A bio-based polyimide and preparation method thereof

Abstract

The present invention provides a bio-based polyimide and a preparation method thereof, belonging to the technical field of polymer materials. A bio-based polyimide, the structure of which is shown below. The present invention uses a series of self-made diamine monomers derived from aromatic bio-based raw materials to carry out polycondensation with different aromatic dianhydride monomers to prepare a series of soluble high-temperature resistant polyimide resins derived from bio-based raw materials.

Description

Technical Field

[0001] The invention relates to the technical field of polymer materials, and in particular to a bio-based polyimide and a preparation method thereof. Background Art

[0002] Polyimide is a high-performance engineering material with excellent comprehensive performance. Due to its high heat resistance, chemical stability, low dielectric constant and good mechanical properties, it is widely used in high-end fields such as aerospace, microelectronics, military industry, optical equipment, etc. At present, most of the raw materials for preparing polyimide come from petrochemicals, and most of the monomer raw materials are toxic, which has a certain impact on the environment and even affects human physical and mental health. With the development of industrial economy, the shortage of fossil raw material resources is becoming more and more serious. At the same time, the development of petrochemical industry has also seriously aggravated environmental pollution. In recent years, the use of renewable resources to prepare bio-based polyimide has attracted widespread attention at home and abroad. At present, a large number of bio-based polyimides have been reported. However, due to the introduction of a large number of aliphatic structural units in the main chain of these bio-based polyimides, although the solubility and transparency of the polymer are increased, the temperature resistance of these bio-based polyimides is significantly reduced. Summary of the invention

[0003] In order to solve the problem of poor heat resistance of existing bio-based polyimide, the present invention designs and synthesizes a new bio-based diamine monomer containing an aromatic structure from the perspective of molecular structure design, and polymerizes it with different aromatic dianhydride monomers to prepare a series of soluble high-temperature resistant polyimide resins derived from bio-based raw materials.

[0004] The technical solution of the present invention is achieved in this way:

[0005] The present invention provides a bio-based polyimide, characterized in that its structure is as shown in Formula I:

[0006] Formula I;

[0007] Wherein, n=10-1000; Ar has at least one of the following structures:

[0008] , , , , , , , , ;

[0009] Ar' has at least one of the following structures:

[0010] , , , , , , , , , , , , .

[0011] As a further improvement of the present invention, the bio-based derived diamine monomer and the dianhydride monomer are reacted to obtain the product.

[0012] As a further improvement of the present invention, the bio-derived diamine monomer is selected from at least one of the following structures:

[0013] , , , , , , , , .

[0014] As a further improvement of the present invention, the dianhydride monomer is selected from at least one of the following structures:

[0015] , , , , , , , , , , , , .

[0016] As a further improvement of the present invention, the following steps are included:

[0017] (1) adding a bio-derived diamine monomer into an aprotic polar organic solvent under inert gas protection conditions;

[0018] (2) after the bio-based derived diamine monomer is completely dissolved, adding the dianhydride monomer to the solution at low temperature, and after the addition is completed, warming the solution to room temperature and performing a polymerization reaction to obtain a polymer solution;

[0019] (3) Finally, acetic anhydride / pyridine catalyst is added to the solution, and the polymerization reaction is continued at room temperature to obtain bio-based polyimide.

[0020] As a further improvement of the present invention, the molar ratio of the bio-derived diamine monomer to the dianhydride monomer is (0.9-1.1): (0.9-1.1).

[0021] As a further improvement of the present invention, the molar ratio of the acetic anhydride / pyridine catalyst is (1-10):1.

[0022] As a further improvement of the present invention, the aprotic polar organic solvent is one of N-methylpyrrolidone, N,N-dimethylacetamide, N,N-dimethylformamide and dimethyl sulfoxide.

[0023] As a further improvement of the present invention, the low temperature in step (2) is 0-10° C., and the polymerization reaction time is 10-14 h.

[0024] As a further improvement of the present invention, the polymerization reaction time in step (3) is 20-28 hours.

