A fluorinated anthracene-containing polyimide copolymer and a method for preparing the same

Abstract

The application discloses a fluorinated polyimide copolymer containing anthrone structure and a preparation method thereof, and belongs to the technical field of high polymer materials. The fluorinated polyimide copolymer containing anthrone structure has the following molecular structure: wherein n / (n+m) = 0.2-0.8; the fluorinated polyimide copolymer containing anthrone structure has high thermal stability and mechanical strength, simultaneously shows high transparency, good dissolving and processing performance and low dielectric constant, and has a wide application prospect.

Description

Technical Field

[0001] The invention relates to a polyimide material, in particular to a fluorinated anthrone-containing polyimide copolymer and a preparation method thereof, belonging to the technical field of polyimide modification. Background Art

[0002] Polyimide (PI) is a type of high-performance polymer with an imide ring in the main chain. According to its structural unit, polyimide can be divided into linear polyimide and cyclic polyimide, among which cyclic polyimide can be divided into aliphatic and aromatic polyimide. Because the polyimide main chain contains an imide ring structure, it has excellent comprehensive performance, which is mainly reflected in the following aspects: (1) High and low temperature resistance. The thermal decomposition temperature of polyimide is generally greater than 500℃, and the glass transition temperature is above 250℃. Moreover, polyimide can also withstand extremely low temperatures and will not crack even in liquid nitrogen at -269℃. Therefore, polyimide has excellent high and low temperature resistance. (2) Excellent mechanical properties: Polyimide has excellent mechanical properties. The tensile strength of its film is generally above 100MPa and the elastic modulus is 3~4GPa. The elastic modulus of polyimide fiber is even higher. (3) Good dimensional stability: Polyimide has a highly conjugated structure, which gives it a low coefficient of thermal expansion (CTE), generally between 20 and 50 ppm / K. It can also be structurally modified to reduce the length of the flexible chain segment so that it has a thermal expansion coefficient comparable to that of silicon wafers, and is then used in materials such as flexible substrates and flexible transistors. (4) Good chemical stability: Polyimide has good chemical corrosion resistance. In addition, polyimide also has good water resistance and can remain stable in high-temperature water for a long time. (5) Good dielectric and insulating properties: The dielectric constant of traditional polyimide is usually around 3 to 4 and remains stable over a wide temperature and frequency range. (6) Flame retardancy: Polyimide has self-extinguishing properties and can automatically extinguish when burned in air. It has a low smoke rate and a limiting oxygen index range of 35 to 75%. Based on its various excellent properties, it is used in various fields such as adhesives, coatings, fibers, foams, medicine, aerospace, and films.

[0003] Currently, most of the traditional aromatic polyimides are synthesized from aromatic diamines and aromatic dianhydrides, in which the aromatic benzene structure contained can enhance the heat resistance, mechanical properties and chemical resistance of the polymer. However, the aromatic benzene structure has a high conjugation effect and strong intermolecular interaction force, resulting in the difficulty in processing of the polyimide film. Moreover, strong charge transfer effect occurs between the electron donor aromatic diamine and the electron acceptor aromatic dianhydride, in which the number of electrons around the donor is reduced due to the attraction of the carbonyl group of the electron acceptor, and the two are tightly arranged together by the mutual attraction between the electron clouds, causing the polymer molecular chain to be tightly stacked, and the adjacent units to form a charge transfer complex (CTC), so that the polyimide film has strong absorption in the visible light region, presenting a deep color, thereby limiting its application in optoelectronic devices.

[0004] Therefore, in view of the limitations of polyimide in terms of solubility and optical transparency, the existing technology mainly uses the following modification methods to prepare soluble transparent polyimide materials: 1) by introducing flexible groups to affect the orientation and flexibility of the polymer molecular chain, improve the close stacking of the molecular chain, hinder the electronic mobility of the molecular chain, and enhance the solubility and optical transparency of the polymer in organic solvents, but more flexible structures will accelerate the movement of the molecular chain due to single bond rotation, thereby affecting the thermal stability and glass transition temperature of the polyimide. ("Synthesis and properties of soluble polyimides containing tert-butyl, ether linkages, and triphenylmethane units", Qin Z, et al. High Performance Polymers, 2020, 32 (8): 924-932.) A diamine monomer containing tert-butyl, ether linkage and triphenylmethane was synthesized and polymerized with aromatic dianhydride to obtain a series of aromatic polyimides with good solubility and good optical transparency. 2) By introducing a twisted non-coplanar structure, the molecular backbone can be twisted, hindering the stacking of polyimide molecular chains and effectively destroying the formation of charge transfer complexes (CTCs), thereby improving their solubility, melt processing properties, and optical transparency. For example, (“Heat-resistant colorless polyimides from benzimidazolediamines: synthesis and properties”, Li D, et al. Polymer, 2022, 254: 125078.) designed and synthesized 6-amino-2-(2'-methyl-4'-aminophenyl)-N-phenylbenzimidazole and 6-amino-2-(2'-trifluoromethyl-4'-aminophenyl)-N-phenylbenzimidazole monomers, and further obtained polyimide films with a transmittance of up to 80% at 400 nm.3) Introducing bulky side groups into the molecular chain of polyimide can increase the distance between molecular chains, effectively reduce chain stacking and weaken the intermolecular interaction force, inhibit chain segment movement, increase the rigidity of the chain segment, and reduce the impact on its thermal properties while improving solubility and optical transparency. For example, ("Binary / ternary memory behavior of organo-solubility polyimides containing flexible imide linkages and pendent triphenylamine or 3,4,5-trifluobenzene moieties", Ye Q, et al, European Polymer Journal, 2020, 125: 109473.) An aromatic diamine monomer containing a 3,4,5-trifluorophenyl group was synthesized, and TPA groups and 3,4,5-trifluorophenyl groups were introduced into the side chain. A soluble polyimide was synthesized by a two-step method, which has good thermal stability in the range of 370-420°C. The above modification methods can improve the transparency and solubility processing properties of polyimide to a certain extent, but at the same time will cause a significant loss of its thermal stability and mechanical strength. Summary of the Invention

