Fluorine-containing diamine monomer, polyimide and preparation method and application thereof
Polyimide films were prepared by reacting fluorinated diamine monomers with non-rigid tetracarboxylic acid dianhydrides, which solved the problem of low light transmittance of polyimide films and achieved polyimide films with high transparency and mechanical strength, suitable for a variety of flexible electronic devices.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-22
- Publication Date
- 2026-04-07
AI Technical Summary
Conventional polyimide films have low transmittance in the visible light wavelength range, mainly due to the formation of charge transfer complexes between diamine and tetracarboxylic dianhydride, resulting in dense molecular chain stacking and dark color, which limits their applications.
Polyimide films were prepared by reacting fluorinated diamine monomers with specific non-rigid tetracarboxylic acid dianhydrides. By introducing fluorine atoms and alkyl substituents onto the diamine monomers, a novel structure was formed, reducing the molecular chain packing density.
The prepared polyimide film has good light transmittance, thermal properties and mechanical strength, and is suitable for flexible display substrates, printed circuit boards, solar cell substrates and flexible encapsulation films.
Smart Images
Figure CN121800664A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of materials science and technology, and in particular to a fluorinated diamine monomer, a polyimide, its preparation method, and its application. Background Technology
[0002] Polyimide, known as a class of polymer compounds with an imide ring on its main chain, is widely used in aerospace, microelectronics, biomedicine, and sensors. In recent years, with the development of flexible displays, optoelectronics, and other fields, high-performance, highly transparent polymer materials have gradually become lightweight, ultra-thin, and flexible, and have been successfully applied in many fields such as display devices, flexible printed circuit boards, and touch screens. However, to ensure the quality of these devices, polymer films need to exhibit excellent comprehensive performance.
[0003] Conventional polyimide films appear dark yellowish-brown in the visible light wavelength range and have low light transmittance. The main reason for their dark color is that in the polyimide molecular structure, the diamine, which acts as an electron donor, and the tetracarboxylic dianhydride, which acts as an electron acceptor, form a charge-transfer complex (CTC). This results in a tight molecular chain packing, which makes the polyimide film exhibit strong absorption in the visible light range. The stronger the electron-donating and electron-withdrawing capabilities of the diamine and the tetracarboxylic dianhydride, the easier it is to form a charge-transfer complex, thus making the polyimide film even darker and severely limiting the application of polyimide. Summary of the Invention
[0004] The purpose of this invention is to provide a fluorinated diamine monomer that solves the above-mentioned technical problems and can be used to synthesize polyimide, and a method for preparing the same.
[0005] Another object of the present invention is to provide a polyimide prepared using the above-mentioned fluorinated diamine monomer and a method thereof.
[0006] Another object of the present invention is to provide the above-mentioned polyimide film and its application.
[0007] Therefore, the technical solution of the present invention is as follows:
[0008] A fluorinated diamine monomer has the following chemical structural formula:
[0009]
[0010] In Formula I, R1 and R2 are selected from methyl, ethyl, or propyl.
[0011] A method for preparing the above-mentioned fluorinated diamine monomer, comprising the following steps:
[0012] Step 1: Dissolve phenol containing amino and dialkyl groups in an aprotic polar solvent, add alkali, and react at room temperature for 1 to 2 hours;
[0013] Step 2: Under low temperature conditions, hexafluorobenzene is slowly added dropwise to the system in step S1. After stirring evenly, the mixture is raised to room temperature and the reaction continues for 2-6 hours to prepare a fluorinated diamine monomer.
[0014] In steps 1 and 2, the room temperature is preferably 23°C to 26°C.
[0015] Preferably, in step 1, the aprotic polar solvent is at least one selected from dimethyl sulfoxide, N-methylpyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide, and sulfolane, more preferably N,N-dimethylformamide.
[0016] Preferably, in step 1, the amount of aprotic polar solvent used is 5 to 10 times the weight of the phenol containing amino and dialkyl groups.
[0017] Preferably, in step 1, the alkali is K2CO3, NaCO3, Cs2CO3, KOH, NaOH, or Et3N, more preferably NaOH.
[0018] Preferably, in step 1, the amount of alkali used is 1:(1 to 3) of the molar amount of phenol containing amino and dialkyl groups, more preferably 1:(1 to 1.2).
[0019] Preferably, in step 2, the molar ratio of phenol with amino and dialkyl groups to hexafluorobenzene is 1:(0.5 to 0.7).
[0020] Preferably, in step 2, the reaction temperature under low-temperature conditions is -5℃ to 10℃, more preferably 0℃.
[0021] Preferably, in step 2, under stirring conditions, water is added to the reaction product to precipitate a solid. The solid is then filtered, washed with water, vacuum dried, subjected to column chromatography once, and then vacuum dried again.
[0022] A polyimide is prepared by polymerizing a fluorinated diamine monomer with a tetracarboxylic acid dianhydride as described above to obtain a polyamic acid, followed by imidization; wherein the tetracarboxylic acid dianhydride is selected from, but not limited to, 4,4'-(hexafluoroisopropylidene)phthalic anhydride, 4,4'-oxobisphthalic anhydride, and 9,9-bis(trifluoromethyl)oxanthracene-2,3,6,7-tetracarboxylic dianhydride.
[0023] The polyimide comprises the following repeating structural units:
[0024]
[0025] In the formula, Ar is the residue of a tetracarboxylic acid dianhydride containing an aromatic ring or an alicyclic ring after removing 4 carboxyl groups, and n is 100-200.