[0025] The present invention has the following beneficial effects:

[0026] The present invention designs and synthesizes a novel bio-based diamine monomer containing an aromatic structure from the perspective of molecular structure design, and polymerizes it with different aromatic dianhydride monomers to prepare a series of soluble high-temperature resistant polyimide resins derived from bio-based raw materials. The preparation method of the present invention is simple and suitable for large-scale production. The prepared bio-based polyimide has high heat resistance and good solubility, which promotes the sustainable development of environmentally friendly polyimide. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0028] Figure 1This is the hydrogen spectrum of carvacrol obtained in Preparation Example 1 of the present invention;

[0029] Figure 2 The hydrogen spectrum of the dinitro diether compound prepared in Preparation Example 1 of the present invention;

[0030] Figure 3 This is the hydrogen spectrum of the diamine monomer 8 prepared in Preparation Example 1 of the present invention;

[0031] Figure 4 This is the hydrogen spectrum of bisphenol A phthalimide prepared in Preparation Example 2 of the present invention;

[0032] Figure 5 This is the hydrogen spectrum of the bisphenol A type tetraacid reactant prepared in Preparation Example 2 of the present invention;

[0033] Figure 6 This is the hydrogen spectrum of the aromatic dianhydride monomer 4' prepared in Preparation Example 2 of the present invention;

[0034] Figure 7 8-4 obtained in Example 7 of the present invention ' Infrared spectrum of bio-based polyimide. DETAILED DESCRIPTION

[0035] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0036] The aromatic bio-based diamine monomer structure is at least one of the following structures, all of which are synthesized by this laboratory;

[0037]

[0038] The aromatic dianhydride monomer is at least one of the following structures, all of which are synthesized in this laboratory;

[0039]

[0040] Preparation Example 1 Preparation of Aromatic Bio-based Diamine Monomer

[0041] 1. Preparation of diphenol intermediates

[0042] .

[0043] Synthesis method: 101.85 g carvacrol, 35.97 g benzaldehyde and 80 mL anhydrous ethanol were added to a 500 mL flask in sequence, stirred to fully dissolve into a homogeneous solution, and then about 14 ml of concentrated hydrochloric acid was added to the system, and the reaction was carried out at 50 °C for about 24 h. After the reaction was completed, it was cooled to room temperature and filtered. The filter cake was stirred and washed with a mixed solution of ethanol and water (volume ratio 1 / 1) in a beaker and filtered three times until the washing liquid was transparent and colorless. Finally, it was vacuum dried at 80 °C for 12 h to obtain white crystalline powder carvacrol, and its hydrogen spectrum is shown as follows: Figure 1 .

[0044] 2. Preparation of dinitro intermediates

[0045] .

[0046] Synthesis method: A 250ml three-necked flask equipped with a nitrogen conduit and a spherical condenser is passed through nitrogen protection. 19.4275g of carvacrol and 13.82g of anhydrous potassium carbonate are weighed and added to the flask, and then 70ml of DMF is added. After stirring, 15.9652g of 4-nitrochlorobenzene is weighed and added. The temperature is raised to reflux of the solution. The reaction is continued for 8 hours at the reflux temperature. After the reaction is completed, the solution is precipitated into cold water and filtered. The filter cake is washed once with alkaline solution at 80°C, filtered, washed with deionized water until neutral, and washed 3 times with industrial alcohol, filtered, and the filter cake is dried in a vacuum oven at 80°C for 48 hours to obtain a light yellow fine powder product dinitro diether compound. Its hydrogen spectrum is as follows Figure 2 .

[0047] 3. Preparation of diamine monomer

[0048] .

[0049] Synthesis method: Weigh 7.00g of dinitrodiether compound, 1.24g of palladium carbon (5% content) and 80ml of ethanol and add them into an autoclave. After evacuation, begin to introduce hydrogen to a pressure of 0.5MPa. The reaction is terminated after reacting at 25°C and maintaining the pressure for 10h. The solution is filtered to remove palladium carbon. The filtrate is precipitated into saturated brine to precipitate flocculent precipitates. The filter cake is washed with deionized water for several times and then filtered again. The filter cake is dried in a vacuum oven at 60°C for 48h to obtain a white product. Its hydrogen spectrum is as shown below: Figure 3 .

[0050] Preparation Example 2 Preparation of Aromatic Dianhydride Monomer

[0051] 1. Synthesis of phthalimide intermediates

[0052] .

