Preparation method of composite multifunctional PI aerogel

Abstract

A preparation method of composite multifunctional PI aerogel belongs to the technical field of aerogel, and comprises the following steps: step 1, mixing a polymer monomer with an organic solvent to prepare a PAA precursor; 2, the PAA precursor, a catalyst and an additive are subjected to a mixed reaction, and the composite multifunctional PI aerogel is prepared. The invention discloses a preparation method of composite multifunctional PI aerogel, which not only successfully improves the flexibility and compression resistance of aerogel, but also effectively reduces the production cost through innovative design and optimized preparation process. Meanwhile, the polyimide aerogel is endowed with excellent antibacterial performance, and the antibacterial rate exceeds 90% in antibacterial experiments of escherichia coli and staphylococcus aureus. In addition, the material also has excellent hydrophobicity, and the contact angle reaches 130 degrees. The optimized design obviously promotes the popularization and development of the multifunctional polyimide aerogel in practical application.

Description

Technical Field

[0001] The invention belongs to the technical field of aerogels, and in particular relates to a method for preparing a composite multifunctional PI aerogel. Background Art

[0002] Aerogel is a material with a three-dimensional network structure. It has high specific surface area, porosity, ultra-low density and low thermal conductivity. It is widely used in aerospace, catalysis, sensors, thermal insulation and sound insulation. However, the mechanical properties of aerogel are poor, especially the compressive strength and flexibility are insufficient. It is easy to deform or break under the action of external force, which limits its practical application. At present, there are two main methods for preparing flexible aerogels: one is to replace rigid monomers with flexible monomers, and the other is to design a network with a deformable microstructure. The former may lead to unstable performance of composite aerogels. Although the latter improves flexibility and mechanical properties, it increases cost and preparation complexity. Therefore, how to achieve the synergistic optimization of low cost and high performance while maintaining excellent functional performance has become the key to flexible aerogel research.

[0003] Patents CN119060401A and CN118909301A propose modification and multifunctionalization schemes for polyimide (PI) aerogels, but their preparation cycle is long and solvent replacement is required, which significantly increases the time and cost of industrial production. Summary of the invention

[0004] The present invention discloses a method for preparing a composite multifunctional PI aerogel. Through innovative design and optimized preparation process, the flexibility and compressive resistance of the aerogel are successfully improved, and the production cost is effectively reduced. At the same time, the polyimide aerogel is endowed with excellent antibacterial properties. In the antibacterial experiments on Escherichia coli and Staphylococcus aureus, the antibacterial rate exceeds 90%. In addition, the material also has excellent hydrophobic properties, with a contact angle of 130°. This optimized design has significantly promoted the popularization and development of multifunctional polyimide aerogels in practical applications.

[0005] To achieve the above purpose, the technical solution of the present invention is:

[0006] A method for preparing a composite multifunctional PI aerogel comprises the following steps: step 1, preparing a PAA precursor by mixing a polymer monomer with an organic solvent; step 2, preparing a composite multifunctional PI aerogel by mixing and reacting the PAA precursor with a catalyst and an additive.

[0007] Preferably, in the step 1, the polymer monomer is one or a mixture of p-phenylenediamine, 1,3-bis(4'-aminophenoxy)benzene, 4,4'-diamino-2,2'-dimethylbiphenyl, toluene diisocyanate, diphenylmethane diisocyanate, pyromellitic anhydride, 4,4'-diphenoxyphthalic anhydride, 3,3',4,4'-dibenzophenonetetracarboxylic anhydride, 4,4'-oxydiphthalic anhydride; and the organic solvent is one or a mixture of dimethylacetamide, N,N-dimethylformamide, dimethyl phthalate, dimethyl sulfoxide, and N-methylpyrrolidone.

[0008] Preferably, the step 1 comprises the following specific steps:

[0009] (11) adding the polymer monomer to the organic solution and stirring to fully mix at room temperature; wherein the mass ratio of the polymer monomer to the organic solvent is: 1-1.5:2.5-3;

[0010] (12) The mixed solution of step (11) is washed with pure water and freeze-dried to obtain a PAA precursor.