[0005] In view of the defects of the prior art, the first object of the present invention is to provide a fluorinated anthrone-containing polyimide copolymer, which has high thermal stability and mechanical strength while exhibiting high transparency, good solubility and processing properties, and a low dielectric constant.

[0006] The second object of the present invention is to provide a method for preparing a fluorinated polyimide copolymer containing anthrone structure, which is simple, has mild conditions, and is conducive to large-scale production.

[0007] In order to achieve the above technical objectives, the present invention provides a fluorinated anthrone-containing polyimide copolymer having the following molecular structure:

[0008]

[0009] Among them, n / (n+m)=0.2~0.8.

[0010] The key to the fluorinated anthrone-containing polyimide copolymer provided by the present invention is the simultaneous introduction of an anthrone structure and a trifluoromethyl-containing aryl ether structure into the polyimide through a copolymerization method. This effectively improves the transparency and solubility of the polyimide while also exhibiting good mechanical properties and thermal stability. On the one hand, by introducing trifluoromethyl side groups into the polyimide's molecular backbone, the trifluoromethyl group, through its strong electron-withdrawing ability, effectively weakens the formation of charge transfer complexes (CTCs) between dianhydrides and diamines, thereby improving the optical transparency of the system. Furthermore, as a side chain modification, it has a certain steric effect, which can increase the distance between the molecular chains and hinder the close packing of the molecular chains, thereby improving the solubility of the polyimide. On the other hand, the anthrone structure introduced into the polyimide molecular backbone not only has a twisted non-coplanar structure, but also has a large spatial volume and strong polarity. This twisted non-coplanar structure can distort the molecular backbone, hindering the stacking of polyimide molecular chains and effectively disrupting the formation of charge transfer complexes (CTCs), thereby improving its solubility, melt processing properties, and optical transparency to a certain extent. Its large spatial volume can effectively reduce the polymer's packing density, increase the distance between molecular chains, and regulate the molecular aggregation state, thereby improving its solubility and optical transparency. Furthermore, the anthrone, with its excellent thermal properties, acts as a side group, enhancing the rigidity of the molecular chain segments and inhibiting their motion, thereby improving the thermal performance of the system. Furthermore, the carbonyl group in the anthrone structure imparts strong polarity, improving its solubility and weakening the formation of charge transfer complexes between dianhydrides and diamines. Thirdly, the introduction of ether bonds into the polyimide backbone can influence the orientation and flexibility of the polymer chains, improve the close packing of the chains, hinder the electron mobility of the chains, and enhance the polymer's solubility and optical transparency in organic solvents. In summary, the fluorinated anthrone-containing polyimide copolymer, by introducing trifluoromethyl side groups, anthrone structures, and ether bonds into the backbone, synergistically improves the solubility and transparency of the polyimide and achieves a lower dielectric constant, while maintaining high mechanical properties and thermal stability.

[0011] As a preferred embodiment, the fluorinated anthrone-containing polyimide copolymer has a molecular structure where n / (n+m) = 0.5 to 0.8. With the increase in 1,4-bis(4-amino-2-trifluoromethylphenoxy)benzene (DABTF) units, the transmittance of the polyimide film at 500 nm gradually increases. In particular, when the DABTF ratio exceeds 0.5, the transmittance exceeds 86%, demonstrating excellent optical transparency.

[0012] As a preferred solution, the number average molecular weight of the fluorinated anthrone-containing polyimide copolymer is 70,000 to 120,000, and the molecular weight distribution index is 1.1 to 1.6.

[0013] The present invention also provides a method for preparing a fluorinated polyimide copolymer containing anthrone structure. The method comprises the following steps: dissolving 4,4'-diaminobiphenyl and 1,4-bis(4-amino-2-trifluoromethylphenoxy)benzene in an organic solvent, first adding 10,10-bis[4-(3,4-dicarboxyphenoxy)phenyl]-9(10H)-anthrone dianhydride to carry out an amidation reaction, and then adding acetic anhydride and pyridine to carry out an imidization reaction to obtain the fluorinated polyimide copolymer.

[0014] As a preferred solution, the amidation reaction conditions are: first reacting in an ice bath for 0.5 to 1.5 hours, and then reacting at room temperature for 12 to 15 hours.

[0015] As a preferred solution, the conditions for the imidization reaction are: first react at room temperature for 0.5 to 1.5 hours, and then react at 105 to 115° C. for 3 to 5 hours.

