Fluorinated polyetherimide containing carbazole structure and preparation method thereof

Abstract

The invention discloses fluorinated polyetherimide containing a carbazole structure and a preparation method of the fluorinated polyetherimide, and belongs to the technical field of modified polyimide materials. The fluorinated polyetherimide containing the carbazole structure has the following repetitive structural units: # imgabs0 #. A carbazole structural unit which simultaneously contains trifluoromethyl, an ether bond, a large molecular volume and an asymmetric polar structure is introduced into a main chain of the fluorinated polyetherimide containing the carbazole structure; and the composition is endowed with good comprehensive properties such as solubility, heat resistance, optical property, mechanical property, dielectric property, hydrophobicity and the like.

Description

Technical Field

[0001] The invention relates to a polyetherimide, in particular to a fluorinated polyetherimide containing a carbazole structure and a preparation method thereof, belonging to the technical field of polymer materials. Background Art

[0002] Polyimide (PI) boasts excellent properties such as high-temperature resistance, chemical corrosion resistance, and wear resistance, garnering widespread attention in fields such as aerospace, microelectronics, and separation membranes. However, these materials still suffer from inherent drawbacks in practical applications, most notably the insolubility and infusibility of aromatic polyimides, which severely restricts their processing performance and application range. Given the current limited availability of functional materials and the long and costly development cycles for new PIs, molecular structural modification of existing polyimide materials has become a more cost-effective research direction.

[0003] So far, researchers have mainly studied the modification of polyimides from the following aspects: (1) Introduction of flexible structural units. The introduction of an appropriate amount of flexible groups (such as ether bonds, methyl groups, etc.) can not only improve the packing density of the molecular chain, but also hinder the formation of charge transfer complexes (CTCs), thereby improving the solubility and optical transparency of PI. For example, the literature ("Preparation and properties of highly organosoluble polyimides derived from 2,2'-disubstituted-4,4'-oxydianilines", Zhao J, et al. High Performance Polymers, 2017, 30 (4): 456-464) discloses a series of polyimide PIs. Due to the introduction of ether bonds, the orientation and flexibility of the polymer molecular chain are affected, the close stacking of the molecular chain is hindered, and the PIs have good solubility. At the same time, due to the presence of rigid biphenyl or naphthalene, the PIs have good thermal stability and are expected to be candidate materials in the electronic field. (2) Introducing twisted non-coplanar structures: By introducing twisted non-coplanar structures, the molecular configuration can be effectively changed, the stacking of PI molecular chains can be hindered, and the formation of CTC can be effectively destroyed, thereby improving the comprehensive performance of the material, including improving solubility, enhancing melt processing performance, and optimizing optical transparency. For example, the literature ("Synthesis and optoelectronic properties of polyimides with naphthyldiphenyl-amine chromophores", Hsiao SH, et al. Journal of Polymer Research, 2014, 21 (4): 407) discloses that a series of electroactive polyimides containing naphthyldiphenylamine units were synthesized using N, N'-di(4-aminophenyl)-N, N'-di-2-naphthyl-1,4-phenylenediamine and four tetracarboxylic dianhydrides as raw materials. Since triphenylamine is a twisted non-coplanar structure, PIs are easily soluble in many organic solvents, and the solution can be cast into a tough amorphous film. Due to the rigidity of naphthalene, it also exhibits good thermal properties, T gis 288-329°C, and there is no significant decomposition before 500°C. (3) Introduction of bulky side groups: The introduction of bulky side groups into the PI molecular chain effectively reduces the stacking of the molecular chain. At the same time, this structural modification can inhibit the movement of the chain segments and improve the rigidity of the molecular chain. For example, the literature ("Fabrication and characterization of novel high-performance fluorinated polyimides with xanthene pendent architecture: Study of thermal, photophysical, antibacteria and heavy metal ion adsorption behavior", Amininasab SM, et al. Journal of Fluorine Chemistry, 2016, 192: 48-57) discloses a series of high-performance fluorinated polyimides with xanthene pendent chains having different functional groups. These polymer PIs show good solubility and thermal stability, and have a high glass transition temperature T g(235-303°C) and 10% weight loss (402-498°C), with a residue of more than 62% at 800°C in a N2 atmosphere. This is due to the presence of functional groups such as ether bonds and bulky side groups such as -CF3, substituted imidazole, and xanthene on the main chain, which allows PIs to improve the solubility of the polymer while maintaining thermal stability. (4) Introduction of alicyclic structures: The introduction of alicyclic structures can hinder the packing density of the molecular chain and inhibit the CTC effect. Therefore, the introduction of alicyclic structures can make the polymer have good solubility and optical transparency. For example, the document (“Synthesis and properties of polyimides derived from bis-(aminophenoxy)containing naphthalene, [phenyl]propane and [methyl]cyclohexane segment and 4,4'-carbonyldiphthalic anhydride”, Mirsamiei A, Journal of Macromolecular Science, Part A, 2018, 55(7): 519-525) discloses that three types of fully aromatic, semi-aromatic and aliphatic-aromatic polyimides containing naphthalene, phenylpropane and cyclohexane structures, respectively, were synthesized by two-step chemical and thermal imidization reactions using bis(ether-amine) and 4,4'-carbonyldiphthalic anhydride (CDPA) as raw materials. Tests show that polyimides containing cyclohexane segments have better transparency, low dielectric constant and hygroscopicity, and are suitable for application in the fields of optoelectronics and microelectronics. (5) Introduction of fluorine-containing structures: Studies have shown that fluorine atoms have a small atomic radius and high electronegativity, which can effectively reduce the polarization degree and packing density of PI molecular chains to a certain extent, which not only improves the optical transparency of PI, but also reduces the dielectric constant of PI films. It is worth noting that a simple fluorine substitution strategy can maximize the thermal stability and mechanical strength of PI without sacrificing the rigidity of the main chain and maintaining the close arrangement of the molecular chains. Compared with single fluorine atom substitution, the introduction of trifluoromethyl will produce more significant effects. -CF3, as a strong electron-withdrawing group, can improve the close packing of PI by increasing the gap between the molecular chains. This not only improves the solubility and light transmittance of PI, but also significantly reduces its water absorption and dielectric constant due to its inherent hydrophobic properties, which makes this type of modified material have broad application prospects in the field of optoelectronic devices.For example, the document (“Tristable data-storage device of soluble polyimides based on novel asymmetrical diamines containing carbazole”, Zhao J, et al. Polymer Chemistry, 2016, 7(9): 1765-1772) discloses the synthesis of a novel fluorine-containing asymmetrical diamine using 9-(2-bromobenzyl)-3,6-diaminocarbazole as a raw material, condensing it with two dianhydrides in DMAc, and then chemically imidizing it to obtain two functional soluble PIs. Due to the introduction of fluorine atoms, the polarizability and bulk density of the polyimide molecular chain are effectively reduced, so the resulting polymer has excellent organic solubility and high thermal stability, and loses 5% weight in a nitrogen atmosphere above 300°C. Although there are many methods for modifying polyimides in the prior art, these modification methods are all single and limited, and the comprehensive performance of polyimides is difficult to be effectively improved. Summary of the Invention