[0026] A polyimide film is prepared using the aforementioned polyimide. The preparation method of the polyimide film is not particularly limited; it can be prepared by first preparing a polyimide precursor, polyamic acid, and coating it into a film, followed by thermal imidization or chemical imidization, with thermal imidization being preferred.
[0027] A method for preparing a polyimide film, the specific preparation steps of which are as follows:
[0028] S1. Tetracarboxylic acid dianhydride is added in batches to an organic solvent containing fluorinated diamine monomer, and stirred at 0℃-10℃ for 10h-16h to obtain polyamic acid with a solid content of 10wt% to 30wt%.
[0029] In step S1, the molar ratio of the fluorinated diamine monomer to the tetracarboxylic acid dianhydride is 1:(1.02-1.06), preferably 1:1.02.
[0030] In step S1, the solid content of the polyamic acid solution is 10wt% to 30wt%.
[0031] In step S1, the organic solvent is dimethylformamide, dimethylacetamide, N-methylpyrrolidone or dimethyl sulfoxide, etc., more preferably dimethylacetamide; wherein, the amount of organic solvent added is: 2.45 mL to 3.5 mL of organic solvent is added for every 1 mol of fluorinated diamine monomer.
[0032] S2. After degassing, the polyamic acid solution is coated into a film. After drying to remove the solvent, a thermal imidization method is performed to prepare a polyimide film.
[0033] The degassing step S2 is as follows: at room temperature, the polyamic acid solution is placed in a vacuum environment for 0.5h-2h, more preferably 0.5h-1h.
[0034] Step S2, the coating step, involves pouring the polyamic acid solution onto a clean, dry substrate and using a spiral fine-tuning coating tool in conjunction with an automatic coating machine to coat a polyamic acid film of controllable thickness. The substrate can be a glass substrate, a metal substrate or metal strip such as SUS, or a plastic film made of polyethylene terephthalate, polycarbonate, polyacrylate, polyethylene naphthalate, or triacetyl cellulose, but is not limited to these. The thickness of the polyamic acid film in step S2 is 15μm-25μm, the same as the thickness of the polyimide film.
[0035] The drying step S2 is as follows: drying at a temperature of 60℃~80℃ for 2h~5h to remove most of the solvent; more preferably, vacuum drying at 80℃ for 3h-3.5h.
[0036] The thermal imidization step S2 is as follows: the temperature is increased from room temperature to 280°C at a rate of 1°C / min to 2°C / min under a nitrogen atmosphere, and then maintained for 1 hour each at 100°C, 200°C and 280°C. After that, it is naturally cooled to room temperature to obtain a polyimide film.
[0037] One application of the above-mentioned polyimide film is that it can be used in the fields of flexible display substrates, printed circuit boards, solar cell substrates, and flexible encapsulation films.
[0038] Compared with existing technologies, this fluorinated diamine monomer introduces fluorine atoms, alkyl substituents and ether bonds into a traditional diamine monomer to form a diamine monomer with a novel structure. This diamine monomer reacts with a specific non-rigid tetracarboxylic dianhydride to prepare polyimide films, which have good light transmittance, thermal properties and mechanical strength, and have good application prospects in the field of optical films such as flexible display substrates, printed circuit boards, solar cell substrates and flexible encapsulation films. Attached Figure Description
[0039] Figure 1 The 1H NMR spectrum of 4,4'-((perfluoro-1,4-benzene)bis(oxy))bis(2,6-dimethylaniline) prepared in Example 1 of the present invention;
[0040] Figure 2 The nuclear magnetic fluorine spectrum of 4,4'-((perfluoro-1,4-benzene)bis(oxy))bis(2,6-dimethylaniline) prepared in Example 1 of the present invention;
[0041] Figure 3 The infrared spectra of polyimide films prepared by Examples 11 to 14 and Comparative Examples 4 to 5 of the present invention, and prepared with 6 different tetracarboxylic dianhydrides. Detailed Implementation
[0042] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, but the following embodiments are by no means intended to limit the present invention.
[0043] Example 1
[0044] At room temperature, 6.9 g (50 mmol) of 4-amino-3,5-dimethylphenol was dissolved in 40 mL of DMF, and 2.04 g (51 mmol) of NaOH was added with stirring. The mixture was stirred for 2 h at room temperature. The system was gradually cooled to 0 °C, and 4.65 g (25 mmol) of hexafluorobenzene was slowly added dropwise. After the addition was completed, the mixture was stirred for 20 min. Then the system temperature was gradually raised to room temperature, and the reaction was continued for 3 h. The reaction was monitored by TLC until it was complete. Under stirring, 250 mL of water was gradually added to the reaction product, and a solid precipitated. The solid was filtered, washed with water, vacuum dried, and column chromatographically analyzed once. It was then vacuum dried again to prepare 4,4'-((perfluoro-1,4-phenyl)bis(oxy))bis(2,6-dimethylaniline).
[0045] Example 2
[0046] At room temperature, 6.9 g (50 mmol) of 4-amino-3,5-dimethylphenol was dissolved in 40 mL of DMF, and 2.08 g (52 mmol) of NaOH was added with stirring. The mixture was stirred for 2 h at room temperature. The system was gradually cooled to 0 °C, and 4.65 g (25 mmol) of hexafluorobenzene was slowly added dropwise. After the addition was completed, the mixture was stirred for 20 min. Then the system temperature was gradually raised to room temperature and the reaction was continued for 4 h. The reaction was monitored by TLC until it was complete. Under stirring, 250 mL of water was gradually added to the reaction product, and a solid precipitated. The solid was filtered, washed with water, vacuum dried, and column chromatographically analyzed once. It was then vacuum dried again to prepare 4,4'-((perfluoro-1,4-phenyl)bis(oxy))bis(2,6-dimethylaniline).
