Multifunctional polyimide nanofiber aerogel and preparation method and application thereof

Abstract

The application discloses a kind of multifunctional polyimide nanofiber aerogel and its preparation method and application, belong to aerogel material technical field.The preparation method of the present application includes the following steps: preparation polyamide acid solution;The polyamide acid solution is electrospun, and polyamide acid nanofiber membrane is prepared;The polyamide acid nanofiber membrane is immersed in liquid nitrogen for 1-10min, and polyamide acid nanofiber aerogel precursor is obtained by swelling;The polyamide acid nanofiber aerogel precursor is subjected to thermal imidization treatment, and it is obtained.The preparation method provided by the present application does not need long drying process, and the energy consumption is low, the preparation process is simple and efficient;The aerogel prepared has good mechanical properties, heat insulation performance, sound absorption performance and flame retardant performance and other multiple performances.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of aerogel materials, and particularly relates to a multifunctional polyimide nanofiber aerogel and a preparation method and application thereof. BACKGROUND

[0002] The information disclosed in the background of the present application is only intended to increase the understanding of the overall background of the present application and should not necessarily be regarded as acknowledging or implicitly suggesting that this information constitutes prior art known to those of ordinary skill in the art.

[0003] As a new type of aerogel, electrospun nanofiber aerogel has a wide application prospect in the fields of thermal insulation, sound absorption, flexible electronic devices, catalysis and energy storage due to its high specific surface area, high porosity, lightweight and flexibility. At present, the preparation methods of nanofiber aerogel mainly include reorganization of chopped nanofibers, chemical foaming agent foaming, use of liquid bath collector and direct electrospinning. The method of reorganization of chopped nanofibers and freeze-drying to construct nanofiber aerogel usually results in poor mechanical properties of the aerogel due to the discontinuity of nanofibers. Composite aerogels prepared by adding other components to enhance the interaction and multifunctionality usually sacrifice density and porosity in exchange for mechanical properties. Although the other several methods can prepare continuous nanofiber porous materials, these materials usually present a loose stacked structure, and the interaction between the nanofibers is weak, so the mechanical strength is not significantly improved. In addition, the above preparation methods usually involve long drying time, complex preparation process and high cost, which limits the application of nanofiber aerogel.

[0004] Therefore, how to provide a method for simply and quickly preparing polyimide aerogel with good mechanical properties and multifunctionality is a problem to be solved. SUMMARY

[0005] Therefore, the present application provides a multifunctional polyimide nanofiber aerogel and a preparation method and application thereof. The preparation method of the present application is simple and fast, and the prepared polyimide nanofiber aerogel has a fluffy multi-level porous structure, can realize stretching, compression and has good flexibility, and has low density, low thermal conductivity and wide temperature resistance and other properties.

[0006] In a first aspect, the present application provides a preparation method of a multifunctional polyimide nanofiber aerogel, comprising the following steps:

[0007] preparing a polyamide acid solution;

[0008] electrospinning the polyamide acid solution to prepare a polyamide acid nanofiber membrane;

[0009] The polyamide acid nanofiber membrane is immersed in liquid nitrogen for 1-10 min to expand to obtain a polyamide acid nanofiber aerogel precursor.

[0010] The polyamide acid nanofiber aerogel precursor is subjected to thermal imidization treatment, and the polyamide acid nanofiber aerogel is obtained.

[0011] Preferably, the step of preparing the polyamide acid solution specifically comprises: reacting a diamine monomer and a dianhydride monomer in a polar solvent to obtain the polyamide acid solution.

[0012] Further, the diamine monomer is selected from one or more of 4,4'-oxydianiline (ODA) or p-phenylenediamine (PDA); the dianhydride monomer is selected from one or more of pyromellitic dianhydride (PMDA), biphenyl tetracarboxylic dianhydride (BPDA), benzophenone tetracarboxylic dianhydride (BPDA), or 4,4'-oxydiphthalic anhydride (ODPA); and the polar solvent is selected from one or more of N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAc), or N-methyl pyrrolidone (NMP).

[0013] Further, the concentration of the polyamide acid solution is 10-20 wt%; the reaction temperature is -5-5℃, and the reaction time is 5-24 h.

[0014] Preferably, the electrospinning parameters are as follows: the spinning voltage is 18-28 kV, the liquid feeding speed is 0.5-1.2 mL / h, the drum rotation speed is 500-1000 rpm, and the distance between the needle and the drum is 10-20 cm.

