A polymer and its preparation method and application as aerogel

Abstract

The present invention discloses a type of high specific surface area, low shrinkage, lightweight cross-linked polyimide aerogel material, and a preparation method and application thereof. The structure of the cross-linked polyimide aerogel is shown below, and the preparation method thereof is to carry out a condensation reaction of a material containing an aromatic dianhydride and an aromatic diamine containing a trifluoro group to obtain a polyamic acid oligomer, and then carry out a cross-linking reaction with the aromatic amine, and then dry and imidize to obtain an aerogel. The raw material of the present invention is a commercial product; the synthesis route is simple, the yield is high, and the synthesis method has universal applicability. The polyimide aerogel of the present invention has a high specific surface area, a shrinkage rate as low as 5%, very good dimensional stability, and good application prospects in extreme environments.

Description

Technical Field

[0001] The invention belongs to the field of materials and relates to a polymer and a preparation method thereof and application of the polymer as an aerogel. Background Art

[0002] Polyimide aerogel material (PI) is a type of micro-nano porous network material with an imide ring structure in the main chain. It has the advantages of light weight, high and low temperature resistance, high specific surface area, low dielectric, low thermal conductivity, radiation resistance, and flame retardancy. It has been widely used in high temperature resistant coatings, RF antenna substrates, aerospace, gas separation and other fields.

[0003] At present, there are two main methods for preparing polyimide aerogels. One is to react isocyanate with dianhydride to obtain a polyimide solution, which is then dried to obtain the product; the other is to start from dianhydride and diamine monomers, first perform a polycondensation reaction to obtain a polyamic acid oligomer, then react with a crosslinker to obtain a polyamide salt precursor, and then dry and imidize to obtain an aerogel product. Currently, the second method is mostly used, but the polyimide aerogel obtained by the existing crosslinker still has problems such as high shrinkage and high water absorption, which affect its thermodynamic properties. Therefore, it has become a very important research direction to develop new crosslinkers and reduce the shrinkage and hygroscopicity of polyimide aerogels through reasonable monomer structure design. Summary of the invention

[0004] The purpose of the present invention is to provide a novel polyimide aerogel with a high specific surface area and a preparation method thereof, that is, by introducing tetraphenylethylene and diphenylethylene structures into the polyimide structure, chemical crosslinking is used to realize the formation of a three-dimensional network structure of the aerogel and further reduce the shrinkage rate of the aerogel, thereby increasing the specific surface area of ​​the aerogel.

[0005] According to one aspect of the present application, a polymer is provided, wherein the polymer is a random copolymer;

[0006] The repeating unit of the polymer includes structural unit A and structural unit B;

[0007] The structural unit A has a structure shown in Formula I:

[0008]

[0009] The structural unit B has a structure shown in formula II:

[0010]

[0011] Among them, a1 and a2 are the two ends of the structural unit A, and b is the end of the structural unit B;

[0012] a2 is connected to a1, or a2 is connected to b;

[0013] In the polymer, the ratio of the number of structural units A to the number of structural units B is 30-60;

[0014] In the structural unit A, R1 is selected from one of the structures A-1, A-2, A-3, A-4, A-5, A-6, A-7, A-8, A-9, and A-10:

[0015]

[0016]

[0017] R2 is selected from one of the structures B-1, B-2, B-3, B-4, B-5, B-6, B-7, B-8, B-9, B-10, B-11, B-12, and B-13:

[0018]

[0019]

[0020] In the structural unit B, R3 is selected from one of the structures X or Y:

[0021]

[0022] According to another aspect of the present application, a method for preparing the above-mentioned polymer is provided, characterized in that it comprises at least the following steps:

[0023] The raw materials containing the dianhydride compound and the diamine compound are mixed to undergo a polycondensation reaction, and then mixed with a quaternary aromatic amine compound to undergo a cross-linking reaction to obtain the polymer.

