mmol) to a thoroughly dried three-necked flask, add anhydrous DMAc (9mL), stir magnetically to dissolve, place the flask in an ice bath for 20min, and then add 2,2'-(2,2'-bis(trifluoromethyl)-[1,1'-biphenyl]-4,4'-diyl)bis(1,3-dioxoisoindolin-5-yl chloride) (1mmol) in several portions to ensure the uniformity of the reaction. After the addition is complete, react in an ice bath for 2h and at room temperature for 4h. Then add 3-aminophenylboronic acid (0.4mmol) and react at room temperature for 12h. After the reaction is complete, slowly pour it into a mixed solvent of ethanol and water (1:1) under vigorous stirring to precipitate a white fibrous resin, which is dried at 100℃ for 24h.

[0050] The dried resin was dissolved in DMAc to prepare a 10wt% solution. Then it was slowly poured onto a flat glass plate and coated at a height of 1000 to form a film. Then it was dried at a temperature program of 50℃ / 2h, 80℃ / 1h, 120℃ / 1h, and 150℃ / 1h. Then it was transferred to a vacuum oven preheated to 150℃, and then the solvent was completely removed and cross-linked at 180℃ / 1h, 210℃ / 1h, and 250℃ / 1h. Finally, after it was naturally cooled to room temperature, it was taken out to obtain a terminal boric acid cross-linked fluoropolyamideimide film sample.

[0051] Example 3

[0052] The preparation method of ((perfluoropropane-2,2-diyl)bis(4,1-phenyl))bis(1,3-dioxoisoindoline-5-yl chloride) is as follows: 10mmol 2,2-bis(4-aminophenyl)hexafluoropropane and 20mmol trimellitic anhydride are added to 60mL glacial acetic acid and refluxed at 115°C for 24 hours. After the system temperature drops to room temperature, it is poured into ethanol, the precipitate is collected, filtered, and repeatedly rinsed with ethanol for 3 times, and finally dried in a vacuum oven at 150°C for 24 hours.

[0053] Under nitrogen, add 2,2-bis(4-aminophenyl)hexafluoropropane (0.8mmol) to a thoroughly dried three-necked flask, add anhydrous DMAc (9mL), stir magnetically to dissolve, place the flask in an ice bath for 20min, and then add 2,2'-((perfluoropropane-2,2-diyl)bis(4,1-phenyl))bis(1,3-dioxoisoindole-5-yl chloride) (1mmol) in several portions to ensure the uniformity of the reaction. After the addition is complete, react in an ice bath for 2h and at room temperature for 4h. Then add 3-aminophenylboronic acid (0.4mmol) and react at room temperature for 12h. After the reaction is complete, slowly pour it into a mixed solvent of ethanol and water (1:1) under vigorous stirring to precipitate a white fibrous resin, which is dried at 100℃ for 24h.

[0054] The dried resin was dissolved in DMAc to prepare a 10wt% solution. Then it was slowly poured onto a flat glass plate and coated at a height of 1000 to form a film. Then it was dried at a temperature program of 50℃ / 2h, 80℃ / 1h, 120℃ / 1h, and 150℃ / 1h. Then it was transferred to a vacuum oven preheated to 150℃, and then the solvent was completely removed and cross-linked at 180℃ / 1h, 210℃ / 1h, and 250℃ / 1h. Finally, after it was naturally cooled to room temperature, it was taken out to obtain a terminal boric acid cross-linked fluoropolyamideimide film sample.

[0055] Example 4

[0056] Under nitrogen, add 4,4'-diamino-2,2'-bistrifluoromethylbiphenyl (0.8mmol) to a thoroughly dried three-necked flask, add anhydrous DMAc (9mL), stir magnetically to dissolve, place the flask in an ice bath for 20min, and then add 2,2'-((perfluoropropane-2,2-diyl)bis(4,1-phenyl))bis(1,3-dioxoisoindoline-5-acid chloride) (1mmol) in several portions to ensure the uniformity of the reaction. After the addition is complete, react in an ice bath for 2h and at room temperature for 4h. Then add 3-aminophenylboronic acid (0.4mmol) and react at room temperature for 12h. After the reaction is complete, slowly pour it into a mixed solvent of ethanol and water (1:1) under vigorous stirring to precipitate a white fibrous resin, which is dried at 100℃ for 24h.