[0004] In response to the technical defects of the prior art, the first object of the present invention is to provide a fluorinated polyetherimide containing a carbazole structure. The key feature of this polyetherimide is the introduction of a carbazole unit containing a trifluoromethyl group, an ether bond, a bulky molecular volume, and an asymmetric polar structure into the main chain, which gives it excellent solubility, heat resistance, optical properties, mechanical properties, dielectric properties, hydrophobicity and other comprehensive properties.

[0005] The second object of the present invention is to provide a method for preparing a fluorinated polyetherimide containing a carbazole structure, which can be synthesized using a mature polymerization process, has simple and controllable operation, and is conducive to industrial production.

[0006] In order to achieve the above technical objectives, the present invention provides a fluorinated polyetherimide containing a carbazole structure, which has the following repeating structural units:

[0007]

[0008] in,

[0009] Ar is

[0010] The key to the fluorinated polyetherimide containing a carbazole structure of the present invention is to endow it with good comprehensive properties by designing a special carbazole structural unit and introducing it into the main chain of the polyimide molecular structure. The carbazole structural unit has the following characteristics: (1) It has a flexible ether bond (–O–), which can destroy the regularity of the main chain of the aromatic polyimide molecule, reduce the rigidity of the main chain structure, and improve the solubility and flexibility of the polyimide; (2) It has a non-planar, asymmetric polar structure, which can destroy the regularity of the main chain of the aromatic polyimide, and give it polarity, thereby improving its solubility; (3) It introduces a trifluoromethyl side group, which can not only effectively prevent the close stacking of the polymer molecular chains and weaken its crystallization ability, but also improve its solubility, while giving it a low dielectric constant and improving its hydrophobicity; (4) It has a large side group, which can reduce the regularity of the main chain and increase the spacing between polymer chains, thereby effectively reducing the stacking degree of the main chain, weakening the interaction between molecular chains and within the chain, and the probability of CTC formation, thereby improving the solubility and transmittance of the polyimide. (5) Carbazole, due to its inherent rigidity, is introduced into the polyimide molecular chain, effectively maintaining the excellent heat resistance and mechanical strength of the polyimide material. In summary, the present invention, by designing a carbazole structural unit containing an ether bond, a trifluoromethyl group, and a large volume, and introducing it into the polyimide molecular backbone, imparts the polyimide with excellent optical, electrical, and thermal properties.

[0011] As a preferred solution, the number average molecular weight of the fluorinated polyetherimide containing carbazole structure is 4×10 4 ~6×10 4 Fluorinated polyetherimide containing carbazole structure has a large molecular weight and good film-forming processing performance.

[0012] The present invention also provides a method for preparing a fluorinated polyetherimide containing a carbazole structure, which comprises the following steps:

[0013] 1) subjecting a diamine monomer and a dianhydride monomer to a condensation polymerization reaction to obtain a polyamic acid intermediate;

[0014] 2) chemically imidizing the polyamic acid intermediate under the promotion of acetic anhydride and pyridine to obtain a fluorinated polyetherimide containing a carbazole structure;

[0015] The diamine monomer has the following molecular structure:

[0016]

[0017] The dianhydride monomer has the following molecular structure:

[0018]

[0019] Among them, Ar is

[0020] As a preferred solution, the conditions of the polycondensation reaction are: first react at a temperature of -5°C to 5°C for 0.5 to 1.5 hours, and then react at room temperature with stirring for 12 to 14 hours.

