A heterocyclic aramid nanofiber membrane and a preparation method thereof

Abstract

The present application relates to a kind of heterocyclic aramid nanofiber membrane and its preparation method, belong to aramid membrane technical field, by introducing crown ether compound copolymerization modification heterocyclic aramid, prepare the heterocyclic aramid nanofiber membrane with high tensile strength, low dielectric constant, low dielectric loss.The heterocyclic aramid nanofiber membrane of the present application is by adding crown ether in the process of polymerization and copolymerization, using the principle that crown ether can form hydrogen bond interaction with amino, regulates the polymerization-induced self-assembly behavior in the process of heterocyclic aramid polymerization, crown ether can be nested on the heterocyclic aramid segment by hydrogen bond interaction, so as to regulate the morphology of heterocyclic aramid nanofiber, the size of the obtained nanofiber is uniform, and interlocking structure is easily formed between fibers, can improve the tensile strength of membrane, the crown ether nested on segment plays the role of plasticizer, can improve the toughness of membrane, while the introduction of crown ether increases the free volume of polymer, improves the dielectric property of film material.

Description

TECHNICAL FIELD

[0001] The present application relates to aramid film technical field, especially to a kind of heterocyclic aramid nanofiber membrane and preparation method thereof. BACKGROUND

[0002] With the rapid growth of electronic information industry, especially with the advent of 5G era, the demand for high-end electronic information field materials is increasingly demanding, the development of ultra large scale integrated circuit puts forward higher performance standard to low dielectric material, including excellent strength, higher thermal stability, lower dielectric constant and dielectric loss.

[0003] Heterocyclic aramid is a kind of high performance polymer, which is copolymerized by p-phenylenediamine, terephthaloyl chloride and heterocyclic monomer, also known as "aromatic III" or "F-12". Heterocyclic aramid has the characteristics of light weight, high strength, high thermal stability and flame retardance, which makes it possible to be applied in low dielectric polymer materials. How to further improve the mechanical properties of aramid material, reduce its dielectric constant, dielectric loss and other properties is an important research direction.

[0004] At present, researchers have explored various means to improve the performance of aramid material, including surface modification technology, introduction of nano filler, introduction of other monomer copolymerization and other methods. However, there is no method for improving the performance of aramid material by introducing crown ether compound copolymerization to adjust the morphology of heterocyclic aramid nanofiber polymerization induced self-assembly at present. SUMMARY

[0005] In view of the above analysis, the present application aims to provide a kind of heterocyclic aramid nanofiber membrane and preparation method thereof, to solve the problem that there is no method for improving the performance of aramid material by introducing crown ether compound copolymerization to modify heterocyclic aramid at present, and to prepare heterocyclic aramid nanofiber membrane with high tensile strength, low dielectric constant and low dielectric loss.

[0006] In the first aspect, the present application provides a kind of heterocyclic aramid nanofiber membrane, which is obtained by copolymerization of p-phenylenediamine, terephthaloyl chloride, 2-(4-aminophenyl)-5-aminobenzimidazole and crown ether.

[0007] Further, the heterocyclic aramid nanofiber membrane has nanofibers with uniform size, and the nanofibers form an interlocking structure.

[0008] Further, the tensile strength of the heterocyclic aramid nanofiber membrane is ≥ 150 MPa, the dielectric constant is ≤ 3, and the dielectric loss is ≤ 0.01.

[0009] In the second aspect, the present application provides a preparation method of the above-mentioned heterocyclic aramid nanofiber membrane, comprising the following steps:

[0010] (1) adding a cosolvent salt and a crown ether into a polymerization organic solvent, adding p-phenylenediamine and 2-(4-aminophenyl)-5-aminobenzimidazole under the atmosphere of a protective gas, stirring until dissolved to obtain a mixture system;

[0011] (2) adding terephthaloyl chloride into the mixture system under the atmosphere of a protective gas, stirring at high speed to cause a polymerization reaction, stopping the reaction when the Wiesenberg effect appears to obtain a heterocyclic aramid nanofiber polymerization solution;

[0012] (3) taking the heterocyclic aramid nanofiber polymerization solution as a casting solution, vacuum deaerating the casting solution, coating into a film by scraping, immersing into a coagulation bath, drying to obtain the heterocyclic aramid nanofiber film.

[0013] Further, in step (1), the cosolvent salt includes one or more of lithium chloride, calcium chloride, lithium bromide or calcium bromide;

[0014] and / or, the crown ether includes one or more of 12-crown-4, 15-crown-5, 18-crown-6, 2-benzo-21-crown-7 and 2-benzo-24-crown-8;

[0015] and / or, the polymerization organic solvent is one or more of N,N-dimethylacetamide, N,N-dimethylformamide, N-methylpyrrolidone and 2-methyl-1-pyrrolidinyl cyclopropanone.

