Binary aromatic diacids, linear poly(arylamide)s and crosslinked poly(arylamide)s and methods of making

Abstract

A binary aromatic acid containing a benzocyclobutene structure, the structural formula is: A linear polyaromatic amide containing a benzocyclobutene structure, the structural formula is: X is 1-40, Y is 0-39. A crosslinked polyaromatic amide containing a dibenzo octacyclic structure, the structural formula is: X is 1-40, Y is 0-39. The application introduces a benzocyclobutene structural unit in the side chain, so that the regularity of the polyaromatic amide molecular chain is reduced, the crystallinity is reduced, so that the solubility of the polymer is greatly improved, and the high temperature resistance is still maintained.

Description

Technical Field

[0001] This invention belongs to the field of polyamide material technology, specifically relating to a dibasic aromatic acid, linear polyaromatic amide, and crosslinked polyaromatic amide, and their preparation methods. Background Technology

[0002] Polyamides are a general term for polymers whose main chain repeating units contain amide groups. Polyamides can be obtained by ring-opening polymerization of amines or by condensation polymerization of diamines and diacids. Polyamides possess excellent comprehensive properties, including mechanical properties, heat resistance, wear resistance, chemical resistance, and self-lubricating properties. They also have a low coefficient of friction, some flame retardancy, and are easy to process. They are suitable for reinforcement and modification with glass fibers and other fillers to improve performance and expand applications. Based on the different comonomers, polyamides can be divided into polyarylamides and aliphatic polyamides. Compared to aliphatic polyamides, polyarylamides have superior heat resistance, melting temperature, strength, and chemical resistance.

[0003] Polyarylamides are an important class of high-performance engineering plastics, polymers whose main molecular chain contains at least 85% amide groups directly linked to two aromatic rings. Based on the position of the amide groups connected to the benzene ring, polyarylamides can be further classified into para-polyarylamides, meta-polyarylamides, and ortho-polyarylamides. Due to the rigidity of their molecular chains, polyarylamides possess excellent thermal stability, very high mechanical strength and melting temperature, and chemical stability, making them widely used in military and transportation fields. However, due to the very strong hydrogen bonding between polymer chains, their glass transition temperature is very high, and their solubility in organic solvents is poor. Generally, they can only be processed after dissolving in concentrated sulfuric acid, which is highly corrosive and easily corrodes processing equipment. Furthermore, the polymer is easily degraded in sulfuric acid, significantly limiting the applications of polyarylamides. Currently, much research is being conducted to improve their solubility, thereby facilitating processing, reducing production costs, simplifying synthesis processes, and achieving a balance of excellent performance. Introducing flexible segments such as ether bonds or side groups that disrupt the regularity of the molecular chain into the rigid molecular structure of polyarylamides can produce polyarylamides with good solubility and thermal stability. Simultaneously, the polymers also exhibit good film-forming properties and high mechanical strength. For example, US Patent 4355151 reports the copolymerization of 3,4'-diaminodiphenyl ether as a third monomer. The resulting polymer solution is directly spun into fibers using a specific spinning process. After appropriate post-treatment, high-performance fibers with excellent strength, modulus, and elongation are obtained. Summary of the Invention

[0004] The purpose of this invention is to provide a dibasic aromatic acid, a linear polyaromatic amide, and a cross-linked polyaromatic amide, as well as a preparation method thereof. By introducing benzocyclobutene structural units into the side chain, the regularity of the polyaromatic amide molecular chain is reduced, and the crystallinity is decreased, thereby greatly improving the solubility of the polymer while maintaining high temperature resistance.

[0005] A diaromatic acid containing a benzocyclobutene structure, with the following structural formula: .

[0006] A linear polyaromatic amide containing a benzocyclobutene structure, with the following structural formula: X is 1-40, Y is 0-39.

[0007] A cross-linked polyarylamide containing a dibenzo-eight-membered ring structure, with the following structural formula: X is 1-40, Y is 0-39.