[0016] As a preferred embodiment, the 10,10-bis[4-(3,4-dicarboxyphenoxy)phenyl]-9(10H)-anthrone dianhydride is prepared by the following method: 4-nitrophthalonitrile and 10,10-bis(4-hydroxyphenyl)-9(10H)-anthrone are subjected to a nucleophilic substitution reaction to obtain 10,10-bis[4-(3,4-dicyanophenoxy)phenyl]-9(10H)-anthrone; and the 10,10-bis[4-(3,4-dicyanophenoxy)phenyl]-9(10H)-anthrone is subjected to a hydrolysis reaction and a dehydration cyclization reaction to obtain 10,10-bis[4-(3,4-dicarboxyphenoxy)phenyl]-9(10H)-anthrone dianhydride.

[0017] As a preferred solution, the substitution reaction is carried out under the action of potassium carbonate at room temperature for 8 to 10 hours.

[0018] As a preferred solution, the hydrolysis reaction conditions are: in an alcohol-water mixed solvent, under the action of potassium hydroxide, the reaction is carried out at 95-115° C. for 12-14 hours.

[0019] As a preferred solution, the condensation reaction conditions are: reflux at 120-130° C. for 3-5 hours in a glacial acetic acid and acetic anhydride system.

[0020] Compared with the existing technology, the present invention has the following beneficial technical effects:

[0021] The fluorinated polyimide copolymer containing anthrone structure of the present invention obtains good comprehensive performance by introducing trifluoromethyl and flexible ether bonds, as well as anthrone structure. The film material thereof has high thermal stability and mechanical strength, and exhibits high transparency, good solubility and processing properties, and low dielectric constant. For example: (1) The transmittance of the fluorinated polyimide film containing anthrone structure at 500nm is 77.9-87.2%, and the cutoff wavelength is 362-371nm. (2) The fluorinated polyimide material containing anthrone structure is soluble in low-boiling point solvents such as pyridine (Py) and tetrahydrofuran (THF). (3) The fluorinated polyimide material containing anthrone structure has a 5% thermal weight loss temperature of 505.8-523.4°C and a 10% thermal weight loss temperature (T 10％ ) is 534.6~552.3℃. (4) The glass transition temperature (T g ) Within the temperature range of 257.6-369.3°C, the tensile strength is 66.27-91.17 MPa, the elastic modulus is 1.27-2.34 GPa, and the elongation at break is 5.19-12.70%. (5) The water absorption and contact angle of the fluorinated anthrone-containing polyimide film range from 0.55-0.76% and 89.5-98.4°, respectively, indicating excellent hydrophobicity. (6) The dielectric constant of the fluorinated anthrone-containing polyimide film at a frequency of 0.1 kHz is 1.89-2.63.

[0022] The preparation method of the fluorinated anthrone-containing polyimide copolymer of the present invention is simple, requires mild conditions, and is conducive to large-scale production. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is the FT-IR spectrum of BDCOPPAD.

[0024] Figure 2 For BDCOPPAD 1 H NMR spectrum.

[0025] Figure 3 For BDCOPPAD 13 C NMR spectrum.

[0026] Figure 4 For M-9 1 H NMR spectrum.

[0027] Figure 5 For M-5 1 H NMR spectrum.

[0028] Figure 6 Infrared spectra of M-1 to M-9.

[0029] Figure 7UV-Vis curves and film appearance photos of M-1 to M-9.

[0030] Figure 8 Thermogravimetric curves (a) and DSC curves (b) of M-1 to M-9.

[0031] Figure 9 These are the stress-strain curves of M-1 to M-9.

[0032] Figure 10 These are the WAXD curves of M-1 to M-9. DETAILED DESCRIPTION

[0033] The following specific examples are intended to further illustrate the present invention, rather than to limit the scope of protection of the claims.

[0034] Unless otherwise specified, the chemical agents involved in the following specific embodiments are conventional commercially available agents.

[0035] The testing and characterization methods involved in the following specific examples are:

[0036] (1) Solubility test: Weigh 10 mg of sample into 1 mL of organic solvent and observe its dissolution at room temperature. If it is not completely dissolved, heat it to 60°C and continue to observe its dissolution to obtain the solubility of each polymer.

[0037] (2) Molecular weight test (GPC): The molecular weight of the polymer was determined by using a DAWN HELEOS II multi-angle laser light scattering instrument from Wyatt Technology, USA. DMF was used as the mobile phase (NMP was used as the mobile phase if the sample was not dissolved). The sample was prepared into a 3 mg / mL solution at a flow rate of 0.3 mL / min and tested at 40°C to obtain the weight average molecular weight (M w ), number average molecular weight (M n ) and polydispersity index (PDI).

[0038] (3) Thermogravimetric analysis (TGA): Thermogravimetric analysis was performed using a Diamond TG / DTA EXSTAR6000 high-temperature thermogravimetric-differential thermal analyzer (PerkinElmer, USA) in a nitrogen atmosphere with a nitrogen flow rate of 10°C / min, a heating rate of 10°C / min, and a test temperature range of 0–800°C.

[0039] (4) Differential Scanning Calorimetry (DSC): The test was performed using a DSC 800 differential scanning calorimeter from PerkinElmer, USA. The sample was dried at 120°C for 4 h before the test. 5-10 mg of the sample was weighed and tested in a N2 atmosphere with a nitrogen flow rate of 20 mL / min. The first heating rate was 20°C / min, and the heating temperature range was 40-400°C. The temperature was maintained at 400°C for 2 min. The temperature was then rapidly lowered, and the temperature range was 40-400°C. The temperature was maintained at 40°C for 2 min. The second heating was performed with a heating rate of 20°C / min, and the heating temperature range was 40-400°C.