[0015] Preferably, the thickness of the polyamide acid nanofiber membrane is 2-6 mm.

[0016] Preferably, after the electrospinning step, the prepared polyamide acid nanofiber membrane is further subjected to a drying step at 50-80℃ for 1-3 h.

[0017] Preferably, the polyamide acid nanofiber membrane is immersed in liquid nitrogen for 2-5 min to expand to obtain the polyamide acid nanofiber aerogel precursor.

[0018] Preferably, the reaction temperature of the thermal imidization is 230-390℃, and the reaction time is 4-8 h.

[0019] In a second aspect, the present application provides a multifunctional polyimide nanofiber aerogel prepared by the above preparation method.

[0020] In a third aspect, the present application provides an application of the multifunctional polyimide nanofiber aerogel as an oil-water separation material, a sound absorption material, or a heat insulation and flame retardant material.

[0021] Compared with the prior art, the present application has the following beneficial effects:

[0022] (1) The present application utilizes the vaporization of liquid nitrogen to generate a significant pressure difference between nanofibers, which can realize the expansion of a 2D nanofiber membrane into a 3D super-loft multi-level porous aerogel within a few minutes, without a long drying process, low energy consumption, simple and efficient preparation process;

[0023] (2) The polyimide nanofiber aerogel prepared by the preparation method of the present application exhibits excellent mechanical properties, including high specific tensile strength, good compression cycle resistance (the compression strength remains more than 60% after 1000 cycles, and can be as high as more than 90%) and excellent flexibility at ultra-low temperature. Benefiting from the low density and complex multi-level porous structure of the aerogel of the present application, the aerogel exhibits excellent thermal insulation performance, with the minimum out-of-plane thermal conductivity being less than 30 mW·m -1 ·K -1 .

[0024] (3) The aerogel of the present application has excellent thermal insulation, sound absorption, oil absorption and flame retardant properties, so that it can be used as an oil-water separation material, a sound absorption material or a thermal insulation and flame retardant material, and is expected to be applied in the fields of aerospace, flexible electronic devices, catalysis and energy processing. BRIEF DESCRIPTION OF DRAWINGS

[0025] The drawings accompanying the specification of the present application serve to provide a further understanding of the present application, and the schematic embodiments of the present application and the description thereof serve to explain the present application, and do not constitute an improper limitation on the present application. Obviously, other drawings can also be obtained by those of ordinary skill in the art without creative labor on the basis of these drawings.

[0026] Figure 1 Scanning electron microscope images of the polyimide nanofiber aerogels prepared for Examples 1 to 3 of the present application; wherein (a) and (d) are cross-sectional and surface SEM morphology images of Example 1, (b) and (e) are cross-sectional and surface SEM morphology images of Example 2, and (c) and (f) are cross-sectional and surface SEM morphology images of Example 3;

[0027] Figure 2 Specific tensile strength (a) and compression stress-strain curve (b) of the polyimide nanofiber aerogels prepared for Examples 1 to 3 of the present application;

[0028] Figure 3 Flexibility display of the polyimide nanofiber aerogels prepared for Examples 1 to 3 of the present application at room temperature (a) and in liquid nitrogen (b);

[0029] Figure 4Bulk and anisotropic thermal conductivity of polyimide nanofiber aerogels prepared in Examples 1-3 of the present invention;

[0030] Figure 5 Thermogravimetric curve (a) and combustion test picture (b) of polyimide nanofiber aerogels prepared in Examples 1-3 of the present invention.

[0031] Figure 6 Oil-water separation capacity display of polyimide nanofiber aerogels prepared in Examples 2 and 3 of the present invention;

[0032] Figure 7 Sound absorption coefficient of polyimide nanofiber aerogels prepared in Examples 1-3 of the present invention. DETAILED DESCRIPTION

[0033] It should be noted that the following detailed description is exemplary in nature and is intended to provide further description of the present invention. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the present invention belongs.

[0034] The present invention provides a preparation method of multifunctional polyimide nanofiber aerogels, comprising the following steps:

[0035] Preparation of polyamide acid solution;

[0036] Electrospinning of the polyamide acid solution to prepare polyamide acid nanofiber membrane;

[0037] Swelling of the polyamide acid nanofiber membrane in liquid nitrogen for 1-10 min to obtain polyamide acid nanofiber aerogel precursor;

[0038] Thermal imidization of the polyamide acid nanofiber aerogel precursor.