[0008] A method for preparing a diaromatic acid containing a benzocyclobutene structure, comprising the following steps: Step 1: Add 4-aminobenzocyclobutene, concentrated hydrochloric acid, and NaNO2 aqueous solution to a reaction vessel and react. After purification and drying, compound 1 is obtained, with the following structural formula: ; Step 2: Add p-benzoquinone, NaHCO3, and compound 1 obtained in Step 1 to a reaction vessel and react. After purification and drying, compound 2 is obtained, with the following structural formula: ; Step 3: Add compound 2 obtained in step 2 to the reaction vessel, dissolve it in diethyl ether, add Na2S2O4 aqueous solution dropwise to react, purify and dry to obtain compound 3, with the following structural formula: ; Step 4: Add compound 3 obtained in step 3, p-chlorobenzonitrile or p-fluorobenzonitrile, and K2CO3 to the reaction vessel, add DMF to dissolve, react, purify and dry to obtain compound 4, with the following structural formula: ; Step 5: Add compound 4, an aqueous solution of ethanol in a volume ratio of 1:(1-3), and KOH to the reaction vessel. After the reaction is complete, adjust the pH of the solution to 1-6 with hydrochloric acid, purify and dry to obtain the diaromatic acid containing the benzocyclobutene structure, with the following structure: ; Furthermore, in step 1, the reaction temperature is 0-5℃ and the reaction time is 1-2 hours; in step 2, the reaction temperature is room temperature and the reaction time is 8-10 hours; in step 3, the reaction temperature is room temperature and the reaction time is 6-10 hours; in step 4, the reaction temperature is 100-150℃ and the reaction time is 6-8 hours; and in step 5, the reaction temperature is room temperature and the reaction time is 10-30 minutes.

[0009] Further, in step 1, the molar ratio of 4-aminobenzocyclobutene, concentrated hydrochloric acid, and NaNO2 is 1:(4-6):(1-1.1); in step 2, the molar ratio of p-benzoquinone, NaHCO3, and compound 1 is (1-1.1):(3.5-4.5):1. In step 3, the molar ratio of compound 2 to Na2S2O4 is 1:(1-1.3); in step 4, the molar ratio of compound 3, p-chlorobenzonitrile or p-fluorobenzonitrile and K2CO3 is 1:(2-2.2):(2-2.5); in step 5, the molar ratio of compound 4 to KOH is 1:(5-50).

[0010] A method for preparing a linear polyaromatic amide containing a benzocyclobutene structure, comprising the following steps: A diaromatic acid, 3,4'-diaminodiphenyl ether, and CaCl2 were added to a reaction vessel. After purging with nitrogen, P(OPh)3, pyridine, and NMP were added, and the reaction was carried out to obtain the linear polyaromatic amide containing the benzocyclobutene structure, with the following structural formula: X is 1-40, Y is 0-39.

[0011] The diaromatic acid comprises two components, the first component being the diaromatic acid containing a benzocyclobutene structure as described in claim 1; The second component is 4,4'-dicarboxylic diphenyl ether, with the following structural formula: ; The molar percentage of the diaromatic acid containing the benzocyclobutene structure is 1-100% of the total diaromatic acid. The diaryl amine monomer is 3,4'-diaminodiphenyl ether, with the following structural formula: .

[0012] Furthermore, the molar ratio of the diaromatic acid, 3,4'-diaminodiphenyl ether, CaCl2, P(OPh)3, and pyridine is 1:1:(2-5):(4-8):(6-12).

[0013] Furthermore, the reaction temperature is 100-150℃, and the reaction time is 12-24 hours.

[0014] A method for preparing crosslinked polyaromatic amides containing a dibenzo-eight-membered ring structure, characterized by the following steps: Under inert gas conditions, the linear polyaromatic amide containing the benzocyclobutene structure of claim 2 is heated to 270°C and annealed for 6-10 hours, and then annealed at 300°C for 12-20 hours. After the reaction is completed, the crosslinked polyaromatic amide containing the benzooctane ring structure is obtained.

[0015] The advantages of this invention over the prior art are as follows: 1. The linear polyarylamide and cross-linked polyarylamide prepared by this invention have excellent mechanical strength and thermal stability and can be used repeatedly for a long time.

[0016] 2. The linear polyaromatic amides and cross-linked polyaromatic amides prepared by this invention can adjust the benzocyclobutene content in their structure according to the application scenario, thereby changing their mechanical strength and thermal stability to meet different needs. Attached Figure Description

[0017] Figure 1a 1b is the 1H NMR spectrum of Example 1, and 1b is the 1H NMR spectrum of the linear polyarylamides in Examples 2-7.

[0018] Figure 2 This is the TGA test spectrum of Example 5.

[0019] Figure 3 The images show the temperature-ramp DSC test spectra of the linear polyarylamides in Examples 2-7.

[0020] Figure 4 The following are the cooling DSC test spectra of Examples 6 and 7.

[0021] Figure 5 The XRD patterns of the linear polyarylamides in Examples 2-7 are shown.

[0022] Figure 6 The image shows the XRD patterns comparing the crystallinity before and after crosslinking in Example 6.

[0023] Figure 7 The loading and unloading curves of the nanoindenter before and after crosslinking in Example 6 are shown.

[0024] Figure 8 The cross-linked polyarylamide film material is from Example 5. Detailed Implementation

[0025] The present invention will be further described in detail below through embodiments.