[0057] The dried resin was dissolved in DMAc to prepare a 10wt% solution. Then it was slowly poured onto a flat glass plate and coated at a height of 1000 to form a film. Then it was dried at a temperature program of 50℃ / 2h, 80℃ / 1h, 120℃ / 1h, and 150℃ / 1h. Then it was transferred to a vacuum oven preheated to 150℃, and then the solvent was completely removed and cross-linked at 180℃ / 1h, 210℃ / 1h, and 250℃ / 1h. Finally, after it was naturally cooled to room temperature, it was taken out to obtain a terminal boric acid cross-linked fluoropolyamideimide film sample.

[0058] Example 5

[0059] Under nitrogen, add 4,4'-diamino-2,2'-bistrifluoromethylbiphenyl (0.9mmol) to a thoroughly dried three-necked flask, add anhydrous DMAc (9mL), stir magnetically to dissolve, place the flask in an ice bath for 20min, and then add 2,2'-((perfluoropropane-2,2-diyl)bis(4,1-phenyl))bis(1,3-dioxoisoindoline-5-yl chloride) (1mmol) in several portions to ensure the uniformity of the reaction. After the addition is complete, react in an ice bath for 2h and at room temperature for 4h. Then add 3-aminophenylboronic acid (0.4mmol) and react at room temperature for 12h. After the reaction is complete, slowly pour it into a mixed solvent of ethanol and water (1:1) under vigorous stirring to precipitate a white fibrous resin, which is dried at 100℃ for 24h.

[0060] The dried resin was dissolved in DMAc to prepare a 10wt% solution. Then it was slowly poured onto a flat glass plate and coated at a height of 1000 to form a film. Then it was dried at a temperature program of 50℃ / 2h, 80℃ / 1h, 120℃ / 1h, and 150℃ / 1h. Then it was transferred to a vacuum oven preheated to 150℃, and then the solvent was completely removed and cross-linked at 180℃ / 1h, 210℃ / 1h, and 250℃ / 1h. Finally, after it was naturally cooled to room temperature, it was taken out to obtain a terminal boric acid cross-linked fluoropolyamideimide film sample.

[0061] Table 1. Main properties of the fluoropolyamideimide films prepared in Examples 1-5

[0062] serial number Thermal expansion coefficient (ppm / K) Tensile strength(MPa) <![CDATA[T 550 (%)]]> Example 1 9.6 195 85 Example 2 10.3 201 84 Example 3 10.5 198 85 Example 4 11.3 193 84 Example 5 12.4 178 87

[0063] The thermal expansion coefficient (CTE) of the film was measured by a static mechanical analyzer (TMA) in a nitrogen atmosphere at a test temperature range of 50-250° C. The thermal expansion curve of the terminal boric acid cross-linked fluoropolyamideimide film of Example 1 is shown in FIG. Figure 1 As shown in Table 1, the thermal expansion coefficient is 9.6 ppm / K.

[0064] The tensile properties of the film were tested in accordance with the national standard GB / T1040.3-2006 on a universal testing machine. No less than five groups of samples were tested and the average value was taken. The stress-strain curve of the terminal boric acid cross-linked fluoropolyamide-imide film of Example 1 is shown in Figure 2 shown.

[0065] The transmittance of the film was measured by UV-visible spectrometer. 550 is the transmittance of a film with a thickness of about 20 μm at 550 nm. The visible light transmittance curve of the terminal boric acid cross-linked fluoropolyamideimide film of Example 1 is shown in FIG. Figure 3 shown.

[0066] The thermal expansion coefficient of the terminal boric acid cross-linked fluoropolyamide-imide film prepared in Examples 1 to 5 is less than 12.5 ppm / K and the lowest reaches 9.6 ppm / K, the tensile strength is greater than 175 MPa and the highest exceeds 200 MPa, T 550 It is 84% ​​and above, with excellent comprehensive performance.