[0047] Example 3
[0048] At room temperature, 6.9 g (50 mmol) of 4-amino-3,5-dimethylphenol was dissolved in 40 mL of DMF, and 2 g (50 mmol) of NaOH was added with stirring. The mixture was stirred for 2 h at room temperature. The system was gradually cooled to 0 °C, and 4.65 g (25 mmol) of hexafluorobenzene was slowly added dropwise. After the addition was completed, the mixture was stirred for 20 min. Then the system temperature was gradually raised to room temperature and the reaction was continued for 5 h. The reaction was monitored by TLC until it was complete. Under stirring, 250 mL of water was gradually added to the reaction product, and a solid precipitated. The solid was filtered, washed with water, dried under vacuum, and subjected to column chromatography once. It was then dried under vacuum again to prepare 4,4'-((perfluoro-1,4-phenyl)bis(oxy))bis(2,6-dimethylaniline).
[0049] Example 4
[0050] At room temperature, 6.9 g (50 mmol) of 4-amino-3,5-dimethylphenol was dissolved in 50 mL of DMF, and 2.04 g (51 mmol) of NaOH was added with stirring. The mixture was stirred for 2 h at room temperature. The system was gradually cooled to 0 °C, and 5.02 g (27 mmol) of hexafluorobenzene was slowly added dropwise. After the addition was completed, the mixture was stirred for 20 min. Then the system temperature was gradually raised to room temperature and the reaction was continued for 6 h. The reaction was monitored by TLC until it was complete. Under stirring, 250 mL of water was gradually added to the reaction product, and a solid precipitated. The solid was filtered, washed with water, vacuum dried, and column chromatographically analyzed once. It was then vacuum dried again to prepare 4,4'-((perfluoro-1,4-phenyl)bis(oxy))bis(2,6-dimethylaniline).
[0051] Example 5
[0052] At room temperature, 6.9 g (50 mmol) of 4-amino-3,5-dimethylphenol was dissolved in 50 mL of DMF, and 2.2 g (55 mmol) of NaOH was added with stirring. The mixture was stirred for 2 h at room temperature. The system was gradually cooled to 0 °C, and 4.84 g (26 mmol) of hexafluorobenzene was slowly added dropwise. After the addition was completed, the mixture was stirred for 20 min. Then the system temperature was gradually raised to room temperature and the reaction was continued for 6 h. The reaction was monitored by TLC until it was complete. Under stirring, 300 mL of water was gradually added to the reaction product, and a solid precipitated. The solid was filtered, washed with water, dried under vacuum, and subjected to column chromatography once. It was then dried under vacuum again to prepare 4,4'-((perfluoro-1,4-phenyl)bis(oxy))bis(2,6-dimethylaniline).
[0053] Example 6
[0054] At room temperature, 6.9 g (50 mmol) of 4-amino-3,5-dimethylphenol was dissolved in 50 mL of DMF, and 2.2 g (55 mmol) of NaOH was added with stirring. The mixture was stirred for 2 h at room temperature. The system was gradually cooled to 0 °C, and 5.02 g (27 mmol) of hexafluorobenzene was slowly added dropwise. After the addition was completed, the mixture was stirred for 20 min. Then the system temperature was gradually raised to room temperature and the reaction was continued for 3 h. The reaction was monitored by TLC until it was complete. Under stirring, 300 mL of water was gradually added to the reaction product, and a solid precipitated. The solid was filtered, washed with water, vacuum dried, and column chromatographically analyzed once. It was then vacuum dried again to prepare 4,4'-((perfluoro-1,4-phenyl)bis(oxy))bis(2,6-dimethylaniline).
[0055] Example 7
[0056] At room temperature, 5.49 g (40 mmol) of 4-amino-3,5-dimethylphenol was dissolved in 40 mL of DMF, and 1.92 g (48 mmol) of NaOH was added with stirring. The mixture was stirred for 2 h at room temperature. The system was gradually cooled to 0 °C, and 4.65 g (25 mmol) of hexafluorobenzene was slowly added dropwise. After the addition was completed, the mixture was stirred for 20 min. Then the system temperature was gradually raised to room temperature and the reaction was continued for 3 h. The reaction was monitored by TLC until it was complete. Under stirring, 250 mL of water was gradually added to the reaction product, and a solid precipitated. The solid was filtered, washed with water, vacuum dried, and column chromatographically analyzed once. It was then vacuum dried again to prepare 4,4'-((perfluoro-1,4-phenyl)bis(oxy))bis(2,6-dimethylaniline).
[0057] Example 8
[0058] At room temperature, 5.49 g (40 mmol) of 4-amino-3,5-dimethylphenol was dissolved in 40 mL of DMF, and 1.76 g (44 mmol) of NaOH was added with stirring. The mixture was stirred for 1 h at room temperature. The system was gradually cooled to 0 °C, and 4.09 g (22 mmol) of hexafluorobenzene was slowly added dropwise. After the addition was completed, the mixture was stirred for 20 min. Then the system temperature was gradually raised to room temperature and the reaction was continued for 4 h. The reaction was monitored by TLC until it was complete. Under stirring, 250 mL of water was gradually added to the reaction product, and a solid precipitated. The solid was filtered, washed with water, vacuum dried, and column chromatographically analyzed once. It was then vacuum dried again to prepare 4,4'-((perfluoro-1,4-phenyl)bis(oxy))bis(2,6-dimethylaniline).
