N-aryl-substituted dichlorodiaryl ketimine monomers, N-aryl-substituted polyaryl ketimines, thermally self-crosslinking polyaryl ketimine films and their applications

Abstract

This invention relates to an N-aryl-substituted dichlorodiaryl ketimide monomer, an N-aryl-substituted polyaryl ketimide, a thermally self-crosslinked polyaryl ketimide film, and their applications, belonging to the field of polymer materials and functional membrane technology. The monomer is prepared by condensation of 4,4′-dichlorobenzophenone and an aromatic primary amine to obtain a ketimide structure. It can be used for subsequent aryl-aryl coupling polymerization without the introduction of polymer functional groups, achieving a direct connection between monomer preparation and polymer backbone construction. A dense, self-supporting precursor film is prepared from the N-aryl-substituted polyaryl ketimide via solution casting. Heat treatment at 300–360 °C for 2–5 h under a nitrogen atmosphere causes thermal self-crosslinking of the polymer molecular chains without the addition of a crosslinking agent, forming a solvent-resistant crosslinked membrane structure. The resulting polyaryl ketimide film maintains a continuous dielectric response and exhibits gas separation performance, thus enabling its application in solvent-resistant barrier membranes, dielectric membranes, and gas separation membranes.

Description

Technical Field

[0001] This invention belongs to the field of polymer compounds and functional membrane technology, specifically relating to an N-aryl-substituted dichlorodiaryl ketone imine monomer, an N-aryl-substituted polyaryl ketone imine, a thermally self-crosslinking polyaryl ketone imine film, and their applications. Background Technology

[0002] Rigid aromatic polymers, with a high proportion of aromatic structures in their molecular backbone, typically exhibit good heat resistance, dimensional stability, and mechanical properties, thus attracting widespread attention in high-performance films, dielectric materials, and gas separation materials. However, the strong interaction between the rigid backbone and aromatic rings often reduces the polymer's solubility, making it difficult to process into films using methods such as solution casting. Introducing ketimine structures into aromatic polymers can, to some extent, modulate the inter-chain interactions and the polymer's solubility and processability. However, linear polymers, even after being formed into films, may still swell, deform, or even dissolve upon contact with organic solvents. Under high temperatures, pressures, or specific gas environments, the molecular chains may also undergo movement, rearrangement, or plasticization, leading to changes in film size, dielectric properties, or gas transport properties. Crosslinking between molecular chains is an effective means of improving material stability. Conventional chemical crosslinking usually requires the introduction of exogenous crosslinking agents, initiators, or other reactive components, increasing the complexity of material composition and processing, and having additional effects on the original polymer system. Limited by molecular structure, good solution processability and performance stability are often difficult to achieve simultaneously, and the occurrence of crosslinking directly leads to the loss of material solubility. If the solution processability of the polymer can be maintained before film formation, and cross-linking can be achieved through heat treatment using the polymer's own structure after film formation, the material can be transformed from a solution processable state to a cross-linked state with higher structural stability, thus balancing the polymer's processing and film formation capabilities with its post-film formation stability. Summary of the Invention

[0003] This invention provides an N-aryl-substituted dichlorodiaryl ketone imine monomer having two para-aryl chloride polymerization sites, an N-aryl-substituted polyaryl ketone imine obtained by polymerizing the monomer, and a thermally self-crosslinking polyaryl ketone imine film made from the N-aryl-substituted polyaryl ketone imine, and its application in solvent-resistant barrier membranes, dielectric membranes, and gas separation membranes.

[0004] The first objective of this invention is to provide an N-aryl-substituted dichlorodiaryl ketone imine monomer having two para-aryl chloride polymerization sites, the structural formula of which is shown in (I). This monomer has a diaryl ketone imine as its core, with each of the two aromatic rings connected to the carbon atom of the ketone imine retaining a para-chlorine substituent, and the nitrogen atom of the ketone imine directly connected to a substituted or unsubstituted aryl group.

[0005]

[0006] Wherein, R is -C6H5, -C6H4SO2CH3, -C6H4NO2, -C6H3(CF3)2 or -C6H4CN, and the corresponding monomer names are N-phenyl-4,4′-dichlorobenzophenone imine, N-[4-(methylsulfonyl)phenyl]-4,4′-dichlorobenzophenone imine, N-(4-nitrophenyl)-4,4′-dichlorobenzophenone imine, N-[3,5-bis(trifluoromethyl)phenyl]-4,4′-dichlorobenzophenone imine, and N-(4-cyanophenyl)-4,4′-dichlorobenzophenone imine.

[0007] This monomer can be directly used as a bifunctional monomer for the subsequent preparation of aryl-aryl coupling polymerization of N-aryl substituted polyaryl ketimines without further halogenation or the introduction of polymerization functional groups.

[0008] The second objective of this invention is to provide an N-aryl-substituted polyaryl ketimine with the structure shown in formula (II), which is prepared by Yamamoto coupling polymerization of the N-aryl-substituted dichlorodiaryl ketimine monomer shown in formula (I); during the polymerization process, the two para-aryl chlorine reaction sites of the monomer are coupled to form a polymer backbone linked by aryl-aryl carbon-carbon bonds, while the aryl R linked to the nitrogen atom of the ketimine remains as a polymer side group;

[0009]

[0010] n represents the degree of aggregation, which is an integer greater than 1;

[0011] Wherein, R is -C6H5, -C6H4SO2CH3, -C6H4NO2, -C6H3(CF3)2 or -C6H4CN, and the corresponding polymer names are N-phenyl-substituted polyaryl ketone imine (PNI), N-[4-(methylsulfonyl)phenyl]-substituted polyaryl ketone imine (PNIs), N-(4-nitrophenyl)-substituted polyaryl ketone imine, N-[3,5-bis(trifluoromethyl)phenyl]-substituted polyaryl ketone imine, and N-(4-cyanophenyl)-substituted polyaryl ketone imine.