[0024] The dianhydride compound is selected from:

[0025] At least one of;

[0026] The diamine compound is selected from:

[0027] At least one of;

[0028] The quaternary aromatic amine compound is selected from:

[0029] At least one of .

[0030] The molar fraction of the dianhydride compound is 1.0 to 1.2 parts;

[0031] The molar fraction of the diamine compound is 1.0 to 1.2 parts;

[0032] The molar fraction of the quaternary aromatic amine compound is 0.01 to 0.1 parts.

[0033] The temperature of the polycondensation reaction is 20 to 80°C;

[0034] Optionally, the temperature of the polycondensation reaction is 65°C;

[0035] The polycondensation reaction time is 1 hour to 10 hours;

[0036] Optionally, the polycondensation reaction time is 3 hours;

[0037] The temperature of the cross-linking reaction is 25-80°C;

[0038] Optionally, the temperature of the cross-linking reaction is 40°C;

[0039] The cross-linking reaction time is 1 hour to 5 hours;

[0040] Optionally, the polycondensation reaction time is 2 hours;

[0041] At least the following steps are included:

[0042] The raw materials containing the dianhydride compound and the diamine compound are mixed with a solvent to undergo a polycondensation reaction, and then mixed with a quaternary aromatic amine compound to undergo a crosslinking reaction, and finally imidization is performed to obtain the polymer.

[0043] The solvent is selected from N-methylpyrrolidone or N,N-dimethylformamide;

[0044] The molar proportion of the solvent is 30 to 400 parts.

[0045] The imidization agent is selected from pyridine and acetic anhydride;

[0046] The molar proportion of the imidization agent is 60-100 parts.

[0047] The preparation method of the quaternary aromatic amine compound is to obtain the compound through a one-step McMurray coupling reaction.

[0048]

[0049] According to another aspect of the present application, an aerogel is provided, wherein the aerogel is selected from the above-mentioned polymer or the polymer prepared by the above-mentioned preparation method.

[0050] According to another aspect of the present application, a method for preparing the above-mentioned aerogel is provided, comprising at least the following steps:

[0051] The above polymer or the polymer prepared by the above preparation method is mixed with acetic anhydride and pyridine, and the solvent is replaced and dried to obtain the aerogel;

[0052] The solvent is replaced by N-methylpyrrolidone, acetone and anhydrous ethanol.

[0053] The drying temperature is 45-90°C;

[0054] The drying time is 5 to 12 hours. ;

[0055] The drying pressure is 5-20 MPa.

[0056] The advantages of the present invention are:

[0057] 1. The raw material synthesis route is simple, and the structure of polyimide aerogel is a new molecule, which can be extended to the synthesis of various cross-linked polyimide aerogels;

[0058] 2. Tetraphenylethylene and diphenylethylene polyimide aerogels have high specific surface area, low shrinkage, low density, and better high-temperature dimensional stability, and can be used as thermal insulation materials in extreme environments;

[0059] 3. The tetraphenylethylene and diphenylethylene polyimide aerogels of the present invention have high specific surface area, low shrinkage and low density (specific surface area up to 479 m 2 / g, the minimum shrinkage is 5.0%, and the minimum density is 0.086g / cm 3 ), and has very good application prospects in aerospace and other fields. DETAILED DESCRIPTION

[0060] The present invention is further described below in conjunction with specific examples, but the present invention is not limited to the following examples. The methods described are conventional methods unless otherwise specified. The raw materials described can all be obtained from public commercial channels.