[0040] (5) Optical performance test (UV-Vis): The test was performed using a U-3310 ultraviolet-visible spectrometer (UV-Vis) produced by Hitachi, Japan. A polyimide film with a thickness of 40 to 50 μm was cut into a size of 20 mm × 40 mm, and the transmittance was tested in the wavelength range of 200 to 800 nm.

[0041] (6) Mechanical property test: The tensile test was performed using a CMT8012 universal electronic testing machine from Shanghai Zhongchen Digital Technology Equipment Co., Ltd. The polyimide film with a thickness of 40 to 50 μm was cut into a size of 2 mm × 50 mm. The tensile speed was 10 mm / min. Each sample was tested 3 to 5 times, and the results were averaged.

[0042] (7) Water absorption test (WU): Cut a polyimide film with a thickness of 40-50 μm into a size of 10 mm × 10 mm, first dry it in a 100 °C oven for 4 h, weigh its mass, and then soak it in deionized water for 24 h. Quickly wipe the moisture on the surface of the film with a paper towel, weigh the mass after water absorption, and calculate the water absorption rate of the sample. Each sample is tested 3-5 times, and the results are averaged.

[0043] Water absorption calculation formula: Among them, m dry is the mass of the dry sample (g), m wet is the mass of the sample after water absorption (g).

[0044] (8) Water contact angle test: The test was performed using a German OCA15EC contact angle meter. The film was cut and placed on a sample table. Distilled water was used as the test liquid. Each sample was tested 4 to 6 times at room temperature, and the results were averaged.

[0045] (9) Dielectric performance test (DC): The test was performed using a KEYSIGHT E4980A precision impedance analyzer. A polyimide film with a thickness of 40 to 50 μm was cut into a size of 10 mm × 20 mm, and the contact area with the conductive adhesive was 8 mm × 8 mm. The test temperature was 30°C, and the test frequency was 0.1 kHz to 100 kHz. Each sample was tested 3 to 5 times, and the results were averaged.

[0046] (10) Crystallization performance test (WAXD): The test was performed using the Dadvance polycrystalline X-ray diffraction analyzer of Bruker, Germany. The polyimide film was cut into a size of 20 mm × 20 mm and placed on the sample cell. The scanning angle range was 2θ = 5 to 90°.

[0047] Example 1

[0048] Synthesis of 10,10-bis[4-(3,4-dicarboxyphenoxy)phenyl]-9(10H)-anthrone dianhydride (BDCOPPAD):

[0049]

[0050] (1) Synthesis of 10,10-bis(4-hydroxyphenyl)-9(10H)-anthrone (BHPA)

[0051] 19.4 g (0.1 mol) of anthrone and excess thionyl chloride (60 mL) were heated under reflux in a 250 mL single-necked flask for 6 h. The excess thionyl chloride was removed by atmospheric distillation and reduced pressure distillation. Then, o-xylene (80 mL) and excess phenol 37.0 g (0.39 mol) were added and reacted at 130 ° C for 10 h. After cooling to room temperature, the crude product was filtered and washed with a large amount of dichloromethane. After recrystallization from acetone, 34.4 g of a gray solid was obtained with a yield of 91% and a melting point of 306-307 ° C.

[0052] 1 H NMR (400MHz, DMSO-d6): δ = 9.43 (s, 2H), 8.12 (d, J = 7.7Hz, 2H), 7.59 (t, J = 8.2Hz, 2H), 7. 48(t,J=7.5Hz,2H),7.16(d,J=7.9Hz,2H),6.72(d,J=8.8Hz,4H),6.65(d,J=8.8Hz,4H).

[0053] (2) Synthesis of 10,10-bis[4-(3,4-dicyanophenoxy)phenyl]-9(10H)-anthrone (BDCNPPA)

[0054] To a 100-mL three-necked flask, add 3.46 g (20 mmol) of 4-nitrophthalonitrile and 30 mL of DMSO. After the solid completely dissolved, slowly add 3.78 g (10 mmol) of BHPA and 4.14 g (30 mmol) of KCO. The reaction was allowed to proceed at room temperature for 10 h under a nitrogen atmosphere, with progress monitored by TLC. After completion, the reaction was poured into ice water to precipitate a brownish-yellow solid, which was filtered to obtain a crude product. The crude product was separated by flash column chromatography using dichloromethane / petroleum ether (v:v = 2:1) as the eluent and recrystallized from acetonitrile to afford 5.5 g of white crystals with a yield of 87.3% and a melting point of 367.3-368.6°C.

[0055] 1 H NMR (400MHz, CDCl3): δ = 8.34 (dd, J = 7.8, 1.3Hz, 2H), 7.74 (d, J = 8.7Hz, 2H), 7.60 (t, J = 7.6Hz, 2H), 7.52 (t, J = 7.5Hz, 2H) ,7.32(d,J=2.5Hz,2H),7.27(dd,J=8.9,2.3Hz,2H),7.19(d,J=7.9Hz,2H),7.12(d,J=8.8Hz,4H),6.98(d,J=8.8Hz,4H). 13 C NMR (151MHz, CDCl3): δ=184.07,161.01,152.46,148.16,143.83,135.39,133.00,132.13,130.1 6,127.75,121.77,121.59,119.97,117.60,115.16,114.82,109.20,77.16,76.95,76.74,57.31.