[0059] Example 9
[0060] At room temperature, 5.49 g (40 mmol) of 4-amino-3,5-dimethylphenol was dissolved in 50 mL of DMF, and 1.6 g (40 mmol) of NaOH was added with stirring. The mixture was stirred for 1 h at room temperature. The system was gradually cooled to 5 °C, and 3.9 g (21 mmol) of hexafluorobenzene was slowly added dropwise. After the addition was completed, the mixture was stirred for 10 min. Then the system temperature was gradually raised to room temperature and the reaction was continued for 2 h. The reaction was monitored by TLC until it was complete. Under stirring, 250 mL of water was gradually added to the reaction product, and a solid precipitated. The solid was filtered, washed with water, dried under vacuum, and subjected to column chromatography once. It was then dried under vacuum again to prepare 4,4'-((perfluoro-1,4-phenyl)bis(oxy))bis(2,6-dimethylaniline).
[0061] Example 10
[0062] At room temperature, 5.49 g (40 mmol) of 4-amino-3,5-dimethylphenol was dissolved in 50 mL of DMF, and 1.8 g (45 mmol) of NaOH was added with stirring. The mixture was stirred for 1 h at room temperature. The system was gradually cooled to 10 °C, and 3.9 g (21 mmol) of hexafluorobenzene was slowly added dropwise. After the addition was completed, the mixture was stirred for 10 min. Then the system temperature was gradually raised to room temperature and the reaction was continued for 2 h. The reaction was monitored by TLC until it was complete. Under stirring, 250 mL of water was gradually added to the reaction product, and a solid precipitated. The solid was filtered, washed with water, vacuum dried, and column chromatographically analyzed once. It was then vacuum dried again to prepare 4,4'-((perfluoro-1,4-phenyl)bis(oxy))bis(2,6-dimethylaniline).
[0063] Example 11
[0064] Under ice-water bath and nitrogen atmosphere conditions, 0.84 g (2 mmol) of 4,4'-((perfluoro-1,4-phenyl)bis(oxy))bis(2,6-dimethylaniline) prepared in Example 1 was dissolved in 2 mL of DMAc. 0.9 g (2.04 mmol) of 4,4'-(hexafluoroisopropylidene) phthalic anhydride (6FDA) was slowly added, and 2.9 mL of DMAc was added in four portions over the first 2 hours, for a total reaction time of 16 hours, to prepare a polyamic acid solution. The polyamic acid solution with a solid content of 27.5 wt% was placed in a vacuum oven for degassing at room temperature for 1 hour, then cast onto a glass plate and dried in a vacuum oven at 80 °C for 3 hours. It was then transferred to a muffle furnace for thermal imidization, and the temperature was gradually increased under a nitrogen atmosphere, and the temperature was maintained at 100 °C, 200 °C and 280 °C for 1 hour each to prepare a colorless and transparent polyimide film with a thickness of 20 μm.
[0065] Example 12
[0066] Under ice-water bath and nitrogen atmosphere conditions, 0.84 g (2 mmol) of 4,4'-((perfluoro-1,4-phenyl)bis(oxy))bis(2,6-dimethylaniline) prepared in Example 1 was dissolved in 2 mL of DMAc, and 0.633 g (2.04 mmol) of 4,4'-oxybisphthalic anhydride (ODPA) was slowly added, with 4 mL of DMAc added in four portions over the first 2 hours, for a total reaction time of 10 hours, to prepare a polyamic acid solution. The polyamic acid solution with a solid content of 20.8 wt% was placed in a vacuum oven for degassing at room temperature for 1 hour, then cast onto a glass plate and dried in a vacuum oven at 80 °C for 3 hours. It was then transferred to a muffle furnace for thermal imidization, and the temperature was gradually increased under a nitrogen atmosphere, and the temperature was maintained at 100 °C, 200 °C and 280 °C for 1 hour each to prepare a colorless transparent polyimide film with a thickness of 20 μm.
[0067] Example 13
[0068] Under ice-water bath and nitrogen atmosphere conditions, 0.84 g (2 mmol) of 4,4'-((perfluoro-1,4-phenyl)bis(oxy))bis(2,6-dimethylaniline) prepared in Example 1 was dissolved in 2 mL of DMAc. 0.94 g (2.04 mmol) of 9,9-bis(trifluoromethyl)-2,3,6,7-anthracene tetracarboxylic acid dianhydride (6FCDA) was slowly added, with 3.5 mL of DMAc added in three portions over the first hour, for a total reaction time of 12 hours, to prepare a polyamic acid solution. The polyamic acid solution with a solid content of 25.7 wt% was placed in a vacuum oven for degassing at room temperature for 1 hour, then cast onto a glass plate and dried in a vacuum oven at 80 °C for 3 hours. It was then transferred to a muffle furnace for thermal imidization, and the temperature was gradually increased under a nitrogen atmosphere, and the temperature was maintained at 100 °C, 200 °C, and 280 °C for 1 hour each to prepare a colorless transparent polyimide film with a thickness of 20 μm.
[0069] Example 14
[0070] Under ice-water bath and nitrogen atmosphere conditions, 0.84 g (2 mmol) of 4,4'-((perfluoro-1,4-phenyl)bis(oxy))bis(2,6-dimethylaniline) prepared in Example 1 was dissolved in 2 mL of DMAc. 1.06 g (2.04 mmol) of bisphenol A diether dianhydride (BPADA) was slowly added, with 5 mL of DMAc added in five portions over the first 2 hours, for a total reaction time of 12 hours, to prepare a polyamic acid solution. The polyamic acid solution with a solid content of 22.5 wt% was placed in a vacuum oven for degassing at room temperature for 1 hour, then cast onto a glass plate and dried in a vacuum oven at 80 °C for 3 hours. It was then transferred to a muffle furnace for thermal imidization, and the temperature was gradually increased under a nitrogen atmosphere, and the temperature was maintained at 100 °C, 200 °C, and 280 °C for 1 hour each to prepare a colorless and transparent polyimide film with a thickness of 20 μm.
