Liquid crystal polyimide aerogel with excellent shape memory performance and preparation method thereof

Abstract

The application discloses a liquid crystal polyimide aerogel with excellent shape memory performance and a preparation method thereof, and belongs to the field of polymer aerogel materials. The liquid crystal polyimide aerogel with excellent shape memory performance has a shape fixing rate of greater than or equal to 99%, a shape recovery rate of greater than or equal to 97%, and a thermal conductivity of greater than or equal to 0.09 W m ‑ 1 K ‑1 at room temperature. The liquid crystal polyimide aerogel is prepared by the following steps: specifically, liquid crystal diamine, flexible diamine, liquid crystal dianhydride monomer and a thermal curing agent are reacted, solvent replacement is performed, and polyamide acid dry filaments are obtained; the polyamide acid dry filaments are formed into an aqueous solution, the aqueous solution is injected into a silica gel mold, and directional freezing casting is performed on a customized refrigeration circulating device with a copper plate at the top; after molding, freeze drying, thermal imidization and curing are performed, and the liquid crystal polyimide aerogel with excellent shape memory performance is obtained.

Description

Technical Field

[0001] This invention relates to a liquid crystal polyimide aerogel with excellent shape memory properties and its preparation method, belonging to the field of polymer aerogel materials. Background Technology

[0002] Shape memory polymer aerogels with high porosity are a novel type of special material with ultra-low density. They combine the unique properties of aerogels (such as ultra-low density, high specific surface area, and porosity) with the advantages of polymers in shape memory, making them promising for applications in sensors, biomimetic structures, and deployable panels. However, current research on shape memory polymer aerogels mainly focuses on materials such as polyurethane, polycaprolactone, and nanocellulose. Shape memory aerogels prepared from these materials suffer from poor mechanical properties and low transition temperatures (below 120℃), failing to meet the requirements of aerospace or other high-temperature applications.

[0003] Polyimide is one of the best-performing organic polymer materials, possessing excellent thermal stability, withstanding temperatures above 400℃ and a long-term operating temperature range of -200 to 300℃. It also exhibits outstanding mechanical properties. Most importantly, its rigid structure allows it to withstand temperatures exceeding 100℃. g Temperatures are generally above 200℃. Therefore, the use of polyimide to prepare shape memory aerogels holds promise for expanding the application of shape memory polymer aerogels in aerospace and other high-temperature fields.

[0004] Aerogel materials made from polyimide possess advantages such as lightweight, high strength, strong molecular designability, and low dielectric constant. However, polyimide aerogels are high-porosity thermal insulation materials, exhibiting low thermal conductivity, which contradicts the rapid thermal response of shape memory. If the thermal conductivity of polyimide aerogels can be appropriately increased, mitigating the contradiction between slow heat transfer in the polyimide aerogel framework and slow response rate, then polyimide aerogels with shape memory properties can be prepared, promoting their application in spatial smart structures.

[0005] Currently, the main way to improve the thermal conductivity of polyimide-based materials is to prepare polyimide-based thermally conductive composites by filling them with thermally conductive materials. This method usually requires the addition of a large amount of thermally conductive filler to obtain the ideal thermal conductivity, which inevitably leads to a reduction in mechanical and processing properties, thus limiting its wider application. Summary of the Invention

[0006] [Technical Issues]

[0007] Existing shape memory polyimide aerogels mainly include polyimide-based composite aerogels and pure polyimide aerogels. Polyimide-based composite aerogels significantly improve thermal conductivity by filling polyimide aerogels with a large amount of filler, but there is still considerable room for improvement in shape memory performance. Meanwhile, the reported pure polyimide aerogels mainly achieve excellent shape memory performance through molecular structure design, but their thermal conductivity has not been significantly improved, and their shape recovery rate is low.

[0008] [Technical Solution]

[0009] To address the shortcomings and deficiencies of existing technologies, the present invention aims to improve the thermal conductivity of shape memory polyimide aerogels, balancing the contradiction between the low thermal conductivity of polyimide aerogels and the rapid thermal response required for shape memory; at the same time, it improves the poor shape memory performance of polyimide aerogels, thereby preparing a polyimide aerogel material with excellent shape memory performance and promoting the application of polyimide aerogel materials in the field of lightweight intelligent deformable materials.