[0016] Further, in step (1), the polymerization organic solvent is further subjected to water removal treatment.

[0017] Further, in step (1), the mass fraction of the cosolvent salt in the polymerization organic solvent is 2-10%;

[0018] and / or, the total molar ratio of the crown ether to p-phenylenediamine and 2-(4-aminophenyl)-5-aminobenzimidazole is 0.1-1:1;

[0019] and / or, the molar ratio of p-phenylenediamine to 2-(4-aminophenyl)-5-aminobenzimidazole is 3:7-8:2;

[0020] The total molar concentration of p-phenylenediamine and 2-(4-aminophenyl)-5-aminobenzimidazole in the mixture system is 0.1-0.3 mol / L.

[0021] Further, in step (2), the total molar ratio of terephthaloyl chloride to p-phenylenediamine and 2-(4-aminophenyl)-5-aminobenzimidazole in step (1) is 1.001-1.007:1.

[0022] Further, in step (2), the speed of high-speed stirring is 1000-2000 rpm, and the temperature of the polymerization reaction is 0-5 DEG C.

[0023] Further, in step (2), the diameter of the heterocyclic aramid nanofiber in the heterocyclic aramid nanofiber polymerization solution is 3-10 nm.

[0024] Compared with the prior art, the present application can achieve at least one of the following beneficial effects:

[0025] (1) The heterocyclic aramid nanofiber membrane of the present application is prepared by adding crown ether to participate in copolymerization in the polymerization process, and the principle of hydrogen bonding interaction between crown ether and amino groups is used to regulate the polymerization-induced self-assembly behavior of the heterocyclic aramid during polymerization. The crown ether can be nested on the heterocyclic aramid segment through hydrogen bonding interaction, thereby regulating the morphology of the heterocyclic aramid nanofiber, making the obtained nanofiber uniform in size, and the interlocking structure between the fibers is easy to form, which can improve the tensile strength of the membrane. The crown ether nested on the segment acts as a plasticizer, which can improve the toughness of the membrane. At the same time, the introduction of crown ether increases the free volume of the polymer, which can improve the dielectric properties of the membrane material. The tensile strength of the heterocyclic aramid nanofiber membrane is ≥ 150 MPa, the dielectric constant is ≤ 3, and the dielectric loss is ≤ 0.01.

[0026] (2) In the present application, the heterocyclic aramid nanofiber is regulated by crown ether to regulate the self-assembly behavior of the aramid segment during polymerization, so that the heterocyclic aramid nanofiber has regular and uniform morphology, and the tensile strength and dielectric properties of the obtained heterocyclic aramid nanofiber membrane material are significantly improved. The present application uses the principle of supramolecular self-assembly of crown ether and amino-containing polymer to regulate the morphology of the heterocyclic aramid polymer segment, and further regulates the performance of the material. The method is used for preparing a heterocyclic aramid membrane with high tensile strength, low dielectric constant and low dielectric loss. The heterocyclic aramid polymer is regulated by copolymerization with crown ether, and a heterocyclic aramid membrane material with excellent performance is obtained.

[0027] In the present application, the above technical solutions can be combined with each other to achieve more preferred combination schemes. Other features and advantages of the present application will be described in the subsequent specification, and some advantages will become apparent from the specification, or will be understood by implementing the present application. The purpose and other advantages of the present application can be achieved and obtained from the contents specifically pointed out in the specification and the drawings. BRIEF DESCRIPTION OF DRAWINGS

[0028] The accompanying drawings are included to provide a further understanding of the application and are incorporated herein and constitute a part of the application. The drawings illustrate embodiments of the application and, together with the description, serve to explain the principles of the application. In the drawings:

[0029] Figure 1 A physical photo of the heterocyclic aramid nanofiber polymerization solution prepared in Example 1 of the present application;

[0030] Figure 2 A photograph of the heterocyclic aramid nanofiber membrane prepared in Example 1 of the present application;

[0031] Figure 3 A TEM image of the heterocyclic aramid nanofiber polymerization solution prepared in Example 1 of the present application;

[0032] Figure 4 A SEM image of the heterocyclic aramid nanofiber membrane prepared in Example 1 of the present application. DETAILED DESCRIPTION

[0033] The preferred embodiments of the present application will be described in detail below with reference to the drawings, in which the drawings constitute a part of the present application and are used to explain the principles of the present application together with the embodiments of the present application, but are not used to limit the scope of the present application.

[0034] One specific embodiment of the present application discloses a heterocyclic aramid nanofiber membrane, which is obtained by copolymerization of p-phenylenediamine, terephthaloyl chloride, 2-(4-aminophenyl)-5-aminobenzimidazole and crown ether.