[0011] Preferably, in step 2, the catalyst is one of triethylamine and hexamethylenediamine or a mixture of two thereof; the additive is a mixture of one or more of a nano-hydrophobic coating and an antibacterial agent, and the mass of the additive material accounts for 1%-10% of the total mass of the multifunctional PI aerogel.

[0012] Preferably, the step 2 comprises the following specific steps:

[0013] (211) PAA precursor, catalyst, and pure water are mixed in a weight ratio of 2-3:2-3:94-96 at room temperature;

[0014] (212) freezing the mixed solution of step (211) in a refrigerator at -10°C to -20°C for 2-4 hours, and finally freeze-drying for 12-24 hours to obtain PAA aerogel;

[0015] (213) PAA aerogels were heated at 200–300 °C for 3–5 h to obtain PI aerogels;

[0016] (214) The PI aerogel was immersed in the antimicrobial solution and the hydrophobic coating for 5–10 min, respectively, and then transferred to 60–100 °C for drying for 3–5 h to obtain the multifunctional PI aerogel.

[0017] Preferably, the step 2 comprises the following steps:

[0018] (221) The PAA precursor, catalyst, and antimicrobial solvent were stirred and thoroughly mixed at room temperature in a ratio of 2–3:2–3:94–96 by weight;

[0019] (222) freezing the mixed solution of step (221) in a refrigerator at -10°C to -20°C for 2-4 hours, and finally freeze-drying for 12-24 hours to obtain a PAA / antimicrobial agent aerogel;

[0020] (223) The PAA / antimicrobial aerogel was heated at 200–300 °C for 3–5 h to obtain the PI / antimicrobial aerogel;

[0021] (224) The PI / antimicrobial agent aerogel was infiltrated under the hydrophobic coating for 5–10 min and transferred to 60–100 °C for drying for 3–5 h to obtain the multifunctional PI aerogel.

[0022] Preferably, the step 2 comprises the following specific steps:

[0023] (231) The PAA precursor, catalyst, and antimicrobial agent / hydrophobic coating mixed solution were stirred and thoroughly mixed at room temperature in a weight ratio of 2–3:2–3:94–96;

[0024] (232) freezing the mixed solution of step (231) in a refrigerator at -10°C to -20°C for 2-4 hours, and finally freeze-drying for 12-24 hours to obtain PAA / antimicrobial agent / hydrophobic aerogel;

[0025] (233) The PAA antimicrobial agent / hydrophobic aerogel was heated at 200–300 °C for 3–5 h to obtain the multifunctional PI aerogel.

[0026] The beneficial effects of the preparation method of a composite multifunctional PI aerogel of the present invention are as follows: the present invention successfully improves the flexibility and compressive resilience of polyimide (PI) aerogel through innovative design and optimization of the preparation process, while effectively reducing the production cost. In addition, by adding different additives, the PI aerogel is further endowed with multifunctionality, enhancing its application potential in multiple fields. This technology is expected to promote the widespread popularization of multifunctional PI aerogels in practical applications, meet the growing market demand, and expand its application prospects in various industrial and scientific research fields. In summary, the present invention has the following advantages: 1. By adjusting the ratio of polymer monomers, the mechanical properties of PI aerogels are improved. 2. The composite functions of aerogels (antibacterial, hydrophobic, heat insulating, compression recoverable, friction sensing) are increased. 3. The preparation method is simple and easy to operate, which is conducive to large-scale production. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is a physical picture of the multifunctional polyimide aerogel provided by the present invention.

[0028] Figure 2A physical picture of the flexible bending of the multifunctional polyimide aerogel provided by the present invention.

[0029] Figure 3 This is an electron microscope image of multifunctional polyimide aerogel.

[0030] Figure 4 This is the compression-rebound state diagram of multifunctional polyimide aerogel. DETAILED DESCRIPTION

[0031] The following description is only a preferred embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

[0032] The following embodiments may be understood as individually expressing a part of a local structure or method of the present invention, or may be understood as a combination of the embodiments to explain the connotation of a larger structure or method of the present invention.