[0012] A third objective of this invention is to provide a thermally self-crosslinked polyaryl ketimide film, which is prepared by thermal self-crosslinking of the N-aryl substituted polyaryl ketimide.

[0013] The term "thermal self-crosslinking" in this invention refers to the process by which N-aryl-substituted polyaryl ketimide is added to a solvent and cast into a precursor film. Without the addition of an external crosslinking agent for forming connections between polymer molecular chains, the polymer's own structure undergoes crosslinking through heat treatment, resulting in a stable crosslinked structure in the film and a dense, self-supporting, and self-crosslinked polyaryl ketimide film.

[0014] The N-aryl-substituted polyaryl ketimides prepared by this invention are solution-processable before heat treatment. They can be cast into precursor films using N,N-dimethylacetamide, N,N-dimethylformamide, N-methyl-2-pyrrolidone, dimethyl sulfoxide, chloroform, or dichloromethane as solvents. After heat treatment to gradually remove the solvent, they are crosslinked to obtain dense, self-supporting, and self-crosslinked polyaryl ketimide films. Preferably, the concentration of the N-aryl-substituted polyaryl ketimide in the solvent is 8-15 mg / mL, and the thickness of the resulting polyaryl ketimide film is 5-150 μm. The heat treatment process is carried out in a nitrogen atmosphere at a temperature of 300-360 °C for 2-5 h, with a heating rate of 2.0-3.0 °C / min.

[0015] Experimental results show that the polyaryl ketimide film obtained in this invention remains insoluble after immersion in N,N-dimethylacetamide at 25℃ for 24 hours, with a mass retention rate of 99%. Infrared, Raman, and N 1s high-resolution X-ray photoelectron spectroscopy results simultaneously indicate changes in the local chemical environment related to the ketimide before and after heat treatment, consistent with the improved solvent resistance of the film after heat treatment.

[0016] A fourth objective of this invention is to provide the application of the thermally self-crosslinked polyaryl ketimide film in solvent-resistant barrier films, dielectric films, and gas separation films.

[0017] Gas separation membranes can be used to separate N2, CO2, O2, CH4, H2, Ar, etc. When separating N2 and CO2, the gas separation performance is evaluated using pure N2 and CO2 gases, and the ideal CO2 / N2 selectivity of the gas separation membrane is characterized by the ratio of the CO2 pure gas permeability coefficient to the N2 pure gas permeability coefficient. Dielectric properties are evaluated using frequency-dependent and temperature-dependent dielectric constants and dielectric losses.

[0018] Beneficial effects of the present invention

[0019] First: This invention uses 4,4′-dichlorobenzophenone and aromatic primary amine as raw materials to prepare N-aryl-substituted dichlorodiaryl ketone imines via carbonyl-amine dehydration condensation reaction; this reaction retains two para-aryl chloride polymerization sites while constructing the ketone imine structure, and the obtained monomer does not need to be further introduced into polymerization functional groups and can be used for subsequent aryl-aryl coupling polymerization, thereby realizing the direct connection between monomer preparation and polymer backbone construction;

[0020] Second: N-aryl substituted polyaryl ketone imines with R as -C6H4SO2CH3, -C6H4NO2, -C6H3(CF3)2 or -C6H4CN can be constructed from the above monomers, while maintaining the common diaryl ketone imine skeleton and the carbon-carbon connection mode of the main chain, and achieving a series of adjustments to the N-aryl para-substitution structure.

[0021] Third: Represented by PNI and PNIs, the polymers can first be used to prepare a dense self-supporting precursor film through solution casting, and then undergo heat treatment at 300~360℃ without the addition of exogenous crosslinking agents to achieve thermal self-crosslinking; the heat-treated film remains insoluble after being immersed in organic solvents (DMF, DMAc, THF, DMSO) at 25℃ for 24h, with a mass retention rate of 99%, providing a basis for the application of this type of film in solvent-resistant barrier films;

[0022] Fourth: PNI and PNIs series thermally self-crosslinked polyaryl ketone imine films maintain continuous dielectric response and exhibit CO2 / N2 gas separation performance, thus providing experimental basis for the application of this type of film in dielectric membranes and gas separation membranes. Attached Figure Description

[0023] Figure 1 The ¹H nuclear magnetic resonance spectrum of the N-phenyl-4,4′-dichlorobenzophenone imine monomer with R being -C6H5 in formula (I);

[0024] Figure 2 The ¹H nuclear magnetic resonance spectrum of the N-[4-(methylsulfonyl)phenyl]-4,4′-dichlorobenzophenone imine monomer with R being -C6H4SO2CH3 in formula (I);

[0025] Figure 3 The ¹H nuclear magnetic resonance spectrum of the N-(4-nitrophenyl)-4,4′-dichlorobenzophenone imine monomer of formula (I) where R is -C6H4NO2;

[0026] Figure 4 The ¹H nuclear magnetic resonance spectrum of the N-[3,5-bis(trifluoromethyl)phenyl]-4,4′-dichlorobenzophenone imine monomer of formula (I) where R is -C6H3(CF3)2;

[0027] Figure 5 The ¹H nuclear magnetic resonance spectrum of the N-(4-cyanophenyl)-4,4′-dichlorobenzophenone imine monomer with R being -C6H4CN in formula (I);

[0028] Figure 6 The ¹H nuclear magnetic resonance spectrum of N-phenyl-substituted polyaryl ketimine (PNI) in formula (II) is given by R being -C6H5.