[0026] Unless otherwise specified, all pharmaceuticals used in the following examples are commercially available products, and all methods used are conventional methods in the art.

[0027] Example 1 A diaromatic acid containing a benzocyclobutene structure, abbreviated as [2,5-bis-(4-phenoxybenzoic acid)-phenyl]-bicyclo[4.2.0]-octyl-1,3,5-triene, is prepared as follows: Step 1, Preparation of Compound 1: Weigh 10 mmol of dried NaNO2 and dissolve it in 5 mL of ice water. Weigh 10 mmol of 4-aminobenzocyclobutene, 3.5 mL of concentrated hydrochloric acid, and 20 mL of ice water and add them to a 100 mL three-necked flask with stirring. Slowly add the prepared NaNO2 solution dropwise to the three-necked flask, controlling the reaction temperature below 5°C, and stir for 1.5 hours to obtain a solution of Compound 1. The structural formula is: ; Step 2, Preparation of Compound 2: Weigh 10 mmol of 1,4-benzoquinone and 40 mmol of NaHCO3 into a 100 mL three-necked flask, then add 5 mL of ice water. Slowly add the Compound 1 solution obtained in the previous step to the three-necked flask. After the addition is complete, control the temperature at 5 °C for 2 hours, then react at room temperature for 6 hours. Column chromatography with petroleum ether-ethyl acetate yielded 21.91 g of pure compound, with a yield of 91%. The structural formula is: ; Step 3, Preparation of Compound 3: Weigh 210 mmol of the compound obtained in Step 2 and add it to a 250 mL single-necked flask, then add 50 mL of diethyl ether. Weigh 12.5 mmol of Na₂S₂O₄ and dissolve it in 5 mL of ice water. Slowly add the prepared Na₂S₂O₄ solution dropwise to the single-necked flask while stirring, and react for 8 hours. After the reaction is complete, extract three times with 20 mL of dichloromethane and evaporate to dryness to obtain the crude product. Column chromatography with petroleum ether-ethyl acetate solvent yields 31.77 g of the pure compound, with a yield of 83%. The structural formula is: ; Step 4, Preparation of Compound 4: Weigh 310 mmol of the compound obtained in Step 3, 21 mmol of p-fluorobenzonitrile, and 22 mmol of anhydrous K₂CO₃ into a 250 mL single-necked flask, then add 20 mL of DMF. Place under nitrogen atmosphere and heat to 120 °C for 8 hours. After the reaction is complete, add 100 mL of deionized water; a black solid precipitates. Extract the aqueous phase three times with 30 mL of ethyl acetate. Combine the organic phases, dry with anhydrous sodium sulfate, filter, concentrate, and then perform column chromatography with petroleum ether-ethyl acetate to obtain 3.90 g of the dinitrile compound, with a yield of 94%. The structural formula is: ; Step 5, the diaromatic acid containing the benzocyclobutene structure, namely [2,5-bis-(4-phenoxybenzoic acid)-phenyl]-bicyclo[4.2.0]-oct-1,3,5-triene: Weigh 410 mmol of the compound obtained in Step 4 and 200 mmol of KOH into a 250 mL single-necked flask, then add 120 mL of an aqueous solution with a volume ratio of 1:1 ethanol, and reflux for 24 hours until the solution is clear and transparent. After complete hydrolysis, adjust the pH of the solution to 1 with hydrochloric acid, and wash three times with 50 mL of anhydrous ethanol to obtain 4.18 g of the diaromatic acid containing the benzocyclobutene structure, with a yield of 92%.

[0028] The final structural formula of the diaromatic acid compound [2,5-bis-(4-phenoxybenzoic acid)-phenyl]-bicyclo[4.2.0]-oct-1,3,5-triene is as follows: .

[0029] like Figure 1a The 1H NMR spectrum analysis is as follows: 1H NMR (400MHz, DMSO-d6): δ12.82(s,1H),7.98(d,J=8.1Hz,2H),7.87(d,J=8.0Hz,2H),7.28(d ,J=7.6Hz,1H),7.24-7.13(m,6H),7.06(d,J=7.6Hz,1H),6.95(d,J=8.2Hz,2H),3.09(s,4H). Example 2 The preparation method of linear polyarylamide is as follows: 1.0 mmol of [2,5-bis-(4-phenoxybenzoic acid)-phenyl]-bicyclo[4.2.0]-oct-1,3,5-triene, 1.0 mmol of 3,4'-diaminodiphenyl ether, and 2.0 mmol of CaCl2 were weighed and added to a 25 mL Schiller tube. After nitrogen purging, 1.0 mL of P(OPh)3, 0.5 mL of pyridine, and 2 mL of NMP were mixed and added to the Schiller tube using a syringe. The reaction system was heated to 120 °C and stirred thoroughly. After reacting for 24 hours, the reaction solution was cooled to room temperature, and 50 mL of methanol was added to cause polymer coagulation. The precipitate was collected by centrifugation, washed thoroughly, and dried under vacuum at 40 °C to obtain 600 mg of linear polyarylamide, with a yield of 97%.