[0071] Comparative Example 1
[0072] Under ice-water bath and nitrogen atmosphere conditions, 0.84 g (2 mmol) of 4,4'-((perfluoro-1,4-phenyl)bis(oxy))bis(2,6-dimethylaniline) prepared in Example 1 was dissolved in 2 mL of DMAc. 0.9 g (2.04 mmol) of 4,4'-(hexafluoroisopropylidene) phthalic anhydride (6FDA) was slowly added, and 2.9 mL of DMAc was added in four portions over the first 2 hours, for a total reaction time of 16 hours, to prepare a polyamic acid solution. The polyamic acid solution was placed in a vacuum oven for degassing at room temperature for 1 hour, then cast onto a glass plate and dried in a vacuum oven at 80 °C for 3 hours. It was then transferred to a muffle furnace for thermal imidization, and the temperature was gradually increased under a nitrogen atmosphere, and the temperature was maintained at 100 °C, 200 °C and 300 °C for 1 hour each to prepare a polyimide film with a thickness of 20 μm. The polyimide film prepared in Comparative Example 1 has irregularly distributed fine cracks on its surface. The reason for this is that the thermal imidization temperature is set too high, which leads to a deterioration in film formation performance.
[0073] Comparative Example 2
[0074] Under ice-water bath and nitrogen atmosphere conditions, 0.84 g (2 mmol) of 4,4'-((perfluoro-1,4-phenyl)bis(oxy))bis(2,6-dimethylaniline) prepared in Example 1 was dissolved in 2 mL of DMAc, and 0.9 g (2.04 mmol) of 4,4'-(hexafluoroisopropylidene) phthalic anhydride (6FDA) was slowly added, with 2.9 mL of DMAc added in four portions over the first 2 hours, for a total reaction time of 16 hours, to prepare a polyamic acid solution. The polyamic acid solution was placed in a vacuum oven for degassing at room temperature for 1 hour, then cast onto a glass plate and dried in a vacuum oven at 80 °C for 3 hours. It was then transferred to a muffle furnace for thermal imidization, and the temperature was gradually increased under a nitrogen atmosphere, and the temperature was maintained at 100 °C, 200 °C and 280 °C for 1 hour each to prepare a polyimide film with a thickness of 30 μm. The light transmittance of the polyimide film prepared in Comparative Example 2 was significantly lower than that of the polyimide film prepared in Example 11. The reason for this is that thickness is an important factor affecting the optical performance of polyimide films; the greater the thickness, the lower the light transmittance.
[0075] Comparative Example 3
[0076] Under ice-water bath and nitrogen atmosphere conditions, 0.84 g (2 mmol) of 4,4'-((perfluoro-1,4-phenyl)bis(oxy))bis(2,6-dimethylaniline) prepared in Example 1 was dissolved in 2 mL of DMAc. 0.9 g (2.04 mmol) of 4,4'-(hexafluoroisopropylidene) phthalic anhydride (6FDA) was slowly added, and 2.9 mL of DMAc was added in four portions over the first 2 hours, for a total reaction time of 16 hours, to prepare a polyamic acid solution. The polyamic acid solution was placed in a vacuum oven for degassing at room temperature for 1 hour, then cast onto a glass plate and dried in a vacuum oven at 80 °C for 3 hours. It was then transferred to a muffle furnace for thermal imidization, and the temperature was gradually increased under a nitrogen atmosphere, and the temperature was maintained at 100 °C, 200 °C, and 280 °C for 1 hour each to prepare a polyimide film with a thickness of 40 μm. The light transmittance of the polyimide film prepared in Comparative Example 3 was further reduced compared to that prepared in Comparative Example 2. The reason for this is that the optical performance decreases as the film thickness gradually increases.
[0077] Comparative Example 4
[0078] Under ice-water bath and nitrogen atmosphere conditions, 0.84 g (2 mmol) of 4,4'-((perfluoro-1,4-phenyl)bis(oxy))bis(2,6-dimethylaniline) prepared in Example 1 was dissolved in 2 mL of DMAc. 0.445 g (2.04 mmol) of pyromellitic dianhydride (PMDA) was slowly added, with 5 mL of DMAc added in five portions over the first hour, for a total reaction time of 12 hours, to prepare a polyamic acid solution. The polyamic acid solution with a solid content of 14.7 wt% was placed in a vacuum oven for degassing at room temperature for 1 hour, then cast onto a glass plate and dried in a vacuum oven at 80 °C for 3 hours. It was then transferred to a muffle furnace for thermal imidization, and the temperature was gradually increased under a nitrogen atmosphere, and the temperature was maintained at 100 °C, 200 °C, and 280 °C for 1 hour each to prepare a colorless and transparent polyimide film with a thickness of 20 μm.
[0079] Comparative Example 5
[0080] Under ice-water bath and nitrogen atmosphere conditions, 0.84 g (2 mmol) of 4,4'-((perfluoro-1,4-phenyl)bis(oxy))bis(2,6-dimethylaniline) prepared in Example 1 was dissolved in 2 mL of DMAc. 0.6 g (2.04 mmol) of biphenyltetracarboxylic dianhydride (BPDA) was slowly added, and 5.5 mL of DMAc was added in five portions over the first 3 hours, for a total reaction time of 11 hours, to prepare a polyamic acid solution. The polyamic acid solution with a solid content of 17 wt% was placed in a vacuum oven for degassing at room temperature for 1 hour, then cast onto a glass plate and dried in a vacuum oven at 80 °C for 3 hours. It was then transferred to a muffle furnace for thermal imidization, and the temperature was gradually increased under a nitrogen atmosphere, and the temperature was maintained at 100 °C, 200 °C and 280 °C for 1 hour each to prepare a colorless and transparent polyimide film with a thickness of 20 μm.