[0029] Figure 7 The ¹H nuclear magnetic resonance spectrum of N-[4-(methylsulfonyl)phenyl]-substituted polyaryl ketimines (PNIs) in formula (II) where R is -C6H4SO2CH3;

[0030] Figure 8FT-IR spectra of PNI, PNI-300, PNI-330, and PNI-360;

[0031] Figure 9 Raman spectra of PNI, PNI-300, PNI-330 and PNI-360;

[0032] Figure 10 High-resolution X-ray photoelectron spectra of N 1s for PNI, PNI-300, PNI-330 and PNI-360;

[0033] Figure 11 High-resolution X-ray photoelectron spectra of N 1s for PNIs, PNIs-300, PNIs-330 and PNIs-360;

[0034] Figure 12 Dielectric property curves for PNI, PNI-300, PNI-330, PNI-360, and PNIs, PNIs-300, PNIs-330, and PNIs-360 films. Detailed Implementation

[0035] Example 1: Preparation of N-aryl-substituted dichlorodiaryl ketone imine monomers with R being -C6H5 in general formula (I)

[0036] Under a nitrogen atmosphere, 21.82 g (87 mmol) of 4,4′-dichlorobenzophenone, 50 g of 4Å molecular sieve, 14 g (150 mmol) of aniline, and 80 mL of toluene were added to a 250 mL three-necked round-bottom flask. The mixture was heated to 160 °C with mechanical stirring, and the reaction system was stirred at 160 °C for 24 hours. The solution changed from pale yellow to orange-red, and then cooled naturally to room temperature. The molecular sieve was removed by filtration, and the resulting solution was concentrated by rotary evaporation to obtain an orange-yellow solid. The crude product was recrystallized three times with methanol, and then dried in a vacuum oven at 60 °C for 12 hours to finally obtain a bright yellow N-phenyl-4,4′-dichlorobenzophenone imine monomer (22.9596 g), with a yield of 81%. The ¹H NMR spectrum of the obtained product is shown below. Figure 1 As shown, multiple well-resolved aromatic proton signals appeared in the δ range of approximately 7.7–6.7 ppm, which can be attributed to the two p-chlorophenyl groups attached to the carbon atom of the ketimine and the aromatic protons on the phenyl group attached to the nitrogen atom. The peak distribution is consistent with the aromatic skeleton of the target monomer. The reaction formula is shown below:

[0037]

[0038] Example 2: Preparation of N-[4-(methylsulfonyl)phenyl]-4,4′-dichlorobenzophenone imine monomer with R of general formula (I) being -C6H4SO2CH3

[0039] Under nitrogen protection, 15.0666 g (60 mmol) of 4,4′-dichlorobenzophenone, 24.0012 g (180 mmol) of anhydrous aluminum trichloride (AlCl3), and 250 mL of chloroform were added to a 500 mL three-necked flask and stirred to ensure thorough mixing. Then, a mixture of 25.6815 g (150 mmol) of 4-methylsulfonylaniline and 54.6426 g (540 mmol) of triethylamine was added dropwise to the reaction system. During the addition, the reaction solution gradually turned orange-yellow. After the addition was complete, the reaction was continued under reflux with chloroform, and the reaction progress was monitored until the starting materials were completely converted. At the end of the reaction, the system was dark reddish-brown.

[0040] The resulting reaction solution was slowly added to a 4 mol / L sodium hydroxide aqueous solution for post-treatment, and the product was extracted with chloroform. The organic phases were combined, and the solvent was removed under reduced pressure to obtain a deep red solid. The solid was recrystallized three times with methanol and then dried under vacuum at 60 °C for 12 h to obtain 16.1675 g of orange-yellow N-[bis(4-chlorophenyl)methylene]-4-(methylsulfonyl)aniline, with a yield of 66.6%. The obtained product corresponds to the N-aryl-substituted dichlorodiaryl ketone imine monomer in formula (I) where R is -SO2CH3. The ¹H NMR spectrum of the obtained product is shown below. Figure 2 As shown, multiple groups of aromatic proton signals appear in the δ range of approximately 7.8–6.9 ppm, which can be attributed to the aromatic protons on the two p-chlorophenyl groups and the p-methylsulfonylphenyl group; a singlet of the methyl proton in the methanesulfonyl group appears at approximately 3.15 ppm. These signals are consistent with the structure of the target monomer. The reaction formula is shown below:

[0041]

[0042] Example 3: Preparation of N-(4-nitrophenyl)-4,4′-dichlorobenzophenone imine monomer with R being -C6H4NO2 in general formula (I)

[0043] Under nitrogen protection, 7.533 g (30 mmol) of 4,4′-dichlorobenzophenone, 12.0006 g (90 mmol) of anhydrous aluminum trichloride (AlCl3), and 300 mL of chloroform were added to a 500 mL three-necked flask, and the mixture was stirred until thoroughly mixed. Then, a mixture of 10.35 g (75 mmol) of 4-nitroaniline and 27.3213 g (270 mmol) of triethylamine was added dropwise to the reaction system. After the addition was complete, the reaction was continued under reflux with chloroform, and the reaction progress was monitored until the starting materials were completely converted.

[0044] The resulting reaction solution was slowly added to a 4 mol / L sodium hydroxide aqueous solution for post-treatment, and the product was extracted with chloroform. The organic phases were combined, the solvent was removed under reduced pressure, and the crude product was recrystallized three times with methanol, followed by vacuum drying at 60 °C for 12 h to obtain approximately 9.02 g of N-(4-nitrophenyl)-4,4′-dichlorobenzophenone imine monomer, with a yield of 81%. The ¹H NMR spectrum of the obtained product is shown below. Figure 3 As shown, multiple groups of aromatic proton signals appear in the δ range of approximately 7.6–6.7 ppm, which can be attributed to the aromatic protons on the two p-chlorophenyl and p-nitrophenyl groups. Due to the electron-withdrawing effect of the nitro group, some aromatic protons of the p-nitrophenyl group are located in a relatively low-field region, and the overall peak distribution is consistent with the structure of the target monomer. The reaction formula is shown below:

[0045]

[0046] Example 4: Preparation of N-[3,5-bis(trifluoromethyl)phenyl]-4,4′-dichlorobenzophenone imine monomer with R of general formula (I) being -C6H3(CF3)2

[0047] Under nitrogen protection, 5.0222 g (20 mmol) of 4,4′-dichlorobenzophenone, 8.0004 g (60 mmol) of anhydrous aluminum trichloride (AlCl3), and 300 mL of chloroform were added to a 500 mL three-necked flask, and the mixture was stirred until thoroughly mixed. Then, a mixture of 6.8736 g (30 mmol) of 3,5-bis(trifluoromethyl)aniline and 18.214 g (180 mmol) of triethylamine was added dropwise to the reaction system. After the addition was complete, the reaction was continued under reflux with chloroform, and the reaction progress was monitored until the starting materials were completely converted.