[0030] The structural formula of the obtained linear polyarylamide is as follows: X is 40, Y is 0.

[0031] like Figure 1b The 1H NMR spectrum analysis is as follows: 1H NMR (400MHz, DMSO-d6): δ10.26(s,1H),10.18(s,1H),8.00(dd,J=15.8,8.1Hz,2H),7.89(dd,J=15.1,8.3Hz,1H),7.79(t,J=9.6Hz,2H), 7.53(d,J=9.6Hz,0.2H),7.49(s,2H),7.30(s,3H),7.18(s,8H),7.06(s,4H),6.99(d,J=8.8Hz,1H),6.75(d,J=7.5Hz,2H),3.08(s,4H). The preparation method of crosslinked polyarylamide involves dissolving linear polyarylamide thoroughly in NMP to prepare a 50 mg / mL polymer solution, which is then dropped onto a clean substrate. After the solvent evaporates, the solution is dried at 110°C for 10 hours. The film is then peeled off from the substrate to obtain a self-supporting film. The film is annealed at 270°C for 6 hours under nitrogen atmosphere, followed by annealing at 300°C for 10 hours. After cooling, the crosslinked polyarylamide is obtained.

[0032] The structural formula of the obtained crosslinked polyarylamide is as follows: X is 40, Y is 0.

[0033] Example 3 The preparation method of linear polyarylamide is as follows: 0.9 mmol of [2,5-bis-(4-phenoxybenzoic acid)-phenyl]-bicyclo[4.2.0]-oct-1,3,5-triene, 0.1 mmol of 4,4'-dicarboxylic acid diphenyl ether, 1.0 mmol of 3,4'-diaminodiphenyl ether, and 2.0 mmol of CaCl2 were weighed and added to a 25 mL Schiller tube. After nitrogen purging, 1.0 mL of P(OPh)3, 0.5 mL of pyridine, and 2 mL of NMP were mixed and added to the Schiller tube using a syringe. The reaction system was heated to 120 °C and stirred thoroughly. After reacting for 24 hours, the reaction solution was cooled to room temperature, and 50 mL of methanol was added to cause polymer coagulation. The precipitate was collected by centrifugation, washed thoroughly, and dried under vacuum at 40 °C to obtain 585 mg of linear polyarylamide, with a yield of 98%.

[0034] The structural formula of the obtained linear polyarylamide is as follows: X is 22, Y is 3.

[0035] like Figure 1b The 1H NMR spectrum analysis is as follows: 1H NMR (400MHz, DMSO-d6): δ10.27(d,J=14.3Hz,0.1H),10.18(s,0.9H),8.00(dd,J=15.8,9.0Hz,1H),7.94-7.85(m,1H),7.88-7.74(m,1H),7.79(s) ,3H),7.57-7.46(m,1H),7.30(s,0.3H),7.20(d,J=8.9Hz,4H),7.06(s, 1H), 6.98 (d, J = 17.4Hz, 0.4H), 6.98 (s, 3H), 6.73 (s, 0.2H), 3.08 (s, 8H). The preparation method of crosslinked polyarylamide involves dissolving linear polyarylamide thoroughly in NMP to prepare a 50 mg / mL polymer solution, which is then dropped onto a clean substrate. After the solvent evaporates, the solution is dried at 110°C for 10 hours. The film is then peeled off from the substrate to obtain a self-supporting film. The film is annealed at 270°C for 6 hours under nitrogen atmosphere, followed by annealing at 300°C for 10 hours. After cooling, the crosslinked polyarylamide is obtained.

[0036] The structural formula of the obtained crosslinked polyarylamide is as follows: X is 22, Y is 3.

[0037] Example 4 The preparation method of linear polyarylamide is as follows: 0.6 mmol of [2,5-bis-(4-phenoxybenzoic acid)-phenyl]-bicyclo[4.2.0]-oct-1,3,5-triene, 0.3 mmol of 4,4'-dicarboxylic acid diphenyl ether, 0.9 mmol of 3,4'-diaminodiphenyl ether, and 2.0 mmol of CaCl2 were weighed and added to a 25 mL Schiller tube. After nitrogen purging, 1.0 mL of P(OPh)3, 0.5 mL of pyridine, and 2 mL of NMP were mixed and added to the Schiller tube using a syringe. The reaction system was heated to 120 °C and stirred thoroughly. After reacting for 24 hours, the reaction solution was cooled to room temperature, and 50 mL of methanol was added to cause polymer coagulation. The precipitate was collected by centrifugation, washed thoroughly, and dried under vacuum at 40 °C to obtain 478 mg of linear polyarylamide, with a yield of 97%.