[0021] As a preferred solution, the polycondensation reaction is carried out in anhydrous DMAc.

[0022] As a preferred solution, the amount of anhydrous DMAc used is to maintain the solid content of the polymerization system at 15-25%.

[0023] As a preferred solution, the chemical imidization conditions are: first add acetic anhydride and pyridine and stir evenly at room temperature, then heat to 105-115° C. and stir to react for 4-6 hours.

[0024] Compared with the existing technology, the technical solution of the present invention brings the following beneficial technical effects:

[0025] The present invention designs a carbazole structural unit having an ether bond, a trifluoromethyl side group and a bulky molecule, and introduces the carbazole structural unit into a polyetherimide molecule, thereby significantly improving the comprehensive physical properties of the polyetherimide.

[0026] (1) The main chain of the fluorinated polyetherimide containing carbazole structure of the present invention contains ether bond and trifluoromethyl structure, which effectively optimizes the flexibility of the molecular chain. Its tensile strength is 135.44-169.65MPa, and its elastic modulus can reach up to 3.00GPa. At the same time, the presence of rigid carbazole structure and imide bond makes it show good thermal stability. Its glass transition temperature (T g ) is 273.5~341.9℃, at T 5％ It is 405.5~530.7℃.

[0027] (2) The fluorinated polyetherimide containing a carbazole structure of the present invention exhibits excellent dielectric properties, which is attributed to the incorporation of bulky carbazole and trifluoromethyl groups into its main chain. These structures can increase the molecular chain spacing and free volume ratio while reducing the proportion of polar groups in the molecular chain, thereby significantly reducing the dielectric constant of the polymer.

[0028] (3) The λ0 of the fluorinated polyetherimide containing a carbazole structure of the present invention is 362 to 385 nm, showing good optical transparency. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 The infrared spectra of fluorinated polyetherimides PI-1 to PI-5 containing carbazole structures.

[0030] Figure 2These are the UV-Vis curves of fluorinated polyetherimides PI-1 to PI-5 containing a carbazole structure.

[0031] Figure 3 The TGA curves (a) and DMA curves (b) of fluorinated polyetherimides containing carbazole structure PI-1 to PI-5.

[0032] Figure 4 These are the stress-strain curves of fluorinated polyetherimides containing carbazole structures PI-1 to PI-5. DETAILED DESCRIPTION

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

[0034] The raw materials and reagents involved in the following examples are all conventional commercially available products.

[0035] Test and characterization methods:

[0036] (1) Fourier transform infrared spectroscopy (FT-IR): The sample was prepared with KBr as the background and tested using a Spectrum Two model FT-IR. The wave number was set to 4000 to 400 cm -1 .

[0037] (2) Nuclear magnetic resonance spectroscopy (NMR): Weigh about 2 mg and dissolve it in CDCl3 or DMSO-d6. Use Avance 400MHz or 600MHz NMR spectrometer to measure the 1 H NMR and 13 C NMR test.

[0038] (3) Melting point test (MP): The melting point was determined using a micro melting point apparatus (FCE-3000).

[0039] (4) Solubility test: Dissolve 10 mg of sample in 1 mL of solvent (common solvents such as NMP, DMAc, and Py) at room temperature and observe the dissolution of the sample. If the sample is not completely dissolved, heat it to 60°C and continue observing and recording its dissolution.

[0040] (5) Molecular weight test (GPC): The sample was prepared into a 3-5 mg / mL solution and measured using a DAWN HELEOS II multi-angle laser light scattering instrument with THF as the mobile phase at a flow rate of 0.5 mL / min to obtain the weight-average M of the polymer. w , number average M n and dispersion index PDI.

[0041] (6) Thermogravimetric analysis (TGA): Thermogravimetric analysis was performed using TG-DTA in a N2 atmosphere, with the temperature increased at 10°C / min. The thermal gravimetric loss of the samples was tested in the range of 20 to 800°C.

[0042] (7) Dynamic mechanical analysis (DMA) test: DMA was used to characterize the heat resistance of the polymer. The film was cut into 5 cm × 5 mm fiber strips, fixed on a fixture, and the heating rate was set to 10 °C / min from room temperature to 420 °C at a parameter of 1 Hz.

[0043] (8) Optical performance test (UV-Vis): The polymer film was cut into 20 mm × 45 mm size and tested using a U-3310 UV-visible spectrometer with the wavelength set to 200-800 nm.

[0044] (9) Mechanical property test: The polymer film was cut into 2 mm × 50 mm size and subjected to tensile test using a CMT8012 universal electronic testing machine. The tensile speed was set to 5 mm / min, and the test was repeated three times to obtain the average value.