[0035] In one specific embodiment, the heterocyclic aramid nanofiber membrane has nanofibers with uniform size, and the nanofibers form an interlocking structure.

[0036] In one specific embodiment, the heterocyclic aramid nanofiber membrane has a tensile strength ≥ 150 MPa, a dielectric constant ≤ 3, and a dielectric loss ≤ 0.01.

[0037] Preferably, the heterocyclic aramid nanofiber membrane has a tensile strength of 150-300 MPa, for example, 150 MPa, 160 MPa, 170 MPa, 180 MPa, 190 MPa, 200 MPa, 210 MPa, 220 MPa, 230 MPa, 240 MPa, 250 MPa, 260 MPa, 270 MPa, 280 MPa, 290 MPa, 300 MPa, and a dielectric constant of 2-3, for example, 2, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9, 3.0.

[0038] The heterocyclic aramid nanofiber membrane of the present application is prepared by adding crown ether into the polymerization process to participate in copolymerization, and the polymerization-induced self-assembly behavior in the polymerization process of the heterocyclic aramid is regulated by using the principle that crown ether can form hydrogen bond interaction with amino groups. The crown ether can be nested on the heterocyclic aramid segment through hydrogen bond interaction, so as to regulate the morphology of the heterocyclic aramid nanofiber, make the obtained nanofiber uniform in size, and easily form interlocking structure between the fibers, so as to improve the tensile strength of the membrane. The crown ether nested on the segment plays the role of plasticizer, so as to improve the toughness of the membrane. Meanwhile, the introduction of crown ether increases the free volume of the polymer, so as to improve the dielectric properties of the membrane material.

[0039] Another specific embodiment of the present application discloses a preparation method of the above-mentioned heterocyclic aramid nanofiber membrane, comprising the following steps:

[0040] (1) adding a cosolvent salt and crown ether into a polymerization organic solvent, adding p-phenylenediamine and 2-(4-aminophenyl)-5-aminobenzimidazole under the atmosphere of a protective gas, stirring until dissolved to obtain a mixture system;

[0041] (2) adding terephthaloyl chloride into the mixture system under the atmosphere of a protective gas, stirring at high speed to cause polymerization reaction, stopping the reaction when the Wilson effect appears, and obtaining a heterocyclic aramid nanofiber polymerization solution;

[0042] (3) taking the heterocyclic aramid nanofiber polymerization solution as a casting solution, vacuum defoaming treatment of the casting solution, blade coating to form a film, immersing into a coagulation bath, drying to obtain the heterocyclic aramid nanofiber membrane.

[0043] The method of the present application uses p-phenylenediamine, terephthaloyl chloride, 2-(4-aminophenyl)-5-aminobenzimidazole and 18-crown-6 to perform low-temperature copolymerization, obtains a heterocyclic aramid nanofiber solution, uses a blade coater to perform blade coating, then performs solvent exchange in deionized water to obtain a self-supporting wet film, washes the self-supporting wet film, and then hot-presses and dries to obtain a heterocyclic aramid membrane with high tensile strength, low dielectric constant and low dielectric loss. The heterocyclic aramid nanofiber uses crown ether to regulate the self-assembly behavior of aramid segment in the polymerization process, so that the heterocyclic aramid nanofiber has regular and uniform morphology, and the tensile strength and dielectric properties of the obtained heterocyclic aramid membrane material are obviously improved. The present application uses the supramolecular self-assembly principle of crown ether and amino-containing polymer to regulate the morphology of the heterocyclic aramid polymer segment, and further regulates the performance of the material. The method is used for preparing a heterocyclic aramid membrane with high tensile strength, low dielectric constant and low dielectric loss. The polymerization of the heterocyclic aramid is regulated by copolymerization with crown ether, and a heterocyclic aramid membrane material with excellent performance is obtained.

[0044] In one embodiment, the cosmotropic salt in step (1) is one or more of lithium chloride, calcium chloride, lithium bromide or calcium bromide.

[0045] In one embodiment, the crown ether is one or more of 12-crown-4, 15-crown-5, 18-crown-6, 2-benzo-21-crown-7, 2-benzo-24-crown-8.

[0046] In one embodiment, the polymeric organic solvent is one or more of N,N-dimethylacetamide, N,N-dimethylformamide, N-methylpyrrolidone, 2-methyl-1-pyrrolidinyl cyclopropanone.

[0047] When the crown ether or the polymeric organic solvent is selected as more than one, they can be mixed in any ratio.