[0010] Specifically, the monomers are copolymerized with liquid crystal diamine, flexible diamine, and liquid crystal dianhydride. After the reaction, a thermosetting agent is added to continue the reaction, resulting in a polyamic acid solution. The polyamic acid solution is then solvent-displaced in ultrapure water, and after freezing and drying, polyamic acid filaments are obtained. The polyamic acid filaments are then mixed with triethylamine to prepare a polyamic acid aqueous solution. The polyamic acid aqueous solution is injected into a silicone mold and directionally cryogenically cast on a custom-designed cryogenic circulation device with a copper plate on top. After molding, the mixture is freeze-dried, thermally imidized, and cured to obtain a liquid crystal polyimide aerogel with excellent shape memory properties.

[0011] To achieve the above objectives, the present invention adopts the following technical solution:

[0012] The first objective of this invention is to provide a liquid crystal polyimide aerogel with excellent shape memory properties, wherein the shape fixation rate of the liquid crystal polyimide aerogel is ≥99%, the shape recovery rate is ≥97%, and the thermal conductivity at room temperature is ≥0.09 W / m. -1 K -1 .

[0013] A second objective of this invention is to provide a method for preparing a liquid crystal polyimide aerogel with excellent shape memory properties, the method comprising the following steps:

[0014] (1) Liquid crystal diamine, flexible diamine monomer and liquid crystal dianhydride monomer are subjected to polycondensation reaction in N-methylpyrrolidone (NMP). After the reaction, a thermosetting agent is added and the reaction is continued to obtain a polyamic acid solution. The polyamic acid solution is subjected to solvent replacement, and then frozen and freeze-dried to obtain polyamic acid dry filaments.

[0015] (2) Add the polyamic acid filaments obtained in step (1) and triethylamine to ultrapure water, heat and stir until uniform to obtain a polyamic acid aqueous solution;

[0016] (3) The polyamic acid aqueous solution obtained in step (2) is injected into a silicone mold, and the mold is placed on a customized freezing circulation device with a copper plate on top for directional freezing casting. After molding, it is placed in a freeze dryer for freeze drying to obtain polyamic acid aerogel.

[0017] (4) The polyamic acid aerogel obtained in step (3) is subjected to thermal imidization and thermal curing to obtain liquid crystal polyimide aerogel, which is a liquid crystal polyimide aerogel with excellent shape memory properties.

[0018] In one embodiment, the liquid crystal diamine monomer in step (1) is one or both of 1,3-bis(4-aminophenoxy)benzene (TPE-R) and 1,4-bis(4-aminophenoxy)benzene (TPE-Q).

[0019] In one embodiment, the flexible diamine monomer in step (1) is 1,3-bis(3-aminophenoxy)benzene (TPE-M).

[0020] In one embodiment, the liquid crystal dianhydride monomer in step (1) is 4,4'-terephthalic anhydride (HQDPA).

[0021] In one embodiment, the thermosetting machine in step (1) is one or both of 4-ethynylaniline (4-EA) and nadic anhydride (NA).

[0022] In one embodiment, the molar ratio of the liquid crystal diamine monomer and the flexible diamine monomer in step (1) is 1:(0-1), and the molar ratio of the liquid crystal diamine monomer and the liquid crystal dianhydride monomer is 1:(0.95-2.5), preferably 1:(2.01-2.20).

[0023] In one embodiment, the molar ratio of the liquid crystal diamine to the thermosetting agent in step (1) is 1:(0-0.1), preferably 1:0.06.

[0024] In one embodiment, the polycondensation reaction in step (1) is carried out in an ice-water bath for 12-18 hours.

[0025] In one embodiment, the reaction time after adding the thermosetting agent in step (1) is 3-6 hours.

[0026] In one embodiment, the polyamic acid solution in step (1) has a solid content of 10-20 wt%.