[0033] Example 1

[0034] A method for preparing a composite multifunctional PI aerogel comprises the following steps: step 1, preparing a PAA precursor by mixing a polymer monomer with an organic solvent; step 2, preparing a composite multifunctional PI aerogel by mixing and reacting the PAA precursor with a catalyst and an additive.

[0035] Example 2

[0036] Based on Example 1, this example discloses various implementation methods of polymer monomers, specifically:

[0037] The polymer monomers are (A1) 1,3-bis(4'-aminophenoxy)benzene; (A2) p-phenylenediamine; (A3) 4,4'-diamino-2,2'-dimethylbiphenyl; (A4) toluene diisocyanate; (A5) diphenylmethane diisocyanate; (A6) 4,4'-diphenoxyphthalic anhydride; (A7) pyromellitic dianhydride; (A8) 3,3',4,4'-dibenzophenonetetracarboxylic dianhydride; (A9) 4,4'-oxydiphthalic anhydride; wherein (A1) to (A9) are specific implementation number, and the operator can select one or a mixture of several thereof according to the needs (each component of the mixture has the same weight parts).

[0038] Example 3

[0039] Based on Example 1, this example discloses multiple implementation methods of the organic solvent, specifically: the organic solvent is (B1) dimethylacetamide; (B2) N,N-dimethylformamide; (B3) dimethyl phthalate; (B4) dimethyl sulfoxide; (B4) N-methylpyrrolidone; wherein (B1) to (B4) are specific implementation method numbers, and the operator can select one or more of the mixture solutions (the weight proportions of each component of the mixture solution are the same) as needed.

[0040] Example 4

[0041] Based on the above embodiments 1-3, this embodiment discloses: the step 1 includes the following specific steps:

[0042] (11) adding the polymer monomer to the organic solution and stirring to fully mix at room temperature; wherein the mass ratio of the polymer monomer to the organic solvent is 1:2.5;

[0043] (12) The mixed solution of step (11) is washed with pure water and freeze-dried to obtain a PAA precursor.

[0044] Example 5

[0045] Based on the above embodiments 1-3, this embodiment discloses: the step 1 includes the following specific steps:

[0046] (11) adding the polymer monomer to the organic solution and stirring to fully mix at room temperature; wherein the mass ratio of the polymer monomer to the organic solvent is 1.5:3;

[0047] (12) The mixed solution of step (11) is washed with pure water and freeze-dried to obtain a PAA precursor.

[0048] Example 6

[0049] Based on the above embodiments, this embodiment discloses: in the step 2, several implementation modes of the catalyst are as follows: the catalyst is (C1) triethylamine; (C2) hexamethylenediamine; the operator can select one or a mixture of two of them as needed; wherein (C1) and (C2) are specific implementation mode numbers.

[0050] Example 7

[0051] Based on the above embodiments, this embodiment discloses: in the step 2, several implementation methods of the additive are specifically: the additive is (D1) a nano-hydrophobic coating; (D2) an antibacterial agent; the operator can select a mixed solution of one or more thereof, and the type of antibacterial agent can be selected as needed; wherein, (D1) and (D2) are specific implementation method numbers.

[0052] Example 8

[0053] Based on the above embodiments, this embodiment discloses that: in the step 2, the mass of the additive material accounts for 1% of the total mass of the multifunctional PI aerogel.

[0054] Example 9

[0055] Based on the above embodiments, this embodiment discloses that: in the step 2, the mass of the additive material accounts for 10% of the total mass of the multifunctional PI aerogel.

[0056] Example 10

[0057] The step 2 comprises the following specific steps:

[0058] (211) PAA precursor, catalyst, and pure water were mixed in a weight ratio of 2:2:94 at room temperature;

[0059] (212) freezing the mixed solution of step (211) in a refrigerator at -10°C to -20°C for 2-4 hours, and finally freeze-drying for 12-24 hours to obtain PAA aerogel;

[0060] (213) PAA aerogels were heated at 200–300 °C for 3–5 h to obtain PI aerogels;

[0061] (214) The PI aerogel was immersed in the antimicrobial solution and the hydrophobic coating for 5–10 min, respectively, and then transferred to 60–100 °C for drying for 3–5 h to obtain the multifunctional PI aerogel.