[0061] General Synthesis Route of Quaternary Amines

[0062] Weigh zinc powder (1.6 g, 24.0 mmol) and add it to a three-necked flask, then add 40 mL of anhydrous tetrahydrofuran under nitrogen protection. Cool the mixture to -5-0 °C, and slowly add titanium tetrachloride (1.3 mL, 12.0 mmol) at 10 °C with a syringe. Heat the suspended mixture to room temperature, stir for 0.5 hours, and then reflux for 2.5 hours. Cool the mixture again to -5-0 °C, add pyridine (0.5 mL, 6.0 mmol), and stir for 10 minutes. Then add 15 mL of tetrahydrofuran solution of carbonyl compound (2.4 mmol) dropwise. After the dropwise addition, heat to 65 °C and reflux for 12 hours. Cool to room temperature, quench with 10% potassium carbonate aqueous solution (10 mL), and extract with 50 mL of dichloromethane. Collect and concentrate the organic layer. Separate and purify by column chromatography to obtain the target compound.

[0063] Example 1 Preparation of polyimide aerogel PI (PMDA-TFMB / ODA / TAE)

[0064] 2,2'-bis(trifluoromethyl)diaminobiphenyl (TFMB, 1.92 g, 6.0 mmol), 4,4'-diaminodiphenyl ether (ODA, 1.20 g, 6.0 mmol) were added to a 150 mL three-necked flask equipped with a mechanical stirrer, and N-methylpyrrolidone (NMP, 60 mL) was added. After the diamine monomer was completely dissolved, pyromellitic dianhydride (PMDA) (2.70 g, 12.4 mmol) was added. After stirring for 5 hours, 8 mL of tetrakis-(4-aminophenyl)ethylene (TAE, 0.0393 g, 0.10 mmol) NMP solution was added to the reaction system. After 20 minutes, the solution gradually became viscous, and then acetic anhydride (9.4 mL, 99.2 mmol) and pyridine (8.0 mL, 99.2 mmol) were added for cyclization treatment. After mixing evenly, the solution was poured into a mold. After gelation for 30 minutes and further aging for 24 hours, the gel was solvent replaced with NMP, NMP / acetone = 3:1 (v), NMP / acetone = 1:3 (v) and acetone, respectively, at room temperature for one day. Subsequently, supercritical CO2 drying was performed at 70 ° C and 15 MPa to remove the solvent to obtain polyimide aerogel. The specific surface area is 479m 2 / g, shrinkage rate is 5.0%, density is 0.087g / cm 3 .

[0065] Example 2 Preparation of polyimide aerogel PI (PMDA-TFMB / BAPP / TAE)

[0066] 2,2'-bis(trifluoromethyl)diaminobiphenyl (TFMB, 1.92 g, 6.0 mmol, 1.0 equiv.), 2,2'-bis[4-(4-aminophenoxyphenyl)]propane (BAPP, 2.46 g, 6.0 mmol, 1.0 equiv.) were added to a 150 mL three-necked flask equipped with a mechanical stirrer, and N-methylpyrrolidone (NMP, 60 mL) was added. After the diamine monomer was completely dissolved, pyromellitic dianhydride (PMDA) (2.70 g, 12.4 mmol, 2.1 equiv.) was added. After stirring for 5 hours, 8 mL of tetrakis-(4-aminophenyl)ethylene (TAE, 0.0393 g, 0.10 mmol, 0.017 equiv.) NMP solution was added to the reaction system. After 20 minutes, the solution gradually became viscous, and then acetic anhydride (9.4 mL, 99.2 mmol, 16.5 equiv.) and pyridine (8.0 mL, 99.2 mmol, 16.5 equiv.) were added for cyclization. After mixing evenly, the solution was poured into the mold. After gelation for 30 minutes and further aging for 24 hours, the gel was solvent replaced with NMP, NMP / acetone = 3:1 (v), NMP / acetone = 1:3 (v) and acetone, respectively, and soaked at room temperature for one day. Subsequently, supercritical CO2 drying was carried out at 80 ° C and 18 MPa to remove the solvent to obtain polyimide aerogel. The specific surface area is 465m 2 / g, shrinkage rate is 5.9%, density is 0.095g / cm 3 .