[0027] In one embodiment, the solvent replacement time in step (1) is 0.5-2 hours.

[0028] In one embodiment, the heating and stirring speed in step (2) is 500-1000 rpm, the temperature is 36-42℃, and the time is 0.5h-3h.

[0029] In one embodiment, the concentration of polyamic acid in the polyamic acid aqueous solution in step (2) is 100-120 mg / ml.

[0030] In one embodiment, the customized refrigeration circulation device with a copper plate on top in step (3) is specifically a cube-shaped box with a copper plate on top and a layer of insulation material around it, and anhydrous ethanol at -40℃ to 100℃ inside the box.

[0031] In one embodiment, the directional cryogenic casting in step (3) is carried out at a temperature of -120 to -20°C for 1 to 24 hours.

[0032] In one embodiment, the temperature of the freeze dryer in step (3) is -80 to -20°C, and the time is 48 to 96 hours.

[0033] In one embodiment, the temperature of the thermal imidization in step (4) is 25-350°C; the time is 0.5-3h.

[0034] In one embodiment, the thermosetting temperature in step (4) is 270–330°C.

[0035] In one embodiment, the thermal imidization and thermal curing in step (4) can be specifically selected from the following temperature processes: 0.5-1.5 hours at 100-150℃, 0.5-1.5 hours at 200-250℃, and 0.5-1.5 hours at 270-330℃.

[0036] In one embodiment, the thermal imidization and thermal curing in step (4) need to be carried out under an inert atmosphere.

[0037] In one embodiment of the present invention, the high-temperature heat treatment equipment in step (4) is a tubular furnace, which is carried out in a nitrogen atmosphere.

[0038] The third objective of this invention is to provide applications of the above-mentioned liquid crystal polyimide aerogel with excellent shape memory properties in thermal insulation materials, aerospace vehicles, deployable panels, lightweight smart deformable materials, and other fields.

[0039] Compared with the prior art, the present invention has the following advantages:

[0040] (1) This invention has prepared liquid crystal polyimide aerogel with excellent shape memory properties for the first time. Its preparation method is relatively simple and environmentally friendly, with low cost, good formability, and stable aerogel structure. It can be designed into various shapes and is suitable for various extreme environments.

[0041] (2) This invention utilizes a directional freezing strategy to cast a relatively ordered pore structure and a relatively complete pore wall, providing a favorable environment for liquid crystal formation, thereby preparing a liquid crystal polyimide aerogel; the aerogel utilizes the microscopic order of liquid crystal molecules to moderately improve the intrinsic thermal conductivity of the polyimide aerogel, which to a certain extent alleviates the contradiction of slow response rate caused by slow heat transfer in the polyimide aerogel skeleton, and prepares a shape memory polyimide aerogel with fast response time, thus expanding the application of polyimide aerogel in the field of intelligent deformable materials;

[0042] (3) The thermosetting agent added in this invention causes the polyimide aerogel molecular chains to cross-link and solidify during the high-temperature treatment process. On the one hand, it is beneficial to retain part of the liquid crystal structure and improve the thermal conductivity; on the other hand, the chemical cross-linking structure generated by thermosetting will improve the shape recovery ability of polyimide aerogel to a certain extent, providing a strategy for improving the shape memory performance of polyimide aerogel.

[0043] (4) The large amount of flexible monomers added in this invention makes the polyimide molecular chain more flexible, which improves its shape fixation ability to a certain extent. Attached Figure Description

[0044] Figure 1 This is a schematic diagram of the structure of the customized refrigeration cycle device used in this invention;

[0045] Figure 2 The microstructure of the liquid crystal polyimide aerogel prepared in Example 1 of this invention is shown in the diagrams; (a) is a cross-sectional SEM image; (b) is a longitudinal section SEM image.

[0046] Figure 3 The DSC curves of the polyimide aerogels prepared in Example 1 and Comparative Examples 1-3 of this invention during the heating process are shown below.

[0047] Figure 4 The image shows a POM (Polymer Oxide Model) of the liquid crystal polyimide aerogel prepared in Example 1 of this invention during the heating process.