[0081] Comparative Example 6
[0082] At room temperature, 5.5 g (50 mmol) of 4-aminophenol was dissolved in 75 mL of DMF, and 3.2 g (80 mmol) of NaOH was added with stirring. The mixture was stirred for 1 h at room temperature. The system was gradually cooled to 0 °C, and 4.65 g (25 mmol) of hexafluorobenzene was slowly added dropwise. After the addition was completed, the mixture was stirred for 20 min. Then the temperature of the system was gradually raised to room temperature, and the reaction was continued for 2 h. The reaction was monitored by TLC until it was complete. Under stirring, the reaction solution was slowly added dropwise to 280 mL of water, and a solid precipitated. The solid was filtered, washed with water, dried under vacuum, recrystallized, and subjected to column chromatography once. After drying under vacuum again, 4,4'-(perfluoro-1,4-phenylenedioxy)diphenylamine was prepared.
[0083] Under ice-water bath and nitrogen atmosphere, 0.73 g (2 mmol) of 4,4'-(perfluoro-1,4-phenylenedioxy)diphenylamine was dissolved in 2 mL of DMAc, and 0.9 g (2.04 mmol) of 4,4'-(hexafluoroisopropylidene) phthalic anhydride (6FDA) was slowly added. 2.59 mL of DMAc was added in four portions over the first 2 hours, and the reaction was carried out for a total of 16 hours to prepare a polyamic acid solution. The 27.5 wt% polyamic acid solution was placed in a vacuum oven for degassing at room temperature for 1 hour, then cast onto a glass plate and dried in a vacuum oven at 80 °C for 3 hours. It was then transferred to a muffle furnace for thermal imidization, where the temperature was gradually increased under nitrogen atmosphere and held at 100 °C, 200 °C, and 280 °C for 1 hour each to prepare a colorless transparent polyimide film with a thickness of 20 μm.
[0084] Comparative Example 7
[0085] Under ice-water bath and nitrogen atmosphere, 0.40 g (2 mmol) of 4,4'-diaminodiphenyl ether was dissolved in 2 mL of DMAc, and 0.9 g (2.04 mmol) of 4,4'-(hexafluoroisopropylidene) phthalic anhydride (6FDA) was slowly added. 1.66 mL of DMAc was added in four portions over the first 2 hours, and the reaction was carried out for a total of 16 hours to prepare a polyamic acid solution. The 27.5 wt% polyamic acid solution was placed in a vacuum oven for degassing at room temperature for 1 hour, then cast onto a glass plate and dried in a vacuum oven at 80 °C for 3 hours. It was then transferred to a muffle furnace for thermal imidization, where the temperature was gradually increased under nitrogen atmosphere and held at 100 °C, 200 °C, and 280 °C for 1 hour each to prepare a polyimide film with a thickness of 20 μm.
[0086] Performance testing:
[0087] (I) Nuclear magnetic resonance (NMR) and fluorine spectrum tests of fluorinated diamine monomers:
[0088] The following is the synthetic route for 4,4'-((perfluoro-1,4-phenyl)bis(oxy))bis(2,6-dimethylaniline):
[0089]
[0090] like Figure 1 The image shows the 1H NMR spectrum of 4,4'-((perfluoro-1,4-phenyl)bis(oxy))bis(2,6-dimethylaniline) prepared in Example 1; Figure 2 The NMR fluorine spectrum of 4,4'-((perfluoro-1,4-phenyl)bis(oxy))bis(2,6-dimethylaniline) prepared in Example 1 is shown. These two NMR spectra confirm that the chemical structure of the fluorinated diamine monomer prepared in Example 1 is consistent with the synthetic route. Similarly, the 1H NMR and fluorine spectra of the fluorinated diamine monomers prepared in Examples 2 to 10 also yielded the same conclusion, proving the successful synthesis of the fluorinated diamine monomers of the present invention.
[0091] (II) Structural testing of polyimide films:
[0092] The polyimide films prepared in Examples 11 to 14 and Comparative Examples 4 to 5 were characterized by FT-IR.
[0093] like Figure 3 The images show the infrared spectra of polyimide films prepared in Examples 11 to 16 and polymerized with six different dianhydrides. As can be seen from the spectra, all polyimide films exhibit characteristic absorption peaks of the imide groups, including: 1778 cm⁻¹. -1 A symmetrical stretching vibration peak appeared at C=O; at 1718 cm⁻¹ -1An asymmetric stretching vibration peak of C=O appeared; at 1371 cm⁻¹ -1 The stretching vibration peak of CN appeared at 723 cm⁻¹; -1 A bending vibration peak of C=O appeared at 1650 cm⁻¹; in addition, incomplete imidization resulted in a peak at 1650 cm⁻¹. -1 The stretching vibrations of C=O and C-NH in CONH were not observed in the spectrum, and were absent in the 2900-3200 cm⁻¹ region. -1 No absorption peaks for amino and carboxyl groups were observed, proving that the prepared polyimide films were all fully imidized.