[0048] In one embodiment, step (1) further comprises water removal treatment of the polymeric organic solvent, specifically, heating the molecular sieve at 200-400°C for 4-8h, adding the polymeric organic solvent, and naturally cooling to room temperature to obtain the water removal treated polymeric organic solvent.

[0049] Specifically, the water content in the water removal treated polymeric organic solvent is less than 100ppm.

[0050] It should be noted that since the phthaloyl chloride monomer in the heterocyclic aramid polycondensation reaction is extremely sensitive to water and can react with water to form terephthalic acid and hydrochloric acid, it is necessary to sufficiently remove water from the solvent.

[0051] In one embodiment, the protective gas in steps (1) and (2) is nitrogen.

[0052] In one embodiment, the mass fraction of the cosmotropic salt in the polymeric organic solvent in step (1) is 2-10%, for example, 2%, 2.5%, 3.0%, 3.5%, 4.0%, 4.5%, 5.0%, 5.5%, 6.0%, 6.5%, 7.0%, 7.5%, 8.0%, 8.5%, 9.0%, 9.5%, 10%.

[0053] It should be noted that when the cosmotropic salt is too little, the gradually growing polymer molecular chain segments cannot be stabilized in the polymeric organic solvent as the polymerization process proceeds, which will cause the polymer to precipitate in the polymeric organic solvent at a low molecular weight, resulting in polymerization failure. When the cosmotropic salt content is too high, the cosmotropic salt is easy to absorb water to form a cosmotropic salt-hydrated compound, which will cause side reactions in polymerization and make the polymerization effect worse.

[0054] and / or, the total molar ratio of the crown ether to the p-phenylenediamine and 2-(4- aminophenyl)-5-amino benzimidazole is 0.1-1:1, for example, 0.1:1, 0.2:1, 0.3:1, 0.4:1, 0.5:1, 0.6:1, 0.7:1, 0.8:1, 0.9:1, 1:1.

[0055] and / or, the molar ratio of the p-phenylenediamine to the 2-(4-aminophenyl)-5- amino benzimidazole is 3:7-8:2, for example, 3:7, 1:1, 1.5:1, 2:1, 2.5:1, 3:1, 3.5:1, 4:1, which can generate the structure of heterocyclic aramid without other side reactions, and the total molar concentration of the p-phenylenediamine and 2-(4- aminophenyl)-5-amino benzimidazole in the mixed system is 0.1-0.3 mol / L, for example, 0.1 mol / L, 0.12 mol / L, 0.14 mol / L, 0.16 mol / L, 0.18 mol / L, 0.20 mol / L, 0.22 mol / L, 0.24 mol / L, 0.26 mol / L, 0.28 mol / L, 0.3 mol / L.

[0056] In a specific embodiment, in step (2), the total molar ratio of the terephthaloyl chloride to the p-phenylenediamine and 2-(4-aminophenyl)-5-amino benzimidazole in step (1) is 1.001-1.007:1, for example, 1.001:1, 1.002:1, 1.003:1, 1.004:1, 1.005:1, 1.006:1, 1.007:1.

[0057] In a specific embodiment, in step (2), the speed of high-speed stirring is 1000-2000 rpm, for example, 1000 rpm, 1100 rpm, 1200 rpm, 1300 rpm, 1400 rpm, 1500 rpm, 1600 rpm, 1700 rpm, 1800 rpm, 1900 rpm, 2000 rpm, and the temperature of polymerization reaction is 0-5℃, for example, 0℃, 0.5℃, 1℃, 1.5℃, 2℃, 2.5℃, 3℃, 3.5℃, 4℃, 4.5℃, 5℃.

[0058] In a specific embodiment, in step (2), the diameter of the heterocyclic aramid nanofiber in the polymerization solution of the heterocyclic aramid nanofiber is 3-10 nm, preferably, 4-6 nm.

[0059] In a specific embodiment, in step (3), the coagulation bath is one or more of water, ethanol, propanol, acetone, butanone or tert-butanol.

[0060] Specifically, the heterocyclic aramid nanofiber polymerization solution is diluted to obtain a casting solution with a certain solid content. The casting solution is vacuum degassed until all the bubbles in the casting solution are eliminated. Then, the casting solution is coated by using a doctor blade to form a film. The film is peeled off and transferred to a coagulation bath for soaking for a certain period of time to allow the solvent and the coagulation bath to exchange fully. A self-supporting heterocyclic aramid nanofiber wet film is obtained. The heterocyclic aramid nanofiber wet film is dried by vacuum heat pressing to obtain a heterocyclic aramid nanofiber film with high tensile strength, low dielectric constant and low dielectric loss.

[0061] Further, in step (3), the heterocyclic aramid nanofiber polymerization solution is diluted with the polymerization organic solvent of step (1) to obtain the casting solution.