[0062] Embodiment 11

[0063] The step 2 comprises the following specific steps:

[0064] (211) PAA precursor, catalyst, and pure water were mixed in a weight ratio of 3:3:96 at room temperature;

[0065] (212) freezing the mixed solution of step (211) in a refrigerator at -10°C to -20°C for 2-4 hours, and finally freeze-drying for 12-24 hours to obtain PAA aerogel;

[0066] (213) PAA aerogels were heated at 200–300 °C for 3–5 h to obtain PI aerogels;

[0067] (214) The PI aerogel was immersed in the antimicrobial solution and the hydrophobic coating for 5–10 min, respectively, and then transferred to 60–100 °C for drying for 3–5 h to obtain the multifunctional PI aerogel.

[0068] Example 12

[0069] The step 2 comprises the following steps:

[0070] (221) PAA precursor, catalyst, and antimicrobial solvent were stirred and thoroughly mixed at room temperature in a ratio of 2:2:94 by weight;

[0071] (222) freezing the mixed solution of step (221) in a refrigerator at -10°C to -20°C for 2-4 hours, and finally freeze-drying for 12-24 hours to obtain a PAA / antimicrobial agent aerogel;

[0072] (223) The PAA / antimicrobial aerogel was heated at 200–300 °C for 3–5 h to obtain the PI / antimicrobial aerogel;

[0073] (224) The PI / antimicrobial agent aerogel was infiltrated under the hydrophobic coating for 5–10 min and transferred to 60–100 °C for drying for 3–5 h to obtain the multifunctional PI aerogel.

[0074] Embodiment 13

[0075] The step 2 comprises the following steps:

[0076] (221) PAA precursor, catalyst, and antibacterial solvent were stirred and thoroughly mixed at room temperature in a ratio of 3:3:96 by weight;

[0077] (222) freezing the mixed solution of step (221) in a refrigerator at -10°C to -20°C for 2-4 hours, and finally freeze-drying for 12-24 hours to obtain a PAA / antimicrobial agent aerogel;

[0078] (223) The PAA / antimicrobial aerogel was heated at 200–300 °C for 3–5 h to obtain the PI / antimicrobial aerogel;

[0079] (224) The PI / antimicrobial agent aerogel was infiltrated under the hydrophobic coating for 5–10 min and transferred to 60–100 °C for drying for 3–5 h to obtain the multifunctional PI aerogel.

[0080] Embodiment 14

[0081] The step 2 comprises the following specific steps:

[0082] (231) The PAA precursor, catalyst, and antimicrobial agent / hydrophobic coating mixed solution were stirred and thoroughly mixed at room temperature in a weight ratio of 2:2:94;

[0083] (232) freezing the mixed solution of step (231) in a refrigerator at -10°C to -20°C for 2-4 hours, and finally freeze-drying for 12-24 hours to obtain PAA / antimicrobial agent / hydrophobic aerogel;

[0084] (233) The PAA antimicrobial agent / hydrophobic aerogel was heated at 200–300 °C for 3–5 h to obtain the multifunctional PI aerogel.

[0085] Embodiment 15

[0086] The step 2 comprises the following specific steps:

[0087] (231) The PAA precursor, catalyst, and antimicrobial agent / hydrophobic coating mixed solution were stirred and thoroughly mixed at room temperature in a weight ratio of 3:3:96;

[0088] (232) freezing the mixed solution of step (231) in a refrigerator at -10°C to -20°C for 2-4 hours, and finally freeze-drying for 12-24 hours to obtain PAA / antimicrobial agent / hydrophobic aerogel;

[0089] (233) The PAA antimicrobial agent / hydrophobic aerogel was heated at 200–300 °C for 3–5 h to obtain the multifunctional PI aerogel.