[0056] (3) Synthesis of 10,10-bis[4-(3,4-dicarboxyphenoxy)phenyl]-9(10H)-anthrone (BDCOPPA)

[0057] To a 250 mL single-necked flask, 6.30 g (10 mmol) of BDCNPPA, 5.60 g (100 mmol) of KOH, and 100 mL of anhydrous ethanol and water (V:V = 1:1) were added in sequence. The mixture was heated to 100°C and reacted for 13 h. After the ammonia gas was completely released, the mixture was filtered while hot and the filtrate was poured into 200 mL of water. Hydrochloric acid solution was added dropwise to adjust the pH to 1-2. The mixture was filtered and washed several times with copious amounts of deionized water until neutral. The mixture was then dried to obtain 6.51 g of a white solid with a yield of 92.9% and a melting point of 157.6-158.5°C.

[0058] 1H NMR (400MHz, DMSO-d6): δ = 13.54 (s, 4H), 8.19 (dd, J = 7.8, 1.3Hz, 2H), 7.81 (d, J = 8.5Hz, 2H), 7.68 (t, J = 8.3H z,2H),7.56(t,J=7.9Hz,2H),7.27(d,J=7.8Hz,2H),7.24(s,2H),7.15(dd,J=8.5,2.6Hz,2H),7.06(s,8H). 13 C NMR (151MHz, DMSO-d6): δ=183.87,168.70,167.89,158.94,154.51,149.25,142.51,137.11,134.03,132.30,131.91 ,131.66,131.07,128.18,127.29,119.72,119.58,118.17,57.17,40.38,40.24,40.10,39.96,39.82,39.68,39.54.

[0059] (4) Synthesis of 10,10-bis[4-(3,4-dicarboxyphenoxy)phenyl]-9(10H)-anthrone dianhydride (BDCOPPAD)

[0060] In a 100 mL three-necked flask, 7.06 g (10 mmol) of BDCOPPA and 50 mL of glacial acetic acid were added. The mixture was heated until the solid was completely dissolved, and then 25 mL of acetic anhydride was added. The mixture was refluxed at 125°C for 4 h, cooled to room temperature, and filtered to obtain a crude product. The crude product was recrystallized from acetic anhydride / acetonitrile to obtain 5.28 g of white crystals with a yield of 78.8% and a melting point of 252.3-253.6°C.

[0061] 1 H NMR (400MHz, CDCl3): δ = 8.34 (dd, J = 7.8, 1.4Hz, 2H), 7.94 (d, J = 8.3Hz, 2H), 7.60 (t, J = 7.6Hz, 2H), 7.51 (t, J = 7.5Hz, 2H) ,7.46(dd,J=8.3,2.2Hz,2H),7.44(d,J=1.9Hz,2H),7.22(d,J=7.9Hz,2H),7.13(d,J=8.9Hz,4H),7.01(d,J=8.9Hz,4H). 13C NMR (151MHz, CDCl3): δ=184.19,164.46,162.48,162.00,153.03,148.39,143.79,133.93,133.12,13 2.23,132.20,130.34,127.82,127.74,125.25,124.65,120.06,112.83,77.26,77.05,76.84,57.42.

[0062] The infrared spectrum of BDCOPPAD is shown in Figure 2. Figure 1 As shown, the wave number is 1850 cm –1 and 1779cm –1 The peak at 1661 cm is the asymmetric and symmetric stretching vibration peak generated by the vibration coupling of the carbonyl group (C=O) attached to the same oxygen atom in the anhydride. –1 The stretching vibration absorption peak of the carbonyl group (C=O) on anthrone is 1277 cm –1 The peak at 1227 cm is the characteristic strong absorption peak of CO in cyclic anhydride. –1 The peak at is the stretching vibration absorption peak of the ether bond (COC), and all absorption peaks are consistent with the characteristic absorption peaks of the target product structure.

[0063] Example 2

[0064] Preparation of fluorinated polyimide copolymers containing anthrone structure:

[0065]

[0066] The synthesized dianhydride was copolymerized with 1,4-bis(4-amino-2-trifluoromethylphenoxy)benzene (DABTF) and 4,4'-diaminobiphenyl (HMB) in different proportions, and then polyimide was obtained by chemical imidization. The ingredients are shown in Table 1, and the synthesis process is shown in the above reaction formula. Taking polymer M-5 (n(DABTF) / n(HMB)=5 / 5) as an example, 0.1842g (1mmol) 4,4'-diaminobiphenyl (HMB), 0.4283g (1mmol) 1,4-bis(4-amino-2-trifluoromethylphenoxy)benzene (DABTF) and (2mL) NMP were added to a 50mL three-necked flask with N2, and stirred until the solid was completely dissolved. Then, 1.3400g (2mmol) BDCOP PAD was added in batches, and an appropriate amount of NMP was added to adjust the solid content of the solution to 18%. The reaction was carried out under ice bath conditions for 1h and at room temperature for 14h to obtain a polyamic acid viscous solution. The above viscous solution was appropriately diluted and a mixture of 2mL acetic anhydride and 2mL pyridine was added. The mixture was stirred at room temperature for 1h. After mixing evenly, the mixture was heated to 110℃ and stirred for 4h. After cooling to room temperature, the mixture was slowly poured into 100mL methanol solution to obtain a white fibrous solid. The product was washed repeatedly in boiling methanol solution, the solid was collected by filtration, and dried to obtain polymer M-5.