[0094] (III) Optical property testing of polyimide films:
[0095] The polyimide films prepared in Examples 11-14 and Comparative Examples 1-7 were characterized using ultraviolet light. Specifically, a UV-Vis spectrophotometer (Vis-UV) was used. The film dimensions were 30 mm × 3 mm, the UV wavelength range was 200-800 nm, and the resolution was 0.5 nm. In Table 1, 0 represents the cutoff wavelength; T 450 (%), T 500 (%), T 550 (%) represent the light transmittance of the film at 450nm, 500nm and 550nm, respectively.
[0096] The specific test results are shown in Table 1 below.
[0097] Table 1:
[0098] Test case <![CDATA[0(nm)]]> <![CDATA[T 450 (%)]]> <![CDATA[T 500 (%)]]> <![CDATA[T 550 (%)]]> Example 11 318 79.2 85.5 87.2 Example 12 346 78.4 85.1 87.1 Example 13 352 74.1 83.2 86.7 Example 14 353 77.6 83.3 86.0 Comparative Example 1 342 74.8 77.6 80.0 Comparative Example 2 346 76.7 81.2 83.3 Comparative Example 3 353 75.9 80.9 82.5 Comparative Example 4 356 69.1 75.4 78.4 Comparative Example 5 357 70.6 79.5 82.0 Comparative Example 6 352 76.8 80.5 82.6 Comparative Example 7 356 75.4 78.3 81.5
[0099] As can be seen from the test results in Table 1, the polyimide films of Examples 11 to 14 exhibited excellent optical performance. Specifically, the light transmittance of all polyimide films at 550 nm was above 85%. Among them, the polyimide film prepared using 6FDA had the highest light transmittance at 550 nm, reaching approximately 87%. This indicates that the ultraviolet performance of polyimide is closely related to the chemical structure of tetracarboxylic dianhydride. Compared with other dianhydrides, 6FDA contains large-volume side groups, which gives the polyimide structure a larger free volume, reduces the molecular chain packing density, further suppresses the CTC effect, and is beneficial to improving the light transmittance of the film. Similarly, the polyimide films prepared in Examples 11 to 14 exhibited the same optical transmittance performance at 500 nm and 450 nm as at 550 nm.
[0100] Compared to the embodiments, Comparative Example 1 showed cracks on the film surface due to excessively high thermal imidization temperature. This indicates that improving the maximum set temperature of thermal imidization can enhance the film-forming properties of polyimide. Simultaneously, suitable thermal imidization reaction conditions can significantly improve the light transmittance of the polyimide film, such as increasing the light transmittance at 550 nm from 80% to 87%. Therefore, under the premise of ensuring complete imidization of the polyimide film, rationally setting and optimizing the thermal imidization temperature program can guarantee the transparency and integrity of the film, resulting in superior performance and better application effects.
[0101] Compared to the embodiments, the polyimide films prepared in Comparative Examples 2 and 3 had thicknesses of 30 mm and 40 mm, respectively. Based on the test results in Table 1, the optical transmittance decreased with increasing film thickness. Therefore, in practical applications, appropriate film thickness and light transmittance should be selected to meet actual usage requirements.
[0102] Compared with the examples, Comparative Examples 4 and 5 used rigid anhydrides to react with fluorinated diamine monomers to prepare polyimide films. Based on the test results in Table 1, the optical properties of the polyimide films prepared using rigid PMDA and BPDA dianhydride monomers were reduced compared with those prepared in Examples 11 to 14. The main reason is that the rigid dianhydrides reduce the flexibility of the overall molecular chain structure of polyimide, making the molecular chains more prone to orientation. At the same time, these two rigid dianhydrides do not contain side groups to regulate the density and free volume of the molecular chains, which also leads to a decrease in their optical properties.
[0103] Compared to Example 11, Comparative Examples 6 and 7 replaced the diamine monomers and reacted them with the same acid anhydride under the same conditions to prepare corresponding polyimide films. Based on the test results in Table 1, the diamine monomer used in Comparative Example 7 did not contain fluorine atoms or alkyl substituents, resulting in the worst optical performance, specifically a light transmittance of only 81.5% at 550 nm. In contrast, the diamine monomer used in Comparative Example 6 contained fluorine atoms, which increased the light transmittance of the resulting polyimide at 550 nm to 82.6% under the influence of fluorine atoms. Comparative analysis of the films prepared in Comparative Examples 6, 7, and 11 demonstrates that when both fluorine atoms and alkyl substituents are present in the diamine monomer structure, the polyimide exhibits the best suppression effect against the CTC effect under the combined influence of the strong electronegativity of fluorine atoms and the large-volume side groups of alkyl substituents, thus resulting in the most superior optical performance of the film.
[0104] (iv) Thermal property testing of polyimide films:
[0105] The polyimide films prepared in Examples 11–14 were characterized by DSC and TGA. Differential scanning calorimetry (DSC) characterization: 5 mg sample, T... g Under a nitrogen atmosphere, at a flow rate of 20 mL / min, the temperature was increased from room temperature to 400 °C at a rate of 20 °C / min, held for 5 min, then decreased by 40 °C, and then increased again to 400 °C at a rate of 10 °C / min with a nitrogen flow rate of 20 mL / min. The polymer T was measured based on the second heating curve. g Thermogravimetric analysis (TGA): A 5 mg sample was heated from 40 °C to 800 °C at a heating rate of 10 °C / min, with a nitrogen flow rate of 20 mL / min. The specific test results are shown in Table 2 below.
[0106] Table 2:
[0107] Test case <![CDATA[T g (℃) a ]]> <![CDATA[T d5％ (℃) b ]]> <![CDATA[T d10％ (℃) b ]]> <![CDATA[T w800 (%) c ]]> Example 11 284 519 538 50.8 Example 12 257 563 586 56.7 Example 13 358 467 500 42.6 Example 14 219 519 535 60.1
[0108] In Table 2, a represents the heating rate of 10℃ / min under a nitrogen atmosphere; b represents the thermal decomposition temperatures of 5% and 10% recorded at a heating rate of 10℃ / min; and c represents the residual carbon content at 800℃ under a nitrogen atmosphere.