[0062] Preferably, the heterocyclic aramid nanofiber polymerization solution is diluted to a mass fraction of 50-100% of the original solution, for example, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, or 100%.

[0063] In step (3), the soaking time is 6-72 h, for example, 6 h, 10 h, 14 h, 18 h, 22 h, 24 h, 28 h, 32 h, 36 h, 40 h, 44 h, 48 h, 52 h, 56 h, 60 h, 64 h, 68 h, or 72 h. The above soaking time can ensure sufficient exchange of the solvent. After soaking, the film is washed with deionized water for 3-10 times, for example, 3 times, 4 times, 5 times, 6 times, 7 times, 8 times, 9 times, or 10 times, to ensure that impurities on the surface of the film are completely cleaned.

[0064] Specifically, in step (3), the drying is vacuum drying, the drying temperature is 60-150℃, for example, 60℃, 65℃, 70℃, 75℃, 80℃, 85℃, 90℃, 95℃, 100℃, 105℃, 110℃, 115℃, 120℃, 125℃, 130℃, 135℃, 140℃, 145℃, or 150℃, and the drying time is 0.5-2 h, for example, 0.5 h, 0.6 h, 0.7 h, 0.8 h, 0.9 h, 1.0 h, 1.1 h, 1.2 h, 1.3 h, 1.4 h, 1.5 h, 1.6 h, 1.7 h, 1.8 h, 1.9 h, or 2 h.

[0065] The technical solutions of the present application are further explained and described below in combination with specific examples. It should be noted that the two diamines described below are p-phenylenediamine and 2-(4-aminophenyl)-5-aminobenzimidazole.

[0066] Example 1

[0067] The method for preparing a heterocyclic aramid nanofiber film of the present embodiment comprises the following steps:

[0068] (1) 3.5 g of LiCl, 3.965 g of 18-crown-6 (total molar ratio of p-phenylenediamine and 2-(4-aminophenyl)-5-aminobenzimidazole is 1:1) were added to 100 mL of N,N-dimethylacetamide, in which the molecular sieve was heated at 400°C for 4 h, N,N-dimethylacetamide was added, and the temperature was cooled to room temperature to obtain N,N-dimethylacetamide after water removal, the water content was less than 100 ppm, the temperature of the polymerization system was controlled at 0°C, and on the basis of nitrogen gas being introduced, two diamines with a molar concentration of 0.15 mol / L were added, in which the molar ratio of p-phenylenediamine and 2-(4-aminophenyl)-5-aminobenzimidazole was 5:5, i.e., 0.811 g of p-phenylenediamine and 1.682 g of 2-(4-aminophenyl)-5-aminobenzimidazole, and high-speed stirring was performed until complete dissolution to obtain a mixed system;

[0069] (2) On the basis of nitrogen gas being introduced, 3.048 g of terephthaloyl chloride (total molar ratio of the two diamines is 1.001:1) was added to the mixed system, the rotation speed of the reaction device was adjusted to 1000 rpm, high-speed stirring was performed until the Weissenberg effect appeared, and then the polymerization reaction was stopped to obtain a heterocyclic aramid nanofiber polymerization solution, in which the theoretical mass fraction of the polymerization solution was 4.76%, the physical picture is shown in Figure 1 , the TEM picture is shown in Figure 3 , the nanofiber size is uniform, and an interlocking structure is formed;

[0070] (3) The heterocyclic aramid nanofiber polymerization solution was diluted with 100 mL of N,N-dimethylacetamide to a mass fraction of 50% of the original solution to obtain a casting solution, the casting solution was subjected to vacuum defoaming treatment, then was placed on a glass plate and was subjected to blade coating by using a doctor blade coater, the doctor blade thickness was set to 1000 μm, the obtained blade coating film was immersed in deionized water for 24 h to fully exchange the polymerization solvent, and a self-supporting heterocyclic aramid nanofiber wet film was obtained, the wet film was washed with deionized water for 5 times, and the heterocyclic aramid nanofiber wet film was subjected to vacuum 100°C hot-press drying for 1 h to obtain a crown ether-embedded heterocyclic aramid nanofiber film, the thickness was 1000±50 μm, and the physical object is shown in Figure 2 .

[0071] The SEM of the crown ether-embedded heterocyclic aramid nanofiber film prepared in this example is shown in Figure 4 , the obtained film material has a regular morphology, and the cross section presents a multi-layer structure.