[0067] Table 1. Ingredient ratios of M-1 to M-9

[0068]

[0069] Example 3

[0070] Preparation of fluorinated polyimide copolymer films containing anthrone structure:

[0071] Taking polymer M-5 (n(DABTF) / n(HMB)=5 / 5) as an example, the solid was dissolved in DMAc, filtered through a nylon filter, and placed in a refrigerator. After the bubbles disappeared, it was applied to a clean glass plate using a cast method. The solution was then dried at 80°C for 6 hours to remove most of the solvent. The temperature was then programmed to 100°C, 150°C, 200°C, 250°C, and 290°C, with each temperature held for 1 hour. After cooling to room temperature, the glass plate was immersed in water, and the polyimide film was removed. The film was then dried in an oven at 100°C to obtain a dry, transparent polyimide film M-5.

[0072] Structural characterization of fluorinated polyimide copolymers containing anthrone structure:

[0073] This series of polyimide 1 H NMR spectrum Figure 4 and Figure 5 Take M-9 (n(DABTF) / n(HMB)=10 / 0) ​​as an example, Figure 4It can be seen that the doublet peak at chemical shift 8.34ppm and the triplet peak at 7.50-7.61ppm correspond to the anthrone structure in the main chain; and the hydrogen signal corresponding to the DABTF structural unit appears; due to the deshielding effect of the trifluoromethyl group, the chemical shift of the hydrogen protons on the benzene ring is 7-8ppm, and the remaining hydrogen integral areas and ratios are consistent with the target structure, indicating that polyimide M-9 has been successfully synthesized. The rest of the copolymerized polyimides in this series are taken as an example of M-5 (n(DABTF) / n(HMB)=5 / 5). 1 H NMR spectrum Figure 5 The integrated area and chemical shift of the hydrogen signal were attributed to the target structure, indicating that the polyimide with the expected structure had been synthesized.

[0074] M-9: 1 H NMR (400MHz, CDCl3) δ = 8.33 (d, J = 7.6Hz, 1H), 7.90 (d, J = 8.3

[0075] Hz,1H),7.76(d,J=2.3Hz,1H),7.59(t,J=7.5Hz,1H),7.55–7.46(m,3H),7.36(d,J=8.2Hz, 1H),7.23(d,J=7.9Hz,1H),7.16–7.07(m,4H),7.03(d,J=8.9Hz,1H),6.99(d,J=8.8Hz,2H).

[0076] M-5: 1 H NMR (400MHz, CDCl3) δ8.33 (d, J=7.7Hz, 2H), 7.95–7.86 (m, 2H),

[0077] 7.79–7.68(m,3H),7.59(t,J=7.6Hz,2H),7.56–7.49(m,5H),7.48(s,2H),7.36(d,J=8.3H z,2H),7.23(dd,J=7.7,3.7Hz,2H),7.16–7.08(m,6H),7.01(td,J=10.4,8.7,6.7Hz,5H).

[0078] The FT-IR spectra of this series of polyimides are as follows Figure 6 As shown, the wave number is 1778cm –1 and 1720cm –1 The absorption peaks at 733 cm are the symmetric and asymmetric stretching vibration peaks of C=O on the imide ring in polyimide; –1 The peak at 1365cm is the bending vibration absorption peak of C=O on the imide ring; –1The peak at 1235 cm is the stretching vibration absorption peak of CN on the imide ring; –1 The peak at 1321cm is the characteristic absorption peak of ether bond (COC); –1 The peak at is the characteristic absorption peak of trifluoromethyl (-CF3), and as the content of trifluoromethyl increases, the absorption peak becomes stronger and stronger; and at a wave number of 3200cm –1 and 1520cm –1 The above results indicate that imidization has been successful, indicating that the chemical structure of this series of copolymerized polyimides has been confirmed by FT-IR spectrum.

[0079] Molecular Weight of Fluorinated Anthrone-Containing Polyimide Copolymers: The molecular weights of this series of polyimides were determined by gel permeation chromatography and multi-angle laser light scattering with the polymers dissolved in DMF as the mobile phase. Specific data are shown in Table 2. As can be seen from Table 2, the molecular weight decreases with increasing amounts of the third monomer, DABTF. This is because the trifluoromethyl group in DABTF reduces the reactivity of the diamine, leading to a decrease in molecular weight. However, the molecular weights of this series remain relatively high, exceeding 70,000, indicating excellent film-forming properties, which facilitates film-forming and subsequent testing and characterization.

[0080] Table 2. Molecular weight of M-1 to M-9

[0081]

[0082] a Mw: weight average molecular weight; Mn: number average molecular weight; PDI: dispersion index (Mw / Mn).

[0083] Solubility properties of fluorinated polyimide copolymers containing anthrone structure:

[0084] Table 3. Solubility of M-1 to M-9

[0085]

[0086] a Solubility: ++Soluble at room temperature; +–Completely soluble after heating; ––Not soluble after heating.

[0087] The solubility of this series of polyimides in different solvents is shown in Table 3. The overall solubility of the copolymerized polyimides containing trifluoromethyl groups is excellent. They are soluble in common high-boiling-point aprotic polar solvents and low-boiling-point solvents at room temperature. When the ratio of n(DABTF) / n(HMB) is greater than 4 / 6, they are even soluble in tetrahydrofuran at room temperature. This is because the bulky anthrone structure contained in the backbone increases the distance between the molecular chains and reduces the close packing of the molecular chains. As the amount of the third monomer DABTF is continuously increased, the number of trifluoromethyl groups increases, increasing the molecular free volume and disrupting the regularity of the molecular chains, resulting in a lower packing density of the molecular chains. In addition, the presence of a large number of flexible ether bonds improves the rigid biphenyl structure of the original monomer HMB, increasing the intermolecular space and making it easier for small solvent molecules to enter the polymer molecules, thus demonstrating excellent solubility.