[0048] The resulting reaction solution was slowly added to a 4 mol / L sodium hydroxide aqueous solution for post-treatment, and the product was extracted with chloroform. The organic phases were combined, the solvent was removed under reduced pressure, and the crude product was recrystallized three times with methanol, followed by vacuum drying at 60 °C for 12 h to obtain approximately 7.77 g of N-[3,5-bis(trifluoromethyl)phenyl]-4,4′-dichlorobenzophenone imine monomer, with a yield of 84%. The ¹H NMR spectrum of the obtained product is shown below. Figure 4 As shown, multiple groups of aromatic proton signals appeared in the δ range of approximately 7.7–6.7 ppm. Among them, H-2 / H-6 and H-4 on the 3,5-bis(trifluoromethyl)phenyl group constituted two types of aromatic proton environments, while the remaining signals could be attributed to the aromatic protons on the two p-chlorophenyl groups. The peak distribution and proton environment types are consistent with the structure of the target monomer. The reaction formula is shown below:

[0049]

[0050] Example 5: Preparation of N-(4-cyanophenyl)-4,4′-dichlorobenzophenone imine monomer with R being -C6H4CN in general formula (I)

[0051] Under nitrogen protection, 7.533 g (30 mmol) of 4,4′-dichlorobenzophenone, 12.0006 g (90 mmol) of anhydrous aluminum trichloride (AlCl3), and 300 mL of chloroform were added to a 500 mL three-necked flask and stirred. Then, a mixture of 8.8605 g (75 mmol) of 4-aminobenzonitrile and 27.3213 g (270 mmol) of triethylamine was added dropwise to the reaction system. After the addition was complete, the reaction was continued under reflux with chloroform, and the reaction progress was monitored until the starting materials were completely converted.

[0052] The resulting reaction solution was slowly added to a 4 mol / L sodium hydroxide aqueous solution for post-treatment, and the product was extracted with chloroform. The organic phases were combined, the solvent was removed under reduced pressure, and the crude product was recrystallized three times with methanol, followed by vacuum drying at 60 °C for 12 h to obtain approximately 8.64 g of N-(4-cyanophenyl)-4,4′-dichlorobenzophenone imine monomer, with a yield of 82%. The ¹H NMR spectrum of the obtained product is shown below. Figure 5 As shown, multiple groups of aromatic proton signals appear in the δ range of approximately 7.7–6.7 ppm, which can be attributed to aromatic protons on two p-chlorophenyl and p-cyanophenyl rings; some signals from different aromatic rings overlap, and the composition and distribution of the aromatic region signals are consistent with the structure of the target monomer. The reaction formula is shown below:

[0053]

[0054] Example 6: Preparation of polyaryl ketimine (PNI) with R being -C6H5 in general formula (II)

[0055] PNI uses an N-aryl-substituted dichlorodiaryl ketone imine monomer (N-phenyl-4,4′-dichlorobenzophenone imine) corresponding to R being -C6H5 in general formula (I) as the polymerization monomer, and uses Ni(COD)2 and 2,2′-bipyridine to form a coupling system to carry out aryl-aryl coupling polymerization in N,N-dimethylacetamide (DMAc). The reaction route is shown below:

[0056]

[0057] Under argon protection, 2.3716 g (7.27 mmol) of N-[bis(4-chlorophenyl)methylene]aniline, 6.8130 g (43.62 mmol) of 2,2′-bipyridine, 20 mL of DMAc, and 15 mL of toluene were added to a 50 mL double-necked round-bottom flask equipped with a magnetic stirrer, a dehydrator, and a condenser. The system was heated to 155 °C, and after stable reflux was observed at the dehydrator, the reaction was timed for 3 h to remove moisture from the system. After the toluene was removed, the temperature was lowered to 80 °C; 25.000 g (18.18 mmol) of Ni(COD) was added under continuous argon protection, and the system turned purple-black. The reaction was continued for 3 h.

[0058] After the reaction was complete, the resulting reaction solution was transferred to methanol and soaked for 24 h. The resulting solid was washed three times with methanol and three times with deionized water (45 min each time), and then dried under vacuum at 80 °C for 24 h. To reduce residual metal components, the dried product was dissolved in 30 mL of N-methyl-2-pyrrolidone and stirred for 12 h. After centrifugation at 3000 rpm for 20 min, the supernatant was added dropwise to deionized water to precipitate the product. After filtration, the product was washed once with methanol (45 min) and then dried under vacuum at 60 °C for 24 h to obtain a white PNI polymer powder with a yield of 75%. The ¹H NMR spectrum of the obtained product is shown below. Figure 6 As shown, broadened aromatic proton signals with overlapping appearances are observed in the δ range of approximately 7.6–6.5 ppm, which can be attributed to aromatic protons on the polymer aromatic backbone and N-phenyl side groups. Compared to the corresponding monomers, the aromatic region signals of the polymer are significantly broadened and overlapped, consistent with the characteristic of aromatic protons in polymer segments being in multiple approximate chemical environments, supporting the formation of the polymer structure.