[0090] Example 16

[0091] In the first step, 5 parts by weight of diamine monomer (a mixture of 1,3-bis(4'-aminophenoxy)benzene and p-phenylenediamine, with a weight ratio of 1:0.1) and 5 parts by weight of dianhydride monomer (a mixture of 4,4'-diphenyloxyphthalic anhydride and pyromellitic anhydride, with a weight ratio of 1:0.5) are added to a beaker containing 30 parts by weight of N,N-dimethylacetamide solution, stirred for a period of time at room temperature, and fully mixed. In the second step, the above solution is washed with pure water and freeze-dried to obtain a PAA precursor. In the third step, the PAA precursor, catalyst (a mixture of triethylamine and hexamethylenediamine, with a weight ratio of 1:0.1) and pure water are stirred at room temperature for a period of time at a weight ratio of 3:2:95, and fully mixed; in the fourth step, the above solution is frozen in a -10°C refrigerator for 2 hours, and finally freeze-dried for 12 hours to obtain PAA aerogel. In the fifth step, the PAA aerogel is heated at 200°C for 3 hours to obtain a PI aerogel. In the sixth step, the PI aerogel was immersed in the antibacterial solution and the hydrophobic coating for 5 min respectively, and then transferred to 60°C for drying for 3 hours to obtain the multifunctional PI aerogel.

[0092] In this embodiment, each part by weight refers to 1 gram.

[0093] Embodiment 17

[0094] In the first step, 5 parts by weight of diamine monomer (a mixture of 1,3-bis(4'-aminophenoxy)benzene and p-phenylenediamine, with a weight ratio of 1:0.2) and 5 parts by weight of dianhydride monomer (a mixture of 4,4'-diphenyloxyphthalic anhydride and pyromellitic anhydride, with a weight ratio of 1:0.4) are added to a cup containing 30 parts by weight of N,N-dimethylacetamide solution, stirred at room temperature for a period of time, and fully mixed. In the second step, the above solution is washed with pure water and freeze-dried to obtain a PAA precursor. In the third step, the PAA precursor, catalyst (a mixture of triethylamine and hexamethylenediamine, with a weight ratio of 1:0.1) and pure water are stirred at room temperature for a period of time at a weight ratio of 3:2:95, and fully mixed. In the fourth step, the above solution is frozen in a -20°C refrigerator for 4 hours, and finally freeze-dried for 24 hours to obtain PAA aerogel. In the fifth step, the PAA aerogel is heated at 300°C for 5 hours to obtain a PI aerogel. In the sixth step, the PI aerogel was immersed in the antibacterial solution and the hydrophobic coating for 10 min respectively, and then transferred to 100 °C for drying for 5 hours to obtain the multifunctional PI aerogel.

[0095] In this embodiment, each part by weight refers to 1 gram.

[0096] Embodiment 18

[0097] In the first step, 5 parts by weight of diamine monomer (a mixture of 1,3-bis(4'-aminophenoxy)benzene and p-phenylenediamine, with a weight ratio of 1:0.2) and 5 parts by weight of dianhydride monomer (a mixture of 4,4'-diphenyloxyphthalic anhydride and pyromellitic anhydride, with a weight ratio of 1:0.3) are added to a beaker containing 30 parts by weight of N,N-dimethylacetamide, stirred for a period of time at room temperature, and fully mixed. In the second step, the above solution is washed with pure water and freeze-dried to obtain a PAA precursor. In the third step, the PAA precursor, catalyst (a mixture of triethylamine and hexamethylenediamine, with a mixing ratio of 1:0.1), and antibacterial agent solution are stirred at room temperature for a period of time according to a weight ratio of 3:2:95, and fully mixed. In the fourth step, the above solution is frozen in a refrigerator at -10℃ to -20℃ for 2-4 hours, and finally freeze-dried for 12-24 hours to obtain a PAA / antibacterial agent aerogel. The fifth step is to heat the PAA / antimicrobial agent aerogel at 200-300° C. for 3-5 hours to obtain the PI / antimicrobial agent aerogel. The sixth step is to infiltrate the PI / antimicrobial agent aerogel under the hydrophobic coating for 5-10 minutes, transfer to 60-100° C. for drying for 3-5 hours to obtain the multifunctional PI aerogel.