[0048] Figure 5 This is a physical image showing the shape memory performance test of the liquid crystal polyimide aerogel prepared in Example 1 of the present invention.

[0049] Figure 6 The image shows the results of quantitative testing of the shape memory properties of the liquid crystal polyimide aerogel prepared in Example 1 using a dynamic thermomechanical analyzer. Detailed Implementation

[0050] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. The specific embodiments described below further illustrate the present invention.

[0051] The method for determining the shape memory properties of polyimide aerogels involved in this invention:

[0052] The tensile shape memory properties of the prepared polyimide aerogel were tested. The samples were tested at a frequency of 1 Hz in controlled strain mode using a dynamic thermomechanical property tester (DMA Q800, TA Instruments, USA).

[0053] 1. Fixation rate determination

[0054] Dynamic thermomechanical analysis was used to test the shape memory behavior of aerogels under film stretching mode, and the shape retention rate of the aerogel shape memory process was obtained by analyzing the test data. The calculation formula is as follows:

[0055] Fixed rate (%) = (ε) unload -ε0) / (ε load -ε0);

[0056] Where, ε load Represents the maximum strain under load, ε0 is the initial strain, ε unload This represents the constant strain after cooling and unloading.

[0057] 2. Response rate determination

[0058] Dynamic thermomechanical analysis was used to test the shape memory behavior of aerogels under film stretching mode, and the shape recovery rate of the aerogel shape memory process was obtained by analyzing the test data. The calculation formula is as follows:

[0059] Response rate (%) = (ε) unload -ε rec ) / (ε load -ε0);

[0060] Where, ε load and ε rec Represents the maximum strain and recovered strain under load, where ε0 is the initial strain and ε unload This represents the constant strain after cooling and unloading.

[0061] 3. Response time measurement

[0062] The shape memory recovery rate of the sample was determined by bending experiment. The specific experimental steps are as follows: (1) Place the sample in a container that has been heated to the transition temperature (T). g (1) Keep the sample in a muffle furnace at 20°C for 1 min; (2) Apply stress to bend the sample 180° and remove the sample from the muffle furnace. Continue to apply stress at room temperature and cool and set for 1 min; (3) Put the sample back into the muffle furnace and observe its shape recovery process. The recovery time is the time required for the sample to fully recover or recover to the maximum extent (when it cannot be fully recovered).

[0063] Example 1

[0064] A method for preparing a liquid crystal polyimide aerogel with excellent shape memory properties includes the following steps:

[0065] (1) Dissolve 1.4190g of 1,3-bis(4-aminophenoxy)benzene and 1.4209g of 1,3-bis(3-aminophenoxy)benzene in 38.51ml of N-methylpyrrolidone, add 4.0745g of 4,4'-terephthalic anhydride, and react in an ice-water bath for 18h; then add 0.0718g of 4-ethynylaniline and continue the reaction for 6h to prepare a polyamic acid solution with a solid content of 15%; precipitate the prepared polyamic acid solution with ultrapure water, freeze it in a -80℃ freezer for 2h, and then dry it in a -80℃ freeze dryer for 72h to obtain polyamic acid dried filaments;

[0066] (2) Take 1.1g of the polyamic acid filaments obtained in step (1) and dissolve them in 10ml of ultrapure water. Add 0.32g of triethylamine to accelerate dissolution. Stir evenly at 38℃ to obtain a polyamic acid aqueous solution with a polyamic acid concentration of 110mg / ml.

[0067] (3) Inject the polyamic acid aqueous solution obtained in step (2) into the silicone mold, and then place the mold in a custom-made cryogenic circulation device with a copper plate on top at -80°C (e.g., Figure 1 The sample was oriented and frozen for 3 hours. After freezing, the sample was placed in a freeze dryer at -80°C and freeze-dried for 72 hours to obtain polyamic acid aerogel.