[0039] The polyamide acid nanofiber membrane is prepared by electrospinning, and then the nanofiber membrane is immersed in liquid nitrogen, the liquid nitrogen rapidly vaporizes at room temperature, thereby a significant pressure difference is generated between the nanofibers, and the nanofiber membrane is stretched in 1-10 min, so that the 2D nanofiber membrane is expanded into a 3D super-loft multi-level porous aerogel. The polyamide acid nanofiber membrane can maintain flexibility in liquid nitrogen, which mainly depends on the combined action of the flexibility of the molecular structure and the size effect of the nanofiber. Specifically: (1) the flexibility of the molecular structure: the amide bond and carboxyl group contained in the polyamide acid molecular chain make the molecular structure have a certain flexibility, even at extremely low temperature (such as in liquid nitrogen environment), although the movement of the molecular chain is limited, but it will not be completely rigid, which makes the polyamide acid still have certain toughness and deformation ability in extremely low temperature; (2) the size effect of the nanofiber: due to the extremely small diameter of the fiber (usually several tens to several hundred nanometers), the stress concentration effect of the nanoscale material is significantly reduced, and the crack is not easy to generate. This microstructure can effectively disperse stress and prevent the material from being brittle at low temperature. Since the nanofiber membrane does not need to be redissolved or dispersed, the nanofibers have strong interaction between them, so the aerogel with good mechanical properties can be obtained, and the time-consuming and energy-consuming steps such as vacuum freeze drying are not needed.

[0040] In the present application, the step of preparing the polyamide acid solution is specifically: reacting diamine monomers and dianhydride monomers in a polar solvent to obtain the polyamide acid solution.

[0041] In the present application, the diamine monomers are selected from one or more of 4,4'-diamino diphenyl ether (ODA) or p-phenylenediamine (PDA); the dianhydride monomers are selected from one or more of pyromellitic dianhydride (PMDA), biphenyl tetracarboxylic dianhydride (BPDA), benzophenone tetracarboxylic dianhydride (BPDA) or 4,4'-oxydiphthalic anhydride (ODPA); and the polar solvent is selected from one or more of N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAc) or N-methyl pyrrolidone (NMP). The present application does not make special limitations on the molar ratio of diamine monomers and dianhydride monomers, and the molar ratio commonly used in the art for preparing polyamide acid can be used.

[0042] In the present application, the concentration of the polyamide acid solution is 10-20wt%, more preferably 14-18wt%. If the solid content is too high, the apparent viscosity of the polyamide acid spinning solution will be too high, the flowability will be poor, and the polyamide acid fibers cannot be normally sprayed through the spinneret to prepare the polyamide acid fibers. If the solid content is too low, the apparent viscosity of the polyamide acid spinning solution will be too low, the spraying pressure will be insufficient, and the polyamide acid fibers cannot be normally sprayed through the spinneret to prepare the polyamide acid fibers.

[0043] In the present application, the temperature for the reaction of the diamine monomer with the dianhydride monomer is -5-5℃, preferably under ice bath conditions; the reaction time is 5-24h, preferably 12-24h.

[0044] In the present application, the electrospinning parameters are as follows: the spinning voltage is 18-28kV, the liquid feeding speed is 0.5-1.2mL / h, the drum rotation speed is 500-1000rmp, and the distance between the needle and the drum is 10-20cm.

[0045] In the present application, the thickness of the polyamide acid nanofiber membrane is 2-6mm, and the thickness of the finally prepared polyimide nanofiber aerogel is 10-20mm.

[0046] In the present application, after the electrospinning step, the prepared polyamide acid nanofiber membrane is dried at 50-80℃ for 1-3h, which is to remove the residual solvent after electrospinning. Alternatively, natural drying at room temperature can be selected, and the corresponding drying time also needs to be extended. The skilled person in the art can select according to the actual needs. The dried polyamide acid nanofiber membrane is then immersed in liquid nitrogen.

[0047] In the present application, the polyamide acid nanofiber membrane is preferably immersed in liquid nitrogen for 2-5min to obtain a polyamide acid nanofiber aerogel precursor by expansion.