[0059] Example 7: Preparation of polyaryl ketimines (PNIs) in general formula (II) where R is -C6H4SO2CH3

[0060] PNIs uses the dichlorodiaryl ketone imine monomer (N-[bis(4-chlorophenyl)methylene]-4-(methylsulfonyl)aniline) corresponding to -C6H4SO2CH3 in formula (I) as the polymerization monomer, and Ni(COD)2 and 2,2′-bipyridine form the coupling system. Aryl-aryl coupling polymerization is carried out in DMAc. The reaction route is shown below:

[0061]

[0062] Under argon protection, 2.9400 g (7.27 mmol) of N-[bis(4-chlorophenyl)methylene]-4-(methanesulfonyl)aniline, 6.8130 g (43.62 mmol) of 2,2′-bipyridine, 20 mL of DMAc, and 15 mL of toluene were added to a 50 mL double-necked round-bottom flask equipped with a magnetic stirrer, a dehydrator, and a condenser. The system was heated to 155 °C, and after stable reflux was observed at the dehydrator, the reaction was timed for 3 h to remove moisture from the system. After the toluene was removed, the temperature was lowered to 80 °C; 25.000 g (18.18 mmol) of Ni(COD) was added under continuous argon protection, and the system turned purple-black. The reaction was continued for 3 h.

[0063] After the reaction was complete, the resulting reaction solution was transferred to methanol and soaked for 24 h. The resulting solid was washed three times with methanol and three times with deionized water (45 min each time), and then dried under vacuum at 80 °C for 24 h. Subsequently, following the same method for removing residual metals as PNI, the sample was dissolved in 30 mL of N-methyl-2-pyrrolidone and stirred for 12 h. After centrifugation at 3000 rpm for 20 min, the supernatant was added dropwise to deionized water to precipitate the product. After filtration, the product was washed once with methanol (45 min) and then dried under vacuum at 60 °C for 24 h to obtain a pale white PNI polymer powder with a yield of 78%. The ¹H NMR spectrum of the obtained product is shown below. Figure 7 As shown, broadened and overlapping aromatic proton signals appear in the range of approximately 7.8–6.6 ppm, which can be attributed to aromatic protons on the aromatic backbone of the polymer and the p-methylsulfonyl phenyl side group; the characteristic signal of the methyl proton in the methanesulfonyl group can still be observed at approximately 3.1 ppm. The broadening of the aromatic region signal and the retention of the methanesulfonyl group signal support the formation of the corresponding polymer and the retention of the side group structure.

[0064] Example 8: Preparation of polyaryl ketimine with R being -C6H4NO2 in general formula (II)

[0065] The N-(4-nitrophenyl)-substituted polyaryl ketone imine uses the dichlorodiaryl ketone imine monomer (N-(4-nitrophenyl)-4,4′-dichlorobenzophenone imine) corresponding to -C6H4NO2 in formula (I) as the polymerization monomer, and Ni(COD)2 and 2,2′-bipyridine as the coupling system to carry out aryl-aryl coupling polymerization in DMAc. The reaction route is shown below:

[0066]

[0067] Under argon protection, 0.453 g (1.220 mmol) of N-(4-nitrophenyl)-4,4′-dichlorobenzophenone imine, 1.136 g (7.274 mmol) of 2,2′-bipyridine, 5 mL of DMAc, and 10 mL of toluene were added to a 50 mL double-necked round-bottom flask equipped with a magnetic stirrer, a dehydrator, and a condenser. The system was heated to 155 °C, and after stable reflux was observed at the dehydrator, the reaction was timed for 3 h to remove moisture from the system. After the toluene was removed, the temperature was lowered to 80 °C; 1.000 g (3.636 mmol) of Ni(COD)2 was added under continuous argon protection, and the system turned black. The reaction was continued for another 3 h.

[0068] After the reaction was completed, the resulting reaction solution was transferred to methanol and soaked for 24 h. The resulting solid was washed three times with methanol and three times with deionized water (45 min each time), and then dried under vacuum at 80 °C for 24 h. Subsequently, following the same residual metal removal method as PNI, the sample was dissolved in 30 mL of N-methyl-2-pyrrolidone and stirred for 12 h. After centrifugation at 3000 rpm for 20 min, the supernatant was added dropwise to deionized water to precipitate the solid. After filtration, the solid was washed once with methanol (45 min) and then dried under vacuum at 60 °C for 24 h to obtain approximately 0.3005 g of pale yellow N-(4-nitrophenyl)-substituted polyaryl ketone imine powder, with a yield of 82%.

[0069] Example 9: Preparation of polyaryl ketimine with R being -C6H3(CF3)2 in general formula (II)

[0070] The O-[3,5-bis(trifluoromethyl)phenyl]-substituted polyaryl ketone imine uses the dichlorodiaryl ketone imine monomer (N-[3,5-bis(trifluoromethyl)phenyl]-4,4′-dichlorobenzophenone imine) corresponding to -C6H3(CF3)2 in formula (I) as the polymerization monomer, and Ni(COD)2 and 2,2′-bipyridine as the coupling system to carry out aryl-aryl coupling polymerization in DMAc. The reaction route is shown below:

[0071]

[0072] Under argon protection, 0.56014 g (1.212 mmol) of N-[3,5-bis(trifluoromethyl)phenyl]-4,4′-dichlorobenzophenone imine, 1.136 g (7.274 mmol) of 2,2′-bipyridine, 6.18 mL of DMAc, and 10 mL of toluene were added to a 50 mL double-necked round-bottom flask equipped with a magnetic stirrer, a dehydrator, and a condenser. The system was heated to 155 °C, and after stable reflux was observed at the dehydrator, the reaction was timed for 3 h to remove moisture from the system. After the toluene was removed, the temperature was lowered to 80 °C; under continuous argon protection, 1.000 g (3.636 mmol) of Ni(COD)₂ was added, and the system turned black. The reaction was continued for 3 h.