[0045] (10) Water absorption test (W U ): First, dry the polymer film in an oven at 100°C, cut the dried film into 10mm×10mm sizes, and weigh M dry , soak in deionized water for 24 hours, wipe the surface moisture of the film, weigh M wet , calculate the water absorption rate W U .

[0046] W U Calculation formula: W U =(M wet –M dry )×100% / M dry Among them, M dry : Dry mass / g, M wet : Mass after water absorption / g.

[0047] (11) Water contact angle test: The hydrophobicity of the polymer was tested using a contact angle meter (OCA15EC). The test liquid was distilled water. The film was cut into 8 mm × 8 mm pieces and attached to the double-sided tape on a glass slide. The test was performed at room temperature.

[0048] (12) Dielectric performance test (DC): The E4980A precision impedance analyzer was used for testing. The PA film was cut into 15 mm × 15 mm size, and the conductive adhesive was cut into 8 mm length. The conductive adhesive was pasted to both sides of the film and placed on the test fixture for testing at room temperature. The test frequency was 0.1 kHz to 100 kHz.

[0049] Example 1

[0050] The synthetic route of 3-(4-aminophenoxy)-9-(4-amino-2-trifluoromethylphenyl)carbazole (APATPC) is as follows:

[0051]

[0052] (1) Synthesis of 2-chloro-5-nitrotrifluorotoluene (CNTB):

[0053] To a 500 mL round-bottom flask, add o-chlorobenzotrifluoride (121 g, 0.67 mol) and concentrated sulfuric acid (112 mL) sequentially. Place the mixture in an ice bath and stir. Slowly add a mixed solution of H2SO4 / HNO3 (V:V = 1:1, 225 mL) dropwise. Remove the ice and allow the reaction to proceed at room temperature for 8 hours. Upon completion of the reaction, slowly pour the mixture into an ice / water mixture. Extract the lower oily layer with distilled water until neutral, dry over anhydrous MgSO4, and filter. The resulting product is CNTB with a yield of 93%.

[0054] 1 H NMR (400MHz, CDCl3): δ=8.58 (d, J=2.3Hz, 1H), 8.36 (dd, J=8.7, 2.3Hz, 1H), 7.73 (d, J=8.8Hz, 1H).

[0055] (2) Synthesis of N-(4-nitro-2-trifluoromethylphenyl)carbazole (NTPC):

[0056] To a 500mL three-necked flask, carbazole (16.72g, 0.10mol), K2CO3 (13.80g, 0.10mol), and DMF (200mL) were added sequentially. Under nitrogen, 2-chloro-5-nitrobenzotrifluoride (CNTB) (24.81g, 0.11mol) was injected via syringe. The temperature was raised to 150°C and refluxed for 24 hours. After cooling to room temperature, the product was slowly added dropwise to ice water for precipitation. The product was then loaded onto a column by rotary evaporation and eluted with pure PE to obtain a yellow powder. The precipitated yellow crystals were recrystallized from anhydrous ethanol, yielding NTPC in 86.8% yield. The melting point was 74-76°C.

[0057] 1 H NMR (400MHz, CDCl3): δ = 8.86 (s, 1H), 8.62 (d, J = 10.9Hz, 1H), 8.15 (d, J = 7.7Hz, 2H), 7.6 1(d,J=8.6Hz,1H), 7.40(t,J=7.6Hz,2H), 7.33(t,J=7.5Hz,2H), 6.93(d,J=8.1Hz,2H).

[0058] (3) Synthesis of 3-acetyl-9-(4-nitro-2-trifluoromethylphenyl)carbazole (ANTPC):

[0059] To a 50 mL round-bottom flask placed in an ice bath, AlCl₃ (1.60 g, 15 mmol), dichloromethane (DCM) (20 mL), and AcCl (1.96 g, 25 mmol) were added sequentially and activated for 10 min. The activated solution was slowly added dropwise via a constant pressure funnel to a solution of N-(4-nitro-2-trifluoromethylphenyl)carbazole (3.56 g, 10 mmol) and DCM (30 mL) in an ice bath. The mixture was then ice bathed for 30 min. The ice bath was removed and the reaction was allowed to proceed at room temperature for 3 h. Upon completion of the reaction, HCl:H₂O (10 mL:25 mL) was added to quench the reaction for 10 min, causing the solution to change from dark green to yellow. The product was extracted with DCM and loaded onto a column with a 5:1 ratio of PE:EA to afford a yellow powder in a 60% yield. The melting point was 156.4-158.3°C.

[0060] 1 H NMR (400MHz, CDCl3): δ=8.88(s,1H), 8.79(s,1H), 8.66(d,J=10.8Hz,1H), 8.21(d,J=7.6Hz,1H), 8.05(d ,J=8.6Hz,1H), 7.65(d,J=8.6Hz,1H), 7.42(dt,J=22.0,7.3Hz,2H), 6.95(d,J=8.3Hz,2H), 2.73(s,3H).

[0061] IR(KBr):υ max =3054cm -1 (-CH3 stretching vibration); 1673cm -1 (C=O stretching vibration); 1589cm -1 (Carbazole CN bond stretching vibration); 1349 and 1533 cm -1 (symmetric and antisymmetric stretching vibrations of -NO2); 1307cm -1 (CF stretching vibration); 732cm -1 (Ar-H bending vibration peak).