[0072] Example 2

[0073] A heterocyclic aramid nanofiber film was prepared by the method of this example, which included the following steps:

[0074] (1) 10 g CaCl2, 0.528 g of 12-crown-4 (total molar ratio of p-phenylenediamine and 2-(4-aminophenyl)-5-aminobenzimidazole is 0.1:1) are added to 100 ml of N-methylpyrrolidone, in which the molecular sieve is heated at 200°C for 8 h, N-methylpyrrolidone is added, and the temperature is cooled to room temperature to obtain N-methylpyrrolidone after water removal, the water content is less than 100 ppm, the temperature of the polymerization system is controlled at 5°C, and on the basis of nitrogen gas being introduced, two kinds of diamines with a total molar concentration of 0.2 mol / L are added, in which the molar ratio of p-phenylenediamine and 2-(4-aminophenyl)-5-aminobenzimidazole is 3:7, i.e. 0.973 g of p-phenylenediamine and 4.709 g of 2-(4-aminophenyl)-5-aminobenzimidazole, and high-speed stirring is performed until complete dissolution to obtain a mixed system;

[0075] (2) On the basis of nitrogen gas being introduced, 4.0807 g of terephthaloyl chloride (total molar ratio of two kinds of diamines is 1.007:1) is subsequently added to the mixed system, the rotation speed of the reaction device is adjusted to 2000 rpm, high-speed stirring is performed until the Weissenberg effect appears, and then the polymerization reaction is stopped to obtain a heterocyclic aramid nanofiber polymerization solution;

[0076] (3) The heterocyclic aramid nanofiber polymerization solution is used as a casting solution, the casting solution is subjected to vacuum defoaming treatment, and then is placed on a glass plate and subjected to blade coating by using a doctor blade coater, the doctor blade thickness is set to 1000 μm, the obtained blade coating film is immersed in ethanol for 6 h to fully exchange the polymerization solvent, a self-supporting heterocyclic aramid nanofiber wet film is obtained, the wet film is washed with deionized water for 10 times, and after the wet film is subjected to vacuum heat pressing at 150°C for 30 min, a crown ether-embedded heterocyclic aramid nanofiber film is obtained, and the thickness is 1000±50 μm.

[0077] Example 3

[0078] A preparation method of a heterocyclic aramid nanofiber film according to the present embodiment includes the following steps:

[0079] (1) 2 g of lithium bromide, 1.101 g of 15-crown-5 (total molar ratio of p-phenylenediamine and 2-(4-aminophenyl)-5-aminobenzimidazole is 0.5:1) were added to 100 ml of N,N-dimethylformamide, in which the molecular sieve was heated at 300°C for 6 h, N,N-dimethylformamide was added, and the temperature was cooled to room temperature to obtain N,N-dimethylformamide after water removal, the water content was less than 100 ppm, the temperature of the polymerization system was controlled at 5°C, and on the basis of nitrogen gas being introduced, two kinds of diamines with a total molar concentration of 0.1 mol / L were added, in which the molar ratio of p-phenylenediamine and 2-(4-aminophenyl)-5-aminobenzimidazole was 8:2, i.e. 0.865 g of p-phenylenediamine and 0.448 g of 2-(4-aminophenyl)-5-aminobenzimidazole, and high-speed stirring was performed until complete dissolution to obtain a mixed system;

[0080] (2) On the basis of nitrogen gas being introduced, 2.032 g of terephthaloyl chloride (total molar ratio of two kinds of diamines is 1.007:1) was subsequently added to the mixed system, the rotation speed of the reaction device was adjusted to 1800 rpm, high-speed stirring was performed until the Weissenberg effect appeared, and then the polymerization reaction was stopped to obtain a heterocyclic aramid nanofiber polymerization solution;

[0081] (3) The heterocyclic aramid nanofiber polymerization solution was diluted with 33.3 ml of N,N-dimethylformamide to a mass fraction of 75% of the original solution to obtain a casting solution, the casting solution was subjected to vacuum degassing treatment, and then was placed on a glass plate and subjected to blade coating using a doctor blade coater, the doctor blade thickness was set to 1000 μm, the obtained blade coating film was immersed in methanol for 8 h to fully exchange the polymerization solvent, and a self-supporting heterocyclic aramid nanofiber wet film was obtained, the heterocyclic aramid nanofiber wet film was washed with deionized water for 7 times, and the heterocyclic aramid nanofiber wet film was subjected to vacuum hot-press drying at 60°C for 2 h to obtain a crown-embedded heterocyclic aramid nanofiber film, and the thickness was 1000±50 μm.