[0073] After the reaction was completed, the resulting reaction solution was transferred to methanol and soaked for 24 h. The resulting solid was washed three times with methanol and three times with deionized water (45 min each time), and then dried under vacuum at 80 °C for 24 h. Subsequently, following the same residual metal removal method as PNI, the sample was dissolved in 30 mL of N-methyl-2-pyrrolidone and stirred for 12 h. After centrifugation at 3000 rpm for 20 min, the supernatant was added dropwise to deionized water to precipitate the solid. After filtration, the solid was washed once with methanol (45 min) and then dried under vacuum at 60 °C for 24 h to obtain approximately 0.3604 g of pale yellow N-[3,5-bis(trifluoromethyl)phenyl]-substituted polyaryl ketone imine powder, with a yield of 76%.

[0074] Example 10: Preparation of polyaryl ketimine with R being -C6H4CN in general formula (II)

[0075] The N-(4-cyanophenyl)-substituted polyaryl ketone imine uses the dichlorodiaryl ketone imine monomer (N-(4-cyanophenyl)-4,4′-dichlorobenzophenone imine) corresponding to -C6H4CN in formula (I) as the polymerization monomer, and Ni(COD)2 and 2,2′-bipyridine as the coupling system to carry out aryl-aryl coupling polymerization in DMAc. The reaction route is shown below:

[0076]

[0077] Under argon protection, 0.4256 g (1.212 mmol) of N-(4-cyanophenyl)-4,4′-dichlorobenzophenone imine, 1.136 g (7.274 mmol) of 2,2′-bipyridine, 4.70 mL of DMAc, and 10 mL of toluene were added to a 50 mL double-necked round-bottom flask equipped with a magnetic stirrer, a desiccant, and a condenser. The system was heated to 155 °C, and after stable reflux was observed at the desiccant, the reaction was timed for 3 h to remove moisture from the system. After the toluene was removed, the temperature was lowered to 80 °C; 1.000 g (3.636 mmol) of Ni(COD)2 was added under continuous argon protection, and the system turned black. The reaction was continued for another 3 h.

[0078] After the reaction was completed, the resulting reaction solution was transferred to methanol and soaked for 24 h. The resulting solid was washed three times with methanol and three times with deionized water (45 min each time), and then dried under vacuum at 80 °C for 24 h. Subsequently, following the same residual metal removal method as PNI, the sample was dissolved in 30 mL of N-methyl-2-pyrrolidone and stirred for 12 h. After centrifugation at 3000 rpm for 20 min, the supernatant was added dropwise to deionized water to precipitate the solid. After filtration, the solid was washed once with methanol (45 min) and then dried under vacuum at 60 °C for 24 h to obtain approximately 0.2684 g of pale yellow N-(4-cyanophenyl)-substituted polyaryl ketone imine powder, with a yield of 79%.

[0079] Example 11: Preparation of PNI / PNIs precursor membrane

[0080] After obtaining PNI and PNIs polymer powders, dense self-supporting films were prepared using a solution casting method with DMAc as the solvent. Both precursor films were prepared using the same process: 0.15 g of polymer powder was dissolved in 15 mL of DMAc and stirred at room temperature for 24 h until completely dissolved, yielding a casting solution. After standing for 12 h to remove bubbles, the casting solution was cast onto a horizontal, clean glass plate (8 cm × 8 cm). The film was then dried sequentially at 80 °C, 100 °C, and 120 °C for 12 h each, followed by heating to 160 °C and vacuuming to remove residual solvent. After natural cooling to room temperature, the glass plate was immersed in deionized water to peel off the film, and then the film was dried in an 80 °C oven for 12 h to obtain a homogeneous, pale yellow, transparent PNI or PNIs precursor film with a thickness of 15 μm.

[0081] Examples 12-14: Thermal self-crosslinking treatment of PNI precursor films

[0082] The PNI precursor film obtained in Example 11 was placed in a tube furnace and heat-treated under nitrogen at 300°C, 330°C, and 360°C, respectively, without the addition of an exogenous crosslinking agent for forming connections between polymer molecular chains, to obtain thermally self-crosslinked PNI-300, PNI-330, and PNI-360 films. Specific conditions are shown in Table 1.

[0083] Table 1: Heat treatment conditions for PNI film

[0084]

[0085] Before heat treatment, the nitrogen was replaced three times with N2, and the N2 flow rate was maintained at 100 mL / min during the heating and holding process; after the holding period, the mixture was allowed to cool naturally.

[0086] Examples 15-17: Thermal self-crosslinking treatment of PNI precursor membranes

[0087] The PNIs precursor film obtained in Example 11 was treated with the same heat treatment method as in Examples 12-14, at 300°C, 330°C, and 360°C under nitrogen atmosphere, respectively, to obtain thermally self-crosslinked PNIs-300, PNIs-330, and PNIs-360 films. Specific conditions are shown in Table 2.

[0088] Table 2: Heat treatment conditions for PNIs membranes

[0089]

[0090] Energy testing and structural characterization

[0091] (1) Infrared spectroscopy test

[0092] like Figure 8 As shown, untreated PNI at 1641 cm⁻¹ -1 A shoulder-shaped acromion, belonging to the C=N stretching vibration, appears nearby, at 1309 cm. -1 and 1255cm -1 An absorption peak related to aromatic CN bonds appeared nearby. After heat treatment at 300℃, 330℃, and 360℃, the peak was 1641 cm⁻¹. -1 The C=N related shoulder peaks near the surface gradually weaken with increasing heat treatment temperature; meanwhile, at 1309 cm⁻¹... -1 and 1255cm -1 The existing CN-related absorptions in the vicinity gradually weakened and broadened, eventually reaching a peak at 1292 cm⁻¹. -1 A broad absorption band is observed nearby. The aforementioned changes exhibit a clear temperature dependence, indicating that heat treatment caused a sustained change in the local chemical environment of the C=N bonds and adjacent CN bonds in the ketoimine group. The main absorption in the aromatic backbone region remains identifiable after heat treatment, suggesting that the bulk aromatic structure of the polymer is preserved. Infrared spectroscopy results confirm that the ketoimine-related structure underwent a thermally induced transformation.