[0068] (4) The polyamic acid aerogel obtained in step (3) is placed in a tube furnace and imidized and thermally cured at high temperature under a nitrogen atmosphere. The high temperature treatment program is 100℃ for 1 hour, 200℃ for 1 hour, and 300℃ for 1 hour. Finally, a liquid crystal polyimide aerogel with excellent shape memory properties is obtained, denoted as PIA-RM1.

[0069] Example 2

[0070] The only difference from Example 1 is that the concentration of polyamic acid in step (2) is adjusted to 70 mg / ml, the mass of polyamic acid filaments is 0.7 g, and the amount of triethylamine added is 0.20 g; other conditions and parameters are the same as in Example 1.

[0071] The properties of the obtained liquid crystal polyimide aerogel were measured, and the results showed that the aerogel had poor morphology and surface cracking due to its low solid content.

[0072] Example 3

[0073] The only difference from Example 1 is that the concentration of polyamic acid in step (2) is adjusted to 150 mg / ml, the mass of polyamic acid filaments is 1.5 g, and the amount of triethylamine added is 0.75 g; other conditions and parameters are the same as in Example 1.

[0074] The properties of the obtained liquid crystal polyimide aerogel were measured, and the results showed that the aerogel had poor formability and defects such as foaming and irregular growth due to the difficulty in removing air bubbles during the preparation process caused by the high solid content.

[0075] Comparative Example 1

[0076] The only difference from Example 1 is that after the polyamic acid aqueous solution prepared in step (3) is poured into the silicone mold, the mold is directly placed in a -80℃ freezer for normal freezing (non-directional). Other conditions and parameters are the same as in Example 1. The resulting polyimide aerogel is denoted as PIA-RMNO.

[0077] Comparative Example 2

[0078] The only difference from Example 1 is that the thermosetting agent 4-ethynylaniline is not added in step (1) of the reaction, and the other conditions and parameters are the same as in Example 1. The resulting polyimide aerogel is denoted as PIA-RM2.

[0079] Comparative Example 3

[0080] The only difference from Example 1 is that the diamine added in step (1) is 1.9439g of 4,4'-diaminodiphenyl ether (the amount of substance is the same as the total amount of diamine in Example 1), and the dianhydride added is 2.9798g of 3,3',4,4'-biphenyltetracarboxylic acid dianhydride (the amount of substance is the same as the amount of dianhydride in Example 1). Other conditions and parameters are the same as in Example 1. The resulting polyimide aerogel is denoted as PIA.

[0081] Performance testing

[0082] 1. Characterization of the structure of liquid crystal polyimide aerogel

[0083] Figure 2 This is a SEM image of the surface of the liquid crystal polyimide aerogel prepared in Example 1. Figure 2 As shown, the liquid crystal polyimide aerogel has a relatively ordered pore structure and relatively complete pore walls, which is conducive to liquid crystal growth.

[0084] 2. Characterization of the liquid crystal structure of liquid crystal polyimide aerogel

[0085] Figure 3 The DSC curves of the liquid crystal polyimide aerogel prepared in Example 1 and the polyimide aerogel of Comparative Example 1 during the heating process are shown below. Figure 3 It can be seen that during the heating process, Example 1 exhibited a complete endothermic peak (peak at around 300°C), which is attributed to the gradual transformation of Example 1 from an amorphous phase to a liquid crystal phase; simultaneously combined with Figure 4 The POM image of Example 1 showed that bright areas (concentric circle diffraction phenomenon) began to appear in the field of view at 300°C. This is because Example 1 has entered the liquid crystal generation temperature range.

[0086] And in Figure 3 It can be seen that Comparative Example 1 only exhibits a glass transition process (approximately 192°C) and does not show a significant transition from the amorphous phase to the liquid crystal phase. This is attributed to the fact that Comparative Example 1 did not undergo directional freezing to generate an ordered pore structure and complete pore walls, making liquid crystal structure growth difficult. This proves that Comparative Example 1, without directional freezing, does not generate a liquid crystal phase during heating (or has very little liquid crystal structure). Comparative Example 2 exhibits thermo-induced liquid crystal behavior and has an endothermic peak for liquid crystal transition (peak at 280°C), but compared to Example 1, the absence of a thermosetting agent prevents its liquid crystal structure from being cured and retained. Comparative Example 3 synthesizes a non-liquid crystal polyimide, which only exhibits a glass transition process.