[0062] (4) Synthesis of 3-acetoxy-9-(4-nitro-2-trifluoromethylphenyl)carbazole (AONTPC):

[0063] 3-Acetyl-9-(4-nitro-2-trifluoromethylphenyl)carbazole (1.99 g, 5 mmol), m-chloroperbenzoic acid (m-CPBA) (1.55 g, 9 mmol), and 10 mL of DCM were added sequentially to a 50 mL round-bottom flask, stirred at room temperature for 5 hours, and filtered. The filtrate was rotary evaporated and loaded onto a column with a 10:1 ratio of PE:EA to afford a yellow powder in a 92% yield. The melting point was 113.9-115.1°C.

[0064] 1 H NMR (400MHz, CDCl3): δ=8.86(d,J=2.6Hz,1H), 8.62(dd,J=8.6,2.6Hz,1H), 8.07(d,J=7.0Hz,1H), 7.85(d,J=2.3Hz,1H), 7.59(d,J=9.0H z,1H), 7.43–7.37(m,1H), 7.32(t,J=7.0Hz,1H), 7.11(dd,J=8.7,2.3Hz,1H), 6.92(d,J=3.6Hz,1H), 6.89(d,J=4.2Hz,1H), 2.37(s,3H).

[0065] IR(KBr):υ max =3087,1754cm -1 (Stretching vibration of carbonyl C=O in ester group), 1589, 1537, 1349, 1307, 1213 cm -1 (Stretching vibration of alkoxy CO in ester group), 747 cm -1 .

[0066] (5) Synthesis of 3-hydroxy-9-(4-nitro-2-trifluoromethylphenyl)carbazole (HNTPC):

[0067] 3-Acetoxy-9-(4-nitro-2-trifluoromethylphenyl)carbazole (0.4143 g, 10 mmol), 10% NaOH solution, and EtOH (10 mL) were placed in a 50 mL round-bottom flask and stirred at 85°C under reflux for 2 h. The reaction solution was slowly added dropwise to ice water, and the pH was adjusted to neutral with 10% HCl. Filtering afforded an orange powder with a yield of 98%. The melting point was 127.9–128.5°C.

[0068] 1H NMR (400MHz, CDCl3): δ = 8.85 (s, 1H), 8.69–8.52 (m, 1H), 8.04 (s, 1H), 7.62 (s, 1H), 7.57–7.52 (m, 1H) ), 7.42–7.33(m,1H), 7.29(d,J=7.1Hz,1H), 7.01–6.85(m,2H), 6.79(d,J=8.7Hz,1H), 4.92(s,1H).

[0069] IR(KBr):υ max =3511 and 3464cm -1 (Characteristic absorption peaks of phenolic hydroxyl group Ar-OH), 1584, 1535, 1349, 1307, 742 cm -1 .

[0070] (6) Synthesis of 3-(4-nitrophenoxy)-9-(4-nitro-2-(trifluoromethylphenyl)carbazole (NPNTPC):

[0071] To a 50 mL round-bottom flask, add 3-hydroxy-9-(4-nitro-2-trifluoromethylphenyl)carbazole (3.7230 g, 10 mmol), p-fluoronitrobenzene (1.4102 g, 10 mmol), CsF (2.7360 g, 18 mmol), and DMSO (20 mL). Reflux and stir at 110°C for 0.75 h. After the reaction is complete, the cooled solution is slowly dripped into ice water and filtered to obtain a yellow powder with a yield of 94%. The melting point is 202.2-203.3°C.

[0072] 1 H NMR (600MHz, CDCl3): δ=8.88(d,J=2.6Hz,1H),8.65(dd,J=8.6,2.6Hz,1H),8.21(d,J=9.3Hz,2H),8.07(d,J=7.8Hz,1H),7.86(d,J=2.3Hz,1H),7. 65(d,J=8.5Hz,1H),7.44(t,J=7.7Hz,1H),7.34(t,J=7.5Hz,1H),7.15(dd,J=8.7,2.3Hz,1H),7.05(d,J=9.3Hz,2H),6.96(dd,J=11.6,8.5Hz,2H).

[0073] IR(KBr):υ max =1589;1514;1340;1305;1224cm -1 (stretching vibration of ether bond Ar-O-Ar); 747 cm -1 .

[0074] (7) Synthesis of 3-(4-aminophenoxy)-9-(4-amino-2-trifluoromethylphenyl)carbazole (APATPC):

[0075] 3-(4-nitrophenoxy)-9-(4-nitro-2-(trifluoromethylphenyl)carbazole (4.93 g, 10 mmol), 0.12 g of Pd / C, and 30 mL of ethanol were added sequentially to a 50 mL three-necked flask. Under N2 protection, 15 mL of hydrazine hydrate was slowly injected. The temperature was raised to 80°C and the reaction was allowed to proceed for 24 h. After the reaction was completed, the Pd / C was removed by hot filtration. After the reaction solution was cooled, it was extracted with DCM. The lower layer was rotary evaporated and loaded onto a column with PE:EA = 2:1 to obtain a light yellow solid with a yield of 76%. The melting point was 105.0-107.7°C.