[0067] like Figure 4 As shown, the terminal boric acid cross-linked fluoropolyamideimide film of Example 1 was redissolved in a complete solvent and anhydrous DMAc at room temperature to obtain a fluoropolyamideimide solution, which could be scraped again, showing excellent reprocessing performance.

[0068] As shown in Table 1, the terminal boric acid crosslinked fluoropolyamideimide film obtained in the present invention has high light transmittance, low linear thermal expansion coefficient, and excellent mechanical properties. Therefore, the terminal boric acid crosslinked fluoropolyamideimide film of the present invention is suitable for the application of transparent layer materials of optical devices, including but not limited to display devices, photoelectric detection devices, etc.

[0069] The above embodiments are only used to further illustrate a terminal boric acid cross-linked fluoropolyamide-imide film and its preparation method and application of the present invention, but the present invention is not limited to the embodiments. Any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention fall within the protection scope of the technical solution of the present invention.

Claims

1. A method for preparing a terminal boric acid cross-linked fluoropolyamide-imide film, characterized in that: The following steps are involved: (1) Under a nitrogen environment, a fluorine-containing diamine is dissolved in an anhydrous organic solvent, and a fluorine-containing diacid chloride containing an imide structure is added in an ice bath to react to form a fluorinated polyamide-imide terminated with an acyl chloride, and 3-aminophenylboronic acid is added to continue the reaction to form a fluorinated polyamide-imide with a terminal group of phenylboronic acid; a precipitant is added to the reaction solution to precipitate, and the resin is obtained after washing and drying; (2) The resin is dissolved in an anhydrous organic solvent to form a solution, and after forming a film using a film-forming process, a terminal boric acid cross-linked fluoropolyamide-imide film is formed by dehydration condensation through heat treatment.

2. The method for preparing the terminal boric acid cross-linked fluoropolyamide-imide film according to claim 1, characterized in that: The fluorine-containing diamine includes At least one of .

3. The method for preparing the terminal boric acid cross-linked fluoropolyamide-imide film according to claim 1, characterized in that: The fluorine-containing and imide-containing diacyl chlorides include At least one of .

4. The method for preparing the terminal boric acid cross-linked fluoropolyamide-imide film according to claim 1, characterized in that: The molar ratio of the fluorine-containing diamine to the fluorine-containing diacyl chloride having an imide structure is 0.8-0.9:

1.

5. The method for preparing the terminal boric acid cross-linked fluoropolyamide-imide film according to claim 1, characterized in that: The molar ratio of the 3-aminophenylboronic acid to the diacyl chloride containing fluorine and imide structure is 0.4-0.8:

1.

6. The method for preparing the terminal boric acid cross-linked fluoropolyamide-imide film according to claim 1, characterized in that: In step (1), the reaction of the fluorine-containing diamine and the fluorine-containing imide-containing diacyl chloride is first carried out in an ice bath for 2-4 hours and then at room temperature for 4-12 hours; after adding 3-aminophenylboronic acid, the reaction is carried out at room temperature for 12-24 hours; during the reaction, the solid content of the reaction solution is controlled to be 10-20%.

7. The method for preparing the terminal boric acid cross-linked fluoropolyamideimide film according to claim 1, characterized in that: In step (2), the heat treatment includes programmed temperature drying and post-programmed temperature heating, and the programmed temperature drying includes the following steps: 50℃-60℃ / 1-2h, 80℃-90℃ / 1-2h, 120℃-130℃ / 1-2h, 150℃-160℃ / 1-2h; the post-programmed temperature heating includes the following steps: 180℃-190℃ / 1-2h, 210℃-220℃ / 1-2h, 250℃-260℃ / 1-2h.

8. A terminal boric acid cross-linked fluoropolyamide-imide film, characterized in that: Obtained by the preparation method according to any one of claims 1 to 7.

9. The terminal boric acid cross-linked fluoropolyamide-imide film according to claim 8, characterized in that: The terminal boric acid cross-linked fluoropolyamideimide has the structure shown below: Wherein, R1 is the residue of the fluorine-containing imide-containing diacyl chloride, and R2 is the residue of the fluorine-containing diamine.

10. Use of the terminal boric acid cross-linked fluoropolyamideimide film according to claim 8 or 9 as a transparent layer material for an optical device.

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