[0098] In this embodiment, each part by weight refers to 1 gram.

[0099] Embodiment 19

[0100] In the first step, 5 parts by weight of diamine monomer (a mixture of 1,3-bis(4'-aminophenoxy)benzene and p-phenylenediamine, with a weight ratio of 1:0.4) and 5 parts by weight of dianhydride monomer (a mixture of 4,4'-diphenyloxyphthalic anhydride and pyromellitic anhydride, with a weight ratio of 1:0.2) are added to a beaker containing 30 parts by weight of N,N-dimethylacetamide, stirred for a period of time at room temperature, and fully mixed. In the second step, the above solution is washed with pure water and freeze-dried to obtain a PAA precursor. In the third step, the PAA precursor, catalyst (a mixture of triethylamine and hexamethylenediamine, with a mixing ratio of 1:0.1), and antibacterial agent solution are stirred at room temperature for a period of time according to a weight ratio of 3:2:95, and fully mixed. In the fourth step, the above solution is frozen in a refrigerator at -10℃ to -20℃ for 2-4 hours, and finally freeze-dried for 12-24 hours to obtain a PAA / antibacterial agent aerogel. The fifth step is to heat the PAA / antimicrobial agent aerogel at 200-300° C. for 3-5 hours to obtain the PI / antimicrobial agent aerogel. The sixth step is to infiltrate the PI / antimicrobial agent aerogel under the hydrophobic coating for 5-10 minutes, transfer to 60-100° C. for drying for 3-5 hours to obtain the multifunctional PI aerogel.

[0101] In this embodiment, each part by weight refers to 1 gram.

[0102] Embodiment 20

[0103] In the first step, 5 parts by weight of diamine monomer (a mixture of 1,3-bis(4'-aminophenoxy)benzene and p-phenylenediamine, with a weight ratio of 1:0.5) and 5 parts by weight of dianhydride monomer (a mixture of 4,4'-diphenyloxyphthalic anhydride and pyromellitic anhydride, with a weight ratio of 1:0.1) are added to a beaker containing 30 parts by weight of N,N-dimethylacetamide, stirred at room temperature for a period of time, and fully mixed. In the second step, the above solution is washed with pure water and freeze-dried to obtain a PAA precursor. In the third step, the PAA precursor, catalyst (a mixture of triethylamine and hexamethylenediamine, with a weight ratio of 1:0.1), and antibacterial agent / hydrophobic coating mixed solution are stirred and fully mixed at room temperature at a weight ratio of 3:2:95. In the fourth step, the above solution is frozen in a refrigerator at -10℃ to -20℃ for 2-4 hours, and finally freeze-dried for 12-24 hours to obtain PAA / antibacterial agent / hydrophobic aerogel. The fifth step is to heat the PAA antimicrobial agent / hydrophobic aerogel at 200-300° C. for 3-5 hours to obtain the PI multifunctional aerogel.

[0104] In this embodiment, each part by weight refers to 1 gram.

[0105] Embodiment 21

[0106] In the first step, 5 parts by weight of diamine monomer (1,3-bis(4'-aminophenoxy)benzene) and 5 parts by weight of dianhydride monomer (4,4'-diphenoxyphthalic anhydride) are added to a beaker containing 30 parts by weight of N,N-dimethylacetamide, stirred at room temperature for a period of time, and fully mixed. In the second step, the above solution is washed with pure water and freeze-dried to obtain a PAA precursor. In the third step, the PAA precursor, catalyst (triethylamine), and antibacterial agent / hydrophobic coating mixed solution are stirred and fully mixed at room temperature in a weight ratio of 3:2:95. In the fourth step, the above solution is frozen in a refrigerator at -10℃ to -20℃ for 2-4 hours, and finally freeze-dried for 12-24 hours to obtain PAA / antibacterial agent / hydrophobic aerogel. In the fifth step, the PAA antibacterial agent / hydrophobic aerogel is heated at 200-300℃ for 3-5 hours to obtain a PI multifunctional aerogel. In this embodiment, each weight portion refers to 1 gram.