[0067] Example 3 Preparation of polyimide aerogel PI (PMDA-TFMB / ODA / TABF)

[0068] 2,2'-bis(trifluoromethyl)diaminobiphenyl (TFMB, 1.92 g, 6.0 mmol, 1.0 equiv.) and 4,4'-diaminodiphenyl ether (ODA, 1.20 g, 6.0 mmol, 1.0 equiv.) were added to a 150 mL three-necked flask equipped with a mechanical stirrer, and N-methylpyrrolidone (NMP, 60 mL) was added. After the diamine monomer was completely dissolved, pyromellitic dianhydride (PMDA) (2.70 g, 12.4 mmol, 2.1 equiv.) was added. After stirring for 5 hours, 8 mL of 2,2',7,7'-tetraamine-9,9'-difluoromethylene (TABF, 0.0388 g, 0.10 mmol, 0.017 equiv.) NMP solution was added to the reaction system. After 20 minutes, the solution gradually became viscous, and then acetic anhydride (9.4mL, 99.2mmol, 16.5equiv.) and pyridine (8.0mL, 99.2mmol, 16.5equiv.) were added for cyclization. After mixing evenly, the solution was poured into the mold. After gelation for 30 minutes and further aging for 24 hours, the gel was solvent replaced with NMP, NMP / acetone = 3:1 (v), NMP / acetone = 1:3 (v) and acetone, respectively, and soaked at room temperature for one day. Subsequently, supercritical CO2 drying was carried out at 76°C and 18MPa to remove the solvent to obtain polyimide aerogel. The specific surface area is 459m 2 / g, shrinkage rate is 6.8%, density is 0.127g / cm 3 .

[0069] Example 4 Preparation of polyimide aerogel PI (PMDA-TFMB / BAPP / TABF)

[0070] 2,2'-bis(trifluoromethyl)diaminobiphenyl (TFMB, 1.92 g, 6.0 mmol, 1.0 equiv.) and 2,2'-bis[4-(4-aminophenoxyphenyl)]propane (BAPP, 2.46 g, 6.0 mmol, 1.0 equiv.) were added to a 150 mL three-necked flask equipped with a mechanical stirrer, and N-methylpyrrolidone (NMP, 60 mL) was added. After the diamine monomer was completely dissolved, pyromellitic dianhydride (PMDA) (2.70 g, 12.4 mmol, 2.1 equiv.) was added. After stirring for 5 hours, 8 mL of 2,2',7,7'-tetraamine-9,9'-difluorene (TABF, 0.0388 g, 0.10 mmol, 0.017 equiv.) NMP solution was added to the reaction system. After 20 minutes, the solution gradually became viscous, and then acetic anhydride (9.4mL, 99.2mmol, 16.5equiv.) and pyridine (8.0mL, 99.2mmol, 16.5equiv.) were added for cyclization treatment. After mixing evenly, the solution was poured into the mold. After gelation for 30 minutes and further aging for 24 hours, the gel was solvent replaced with NMP, NMP / acetone = 3:1 (v), NMP / acetone = 1:3 (v) and acetone, respectively, and soaked at room temperature for one day. Subsequently, supercritical CO2 drying was carried out at 75°C and 16MPa to remove the solvent to obtain polyimide aerogel. The specific surface area is 432m 2 / g, shrinkage rate is 7.2%, density is 0.098g / cm 3 .

[0071] The experimental results show that the aromatic amine cross-linked polyimide aerogel based on tetraphenylethylene and diphenylethylene is an excellent lightweight aerogel material. The present invention is not limited to the reported materials. A series of cross-linked polyimide aerogel materials can be obtained by changing different dianhydrides and different diamine units. The synthesis method provided by the present invention is simple, economical and effective, and has important guiding significance for the synthesis of new lightweight aerogel materials with high specific surface area and low shrinkage.

[0072] The above are only a few embodiments of the present application and do not constitute any form of limitation to the present application. Although the present application is disclosed as above with preferred embodiments, it is not intended to limit the present application. Any technician familiar with the profession, without departing from the scope of the technical solution of the present application, using the technical content disclosed above to make slight changes or modifications are equivalent to equivalent implementation cases and fall within the scope of the technical solution.