[0087] 2. Determination of thermal conductivity of liquid crystal polyimide aerogel

[0088] The thermal conductivity of the liquid crystal polyimide aerogels prepared in Example 1 and Comparative Examples 1-3 was measured multiple times, and the results are shown in Table 1:

[0089] Table 1. Thermal conductivity measurement

[0090] <![CDATA[Temperature ( o °C)]]> <![CDATA[Thermal conductivity (W m -1 K -1 )]]> Example 1 25 0.0953 Comparative Example 1 25 0.0646 Comparative Example 2 25 0.0769 Comparative Example 3 25 0.0631 Example 1 250 0.1174 Comparative Example 1 250 0.0878 Comparative Example 2 250 0.0982 Comparative Example 3 250 0.0775

[0091] Currently, due to the low density and high porosity of aerogels, their thermal conductivity is generally low (typically between 0.01 and 0.05 W / m²). -1 K -1As shown in Table 1, the liquid crystal polyimide aerogel prepared in Example 1 has a relatively high thermal conductivity. Furthermore, it can be observed that the thermal conductivity increases continuously with increasing temperature, suggesting the potential for rapid thermal response of polyimide aerogels in shape memory at high temperatures. In contrast, the aerogel prepared in Comparative Example 1 was not subjected to directional cryogenic casting, resulting in a disordered internal pore structure and missing pore walls, making liquid crystal growth difficult and hindering the formation of good thermal conductivity pathways. Comparative Example 2, lacking a thermosetting agent, retained less or no liquid crystal structure, thus exhibiting relatively low thermal conductivity. Comparative Example 3 is not a liquid crystal polyimide aerogel, therefore, even directional cryogenic casting could not significantly improve its thermal conductivity.

[0092] 3. Determination of shape memory properties of liquid crystal polyimide aerogel

[0093] Table 2. Shape memory properties of liquid crystal polyimide aerogels

[0094]

[0095]

[0096] As shown in Table 2, Comparative Example 1 has a lower fixation rate but a slightly higher recovery rate. This is because the molecular chains of Comparative Example 1 are more disordered than those of Example 1, resulting in more physical entanglement points and relatively weaker fixation ability. Overall, the shape memory performance of Example 1 and Comparative Example 1 is not significantly different, with both shape fixation and recovery rates exceeding 97%, demonstrating excellent shape memory performance. Comparative Example 2 has weaker shape recovery ability due to the absence of chemical crosslinking points generated during curing, while Comparative Example 3 has weaker shape fixation ability due to excessively rigid chain segments. In terms of recovery time, Example 1 has the fastest recovery time, while Comparative Example 1 is relatively weaker. This is because the shape recovery abilities of Example 1 and Comparative Example 1 are almost identical, but Example 1 has a significantly higher thermal conductivity than Comparative Example 1, allowing it to reach the transition temperature more quickly and thus achieve shape recovery faster.

[0097] from Figure 5 The shape memory physical demonstration diagram of Example 1 shows that Example 1 has a rapid thermal response during shape recovery, and at the same time, combined with Figure 6 The thermodynamic curves of multiple shape memory cycles in Example 1 show that the thermodynamic curves of multiple cycles almost completely overlap, indicating that its shape memory performance is very stable and excellent.

[0098] The embodiments provided above are not intended to limit the scope of the invention, nor are the described steps intended to limit the order of execution. Any obvious modifications made to the invention by those skilled in the art based on existing common knowledge also fall within the scope of protection defined by the claims.