[0093] (2) Raman spectroscopy test

[0094] like Figure 9 As shown, untreated PNI at 1182 cm⁻¹ -1 The vicinity exhibits characteristic Raman peaks associated with the local structure of the original ketimine. As the heat treatment temperature increases from 300℃ to 330℃ and 360℃, the peak value reaches 1182 cm⁻¹. -1 The relative intensity of the nearby peaks gradually decreases, while that at 1140cm... -1 The relative intensities of nearby peaks gradually increase, indicating a redistribution of vibrational modes around the nitrogen-containing structure. This trend corresponds to the change observed at 1641 cm⁻¹ in the infrared spectrum. -1The weakening of the C=N related shoulder peak and the change in the CN absorption band corroborate each other, indicating that heat treatment not only causes changes in the physical morphology of the film, but also causes changes in the local chemical structure related to ketimine.

[0095] (3) X-ray photoelectron spectroscopy test

[0096] like Figure 10 and Figure 11 As shown, the high-resolution N 1s spectra of untreated PNI and PNIs are dominated by the C=N*-C type ketimine nitrogen component with a binding energy of approximately 400.1 eV. After heat treatment at 300℃, a new component belonging to the N*(-C)3 type nitrogen-containing local environment appears at approximately 398.8 eV. Furthermore, as the heat treatment temperature increases to 330℃ and 360℃, the relative content of this component gradually increases, while the original C=N*-C component gradually decreases. This indicates that the local electronic environment of the ketimine nitrogen underwent a thermally induced transformation, and the methanesulfonyl substitution did not alter its overall trend. Combined with infrared and Raman spectroscopy and the phenomenon of the film changing from soluble to insoluble after heat treatment, it can be determined that the polymer molecular chains underwent a structural transformation during heat treatment and gradually formed a stable cross-linked network. Figure 10 (a) is the N 1s high-resolution X-ray photoelectron spectrum of PNI. Figure 10 (b) is the N 1s high-resolution X-ray photoelectron spectrum of PNI-300. Figure 10 (c) is the N 1s high-resolution X-ray photoelectron spectrum of PNI-330. Figure 10 (d) is the N 1s high-resolution X-ray photoelectron spectrum of PNI-360; Figure 11 (a) is the N 1s high-resolution X-ray photoelectron spectrum of PNIs. Figure 11 (b) is the N 1s high-resolution X-ray photoelectron spectrum of PNIs-300. Figure 11 (c) is the N 1s high-resolution X-ray photoelectron spectrum of PNIs-330. Figure 11 (d) is the N 1s high-resolution X-ray photoelectron spectrum of PNIs-360.

[0097] (4) Organic solvent resistance test

[0098] To evaluate the resistance to organic solvents before and after heat treatment, 20 mg of PNI, PNIs, and their heat-treated samples were weighed and 10 mL of N,N-dimethylacetamide was added. The samples were allowed to stand at 25 °C, and the dissolution status was recorded at 0 min, 5 min, 1 h, 2 h, 4 h, 8 h, and 24 h. After soaking for 24 h, the heat-treated samples were removed, dried, and weighed. The mass retention rate was calculated as the ratio of the dried mass after soaking to the mass before soaking. In Table 3, "+" indicates soluble, and "-" indicates insoluble.

[0099] Table 3: Dissolution behavior of polymer films in N,N-dimethylacetamide

[0100]

[0101] As shown in Table 3, the untreated PNI and PNIs precursor films were soluble in N,N-dimethylacetamide; the PNI-300, PNI-330, PNI-360, and PNIs-300, PNIs-330, and PNIs-360 films remained insoluble within 24 hours, with a mass retention rate of 99% after immersion for 24 hours. These results indicate that heat treatment significantly improved the structural stability of the films in the tested organic solvents.

[0102] The organic solvent resistance of the heat-treated films was further evaluated using N,N-dimethylformamide (DMF), N-methyl-2-pyrrolidone (NMP), chloroform (CHCl3), dichloromethane (CH2Cl2), tetrahydrofuran (THF), and dimethyl sulfoxide (DMSO). Using the same solid-liquid ratio as in the previous tests, the PNI and PNIs precursor films, as well as the PNI-300, PNI-330, PNI-360, PNIs-300, PNIs-330, and PNIs-360 films, were placed in the aforementioned solvents and immersed at 25°C for 24 hours, and their dissolution state was observed. The results showed that the untreated PNI and PNIs precursor films were soluble in DMF, NMP, THF, and DMSO; the heat-treated PNI-300, PNI-330, PNI-360, PNIs-300, PNIs-330, and PNIs-360 films remained insoluble in DMF, NMP, THF, and DMSO, with a mass retention rate of 99% after immersion for 24 hours.

[0103] (5) Gas permeability and ideal selectivity test

[0104] Table 4: Gas permeation performance and ideal selectivity of different membranes

[0105]

[0106] Gas permeability was evaluated using pure gases N2, CH4, CO2, and O2, respectively, at a test temperature of 35°C and a feed pressure of 2 bar. The gas permeability coefficient P is denoted by Barrer. The ideal selectivity of O2 / N2, CO2 / CH4, and CO2 / N2 was calculated as the ratio of the permeability coefficients of the corresponding two pure gases, i.e., α(O2 / N2) = P(O2) / P(N2), α(CO2 / CH4) = P(CO2) / P(CH4), and α(CO2 / N2) = P(CO2) / P(N2). Untreated PNI and PNIs precursor films served as control samples for the corresponding heat-treated films.

[0107] As shown in Table 4, heat treatment significantly affects the gas permeability and ideal selectivity of PNI and PNIs films. For the PNI series, the permeability coefficients of untreated PNI films for N2, CH4, CO2, and O2 are 0.664, 0.703, 11.779, and 2.037 barrers, respectively; after heat treatment at 360℃, the corresponding permeability coefficients are 0.568, 1.526, 41.585, and 6.471 barrers, respectively, with a significant increase in the permeability coefficients for CO2 and O2. Simultaneously, the ideal selectivity for O2 / N2, CO2 / CH4, and CO2 / N2 increases from 3.07, 16.76, and 17.74 to 11.39, 27.25, and 73.21, respectively.