[0076] 1 H NMR (400MHz, CDCl3): δ = 8.10 (d, J = 7.7Hz, 1H), 7.70 (d, J = 2.4Hz, 1H), 7.34 (t, J = 7.7Hz, 1H), 7.18 (d, J = 7.5Hz, 1H), 7.15 (d, J = 2.4Hz, 1H), 7.07 (d ,J=8.5Hz,1H),6.97(ddd,J=16.7,8.7,2.5Hz,2H),6.89(t,J=8.1Hz,2H) ,6.77(d,J=8.8Hz,2H),6.58(d,J=8.8Hz,2H),6.02(s,2H),4.88(s,2H).

[0077] IR(KBr):υ max =3487 and 3393 cm -1 (symmetric and asymmetric stretching vibrations of -NH2); 1584; 1334; 1260; 747cm -1 .

[0078] Example 2

[0079] The preparation routes of fluorinated polyetherimides PI-1 to PI-5 containing carbazole structures are as follows:

[0080]

[0081] Chemical imidization method: Taking polymer PI-5 as an example, a 50 mL three-necked flask was placed in an ice-water bath. Under N2 protection, 0.8660 g (2 mmol) of 3-(4-aminophenoxy)-9-(4-amino-2-trifluoromethylphenyl)carbazole (APATPC) and 2 mL of DMAc were added to the flask. After stirring until the solid was completely dissolved, 0.8885 g (2 mmol) of 6FDA was added in batches. An appropriate amount of DMAc was added to adjust the solid-to-liquid ratio to approximately 20%. After 1 hour of ice bathing, the ice was removed and the reaction was continued at room temperature for 12 hours to obtain a viscous PAA solution. This solution was appropriately diluted and a mixed solution of 2 mL of Ac2O and 2 mL of Py was added, stirred evenly, and reacted at 110°C for 5 hours. The solution was then slowly added dropwise to 100 mL of methanol, resulting in the precipitation of pale yellow fibers. Extraction with methanol was performed in a Soxhlet extractor for 24 hours, followed by drying to obtain the target polymer PI-5.

[0082] PI-1: 1 H NMR (600MHz, DMSO-d6): δ = 11.02 (s, 1H), 10.41 (d, J = 17.5Hz, 1H), 8.63 (s, 1H), 8 .50–7.51(m,10H),7.42(s,1H),7.20(d,J=46.4Hz,2H),7.01(d,J=24.3Hz,4H).

[0083] PI-2: 1 H NMR (600MHz, DMSO-d6): δ = 8.57 (d, J = 19.3Hz, 1H), 8.49 (s, 1H), 8.46–8.32 (m, 3H), 8.30 (s, 1H), 8.22 (s ,1H),8.11(d,J=25.6Hz,3H),7.89(s,1H),7.47(s,3H),7.27(d,J=36.4Hz,2H),7.10(d,J=65.5Hz,4H).

[0084] PI-3: 1 H NMR (600MHz, DMSO-d6): δ = 8.37–8.06 (m, 10H), 7.85 (s, 1H), 7.45 (s, 3H), 7.25 (d, J = 39.5Hz, 2H), 7.18–7.06 (m, 3H), 7.02 (d, J = 4.9Hz, 1H).

[0085] PI-4: 1H NMR (600MHz, DMSO-d6): δ = 8.28 (d, J = 16.2Hz, 2H), 8.18 (d, J = 6.9Hz, 1H), 8.13–8.02 (m, 3H), 7.81 (s, 1H), 7.7 7–7.57(m,4H),7.41(d,J=5.8Hz,3H),7.24(d,J=41.8Hz,2H),7.10(d,J=26.0Hz,3H),7.01(d,J=7.9Hz,1H).

[0086] PI-5: 1 H NMR (600MHz, DMSO-d6): δ=8.33–8.02(m,6H),7.95(s,2H),7.83(d,J=14.1Hz,2H),7.7 3(s,1H),7.41(d,J=8.2Hz,3H),7.25(d,J=61.0Hz,2H),7.06(dd,J=59.4,7.6Hz,4H).

[0087] Example 3

[0088] Preparation of fluorinated polyetherimide film containing carbazole structure:

[0089] Taking PI-5 as an example, the PI-5 sample (0.1-0.12 g) was dissolved in DMAc (3 mL), filtered with a nanofiltration membrane, and allowed to stand in the refrigerator until the bubbles completely disappeared. Using the extension method, it was evenly dropped onto a preheated glass plate, dried at 80°C for 2 h, heated to 120°C and dried for another 2 h. After cooling to room temperature, it was peeled off to obtain a dry polyetheramide film PI-5.