[0088] Optical properties of fluorinated polyimide copolymers containing anthrone structure:

[0089] The UV-Vis curves and film appearance photos of this series of polyimides are as follows: Figure 7 Specific data are shown in Table 4.

[0090] Table 4. Optical properties of M-1 to M-9

[0091]

[0092] a Transmittance at 500nm, 600nm, 700nm, 800nm;

[0093] b λ0: cutoff wavelength.

[0094] It can be seen from Table 4 that this series has excellent optical transparency, with a transmittance of 77.9-87.2% at 500nm and a cutoff wavelength range of 362-371nm. As the amount of DABTF monomer increases, the transmittance at each wavelength gradually increases, and the optical transparency gradually improves. This is because the trifluoromethyl group contained in the DABTF monomer is a strong electron-withdrawing group with a large dipole moment and free volume, which will reduce the conjugation of the benzene ring electron cloud in the molecular chain, and have a steric hindrance effect and an inductive effect, which gradually increases its optical transparency; and the DABTF monomer also contains a large number of flexible ether bond groups, which can reduce the stacking of the molecular chain and weaken the intermolecular interaction force. These multiple effects inhibit the formation of charge transfer complexes (CTC), thereby improving the optical transparency of the polyimide film. Figure 7 It can be seen that with the increase of DABTF monomer, the color of the polyimide film gradually becomes lighter, and M-9 is even close to colorless.

[0095] Thermal properties of fluorinated polyimide copolymers containing anthrone structure:

[0096] The thermal properties of this series of polyimides are analyzed by thermogravimetric analysis and DSC. The TGA curve is as follows: Figure 8 As shown in (a), the DSC curve is as follows Figure 8 (b) and the specific data are shown in Table 5.

[0097] Table 5. Thermal properties of M-1 to M-9

[0098]

[0099] a T g : glass transition temperature;

[0100] b R w : Residual mass ratio at 800℃;

[0101] c T 5％ : 5% thermal weight loss temperature;

[0102] d T 10％ : 10% thermal weight loss temperature;

[0103] e T max : Maximum thermal weight loss temperature.

[0104] Table 5 shows that this series of polyimides exhibits a relatively high glass transition temperature (Tg), with a temperature range of 257.6 to 369.3°C, a 5% thermal weight loss temperature of 505.8 to 523.4°C, and a 10% thermal weight loss temperature (Tg). 10％ ) is 534.6~552.3℃, the maximum thermal weight loss temperature (T max ) is 541.9~548.5℃, and the residual mass ratio at 800℃ is 56.9~64.4%, showing good thermal stability.

[0105] The third monomer, DABTF, introduced into the backbone contains a trifluoromethyl group and an ether bond. The trifluoromethyl group increases the intermolecular free volume, while the flexible ether bond facilitates molecular chain movement, ultimately leading to a slight decrease in the glass transition temperature. However, the bulky anthrone structure and the rigid biphenyl structure of the backbone maintain a certain degree of heat resistance, so overall, this series of polymers still has good heat resistance.

[0106] Mechanical properties of fluorinated polyimide copolymers containing anthrone structure:

[0107] The mechanical properties of this series of polyimides can be judged from their stress-strain curves, such as Figure 8Specific data are shown in Table 6. As can be seen from Table 6, the tensile strength of this series of copolymerized polyimide films ranges from 66.27 to 91.17 MPa, the elastic modulus ranges from 1.27 to 2.34 GPa, and the elongation at break ranges from 5.19 to 12.70%. As the content of the third monomer, DABTF, increases, the tensile strength and elastic modulus of the film gradually decrease, while the elongation at break gradually increases. This is because the trifluoromethyl group and ether bond contained in DABTF are flexible groups. Increasing the content of these structures weakens the rigidity of the molecular chain and improves the flexibility of the polyimide molecular chain, resulting in a corresponding increase in elongation at break. The interaction between the trifluoromethyl group and the ether bond gradually weakens, resulting in a corresponding decrease in tensile strength.

[0108] Table 6. Mechanical properties of M-1 to M-9

[0109]

[0110] a T s : tensile strength; b T m : elastic modulus; c E b : Elongation at break.

[0111] Water Absorption and Water Contact Angle of Fluorinated Anthrone-Containing Polyimide Copolymers: Detailed data for the water absorption and water contact angle of this series of polyimides are shown in Table 7. This table demonstrates excellent hydrophobicity, with water absorption ranging from 0.55% to 0.76% and contact angles ranging from 89.5° to 98.4°. With increasing amounts of the third monomer, DABTF, the water absorption of the polyimide films decreases and the contact angle increases. This is because the trifluoromethyl groups in the structure are hydrophobic, reducing the interaction between the polymer chain and water molecules, thereby reducing water absorption.

[0112] Table 7. Water absorption and contact angle of M-1 to M-9

[0113]

[0114] Dielectric Properties of Fluorinated Anthrone-Containing Polyimide Copolymers: The dielectric properties of this series of polyimides were analyzed by measuring the dielectric constant at three frequencies (0.1 kHz, 1 kHz, and 10 kHz) at room temperature. The specific data are shown in Table 8. As can be seen from the table, the dielectric constant decreases with increasing amounts of the third monomer, DABTF. This is due to the increasing presence of trifluoromethyl groups in the backbone. The low polarizability and high bond energy of the C-F bond reduce electronic polarizability and increase free volume. Furthermore, this group reduces the water absorption of the polyimide backbone, thereby lowering its dielectric constant. The bulky anthrone structure in the backbone also increases the free volume fraction. These factors work together to lower the dielectric constant of this series of polymers.