[0038] The structural formula of the obtained linear polyarylamide is as follows: X is 14, Y is 8.

[0039] like Figure 1b The 1H NMR spectrum analysis is as follows: 1H NMR (400MHz, DMSO-d6) δ10.32-10.23(m,1H),10.19(s,0.2H),8.02(q,J=14.8,11.3Hz,1H),7.95-7.79(m,1H),7.78(d,J=10.7Hz ,1H),7.58-7.47(m,1H),7.32(d,J=8.7Hz,0H),7.19(s,3H),7.06(s,2H),7.03-6.94(m,1H),6.74(d,J=8.6Hz,1H),3.08(s,1H). The preparation method of crosslinked polyarylamide involves dissolving linear polyarylamide thoroughly in NMP to prepare a 50 mg / mL polymer solution, which is then dropped onto a clean substrate. After the solvent evaporates, the solution is dried at 110°C for 10 hours. The film is then peeled off from the substrate to obtain a self-supporting film. The film is annealed at 270°C for 6 hours under nitrogen atmosphere, followed by annealing at 300°C for 10 hours. After cooling, the crosslinked polyarylamide is obtained.

[0040] The structural formula of the obtained crosslinked polyarylamide is as follows: X is 14, Y is 8.

[0041] Example 5 The preparation method of linear polyarylamide is as follows: 0.5 mmol of [2,5-bis-(4-phenoxybenzoic acid)-phenyl]-bicyclo[4.2.0]-oct-1,3,5-triene, 0.5 mmol of 4,4'-dicarboxylic acid diphenyl ether, 1.0 mmol of 3,4'-diaminodiphenyl ether, and 2.0 mmol of CaCl2 were weighed and added to a 25 mL Schiller tube. After nitrogen purging, 1.0 mL of P(OPh)3, 0.5 mL of pyridine, and 2 mL of NMP were mixed and added to the Schiller tube using a syringe. The reaction system was heated to 120 °C and stirred thoroughly. After reacting for 24 hours, the reaction solution was cooled to room temperature, and 50 mL of methanol was added to cause polymer coagulation. The precipitate was collected by centrifugation, washed thoroughly, and dried under vacuum at 40 °C to obtain 500 mg of linear polyarylamide, with a yield of 96%.

[0042] The structural formula of the obtained linear polyarylamide is as follows: X is 14, Y is 14.

[0043] like Figure 1b The 1H NMR spectrum analysis is as follows: 1H NMR (400MHz, DMSO-d6): δ10.28(d,J=15.8Hz,3H),10.19(s,1H),8.01(dt,J=16.8,9.7Hz,7H),7.90-7.79(m,1H),7.79(s,3H),7.53(d,J= 13.9Hz,0.4H),7.49(s,1H),7.32(d,J=8.8Hz,1H),7.19(s,13H),7.07(s,2H),6.98(t,J=8.9Hz,1H),6.75(d,J=8.0Hz,1H),3.08(s,4H). The preparation method of crosslinked polyarylamide involves dissolving linear polyarylamide thoroughly in NMP to prepare a 50 mg / mL polymer solution, which is then dropped onto a clean substrate. After the solvent evaporates, the solution is dried at 110°C for 10 hours. The film is then peeled off from the substrate to obtain a self-supporting film. The film is annealed at 270°C for 6 hours under nitrogen atmosphere, followed by annealing at 300°C for 10 hours. After cooling, the crosslinked polyarylamide is obtained.

[0044] The structural formula of the obtained crosslinked polyarylamide is as follows: X is 14, Y is 14.

[0045] Example 6 The preparation method of linear polyarylamide is as follows: 0.3 mmol of [2,5-bis-(4-phenoxybenzoic acid)-phenyl]-bicyclo[4.2.0]-oct-1,3,5-triene, 0.6 mmol of 4,4'-dicarboxylic acid diphenyl ether, 0.9 mmol of 3,4'-diaminodiphenyl ether, and 2.0 mmol of CaCl2 were weighed and added to a 25 mL Schiller tube. After nitrogen purging, 1.0 mL of P(OPh)3, 0.5 mL of pyridine, and 2 mL of NMP were mixed and added to the Schiller tube using a syringe. The reaction system was heated to 120 °C and stirred thoroughly. After reacting for 24 hours, the reaction solution was cooled to room temperature, and 50 mL of methanol was added to cause polymer coagulation. The precipitate was collected by centrifugation, washed thoroughly, and dried under vacuum at 40 °C to obtain 426 mg of linear polyarylamide, with a yield of 98%.