[0053] Synthesis method: Add 28.54g of bisphenol A to a 1000ml three-necked flask equipped with a nitrogen conduit, a spherical condenser, and a water separator, then weigh 10g of NaOH, dissolve it in 15ml of deionized water, prepare a NaOH solution and add it to the flask, then weigh 300ml of DMSO and 120ml of toluene respectively, start stirring and heat to 130°C to start reflux with water, after the water is completely removed, evaporate the toluene, then cool to 80°C, weigh and add 51.54g of N-methyl-4-nitrophthalimide, heat to 120°C and react for 7h. After the reaction is completed, the solution is precipitated into cold deionized water, filtered, and the filter cake is washed several times with dilute alkali solution, washed with deionized water until neutral, and dried in a vacuum oven at 80°C for 48h to obtain the white target product bisphenol A phthalimide, the hydrogen spectrum of which is as follows Figure 4 .

[0054] 2. Synthesis of Tetraacid Intermediates

[0055] .

[0056] Synthesis method: In a 100ml three-necked flask equipped with a mechanical stirrer, a condenser, a water separator, and a constant pressure dropping funnel, 2.73g of bisphenol A phthalimide and a NaOH aqueous solution (15gNaOH / 50m deionized water) were added in sequence, and heating was started to reflux. After maintaining the reflux state for 3h, the water separator was used to distill and add water while keeping the water level in the flask unchanged. After reacting for 4h, the heating was stopped, the solution in the flask was poured into a beaker, and concentrated HCl was added dropwise until the pH value of the solution was 2. At this time, a white precipitate appeared in the solution, and it was filtered, and then continued to be washed with cold water until the solution was neutral, and then filtered, and the filter cake was dried in a vacuum oven at 100°C for 24 hours to obtain a white product bisphenol A tetraacid reactant, and its hydrogen spectrum is shown as follows: Figure 5 .

[0057] 3. Synthesis of aromatic dianhydride monomer

[0058] .

[0059] Synthesis method: 2.46 g of bisphenol A type tetraacid reactant was added to a 100 ml three-necked flask equipped with a magnetic stirrer, a spherical condenser, and a calcium chloride drying tube. 50 ml of acetic anhydride (freshly distilled) was gradually added under stirring. The temperature was gradually raised to 120°C and reacted for 5 hours. After the solution was cooled in an ice-water bath, solids precipitated and filtered. The filter cake was washed three times with methyl tert-butyl ether and filtered again. The filtrate was dried in a vacuum oven at 80°C for 24 hours to obtain the target product. Its hydrogen spectrum is shown as follows: Figure 6 .

[0060] Embodiment 1:

[0061] Under nitrogen protection, diamine 1 (6.3035 g, 0.01 mol) and 278 mL N,N-dimethylacetamide were added to a 250 mL dry three-necked round-bottom flask with magnetic stirring. After strong stirring until compound 1 was completely dissolved, dianhydride 1 was slowly added to the solution in batches under nitrogen protection. ' Compound (2.1812 g, 0.01 mol) was added and vigorously stirred for polymerization at 5°C for 24 h to obtain a uniform and transparent viscous solution. 1.9 mL of acetic anhydride / 1.6 mL of pyridine catalyst was added to the solution system and vigorously stirred for 24 h at room temperature to stop the reaction. The viscous solution was poured into a large amount of industrial ethanol to precipitate the polymer. The polymer was extracted with anhydrous ethanol for 48 h, vacuum dried at 100°C for 12 h, and vacuum dried at 180°C for 2 h to obtain 1-1 ' Bio-based polyimide.

[0062] Embodiment 2:

[0063] Under nitrogen protection, diamine 2 (5.7867 g, 0.01 mol) and 125 mL N,N-dimethylformamide were added to a 250 mL dry three-necked round-bottom flask with magnetic stirring. After strong stirring until compound 2 was completely dissolved, dianhydride 1 was slowly added to the solution in batches under nitrogen protection. ' Compound (2.1812 g, 0.01 mol) was added and vigorously stirred for polymerization at 5°C for 24 h to obtain a uniform and transparent viscous solution. 1.9 mL of acetic anhydride / 1.6 mL of pyridine catalyst was added to the solution system and vigorously stirred for 24 h at room temperature to stop the reaction. The viscous solution was poured into a large amount of industrial ethanol to precipitate the polymer. The polymer was extracted with anhydrous ethanol for 48 h, vacuum dried at 100°C for 12 h, and vacuum dried at 180°C for 2 h to obtain 2-1 ' Bio-based polyimide.