Claims

1. A polymer, It is characterized in that The polymer is a random copolymer; The repeating unit of the polymer includes structural unit A and structural unit B; The structural unit A has a structure shown in Formula I: Formula I; The structural unit B has a structure shown in formula II: Formula II; Among them, a1 and a2 are the two ends of the structural unit A, and b is the end of the structural unit B; a2 is connected to a1, or a2 is connected to b; In the polymer, the ratio of the number of structural units A to the number of structural units B is 30-60; In the structural unit A, R 1 At least one selected from structures A-1, A-2, A-3, A-4, A-5, A-6, A-7, A-8, A-9, A-10: R 2 At least one selected from structures B-1, B-2, B-3, B-4, B-5, B-6, B-7, B-8, B-9, B-10, B-11, B-12, B-13: In the structural unit B, R 3 At least one selected from X or Y structures: XY.

2. A method for preparing the polymer according to claim 1, It is characterized in that At least the following steps are included: The raw materials containing the dianhydride compound and the diamine compound are mixed to undergo a polycondensation reaction, and then mixed with a quaternary aromatic amine compound to undergo a cross-linking reaction to obtain the polymer; The dianhydride compound is selected from: or or or or or or or or or At least one of; The diamine compound is selected from: or or or or or or or or or or or or At least one of; The quaternary aromatic amine compound is selected from: or At least one of; The molar fraction of the dianhydride compound is 1.0 to 1.2 parts; The molar fraction of the diamine compound is 1.0 to 1.2 parts; The molar fraction of the quaternary aromatic amine compound is 0.01 to 0.1 parts.

3. The preparation method according to claim 2, It is characterized in that The temperature of the polycondensation reaction is 20 to 80°C; The polycondensation reaction time is 1 hour to 10 hours; The temperature of the cross-linking reaction is 25-80°C; The cross-linking reaction time is 1 hour to 5 hours.

4. The preparation method according to claim 2, It is characterized in that The temperature of the polycondensation reaction was 65°C.

5. The preparation method according to claim 2, It is characterized in that The polycondensation reaction time is 3 hours.

6. The preparation method according to claim 2, It is characterized in that The temperature of the cross-linking reaction is 40°C.

7. The preparation method according to claim 2, It is characterized in that The polycondensation reaction time is 2 hours.

8. The preparation method according to claim 2, It is characterized in that At least the following steps are included: The raw materials containing the dianhydride compound and the diamine compound are mixed with a solvent to undergo a polycondensation reaction, and then mixed with a quaternary aromatic amine compound to undergo a crosslinking reaction, and finally imidization is performed to obtain the polymer.

9. The preparation method according to claim 8, It is characterized in that The solvent is selected from N-methylpyrrolidone or N,N-dimethylformamide; The molar fraction of the solvent is 30 to 400 parts; The imidization agent is selected from pyridine and acetic anhydride; The molar proportion of the imidization agent is 60-100 parts.

10. The preparation method according to claim 2, It is characterized in that The preparation method of the quaternary aromatic amine compound is to obtain the compound through a one-step McMurray coupling reaction.

11. An aerogel, It is characterized in that The aerogel is selected from the polymer described in claim 1 or the polymer prepared by the preparation method described in any one of claims 2 to 10.

12. A method for preparing the aerogel according to claim 11, It is characterized in that At least the following steps are included: The aerogel is obtained by mixing the polymer according to claim 1 or the polymer prepared by the preparation method according to any one of claims 2 to 8 with acetic anhydride and pyridine, replacing the solvent, and drying. The solvent is replaced with N-methylpyrrolidone, acetone, and anhydrous ethanol; The drying temperature is 45-90°C; The drying time is 5 to 12 hours; The drying pressure is 5-20 MPa.

Images