[0048] In the present application, the reaction temperature for the thermal imidization is 230-390℃, and the reaction time is 4-8h. More preferably, the step of thermal imidization is as follows: heating to 230-250℃, holding for 0.5-2h; then heating to 290-310℃, holding for 0.5-2h; then heating to 370-390℃, holding for 0.5-2h. Thermal imidization treatment dehydrates and cyclizes the polyamide acid into polyimide, and at the same time fixes the porous morphology of the aerogel. The present application does not make special limitations on the steps of the thermal imidization treatment, and the steps of the commonly used thermal imidization treatment in the art can be used. Usually, the thermal imidization is carried out in a thermal imidization furnace, and the heating rate is preferably 1-5℃ / min. The reaction is carried out under the condition of inert gas.

[0049] The present application also provides a multifunctional polyimide nanofiber aerogel prepared by the above preparation method, which exhibits excellent mechanical properties, including high specific tensile strength, good compression cycle resistance (the compression strength is still more than 60% after 1000 cycles, and can be as high as more than 90%), and excellent flexibility at ultra-low temperature. Benefiting from the low density and complex multi-level porous structure of the aerogel of the present application, the aerogel also exhibits excellent thermal insulation performance, and the minimum out-of-plane thermal conductivity is less than 30mW·m -1 ·K -1 .

[0050] The application also provides application of the multifunctional polyimide nanofiber aerogel as an oil-water separation material or a heat insulation and flame retardant material. The aerogel has excellent heat insulation, sound absorption, oil absorption and flame retardant properties, so that it can be used as an oil-water separation material, a sound absorption material or a heat insulation and flame retardant material, and is expected to be applied in the fields of aerospace, flexible electronic devices, catalysis and energy processing.

[0051] The technical solutions of the application will be further described below in combination with specific examples.

[0052] Example 1

[0053] The embodiment provides a preparation method of a multifunctional polyimide nanofiber aerogel.

[0054] (1) 1.001 g of 4,4'-diaminodiphenyl ether (ODA) and 0.545 g of p-phenylenediamine (PDA) are added to a beaker, and then 23.56 g of DMF is added, and stirring is performed in an ice water bath until dissolution. Then, 2.942 g of biphenyl tetracarboxylic dianhydride (BPDA) is slowly added, and stirring is continuously performed for 24 h. Finally, a polyamide acid (PAA) solution with a concentration of 16 wt% and a molar ratio of diamine to dianhydride of 1:1 is obtained.

[0055] (2) The electrospinning solution is loaded into a 10 mL syringe, and electrospinning is performed at a voltage of 24 kV. The electrospinning needle has a diameter of 0.5 mm, the liquid feeding speed is 1 mL / h, the drum rotating speed is 1000 rpm, the distance between the needle and the drum is 13 cm, and the spinning time is 5 h, so that a polyamide acid nanofiber membrane with a thickness of about 3 mm is obtained.

[0056] (3) The polyamide acid nanofiber membrane obtained in the above process is dried at 60 ℃ for 2 h, and then immersed in liquid nitrogen for 3 min, so that a polyamide acid nanofiber aerogel precursor is obtained.

[0057] (4) The polyamide acid nanofiber aerogel precursor sample is placed in a tube furnace, and is heated at a speed of 1.5 ℃ / min from room temperature to 240 ℃, and then heated at the same speed to 300 ℃ for 1 h, and then heated at the same speed to 380 ℃ for 1 h, and then cooled with the furnace, so that a multifunctional polyimide nanofiber aerogel is obtained, with a thickness of about 10 mm and a density of 65 mg / cm 3 .

[0058] Example 2

[0059] The embodiment provides a preparation method of a multifunctional polyimide nanofiber aerogel.

[0060] (1) 1.001 g of ODA and 0.545 g of PDA were added to a beaker, and then 23.56 g of DMF was added, and stirring was carried out in an ice water bath until all the diamines were dissolved. Then 2.962 g of BPDA was slowly added, and stirring was continued for 24 h. Finally, an electrospinning solution with a diamine to dianhydride molar ratio of 1:1.007 and a PAA concentration of 16 wt% was obtained.

[0061] (2) The electrospinning solution was loaded into a 10 mL syringe, and electrospinning was carried out at a voltage of 25 kV. The electrospinning needle diameter was 0.5 mm, the liquid inlet speed was 1 mL / h, the drum rotation speed was 1000 rpm, the distance between the needle and the drum was 13 cm, the spinning time was 5 h, and a polyamide acid nanofiber membrane with a thickness of about 3 mm was obtained.