[0108] For the PNIs series, the permeability coefficients of untreated PNIs membranes for N2, CH4, CO2, and O2 were 0.914, 0.663, 1.834, and 1.068 barrers, respectively. After heat treatment at 360°C, the corresponding permeability coefficients were 0.250, 0.302, 14.216, and 2.304 barrers, respectively. The permeation of N2 and CH4 was inhibited, while the permeability coefficients of CO2 and O2 increased. The ideal selectivity of O2 / N2, CO2 / CH4, and CO2 / N2 increased from 1.17, 2.77, and 2.01 to 9.22, 47.07, and 56.86, respectively. These results indicate that, under the given test conditions of this invention, thermal self-crosslinking can alter the gas transport behavior of PNI and PNIs films for N2, CH4, CO2, and O2, and improve their separation selectivity for O2 / N2, CO2 / CH4, and CO2 / N2 gas pairs.

[0109] (6) Dielectric property testing

[0110] like Figure 12As shown, the PNI and PNIs series films exhibit continuous dielectric response under the tested frequency and temperature conditions. The dielectric constant of the PNIs series is generally higher than that of the PNI series; after heat treatment, the dielectric constant and dielectric loss of both types of films change to some extent, but they still maintain a stable dielectric response. Figure 12 (a) shows the frequency-dependent dielectric constant and dielectric loss curves of PNI, PNI-300, PNI-330 and PNI-360 at 25℃; Figure 12 (b) shows the frequency-dependent dielectric constant and dielectric loss curves of PNIs, PNIs-300, PNIs-330 and PNIs-360 at 25℃. Figure 12 (c) shows the temperature-dependent dielectric constant and dielectric loss curves of PNI, PNI-300, PNI-330 and PNI-360 at 1000 Hz. Figure 12 (d) shows the temperature-dependent dielectric constant and dielectric loss curves of PNIs, PNIs-300, PNIs-330 and PNIs-360 at 1000 Hz.

Claims

1. An N-aryl-substituted dichlorodiaryl ketone imine monomer, characterized in that: Its structural formula is shown in (I). Wherein, R is -C6H5, -C6H4SO2CH3, -C6H4NO2, -C6H3(CF3)2 or -C6H4CN, and the corresponding monomer names are N-phenyl-4,4′-dichlorobenzophenone imine, N-[4-(methylsulfonyl)phenyl]-4,4′-dichlorobenzophenone imine, N-(4-nitrophenyl)-4,4′-dichlorobenzophenone imine, N-[3,5-bis(trifluoromethyl)phenyl]-4,4′-dichlorobenzophenone imine, and N-(4-cyanophenyl)-4,4′-dichlorobenzophenone imine.

2. An N-aryl-substituted polyaryl ketimine, characterized in that: Its structure is shown in formula (II), which is prepared by Yamamoto coupling polymerization of the N-aryl-substituted dichlorodiaryl ketone imine monomer shown in formula (I) of claim 1; during the polymerization process, the two para-aryl chlorine reaction sites of the monomer are coupled to form a polymer backbone connected by aryl-aryl carbon-carbon bonds, while the aryl R connected to the nitrogen atom of the ketone imine is retained as a polymer side group. n represents the degree of aggregation, which is an integer greater than 1; Wherein, R is -C6H5, -C6H4SO2CH3, -C6H4NO2, -C6H3(CF3)2 or -C6H4CN, and the corresponding polymer names are N-phenyl-substituted polyaryl ketone imine, N-[4-(methylsulfonyl)phenyl]-substituted polyaryl ketone imine, N-(4-nitrophenyl)-substituted polyaryl ketone imine, N-[3,5-bis(trifluoromethyl)phenyl]-substituted polyaryl ketone imine, and N-(4-cyanophenyl)-substituted polyaryl ketone imine, respectively.

3. A thermally self-crosslinking polyaryl ketone imine film, characterized in that: It is prepared by "thermal self-crosslinking" of the N-aryl substituted polyaryl ketimide as described in claim 2.

4. The thermally self-crosslinking polyaryl ketone imine film as described in claim 3, characterized in that: "Thermal self-crosslinking" refers to the process by which N-aryl-substituted polyaryl ketimide is added to a solvent and cast into a precursor film. Without the addition of an external crosslinking agent for forming connections between polymer molecular chains, the polymer's own structure undergoes crosslinking through heat treatment, resulting in a stable crosslinked structure in the film and a dense, self-supporting, and self-crosslinked polyaryl ketimide film.

5. The thermally self-crosslinking polyaryl ketone imine film as described in claim 4, characterized in that: N-aryl-substituted polyaryl ketimides are solution-processable before heat treatment. A precursor film is cast using N,N-dimethylacetamide, N,N-dimethylformamide, N-methyl-2-pyrrolidone, dimethyl sulfoxide, chloroform, or dichloromethane as a solvent. The solvent is then gradually removed by heat treatment, followed by crosslinking to obtain a dense, self-supporting, and self-crosslinked polyaryl ketimide film.

6. The thermally self-crosslinking polyaryl ketone imine film as described in claim 5, characterized in that: The concentration of N-aryl-substituted polyaryl ketimide in the solvent is 8~15 mg / mL, and the thickness of the resulting polyaryl ketimide film is 5~150 μm. The heat treatment process is carried out in a nitrogen atmosphere, the heat treatment temperature is 300~360℃, the heat treatment time is 2~5 h, and the heating rate during heat treatment is 2.0~3.0℃ / min.

7. The application of the thermally self-crosslinking polyaryl ketone imine film according to any one of claims 3 to 6 in solvent-resistant barrier membranes, dielectric membranes or gas separation membranes.

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