[0090] Performance testing and characterization:

[0091] (1) Infrared spectrum of fluorinated polyetherimide containing carbazole structure:

[0092] The FT-IR spectra of this series of polyetherimides are as follows: Figure 1 As shown, at 3200cm -1 and 1520cm -1 No characteristic absorption peaks of amide bond were observed at 1778 cm-1, and the symmetric and asymmetric stretching vibrations of C=O bond on imide ring appeared at 1778 cm-1, respectively. -1 and 1725cm -1 1599cm -1 The absorption peak at is the stretching vibration of the CN bond in the imide ring; the other absorption peaks also correspond to the characteristic peaks of functional groups such as -NO2, -CF3 and ether bond (Ar-O-Ar).

[0093] (2) Molecular weight of fluorinated polyetherimide containing carbazole structure:

[0094] Table 1 shows the molecular weight GPC values of this series of PEIs. As can be seen from Table 1, the GPC values of this series of polymers all exceed 50,000, indicating a high molecular weight. This characteristic indicates that this series of PEIs has good film-forming properties.

[0095] Table 1. Molecular weight of polyetherimides PI-1 to PI-5

[0096]

[0097]

[0098] a M w : weight average molecular weight; b M n : number average molecular weight; c PDI: dispersion index (M w / M n ).

[0099] (3) Solubility properties of fluorinated polyetherimide containing carbazole structure:

[0100] Table 2 details the solubility of this series of PEIs in various common solvents. As can be seen from Table 2, this series of PEIs generally exhibits good solubility properties. This is attributed to the rich ether bonds and trifluoromethyl flexible groups in the PEI molecules. These structures not only weaken the conjugation effect of the aromatic ring and reduce the rigidity of the molecular chain, but also reduce the close stacking between the molecular chains, effectively hindering the formation of CTCs, allowing PEIs to dissolve in most non-polar solvents (such as DMAc, NMP, and Py) at room temperature. However, PI-2, due to its rigid biphenyl structure, has the worst solubility compared to other PEIs in the series. The other PEIs are all soluble in THF, while PI-3 is only slightly soluble in THF when heated to 60°C.

[0101] Table 2. Solubility of polyetherimides PI-1 to PI-5 in different solvents

[0102]

[0103] +++Soluble at room temperature; ++–Completely soluble at 60°C; +––Slightly soluble when heated; –––Insoluble when heated.

[0104] (4) Optical properties of fluorinated polyetherimide containing carbazole structure:

[0105] Table 3. Light transmission properties of polyetherimides PI-1 to PI-5

[0106]

[0107] T(%): transmittance at 500nm, 600nm, 700nm, and 800nm; λ0: cutoff wavelength.

[0108] The UV-Vis curves of this series of PEIs films are as follows Figure 2 Specific data are shown in Table 3. As can be seen from Table 3, the cutoff wavelength of this series of PEIs films is 362-385 nm, indicating that PEIs have good optical transmittance. This characteristic is mainly attributed to the introduction of bulky carbazole groups and trifluoromethyl groups into the PEIs backbone, which greatly disrupt the orderly arrangement of the molecular chains, effectively hindering the formation of CTCs, thereby improving the optical transparency of the PEIs films.

[0109] Among them, PI-5 has the shortest cutoff wavelength (362nm), and its optical transparency performs best in this series, with a transmittance of up to 83.0% at a wavelength of 500nm. This is due to the double-CF3 group in the 6FDA structure, which effectively inhibits the formation of CTC and significantly enhances the optical transparency of PEIs. In addition, PI-4 also exhibits good optical transparency because it contains a large number of ether bonds, which reduces the stacking density of the molecular chains. In contrast, PI-1 and PI-2 are rich in rigid benzene / biphenyl structures. These structures strengthen the conjugation effect and rigidity of the molecular chains and promote intermolecular interactions, resulting in the transmittance of PI-1 and PI-2 at a wavelength of 500nm reaching only 50.6% and 60.5%, respectively, showing relatively poor transparency.

[0110] (5) Thermal properties of fluorinated polyetherimide containing carbazole structure:

[0111] The thermal properties of this series of polyetherimides are shown in Table 4 and the TGA curves are shown in Figure 3 In (a), DMA curve is shown in Figure 3 (b). As shown in Table 5.5, this series of PEIs exhibits excellent thermal stability, with T g 273.5~341.9℃, T 5％ All above 405.5℃, T max The residual mass ratio at 800°C is generally greater than 54.8%. This excellent performance is mainly attributed to the carbazole group, which increases the free volume of the molecular chain while restricting the movement of the molecular chain, making this series of PEIs have excellent heat resistance.

[0112] Table 4. Thermal properties of polyetherimides PI-1 to PI-5

[0113]

[0114] a T g : glass transition temperature; b T 5％ :5% thermal weight loss temperature; c T 10％ :10% thermal weight loss temperature; d R w : Residual rate at 800℃; e T max : Maximum thermal weight loss temperature.

[0115] From 3(b), we can see that the T of PI-1 g The highest temperature reached 341.9℃, which is mainly due to the presence of rigid benzene units in its structure. These rigid structures significantly enhance the close packing of molecular chains, thereby improving its thermal properties. PI-2 is rich in biphenyl structures, which improves the compactness of PI and leads to a relatively high energy required for its glass transition. In contrast, the main chain of PI-4 contains a large number of ether bonds, which promotes the movement of chain segments, resulting in a corresponding decrease in thermal decomposition temperature, a reduction in residual mass, and a T g (273.5℃) is the lowest in the series.