[0064] Embodiment 3:

[0065] Under nitrogen protection, diamine 3 compound (5.8877 g, 0.01 mol) and 79 mL N,N-dimethylacetamide were added to a 250 mL dry three-necked round-bottom flask with magnetic stirring. After vigorous stirring until compound 3 was completely dissolved, dianhydride 10 mL was slowly added to the solution in batches under nitrogen protection. ' Compound (7.1520 g, 0.01 mol) was stirred vigorously at 5 ° C for 24 h to obtain a uniform and transparent viscous solution. 1.9 mL of acetic anhydride / 1.6 mL of pyridine catalyst was added to the solution system and stirred vigorously for 24 h at room temperature to stop the reaction. The viscous solution was poured into a large amount of industrial ethanol to precipitate the polymer. It was extracted with anhydrous ethanol for 48 h, vacuum dried at 100 ° C for 12 h, and vacuum dried at 180 ° C for 2 h to obtain 3-10' Bio-based polyimide.

[0066] Embodiment 4:

[0067] Under nitrogen protection, diamine 2 (5.7867 g, 0.01 mol) and 78 mL N-methylpyrrolidone were added to a 250 mL dry three-necked round-bottom flask with magnetic stirring. After strong stirring until compound 2 was completely dissolved, dianhydride 13 was slowly added to the solution in batches under nitrogen protection. ' Compound (6.6303 g, 0.01 mol) was added and vigorously stirred for polymerization at 5°C for 24 h to obtain a uniform and transparent viscous solution. 1.9 mL of acetic anhydride / 1.6 mL of pyridine catalyst was added to the solution system and vigorously stirred for 24 h at room temperature. The reaction was stopped and the viscous solution was poured into a large amount of industrial ethanol. The polymer was precipitated and extracted with anhydrous ethanol for 48 h. The product was vacuum dried at 100°C for 12 h and 180°C for 2 h to obtain 2-13 ' Bio-based polyimide.

[0068] Embodiment 5:

[0069] Under nitrogen protection, diamine 6 (6.0522 g, 0.01 mol) and 69 mL of dimethyl sulfoxide were added to a 250 mL dry three-necked round-bottom flask with magnetic stirring. After strong stirring until compound 6 was completely dissolved, dianhydride 9 was slowly added to the solution in batches under nitrogen protection. ' Compound (7.2575 g, 0.01 mol) was stirred vigorously at 5 ° C for 24 h to obtain a uniform and transparent viscous solution. 1.9 mL of acetic anhydride / 1.6 mL of pyridine catalyst was added to the solution system and stirred vigorously for 24 h at room temperature. The reaction was stopped and the viscous solution was poured into a large amount of industrial ethanol. The polymer was precipitated and extracted with anhydrous ethanol for 48 h, vacuum dried at 100 ° C for 12 h, and vacuum dried at 180 ° C for 2 h to obtain 6-9 ' Bio-based polyimide.

[0070] Embodiment 6:

[0071] Under nitrogen protection, diamine 5 compound (6.1577 g, 0.01 mol) and 118 mL N,N-dimethylformamide were added to a 250 mL dry three-necked round-bottom flask with magnetic stirring. After strong stirring until compound 5 was completely dissolved, dianhydride 11 was slowly added to the solution in batches under nitrogen protection. 'Compound (6.2859 g, 0.01 mol) was stirred vigorously at 5 ° C for 24 h to obtain a uniform and transparent viscous solution. Then 1.9 mL of acetic anhydride / 1.6 mL of pyridine catalyst was added to the solution system and stirred vigorously for 24 h at room temperature to stop the reaction. The viscous solution was poured into a large amount of industrial ethanol to precipitate the polymer. It was extracted with anhydrous ethanol for 48 h, vacuum dried at 100 ° C for 12 h, and vacuum dried at 180 ° C for 2 h to obtain 5-11 ' Bio-based polyimide.

[0072] Embodiment 7:

[0073] Under nitrogen protection, diamine 8 compound (5.7078 g, 0.01 mol) and 74 mL N,N-dimethylacetamide were added to a 250 mL dry three-necked round-bottom flask with magnetic stirring. After strong stirring until compound 8 was completely dissolved, dianhydride 4 was slowly added to the solution in batches under nitrogen protection. ' Compound (5.2049 g, 0.01 mol) was stirred vigorously at 5 ° C for 24 h to obtain a uniform and transparent viscous solution. Then 1.9 mL of acetic anhydride / 1.6 mL of pyridine catalyst was added to the solution system and stirred vigorously for 24 h at room temperature to stop the reaction. The viscous solution was poured into a large amount of industrial ethanol to precipitate the polymer. It was extracted with anhydrous ethanol for 48 h, vacuum dried at 100 ° C for 12 h, and vacuum dried at 180 ° C for 2 h to obtain 8-4 ' Bio-based polyimide, its infrared spectrum is as follows Figure 7 , of which 2962cm -1 The stretching vibration peak of CH on the methyl group and benzene ring is 1501 cm -1 Nearby is the benzene ring CC stretching vibration peak, 900 cm -1 The following is the benzene ring CH bending vibration peak, 1725 cm -1 C=O stretching vibration peak, 1400-1000 cm -1 There are stretching vibration peaks of CO and CN in the interval.