[0062] (3) The polyamide acid nanofiber membrane obtained in the above process was dried at 60°C for 2 h, and then immersed in liquid nitrogen for 3 min to obtain a polyamide acid nanofiber aerogel precursor.

[0063] (4) The polyamide acid nanofiber aerogel precursor sample was placed in a tube furnace, and was heated at a rate of 1.5°C / min from room temperature to 240°C under nitrogen, and was kept at 240°C for 1 h. Then it was heated at the same rate to 300°C and kept at 300°C for 1 h. Then it was heated at the same rate to 380°C and kept at 380°C for 1 h. Then it was cooled with the furnace to obtain a multifunctional polyimide nanofiber aerogel with a thickness of about 15 mm and a density of 32 mg / cm 3 .

[0064] Example 3

[0065] The present embodiment provides a method for preparing a multifunctional polyimide nanofiber aerogel.

[0066] (1) 1.001 g of ODA and 0.545 g of PDA were added to a beaker, and then 23.56 g of DMF was added, and stirring was carried out in an ice water bath until all the diamines were dissolved. Then 2.962 g of BPDA was slowly added, and stirring was continued for 24 h. Finally, an electrospinning solution with a diamine to dianhydride molar ratio of 1:1.007 and a PAA concentration of 16 wt% was obtained.

[0067] (2) The electrospinning solution was loaded into a 10 mL syringe, and electrospinning was carried out at a voltage of 25 kV. The electrospinning needle diameter was 0.5 mm, the liquid inlet speed was 1 mL / h, the drum rotation speed was 1000 rpm, the distance between the needle and the drum was 13 cm, the spinning time was 5 h, and a polyamide acid nanofiber membrane with a thickness of about 3 mm was obtained.

[0068] (3) The polyamide acid nanofiber membrane obtained in the above process was dried at 60°C for 2 h, and then immersed in liquid nitrogen for 3 min to obtain a polyamide acid nanofiber aerogel precursor.

[0069] (4) Put the polyamide acid nanofiber aerogel precursor sample in a tube furnace, and raise the temperature from room temperature to 240℃ at a rate of 1.5℃ / min in nitrogen, keep for 1 hour, then raise the temperature to 300℃ at the same rate, keep for 1 hour, and then raise the temperature to 380℃ at the same rate, keep for 1 hour, and then cool down with the furnace to obtain multifunctional polyimide nanofiber aerogel with a thickness of about 20mm and a density of 8.8mg / cm 3 .

[0070] Test example

[0071] 1, Morphology analysis:

[0072] Figure 1 Fig. 1 is a scanning electron microscope image of the polyimide nanofiber aerogel prepared in Examples 1-3 of the present application; wherein (a) and (d) are cross-sectional and surface SEM morphology images of Example 1, (b) and (e) are cross-sectional and surface SEM morphology images of Example 2, and (c) and (f) are cross-sectional and surface SEM morphology images of Example 3; it can be seen from the figure that the aerogel has a multi-level porous structure.

[0073] 2, Mechanical property determination:

[0074] Figure 2 Fig. 2 is specific tensile strength (a) and compression stress-strain curve (b) of the polyimide nanofiber aerogel prepared in Examples 1-3 of the present application; it can be seen from the figure that the prepared aerogel has excellent mechanical properties, can be stretched and compressed, and the aerogel of Example 3 has a specific tensile strength as high as 298.9MPa·cm 3 ·g -1 .

[0075] Table 1 is a compression cycle resistance test of the polyimide nanofiber aerogel prepared in Examples 1-3 at a compression strain of 70%; it can be seen from Table 1 that the compression strength retention rate of the aerogels of Examples 1-3 can reach more than 60% after 1000 cycles, and can reach more than 90% at the highest.

[0076] Table 1 Compression cycle resistance

[0077] Number First compression strength Compression strength after 1000 cycles Compression strength retention (%) Example 1 140 kPa 96.6 kPa 69％ Example 2 56.5 kPa 46.3 kPa 82％ Example 3 12.9 kPa 12.2 kPa 94％

[0078] Note: The compression strength retention rate in Table 1 refers to the compression strength retention rate after 1000 cycles.

[0079] Figure 3 Fig. 4 is a flexibility display of the polyimide nanofiber aerogel prepared in Examples 1-3 of the present application in room temperature (a) and liquid nitrogen (b); it can be seen from the figure that the aerogel shows good flexibility and deformation recovery ability in room temperature and liquid nitrogen.