Claims

1. A method for preparing a composite multifunctional PI aerogel, characterized by: The method comprises the following steps: step 1, preparing a PAA precursor by mixing a polymer monomer with an organic solvent; step 2, preparing a composite multifunctional PI aerogel by mixing the PAA precursor with a catalyst and an additive.

2. The method for preparing a composite multifunctional PI aerogel according to claim 1, characterized in that: In the step 1, the polymer monomer is one or a mixture of p-phenylenediamine, 1,3-bis(4'-aminophenoxy)benzene, 4,4'-diamino-2,2'-dimethylbiphenyl, toluene diisocyanate, diphenylmethane diisocyanate, pyromellitic anhydride, 4,4'-diphenoxyphthalic anhydride, 3,3',4,4'-dibenzophenonetetracarboxylic anhydride, and 4,4'-oxydiphthalic anhydride; and the organic solvent is one or a mixture of dimethylacetamide, N,N-dimethylformamide, dimethyl phthalate, dimethyl sulfoxide, and N-methylpyrrolidone.

3. The method for preparing a composite multifunctional PI aerogel according to claim 2, characterized in that: The step 1 comprises the following specific steps: (11) adding the polymer monomer to the organic solution and stirring to fully mix at room temperature; wherein the mass ratio of the polymer monomer to the organic solvent is 1-1.5:2.5-3; (12) The mixed solution of step (11) is washed with pure water and freeze-dried to obtain a PAA precursor.

4. The method for preparing a composite multifunctional PI aerogel according to claim 3, characterized in that: In the step 2, the catalyst is one of triethylamine and hexamethylenediamine or a mixture of two thereof; the additive is a mixture of one or more of a nano-hydrophobic coating and an antibacterial agent, and the mass of the additive material accounts for 1%-10% of the total mass of the multifunctional PI aerogel.

5. The method for preparing a composite multifunctional PI aerogel according to claim 4, characterized in that: The step 2 comprises the following specific steps: (211) PAA precursor, catalyst, and pure water are mixed in a weight ratio of 2-3:2-3:94-96 at room temperature; (212) freezing the mixed solution of step (211) in a refrigerator at -10°C to -20°C for 2-4 hours, and finally freeze-drying for 12-24 hours to obtain PAA aerogel; (213) PAA aerogels were heated at 200–300 °C for 3–5 h to obtain PI aerogels; (214) The PI aerogel was immersed in the antimicrobial solution and the hydrophobic coating for 5–10 min, respectively, and then transferred to 60–100 °C for drying for 3–5 h to obtain the multifunctional PI aerogel.

6. The method for preparing a composite multifunctional PI aerogel according to claim 4, characterized in that: The step 2 comprises the following steps: (221) The PAA precursor, catalyst, and antimicrobial solvent are stirred and thoroughly mixed at room temperature in a ratio of 2–3:2–3:94–96 by weight; (222) freezing the mixed solution of step (221) in a refrigerator at -10°C to -20°C for 2-4 hours, and finally freeze-drying for 12-24 hours to obtain a PAA / antimicrobial agent aerogel; (223) The PAA / antimicrobial aerogel was heated at 200–300 °C for 3–5 h to obtain the PI / antimicrobial aerogel; (224) The PI / antimicrobial agent aerogel was infiltrated under the hydrophobic coating for 5–10 min and transferred to 60–100 °C for drying for 3–5 h to obtain the multifunctional PI aerogel.

7. The method for preparing a composite multifunctional PI aerogel according to claim 4, characterized in that: The step 2 comprises the following specific steps: (231) The PAA precursor, catalyst, and antimicrobial agent / hydrophobic coating mixed solution were stirred and thoroughly mixed at room temperature in a weight ratio of 2–3:2–3:94–96; (232) freezing the mixed solution of step (231) in a refrigerator at -10°C to -20°C for 2-4 hours, and finally freeze-drying for 12-24 hours to obtain PAA / antimicrobial agent / hydrophobic aerogel; (233) The PAA antimicrobial agent / hydrophobic aerogel was heated at 200–300 °C for 3–5 h to obtain the multifunctional PI aerogel.

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