[0074] Embodiment 8:

[0075] Under nitrogen protection, diamine 6 compound (6.0522 g, 0.01 mol) and 106 mL of dimethyl sulfoxide were added to a 250 mL dry three-necked round-bottom flask with magnetic stirring. After strong stirring until compound 6 was completely dissolved, dianhydride 2 was slowly added to the solution in batches under nitrogen protection. 'Compound (2.9422 g, 0.01 mol) was added and vigorously stirred for polymerization at 5°C for 24 h to obtain a uniform and transparent viscous solution. 1.9 mL of acetic anhydride / 1.6 mL of pyridine catalyst was added to the solution system and vigorously stirred for 24 h at room temperature. The reaction was stopped and the viscous solution was poured into a large amount of industrial ethanol. The polymer was precipitated and extracted with anhydrous ethanol for 48 h, vacuum dried at 100°C for 12 h, and vacuum dried at 180°C for 2 h to obtain 6-2 ' Bio-based polyimide.

[0076] Embodiment 9:

[0077] Under nitrogen protection, diamine 4 compound (5.3660 g, 0.01 mol) and 74 mL N,N-dimethylformamide were added to a 250 mL dry three-necked round-bottom flask with magnetic stirring. After strong stirring until compound 4 was completely dissolved, dianhydride 3 was slowly added to the solution in batches under nitrogen protection. ' Compound (3.1022 g, 0.01 mol) was stirred vigorously at 5 ° C for 24 h to obtain a uniform and transparent viscous solution. 1.9 mL of acetic anhydride / 1.6 mL of pyridine catalyst was added to the solution system and stirred vigorously for 24 h at room temperature to stop the reaction. The viscous solution was poured into a large amount of industrial ethanol to precipitate the polymer. It was extracted with anhydrous ethanol for 48 h, vacuum dried at 100 ° C for 12 h, and vacuum dried at 180 ° C for 2 h to obtain 4-3 ' Bio-based polyimide.

[0078] Embodiment 10:

[0079] Under nitrogen protection, diamine 7 (5.1861 g, 0.01 mol) and 51 mL N,N-dimethylacetamide were added to a 250 mL dry three-necked round-bottom flask with magnetic stirring. After vigorous stirring until compound 7 was completely dissolved, dianhydride 12 was slowly added to the solution in batches under nitrogen protection. ' Compound (6.8075 g, 0.01 mol) was stirred vigorously at 5 ° C for 24 h to obtain a uniform and transparent viscous solution. Then 1.9 mL of acetic anhydride / 1.6 mL of pyridine catalyst was added to the solution system and stirred vigorously for 24 h at room temperature. The reaction was stopped and the viscous solution was poured into a large amount of industrial ethanol. The polymer was precipitated and extracted with anhydrous ethanol for 48 h, vacuum dried at 100 ° C for 12 h, and vacuum dried at 180 ° C for 2 h to obtain 7-12 ' Bio-based polyimide.

[0080] Embodiment 11:

[0081] Under nitrogen protection, diamine 3 (5.8877 g, 0.01 mol) and 81 mL of dimethyl sulfoxide were added to a 250 mL dry three-necked round-bottom flask with magnetic stirring. After vigorous stirring until compound 3 was completely dissolved, dianhydride 11 was slowly added to the solution in batches under nitrogen protection. ' Compound (6.2859 g, 0.01 mol) was stirred vigorously at 5 ° C for 24 h to obtain a uniform and transparent viscous solution. 1.9 mL of acetic anhydride / 1.6 mL of pyridine catalyst was added to the solution system and stirred vigorously for 24 h at room temperature. The reaction was stopped and the viscous solution was poured into a large amount of industrial ethanol. The polymer was precipitated and extracted with anhydrous ethanol for 48 h, vacuum dried at 100 ° C for 12 h, and vacuum dried at 180 ° C for 2 h to obtain 3-11 ' Bio-based polyimide.