[0046] The structural formula of the obtained linear polyarylamide is as follows: X is 22, Y is 33.

[0047] like Figure 1b The 1H NMR spectrum analysis is as follows: 1H NMR (400MHz, DMSO-d6): δ10.28(d,J=13.8Hz,2.7H),10.19(s,0.4H),8.08–7.98(m,7H),7.95-7.74(m,5H),7.52(s,2H) ),7.32(d,J=8.1Hz,1H),7.19(s,9H),7.08(d,J=7.2Hz,6H),6.99(d,J=7.9Hz,1H),6.75(d,J=6.6Hz,2H),3.08(s,2H). The preparation method of crosslinked polyarylamide involves dissolving linear polyarylamide thoroughly in NMP to prepare a 50 mg / mL polymer solution, which is then dropped onto a clean substrate. After the solvent evaporates, the solution is dried at 110°C for 10 hours. The film is then peeled off from the substrate to obtain a self-supporting film. The film is annealed at 270°C for 6 hours under nitrogen atmosphere, followed by annealing at 300°C for 10 hours. After cooling, the crosslinked polyarylamide is obtained.

[0048] The structural formula of the obtained crosslinked polyarylamide is as follows: X is 22, Y is 33.

[0049] Example 7 The preparation method of linear polyarylamide is as follows: 0.1 mmol of [2,5-bis-(4-phenoxybenzoic acid)-phenyl]-bicyclo[4.2.0]-oct-1,3,5-triene, 0.9 mmol of 4,4'-dicarboxylic acid diphenyl ether, 1.0 mmol of 3,4'-diaminodiphenyl ether, and 2.0 mmol of CaCl2 were weighed and added to a 25 mL Schiller tube. After nitrogen purging, 1.0 mL of P(OPh)3, 0.5 mL of pyridine, and 2 mL of NMP were mixed and added to the Schiller tube using a syringe. The reaction system was heated to 120 °C and stirred thoroughly. After reacting for 24 hours, the reaction solution was cooled to room temperature, and 50 mL of methanol was added to cause polymer coagulation. The precipitate was collected by centrifugation, washed thoroughly, and dried under vacuum at 40 °C to obtain 428 mg of linear polyarylamide, with a yield of 97%.

[0050] The structural formula of the obtained linear polyarylamide is as follows: X is 4, Y is 27.

[0051] like Figure 1b The 1H NMR spectrum analysis is as follows: 1H NMR (400MHz, DMSO-d6): δ10.29 (s, 1H), 8.08-7.98 (m, 3H), 7.81 (d, J = 7.7Hz, 2H), 7.54 (d, J = 13.0Hz, 1H), 7.34 (t, J = 7.7Hz, 1H), 7.20 (s, 4H), 7.08 (d, J = 7.7Hz, 2H), 6.75 (d, J = 7.0Hz, 1H), 3.08 (s, 0.4H). The preparation method of crosslinked polyarylamide involves dissolving linear polyarylamide thoroughly in NMP to prepare a 50 mg / mL polymer solution, which is then dropped onto a clean substrate. After the solvent evaporates, the solution is dried at 110°C for 10 hours. The film is then peeled off from the substrate to obtain a self-supporting film. The film is annealed at 270°C for 6 hours under nitrogen atmosphere, followed by annealing at 300°C for 10 hours. After cooling, the crosslinked polyarylamide is obtained.

[0052] The structural formula of the obtained crosslinked polyarylamide is as follows: X is 4, Y is 27.

[0053] Performance testing: As shown in Figure 1, the linear polyarylamides obtained in Examples 2-7 were subjected to NMR testing. The content of benzocyclobutene units in the polyarylamides was calculated by integrating the characteristic peak signal (at 3.08 ppm) of the benzocyclobutene aliphatic region via 1H NMR, based on the molar ratio of [2,5-bis-(4-phenoxybenzoic acid)-phenyl]-bicyclo[4.2.0]-octyl-1,3,5-triene / 4,4'-dicarboxylic acid diphenyl ether / 3,4'-diaminodiphenyl ether. Crosslinked polyarylamides did not dissolve, and no NMR data were obtained.