[0082] Example 4

[0083] A heterocyclic aramid nanofiber film was prepared by the following method:

[0084] (1) 5 g of calcium bromide, 5.662 g of dibenzo 21 crown ether-7 (total molar ratio of p-phenylenediamine and 2-(4-aminophenyl)-5-aminobenzimidazole is 0.3:1) were added into 100 ml of 2-methyl-1-pyrrolidinyl cyclopropanone, wherein the molecular sieve was heated at 250°C for 7 h, 2-methyl-1-pyrrolidinyl cyclopropanone was added, and the temperature was cooled to room temperature to obtain 2-methyl-1-pyrrolidinyl cyclopropanone after water removal, the water content was less than 100 ppm, the temperature of the polymerization system was controlled at 4°C, and on the basis of nitrogen gas being introduced, two kinds of diamines with a total molar concentration of 0.2 mol / L were added, wherein the molar ratio of p-phenylenediamine and 2-(4-aminophenyl)-5-aminobenzimidazole was 6:4, that is, 1.2985 g of p-phenylenediamine and 1.794 of 2-(4-aminophenyl)-5-aminobenzimidazole, and high-speed stirring was performed until complete dissolution to obtain a mixed system;

[0085] (2) On the basis of nitrogen gas being introduced, 4.081 g of terephthaloyl chloride (total molar ratio of two kinds of diamines is 1.005:1) was subsequently added into the mixed system, the rotation speed of the reaction device was adjusted to 1500 rpm, high-speed stirring was performed until the polymerization reaction was stopped after the Weissenberg effect appeared, and a heterocyclic aramid nanofiber polymerization solution was obtained;

[0086] (3) The heterocyclic aramid nanofiber polymerization solution was diluted with 11.1 ml of 2-methyl-1-pyrrolidinyl cyclopropanone to a mass fraction of 90% of the original solution, and then vacuum degassing treatment was performed, and then the obtained solution was placed on a glass plate and scraped by using a scraper to set the thickness of the scraper to 1000 μm, the obtained scraped film was immersed in methanol for 12 h to fully exchange the polymerization solvent, a self-supporting heterocyclic aramid nanofiber wet film was obtained, the wet film was washed with deionized water for 3 times, and after vacuum hot-pressing drying at 80°C for 1.5 h, a crown ether-embedded heterocyclic aramid nanofiber film was obtained, and the thickness was 1000±50 μm.

[0087] Comparative Example 1

[0088] The preparation method of a heterocyclic aramid film in the present comparative example was the same as that in Example 1, except that no crown ether was added in step (1).

[0089] Comparative Example 2

[0090] The preparation method of a heterocyclic aramid film in the present comparative example was the same as that in Example 1, except that no 2-(4-aminophenyl)-5-aminobenzimidazole was added in step (1).

[0091] Comparative Example 3

[0092] The preparation method of a heterocyclic aramid film in the present comparative example was the same as that in Example 1, except that in step (1), N,N-dimethylacetamide was not subjected to water removal treatment.

[0093] Comparative Example 4

[0094] The preparation method of the heterocyclic aramid film of the present comparative example is the same as that of Example 1, except that in step (2), the polymerization temperature is 20℃.

[0095] Test Example 1

[0096] The tensile strength, dielectric constant and dielectric loss of the heterocyclic aramid nanofiber film prepared in Examples 1-4 and the heterocyclic aramid film prepared in Comparative Examples 1-4, the diameter of the nanofiber in the heterocyclic aramid nanofiber polymerization solution were tested respectively, and the results are shown in Table 1.

[0097] Among them, the tensile strength is tested by a universal testing machine, the dielectric constant and dielectric loss are tested by an impedance analyzer, and the frequency is 1MHz.

[0098] Table 1

[0099] Group Tensile strength (MPa) Dielectric constant dielectric loss (x 10 -3 )]]> Fiber diameter (nm) Example 1 190 3 9.75 5 Example 2 300 2.8 9 7 Example 3 250 2.5 9.8 6 Example 4 220 2 8 4 Comparative Example 1 100 3.4 20 15 Comparative Example 2 80 3.6 18 50 Comparative Example 3 90 3 25 20 Comparative Example 4 20 3 22 30

[0100] Comparative Example 1, the tensile strength of the heterocyclic aramid film prepared without adding crown ether is significantly reduced, and the dielectric constant, dielectric loss and fiber diameter are all increased.

[0101] Comparative Example 2, the tensile strength of the heterocyclic aramid film prepared without adding 2-(4-aminophenyl)-5-aminobenzimidazole is significantly reduced, and the dielectric constant, dielectric loss and fiber diameter are all increased.

[0102] Comparative Examples 3 and 4, the performance of the aramid film prepared without using the preparation method or conditions of the present application is poor.

[0103] The present application can effectively regulate the self-assembly behavior of heterocyclic aramid polymerization by adding crown ether compounds to participate in heterocyclic aramid copolymerization, affect the morphology of heterocyclic aramid nanofiber, and further improve the comprehensive performance of heterocyclic aramid composite film.