[0109] As can be seen from the test results in Table 2, the T values of the polyimide films prepared in Examples 11 to 14 are... g The temperature range is between 219°C and 358°C, with the T value of the thin film prepared using 6FCDA in Example 13 being... g The highest glass transition temperature is achieved by 6FDA, which contains two large side groups and ether bonds between benzene rings, enhancing the intermolecular forces to some extent compared to other dianhydrides. While the polyimide prepared with 6FDA in Example 11 has large side groups in its chemical structure, the lack of ether bonds between benzene rings increases the flexibility of its molecular chains compared to Example 13, resulting in a slightly lower glass transition temperature. The polyimide films prepared in Examples 11-14 have high 5% thermal decomposition temperatures, especially the polyimide film prepared in Example 12, which reaches 563°C. This is because ODPA does not contain side-substituents, resulting in a more compact molecular structure, stronger intermolecular forces, and better thermal stability. Films prepared using 6FDA with side-substituents or BPADA with longer molecular chains have slightly lower thermal decomposition temperatures.
[0110] (V) Mechanical property testing of polyimide films:
[0111] The mechanical properties of the polyimide films prepared in Examples 11 to 14 were characterized using a universal tensile testing machine. The tests were conducted at room temperature according to the GB / T 1040.3-2006 standard for films, at a tensile rate of 5.0 mm / min. The PI film samples were 30 mm × 3 mm × 20 μm in size. Tensile strength, tensile modulus, and elongation at break were tested. The specific test results are shown in Table 3 below.
[0112] Table 3:
[0113]
[0114] As shown in Table 3, the tensile strength of the polyimide films prepared in Examples 11 to 14 ranges from 89 MPa to 118.9 MPa, and the tensile modulus ranges from 2.9 GPa to 3.9 GPa. Among them, the polyimide film prepared in Example 13 exhibits the best mechanical properties. This is mainly due to the large side groups and ether bonds of 6FCDA, which enhance the rigidity of the chain and give the film good resistance to deformation. In contrast, the mechanical properties of the film prepared from 6FDA in Example 11 are relatively low. This may be because the film structure, with the simultaneous presence of trifluoromethyl and alkyl substituents, lacks the ether bonds found in the 6FCDA structure, resulting in a more disordered arrangement of molecular chains, a lower molecular chain density, reduced mechanical properties, increased brittleness, and the lowest elongation at break.
[0115] The present invention has been described in detail above with reference to specific embodiments and exemplary examples; however, these descriptions should not be construed as limiting the present invention. Those skilled in the art will understand that various equivalent substitutions, modifications, or improvements can be made to the technical solutions and embodiments of the present invention without departing from the spirit and scope of the invention, and all such modifications and improvements fall within the scope of the present invention. The scope of protection of the present invention is defined by the appended claims.
Claims
1. A fluorinated diamine monomer, characterized in that, In Formula I, R1 and R2 are selected from methyl, ethyl, or propyl.
2. A method for preparing a fluorinated diamine monomer as described in claim 1, characterized in that, The preparation steps are as follows: Step 1: Dissolve phenol containing amino and dialkyl groups in an aprotic polar solvent, add alkali, and react at room temperature for 1 to 2 hours; Step 2: Under low temperature conditions, hexafluorobenzene is slowly added dropwise to the system in step S1. After stirring evenly, the mixture is raised to room temperature and the reaction continues for 2-6 hours to prepare a fluorinated diamine monomer.
3. The method for preparing the fluorinated diamine monomer according to claim 2, characterized in that, In step 1, the aprotic polar solvent is at least one of dimethyl sulfoxide, N-methylpyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide, and sulfolane.
4. The method for preparing the fluorinated diamine monomer according to claim 2, characterized in that, In step 1, the base is K2CO3, NaCO3, Cs2CO3, KOH, NaOH or Et3N, and its amount is 1:(1-3) of the molar amount of phenol containing amino and dialkyl groups.
5. The method for preparing the fluorinated diamine monomer according to claim 2, characterized in that, In step 2, the reaction temperature under low-temperature conditions is -5℃ to 10℃.
6. The method for preparing the fluorinated diamine monomer according to claim 2, characterized in that, In step 2, the molar ratio of phenol with amino and dialkyl groups to hexafluorobenzene is 1:(0.5 to 0.7).
7. A polyimide, characterized in that, It is prepared by polymerizing the fluorinated diamine monomer as described in claim 1 with tetracarboxylic acid dianhydride to obtain polyamic acid, followed by imidization; wherein, the tetracarboxylic acid dianhydride is 4,4'-(hexafluoroisopropylidene)phthalic anhydride, 4,4'-oxobisphthalic anhydride, 9,9-bis(trifluoromethyl)oxanthracene-2,3,6,7-tetracarboxylic acid dianhydride, or bisphenol A type diether dianhydride.
8. The method for preparing the polyimide film according to claim 7, characterized in that, The solid content of polyamic acid is 10wt% to 30wt%, and the maximum temperature for thermal imidization is 280℃.
9. A polyimide film, characterized in that, It is prepared using the polyimide as described in claim 7, and the thickness of the polyimide film is 15μm-25μm.
10. An application of the polyimide film as described in claim 9, characterized in that, Used for flexible display substrates, printed circuit boards, solar cell substrates, or flexible packaging boards.