[0054] The linear and crosslinked polyarylamides obtained in Examples 2-7 were subjected to TGA testing, and the results are shown in Table 1. After crosslinking, the Td5% increased significantly, with an average increase temperature exceeding 60°C; the Td10% also increased to a certain extent, with an average increase temperature exceeding 40°C. Taking Example 5 as an example... Figure 2As shown, the differences in temperature before and after ring-opening for Td,5% and Td,10% are 74.5℃ and 36.8℃, respectively. In summary, the Td,5% of linear polyarylamides ranges from 298-375℃, and the Td,10% ranges from 383-457℃, while the Td,5% of crosslinked polyarylamides ranges from 425-450℃, and the Td,10% ranges from 478.5-504.5℃. Ring-opening and crosslinking improve thermal properties to varying degrees. The Tg of the linear polyarylamides in each example ranges from 194-241℃. The Tg of the crosslinked polyarylamides in Examples 6 and 7 was measured to be 233-270℃. Td,5% is the 5% thermogravimetric temperature, Td,10% is the 10% thermogravimetric temperature, and Tg is the glass transition temperature. Higher values ​​for Td,5% and Td,10% indicate better thermal stability, while the glass transition temperature facilitates processing.

[0055] like Figure 3 As shown, the linear and cross-linked polyarylamides obtained in Examples 2-7 were subjected to heated DSC tests. With the increase of the amount of the third monomer, 4,4'-dicarboxylic acid diphenyl ether, the temperature transition temperature (Tg) gradually increased, reaching a peak at around 270°C, which is the exothermic peak of the ring-opening cross-linking of benzocyclobutene, proving the successful formation of the cross-linked polyarylamide. In Example 3, the formation of microcrystals prevented Tg testing. The Tg of the cross-linked polyarylamides corresponding to linear polyarylamides with a benzocyclobutene monomer content of 12-39 mol% was 237-270°C. When the benzocyclobutene monomer content exceeded 50 mol%, no glass transition temperature was measured, and the corresponding cross-linked polyarylamide was a hot solid.

[0056] like Figure 4 As shown, the crosslinked polyarylamides obtained in Examples 6 and 7 were subjected to cooling DSC tests. The glass transition temperature of the crosslinked polyarylamide obtained in Example 6 was 270°C. The glass transition temperature of the crosslinked polyarylamide obtained in Example 7 was 233°C.

[0057] like Figure 5 As shown, XRD tests were performed on the linear polyarylamides of Examples 2-7. Except for Example 3, all the obtained linear polyarylamides had an amorphous structure. Example 3, in addition to a broad amorphous peak, showed a sharp small peak at 37.8°. Figure 6 The figure shows the XRD test results of linear polyarylamide and crosslinked polyarylamide in Example 6. It shows a broad amorphous peak, proving that both before and after crosslinking are amorphous structures.

[0058] Table 2 shows the hardness and elastic modulus of linear and crosslinked polyarylamides in Examples 2-7, with a force of 50 μN applied to samples measuring 25 × 25 mm. The changes in hardness and Young's modulus of the series of polyarylamides before and after crosslinking were measured. The polymer chains in Examples 2 and 3 are relatively regular, containing a large number of benzocyclobutene groups, resulting in increased hardness and Young's modulus after crosslinking. In Examples 4-7, the increased content of the third monomer segment, coupled with poor heat resistance, led to thermal decomposition during crosslinking, resulting in hardness and Young's modulus that tended to stabilize within a certain range. The higher Young's modulus in Example 6 was due to its relatively larger molecular weight compared to the other examples. Figure 7 The images show the nanoindentation loading and unloading curves before and after crosslinking in Example 6. like Figure 8 As shown, this demonstrates that the polyaramid series has good film-forming properties, and the polyaramid film has good flexibility and transparency.

[0059] In the polymerization reaction, the content of benzocyclobutene units in the prepared linear polyarylamide is changed by adjusting the feeding ratio of the two diaromatic acid monomers. The molar percentage of the first component diaromatic acid monomer is 1-100%, which can be adjusted as needed.

[0060] In this invention, cross-linked polyaromatic amides with varying contents of dibenzo-octane ring structural units can be obtained by adjusting the content of benzocyclobutene units in linear polyaromatic amides. The content of the dibenzo-octane ring is between 1 and 50 mol%. The thermal stability of the final cross-linked polyaromatic amides varies depending on the content of the dibenzo-octane ring structural units.

[0061] Table 1. Thermogravimetric temperature and glass transition temperature of each embodiment. Table 2 Young's modulus and hardness of each embodiment

Claims

1. A diaromatic acid containing a benzocyclobutene structure, characterized in that, The structural formula is: 。 2. A linear polyaromatic amide containing a benzocyclobutene structure, characterized in that, The structural formula is: X is 1-40, Y is 0-39.