[0116] (6) Mechanical properties of fluorinated polyetherimide containing carbazole structure:

[0117] Figure 4 The mechanical property curve of this series of PEIs is shown in Table 5. Specific data can be found in Table 5. As can be seen from Table 5, the tensile strength of this series of PIs films is 135.44 to 169.65 MPa, and the elastic modulus can reach up to 3.00 GPa, so this series of PEIs films has excellent mechanical properties. Among them, the rigid structure of benzene affects the flexibility of the molecular chain, making the tensile strength of PI-1 the lowest in the series (135.44 MPa); while PI-4 is rich in ether bonds and exhibits good tensile strength and elongation at break; because the 6FDA monomer contains multiple trifluoromethyl groups, the tensile strength of PI-5 is the best in the series, even up to 169.65 MPa. In summary, this series of PEIs films exhibits good mechanical properties.

[0118] Table 5. Mechanical properties of polyetherimide PI-1 to PI-5

[0119]

[0120] a T s : tensile strength; b T m : elastic modulus; c E b : Elongation at break.

[0121] (7) Water absorption and water contact angle of fluorinated polyetherimide containing carbazole structure

[0122] Table 6 lists in detail the specific values of the water absorption rate and water contact angle of this series of PEIs. The water absorption rate is 0.23~1.01%, and the contact angle range is 89.6~95.2°. Among them, PI-5 has the lowest water absorption rate because its main chain is rich in hydrophobic groups -CF3, which effectively weakens the interaction with water molecules. PI-4 has the highest water absorption rate and is accompanied by a lower contact angle. This is attributed to the ether bonds contained in its structure, which easily form hydrogen bonds with water molecules, resulting in an increase in its water absorption capacity. In addition, PI-2 exhibits a slightly higher water absorption rate than PI-1. This may be because the presence of the biphenyl structure induces the molecular chain to twist, thereby slightly increasing the contact area with water molecules, resulting in PI-2 having a stronger water absorption capacity than PI-1.

[0123] Table 6. Water absorption and contact angle of polyetherimide PI-1 to PI-5

[0124]

[0125] (8) Dielectric properties of fluorinated polyetherimide containing carbazole structure

[0126] Table 7 lists in detail the specific data on the dielectric properties of this series of PEIs. As can be seen from Table 7, the dielectric constant of the PEIs at a frequency of 1 kHz ranges from 1.23 to 1.86, showing excellent dielectric properties. This phenomenon is mainly attributed to the introduction of carbazole and trifluoromethyl groups in the main chain, which increases the molecular chain spacing and free volume ratio, thereby effectively reducing the dielectric constant of the polymer. Among them, the dielectric constant of PI-5 at a frequency of 1 kHz is as low as 1.23. This is mainly because the 6FDA unit is rich in trifluoromethyl structures. The CF bond, due to its low polarizability and high bond energy characteristics, significantly reduces the electronic polarization of the material and promotes the expansion of the free volume. In addition, the -CF3 group can also reduce the water absorption rate of PEIs, and this effect further promotes the reduction of the dielectric constant of the material. In summary, this series of PEIs materials exhibits excellent dielectric properties.

[0127] Table 7. Dielectric properties of polyetherimides PI-1 to PI-5

[0128]

Claims

1. A fluorinated polyetherimide containing a carbazole structure, characterized in that: Has the following repeating structural units: in, Ar is 2. The fluorinated polyetherimide containing a carbazole structure according to claim 1, wherein: The number average molecular weight is 4×10 4 ~6×10 4 .

3. The method for preparing a fluorinated polyetherimide containing a carbazole structure according to claim 1 or 2, characterized in that: The following steps are involved: 1) subjecting a diamine monomer and a dianhydride monomer to a condensation polymerization reaction to obtain a polyamic acid intermediate; 2) chemically imidizing the polyamic acid intermediate under the promotion of acetic anhydride and pyridine to obtain a fluorinated polyetherimide containing a carbazole structure; The diamine monomer has the following molecular structure: The dianhydride monomer has the following molecular structure: Among them, Ar is 4. The method for preparing a fluorinated polyetherimide containing a carbazole structure according to claim 3, wherein: The conditions of the polycondensation reaction are: first reacting at a temperature of -5°C to 5°C for 0.5 to 1.5 hours, and then stirring and reacting at room temperature for 12 to 14 hours.

5. The method for preparing a fluorinated polyetherimide containing a carbazole structure according to claim 3 or 4, characterized in that: The polycondensation reaction was carried out in anhydrous N,N-dimethylacetamide (DMAc).

6. The method for preparing a fluorinated polyetherimide containing a carbazole structure according to claim 5, wherein: The amount of anhydrous DMAc used is to maintain the solid content of the polymerization system at 15-25%.

7. The method for preparing a fluorinated polyetherimide containing a carbazole structure according to claim 2, wherein: The chemical imidization conditions are as follows: first, add acetic anhydride and pyridine and stir evenly at room temperature, then heat to 105-115° C. and stir to react for 4-6 hours.

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