[0104] The above description is only the preferred specific implementation of the present application, but the protection scope of the present application is not limited thereto, any changes or replacements within the technical range disclosed by the present application can be easily thought by those skilled in the art, which should be covered within the protection scope of the present application.

Claims

1. A heterocyclic aramid nanofiber membrane, characterized in that, The heterocyclic aramid nanofiber membrane was obtained by copolymerization of p-phenylenediamine, terephthaloyl chloride, 2-(4-aminophenyl)-5-aminobenzimidazole and crown ether; The heterocyclic aramid nanofiber membrane was prepared by the following steps: (1) Add the cosolvent and crown ether to the polymerization organic solvent, and under the protective atmosphere, add p-phenylenediamine and 2-(4-aminophenyl)-5-aminobenzimidazole, stir until dissolved, and obtain a mixture system; The polymer organic solvent is subjected to dehydration treatment. Specifically, the molecular sieve is heated at 200~400℃ for 4-8 hours, the polymer organic solvent is added, and the mixture is naturally cooled to room temperature to obtain the dehydrated polymer organic solvent. (2) In the atmosphere of protective gas, terephthaloyl chloride is added to the mixture system, and the mixture is stirred at high speed to produce a polymerization reaction. The reaction is stopped when the Wiesenberg effect occurs to obtain a heterocyclic aramid nanofiber polymer liquid. (3) The heterocyclic aramid nanofiber polymer solution is used as the casting solution. The casting solution is vacuum degassed, coated into a film, added to a coagulation bath for immersion, and dried to obtain the heterocyclic aramid nanofiber film. The heterocyclic aramid nanofiber membrane has a tensile strength ≥150MPa, a dielectric constant ≤3, and a dielectric loss ≤0.

01.

2. The heterocyclic aramid nanofiber membrane according to claim 1, characterized in that, The heterocyclic aramid nanofiber membrane has nanofibers of uniform size, and the nanofibers form an interlocking structure.

3. A method for preparing the heterocyclic aramid nanofiber membrane according to claim 1 or 2, characterized in that, Includes the following steps: (1) Add the cosolvent and crown ether to the polymerization organic solvent, and under the protective atmosphere, add p-phenylenediamine and 2-(4-aminophenyl)-5-aminobenzimidazole, stir until dissolved, and obtain a mixture system; (2) In the atmosphere of protective gas, terephthaloyl chloride is added to the mixture system, and the mixture is stirred at high speed to produce a polymerization reaction. The reaction is stopped when the Wiesenberg effect occurs to obtain a heterocyclic aramid nanofiber polymer liquid. (3) The heterocyclic aramid nanofiber polymer solution is used as the casting solution. The casting solution is vacuum degassed, coated into a film, added to a coagulation bath for immersion, and dried to obtain the heterocyclic aramid nanofiber membrane.

4. The preparation method according to claim 3, characterized in that, In step (1), the solubilizing salt includes one or more of lithium chloride, calcium chloride, lithium bromide or calcium bromide; And / or, the crown ether comprises one or more of 12-crown ether-4, 15-crown ether-5, 18-crown ether-6, 2-benzo21-crown 7, and 2-benzo24-crown 8; And / or, the polymerization organic solvent is one or more of N,N-dimethylacetamide, N,N-dimethylformamide, N-methylpyrrolidone, and 2-methyl-1-pyrrolylcyclopropionate.

5. The preparation method according to claim 3, characterized in that, Step (1) also includes dehydrating the polymerized organic solvent.

6. The preparation method according to claim 3, characterized in that, In step (1), the mass fraction of the co-solvent in the polymerizing organic solvent is 2-10%; And / or, the total molar ratio of the crown ether to p-phenylenediamine and 2-(4-aminophenyl)-5-aminobenzimidazole is 0.1 to 1:1; And / or, the molar ratio of p-phenylenediamine to 2-(4-aminophenyl)-5-aminobenzimidazole is 3:7 to 8:2; The total molar concentration of p-phenylenediamine and 2-(4-aminophenyl)-5-aminobenzimidazole in the mixed system is 0.1~0.3 mol / L.

7. The preparation method according to claim 3, characterized in that, In step (2), the total molar ratio of the terephthaloyl chloride to the p-phenylenediamine and 2-(4-aminophenyl)-5-aminobenzimidazole in step (1) is 1.001~1.007:

1.

8. The preparation method according to claim 3, characterized in that, In step (2), the speed of high-speed stirring is 1000~2000 rpm, and the temperature of polymerization reaction is 0~5℃.

9. The preparation method according to claim 3, characterized in that, In step (2), the diameter of the heterocyclic aramid nanofibers in the heterocyclic aramid nanofiber polymer solution is 3~10nm.

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