[0080] 3. Thermal conductivity measurement:

[0081] Figure 4 Bulk and anisotropic thermal conductivity of polyimide nanofiber aerogels prepared in Examples 1-3 of the present application; it can be seen from the figure that all aerogels exhibit low thermal conductivity, and the bulk thermal conductivity is less than 50 mW·m -1 ·K -1 , and the lowest can be as low as 30 mW·m -1 ·K -1 The following.

[0082] 4. Heat resistance and flame retardancy measurement:

[0083] Figure 5 Thermogravimetric curve (a) and combustion test picture (b) of polyimide nanofiber aerogels prepared in Examples 1-3 of the present application; it can be seen from the figure that the aerogels exhibit good temperature resistance, and the temperature at which 5% mass loss occurs is nearly 600℃; and when burning, there is no open flame, and no molten droplets occur, showing good flame retardancy.

[0084] 5. Oil absorption performance measurement:

[0085] Figure 6 Oil-water separation capacity display of polyimide nanofiber aerogels prepared in Examples 2 and 3 of the present application; it can be seen that the aerogels exhibit good oil-water separation performance; the polyimide nanofiber aerogel of Example 1 has similar oil-water separation capacity, which indicates that the polyimide nanofiber aerogel prepared by the present application has application prospects in the field of oil-water separation.

[0086] 6. Sound absorption performance measurement:

[0087] Figure 7 Sound absorption coefficient of polyimide nanofiber aerogels prepared in Examples 1-3 of the present application; it can be found that the aerogels obtain different sound absorption coefficients and maximum absorption frequencies due to different pore structures. Among them, the polyimide nanofiber aerogel of Example 3 obtains the highest sound absorption coefficient of 0.94 at 2720-2976 Hz, showing good sound absorption performance.

[0088] The above only describes preferred embodiments of the present application and is not intended to limit the present application. For those skilled in the art, the present application can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A method for preparing multifunctional polyimide nanofiber aerogel, characterized in that, The method comprises the following steps: preparing a polyamide acid solution; electrospinning the polyamide acid solution to obtain a polyamide acid nanofiber membrane; The electrospinning parameters are as follows: the spinning voltage is 18-28 kV, the liquid feeding speed is 0.5-1.2 mL / h, the drum rotating speed is 500-1000 rpm, and the distance between the needle and the drum is 10-20 cm; and the thickness of the polyamide acid nanofiber membrane is 2-6 mm. The polyamide acid nanofiber membrane is immersed in liquid nitrogen for 1-10 min to obtain a polyamide acid nanofiber aerogel precursor by swelling; The polyamide acid nanofiber aerogel precursor is subjected to thermal imidization treatment.

2. The production method according to claim 1, wherein The step of preparing the polyamide acid solution specifically comprises: reacting a diamine monomer and a dianhydride monomer in a polar solvent to obtain the polyamide acid solution.

3. The production method according to claim 2, wherein The diamine monomer is selected from one or more of 4,4'-diamino diphenyl ether or p-phenylenediamine; the dianhydride monomer is selected from one or more of pyromellitic dianhydride, biphenyl tetracarboxylic dianhydride, benzophenone tetracarboxylic dianhydride, or 4,4'-oxydiphthalic anhydride; and the polar solvent is selected from one or more of N,N-dimethylformamide, N,N-dimethylacetamide, or N-methylpyrrolidone.

4. The production method according to claim 2, wherein The concentration of the polyamide acid solution is 10-20 wt%; the reaction temperature is -5-5 ℃, and the reaction time is 5-24 h.

5. The production method according to claim 1, wherein After the electrospinning step, the prepared polyamide acid nanofiber membrane is further dried at 50-80 ℃ for 1-3 h.

6. The production method according to claim 1, wherein The polyamide acid nanofiber membrane is immersed in liquid nitrogen for 2-5 min to obtain a polyamide acid nanofiber aerogel precursor by swelling.

7. The production method according to claim 1, wherein The reaction temperature of the thermal imidization is 230-390 ℃, and the reaction time is 4-8 h.

8. The multifunctional polyimide nanofiber aerogel prepared by the preparation method of claim 7.

9. The multifunctional polyimide nanofiber aerogel of claim 8 as an oil-water separation material, a sound absorption material, or a thermal insulation and flame retardant material.

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