[0082] Embodiment 12:

[0083] Under nitrogen protection, diamine 5 (6.1577 g, 0.01 mol) and 74 mL N-methylpyrrolidone were added to a 250 mL dry three-necked round-bottom flask with magnetic stirring. After vigorous stirring until compound 5 was completely dissolved, dianhydride 9 was slowly added to the solution in batches under nitrogen protection. ' Compound (7.2575 g, 0.01 mol) was stirred vigorously at 5 ° C for 24 h to obtain a uniform and transparent viscous solution. 1.9 mL of acetic anhydride / 1.6 mL of pyridine catalyst was added to the solution system and stirred vigorously for 24 h at room temperature to stop the reaction. The viscous solution was poured into a large amount of industrial ethanol to precipitate the polymer. It was extracted with anhydrous ethanol for 48 h, vacuum dried at 100 ° C for 12 h, and vacuum dried at 180 ° C for 2 h to obtain 5-9 ' Bio-based polyimide.

[0084] Comparative Example 1:

[0085] The bio-based polyimide material prepared in Example 1 of patent application number 2019104002348.

[0086] Comparative Example 2:

[0087] The bio-based polyimide material prepared in Example 12 of patent application number 2022109725059.

[0088] Test Example 1:

[0089] The thermal properties and dielectric constants of the bio-based polyimides prepared in Examples 1-12 and similar products prepared in Comparative Examples 1-2 were tested. The results are shown in Table 1.

[0090] Table 1

[0091] .

[0092] It can be seen from the above table that the bio-based polyimide prepared in Examples 1-12 of the present invention has a higher glass transition temperature and better high temperature resistance.

[0093] Test Example 2:

[0094] The bio-based polyimide prepared in Examples 1-12 and the similar products prepared in Comparative Examples 1-2 were dissolved in N,N-dimethylformamide and dried, and after stirring for 1 hour, a bio-based polyimide film with a thickness of 10 μm was prepared by a coater for mechanical property testing. The test was carried out according to GB / T 1040.4-2006 standard, and the tensile speed was 20 mm / min.

[0095] The results are shown in Table 2.

[0096] Table 2

[0097] .

[0098] It can be seen from the above table that the bio-based polyimide prepared in Examples 1-12 of the present invention has good mechanical properties.

[0099] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A bio-based polyimide, characterized in that: Its structure is shown in Formula I: Formula I; Wherein, n=10-1000; Ar has at least one of the following structures: 、 、 、 、 、 、 、 、 ； Ar' has at least one of the following structures: 、 、 、 、 、 、 、 、 、 、 、 、 。 2. A method for preparing a bio-based polyimide as claimed in claim 1, characterized in that: The product is prepared by reacting a bio-derived diamine monomer and a dianhydride monomer.

3. The preparation method according to claim 2, characterized in that: The bio-derived diamine monomer is selected from at least one of the following structures: 、 、 、 、 、 、 、 、 。 4. The preparation method according to claim 2, characterized in that: The dianhydride monomer is selected from at least one of the following structures: 、 、 、 、 、 、 、 、 、 、 、 、 。 5. The preparation method according to claim 2, characterized in that: The following steps are involved: (1) adding a bio-derived diamine monomer into an aprotic polar organic solvent under inert gas protection conditions; (2) after the bio-based derived diamine monomer is completely dissolved, adding the dianhydride monomer to the solution at low temperature, and after the addition is completed, warming the solution to room temperature and performing a polymerization reaction to obtain a polymer solution; (3) Finally, acetic anhydride / pyridine catalyst is added to the solution, and the polymerization reaction is continued at room temperature to obtain bio-based polyimide.

6. The preparation method according to claim 5, characterized in that: The molar ratio of the bio-derived diamine monomer to the dianhydride monomer is (0.9-1.1):(0.9-1.1).

7. The preparation method according to claim 5, characterized in that: The molar ratio of the acetic anhydride / pyridine catalyst is (1-10):

1.

8. The preparation method according to claim 5, characterized in that: The aprotic polar organic solvent is one of N-methylpyrrolidone, N,N-dimethylacetamide, N,N-dimethylformamide and dimethyl sulfoxide.

9. The preparation method according to claim 5, characterized in that: The low temperature in step (2) is 0-10°C, and the polymerization reaction time is 10-14h.

10. The preparation method according to claim 5, characterized in that: The polymerization reaction time in step (3) is 20-28 hours.

Images