[0115] Table 8. Dielectric properties of M-1 to M-9

[0116]

[0117] Crystallization properties of fluorinated polyimide copolymers containing anthrone structure:

[0118] The crystallinity of this series of polyimides is analyzed by wide angle X-ray diffraction (WAXD) curves, such as Figure 10 As shown. Figure 10 It can be seen that all polymers in this series exhibit a non-crystalline amorphous structure, with broad peaks and no sharp crystalline diffraction peaks. This is because the large free volume of the anthrone structure and trifluoromethyl group disrupts the regular and tight arrangement of the molecular chains, inhibiting their movement and crystallization, resulting in an amorphous structure.

[0119] In summary, the fluorinated anthrone-containing polyimide copolymer provided by the present invention exhibits good solubility in common polar solvents and low-boiling-point solvents. Furthermore, as the DABTF content in the polymer backbone increases, the UV cutoff wavelength of the polyimide film gradually decreases from 371 nm to 362 nm, and the transmittance at 500 nm increases from 77.9% to 87.2%. In particular, when the ratio of n(DABTF) / n(HMB) is greater than 5 / 5, the transmittance is higher than 86%, demonstrating excellent optical transparency. The introduction of DABTF reduces the thermal and mechanical properties of the polyimide to a certain extent, and its glass transition temperature (T g) In the temperature range of 257.6-369.3℃, the tensile strength is 66.27-91.17MPa, the elastic modulus is 1.27-2.34GPa, and the elongation at break is 5.19-12.70%. In addition, the water absorption rate and contact angle of this series of fluorinated anthrone-containing polyimide copolymer films are in the range of 0.55-0.76% and 89.5-98.4°, respectively, showing excellent hydrophobicity. The trifluoromethyl group in DABTF has an extremely low polarizability, which makes this series of films have excellent low dielectric properties. The dielectric constant at a frequency of 0.1KHz is 1.89-2.63, especially when the ratio of n(DABTF) / n(HMB) is greater than 6 / 4, the dielectric constant is lower than 2.0.

Claims

1. A fluorinated polyimide copolymer containing anthrone structure, characterized in that: It has the following molecular structure: ； Among them, n / (n+m)=0.2~0.

8.

2. The fluorinated polyimide copolymer containing anthrone structure according to claim 1, characterized in that: n / (n+m)=0.5~0.

8.

3. A fluorinated polyimide copolymer containing anthrone structure according to claim 1 or 2, characterized in that: The number average molecular weight is 70,000~120,000, and the molecular weight distribution index is 1.1~1.

6.

4. The method for preparing a fluorinated polyimide copolymer containing anthrone structure according to any one of claims 1 to 3, characterized in that: After 4,4'-diaminobiphenyl and 1,4-bis(4-amino-2-trifluoromethylphenoxy)benzene were dissolved in an organic solvent, 10,10-bis[4-(3,4-dicarboxyphenoxy)phenyl]-9(10 H )-anthrone dianhydride is subjected to amidation reaction, and then acetic anhydride and pyridine are added to carry out imidization reaction to obtain.

5. The method for preparing a fluorinated anthrone-containing polyimide copolymer according to claim 4, wherein: The conditions of the amidation reaction are: first reacting in an ice bath for 0.5 to 1.5 h, and then reacting at room temperature for 12 to 15 h.

6. The method for preparing a fluorinated polyimide copolymer containing anthrone structure according to claim 4, wherein: The conditions of the imidization reaction are: first react at room temperature for 0.5-1.5 hours, and then react at 105-115° C. for 3-5 hours.

7. The method for preparing a fluorinated polyimide copolymer containing anthrone structure according to claim 4, characterized in that: The 10,10-bis[4-(3,4-dicarboxyphenoxy)phenyl]-9(10 H )-anthrone dianhydride is prepared by the following method: 4-nitrophthalonitrile and 10,10-bis(4-hydroxyphenyl)-9(10 H )-anthrone undergoes nucleophilic substitution reaction to obtain 10,10-bis[4-(3,4-dicyanophenoxy)phenyl]-9(10 H )-anthrone; the 10,10-bis[4-(3,4-dicyanophenoxy)phenyl]-9(10 H )-anthrone undergoes hydrolysis and dehydration cyclization to obtain 10,10-bis[4-(3,4-dicarboxyphenoxy)phenyl]-9(10 H )-anthrone dianhydride.

8. The method for preparing a fluorinated anthrone-containing polyimide copolymer according to claim 7, wherein: The conditions for the nucleophilic substitution reaction are: reacting under the action of potassium carbonate at room temperature for 8 to 10 hours.

9. The method for preparing a fluorinated polyimide copolymer containing anthrone structure according to claim 7, wherein: The hydrolysis reaction conditions are: in an alcohol-water mixed solvent, under the action of potassium hydroxide, at 95-115° C. for 12-14 hours.

10. The method for preparing a fluorinated polyimide copolymer containing anthrone structure according to claim 7, characterized in that: The dehydration cyclization reaction conditions are: in a glacial acetic acid and acetic anhydride system, react at 120-130° C. for 3-5 hours.

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