3. A cross-linked polyarylamide containing a dibenzo-octane ring structure, characterized in that, The structural formula is: X is 1-40, Y is 0-39.

4. A method for preparing a diaromatic acid containing a benzocyclobutene structure as described in claim 1, characterized in that, The steps are as follows: Step 1: Add 4-aminobenzocyclobutene, concentrated hydrochloric acid, and NaNO2 aqueous solution to a reaction vessel and react. After purification and drying, compound 1 is obtained, with the following structural formula: ; Step 2: Add p-benzoquinone, NaHCO3, and compound 1 obtained in Step 1 to a reaction vessel and react. After purification and drying, compound 2 is obtained, with the following structural formula: ; Step 3: Add compound 2 obtained in step 2 to the reaction vessel, dissolve it in diethyl ether, add Na2S2O4 aqueous solution dropwise to react, purify and dry to obtain compound 3, with the following structural formula: ; Step 4: Add compound 3 obtained in step 3, p-chlorobenzonitrile or p-fluorobenzonitrile, and K2CO3 to the reaction vessel, add DMF to dissolve, react, purify and dry to obtain compound 4, with the following structural formula: ; Step 5: Add compound 4, an aqueous solution of ethanol in a volume ratio of 1:(1-3), and KOH to the reaction vessel. After the reaction is complete, adjust the pH of the solution to 1-6 with hydrochloric acid, purify and dry to obtain the diaromatic acid containing the benzocyclobutene structure, with the following structure: .

5. The method for preparing a diaromatic acid containing a benzocyclobutene structure as described in claim 4, characterized in that: In step 1, the reaction temperature is 0-5℃ and the reaction time is 1-2 hours; In step 2, the reaction temperature is room temperature and the reaction time is 8-10 hours; In step 3, the reaction temperature is room temperature and the reaction time is 6-10 hours; In step 4, the reaction temperature is 100-150℃ and the reaction time is 6-8 hours; In step 5, the reaction temperature is room temperature and the reaction time is 10-30 minutes.

6. The method for preparing a diaromatic acid containing a benzocyclobutene structure as described in claim 4, characterized in that: In step 1, the molar ratio of 4-aminobenzocyclobutene, concentrated hydrochloric acid, and NaNO2 is 1:(4-6):(1-1.1); In step 2, the molar ratio of p-benzoquinone, NaHCO3, and compound 1 is (1-1.1):(3.5-4.5):1; In step 3, the molar ratio of compound 2 to Na2S2O4 is 1:(1-1.3); In step 4, the molar ratio of compound 3, p-chlorobenzonitrile or p-fluorobenzonitrile, and K2CO3 is 1:(2-2.2):(2-2.5); In step 5, the molar ratio of compound 4 to KOH is 1:(5-50).

7. A method for preparing a linear polyaromatic amide containing a benzocyclobutene structure as described in claim 2, characterized in that, The steps are as follows: A diaromatic acid, 3,4'-diaminodiphenyl ether, and CaCl2 were added to a reaction vessel. After purging with nitrogen, P(OPh)3, pyridine, and NMP were added, and the reaction was carried out to obtain the linear polyaromatic amide containing the benzocyclobutene structure, with the following structural formula: X is 1-40, Y is 0-39; The diaromatic acid comprises two components: the first component is the diaromatic acid containing a benzocyclobutene structure as described in claim 1; the second component is 4,4'-dicarboxylic acid diphenyl ether, with the following structural formula: ； The molar percentage of the diaromatic acid containing the benzocyclobutene structure is 1-100% of the total diaromatic acid. The diaryl amine monomer is 3,4'-diaminodiphenyl ether, with the following structural formula: 。 8. The method for preparing linear polyaromatic amide containing a benzocyclobutene structure as described in claim 7, characterized in that: The molar ratio of the diaromatic acid, 3,4'-diaminodiphenyl ether, CaCl2, P(OPh)3, and pyridine is 1:1:(2-5):(4-8):(6-12).

9. The method for preparing a linear polyaromatic amide containing a benzocyclobutene structure as described in claim 7, characterized in that: The reaction temperature is 100-150℃, and the reaction time is 12-24 hours.

10. A method for preparing a crosslinked polyarylamide containing a dibenzo-eight-membered ring structure as described in claim 3, characterized in that, The steps are as follows: Under inert gas conditions, the linear polyaromatic amide containing the benzocyclobutene structure of claim 2 is heated to 270°C and annealed for 6-10 hours, and then annealed at 300°C for 12-20 hours. After the reaction is completed, the crosslinked polyaromatic amide containing the benzooctane ring structure is obtained.

Images