Claims

1. A liquid crystal polyimide aerogel with excellent shape memory properties, characterized in that, The liquid crystal polyimide aerogel has a shape fixation rate of ≥99%, a shape recovery rate of ≥97%, and a thermal conductivity of ≥0.09 W / m at room temperature. -1 K -1 ; The preparation method of the liquid crystal polyimide aerogel with excellent shape memory properties includes: (1) The liquid crystal diamine, flexible diamine monomer and liquid crystal dianhydride monomer are placed in N A polycondensation reaction is carried out in methylpyrrolidone, followed by the addition of a thermosetting agent and continued reaction to obtain a polyamic acid solution; the polyamic acid solution is then subjected to solvent replacement, followed by freezing and freeze-drying to obtain polyamic acid filaments; The liquid crystal dianhydride monomer is 4,4'-terephthalodioxydiphthalic anhydride; The thermosetting agent is one or both of 4-ethynylaniline and nadic anhydride; (2) Add the polyamic acid filaments obtained in step (1) and triethylamine to ultrapure water, heat and stir evenly to obtain a polyamic acid aqueous solution; The concentration of polyamic acid in the aqueous solution is 100~120 mg / ml; (3) The polyamic acid aqueous solution obtained in step (2) is injected into a silicone mold, and the mold is placed on a custom-made freezing circulation device with a copper plate on top for directional freezing casting. After molding, it is placed in a freeze dryer for freeze drying to obtain polyamic acid aerogel. The temperature of the directional cryogenic casting is 120~ 20℃, for 1-24 hours; (4) The polyamic acid aerogel obtained in step (3) is subjected to thermal imidization and thermal curing to obtain liquid crystal polyimide aerogel, which is a liquid crystal polyimide aerogel with excellent shape memory properties.

2. A method for preparing the liquid crystal polyimide aerogel with excellent shape memory properties as described in claim 1, characterized in that, The method includes the following steps: (1) The liquid crystal diamine, flexible diamine monomer and liquid crystal dianhydride monomer are placed in N A polycondensation reaction is carried out in methylpyrrolidone, followed by the addition of a thermosetting agent and continued reaction to obtain a polyamic acid solution; the polyamic acid solution is then subjected to solvent replacement, followed by freezing and freeze-drying to obtain polyamic acid filaments; The liquid crystal dianhydride monomer is 4,4'-terephthalodioxydiphthalic anhydride; The thermosetting agent is one or both of 4-ethynylaniline and nadic anhydride; (2) Add the polyamic acid filaments obtained in step (1) and triethylamine to ultrapure water, heat and stir evenly to obtain a polyamic acid aqueous solution; the concentration of polyamic acid in the polyamic acid aqueous solution is 100~120mg / ml; (3) The polyamic acid aqueous solution obtained in step (2) is injected into a silicone mold, and the mold is placed on a custom-made freezing circulation device with a copper plate on top for directional freezing casting. After molding, it is placed in a freeze dryer for freeze drying to obtain polyamic acid aerogel. The temperature of the directional cryogenic casting is 120~ 20℃, for 1-24 hours; (4) The polyamic acid aerogel obtained in step (3) is subjected to thermal imidization and thermal curing to obtain liquid crystal polyimide aerogel, which is a liquid crystal polyimide aerogel with excellent shape memory properties.

3. The method according to claim 2, characterized in that, The liquid crystal diamine monomer in step (1) is one or both of 1,3-bis(4-aminophenoxy)benzene and 1,4-bis(4-aminophenoxy)benzene.

4. The method according to claim 2, characterized in that, The flexible diamine monomer in step (1) is 1,3-bis(3-aminophenoxy)benzene.

5. The method according to claim 2, characterized in that, The molar ratio of liquid crystal diamine monomer and flexible diamine monomer in step (1) is 1:(0-1), and the molar ratio of liquid crystal diamine monomer and liquid crystal dianhydride monomer is 1:(0.95-2.5).

6. The method according to claim 2, characterized in that, The molar ratio of the liquid crystal diamine to the thermosetting agent in step (1) is 1:(0-0.1).

7. The application of the liquid crystal polyimide aerogel with excellent shape memory properties as described in claim 1 or the liquid crystal polyimide aerogel prepared by any of the preparation methods described in claims 2 to 6 in thermal insulation materials, aerospace vehicles, deployable panels, and lightweight intelligent deformable materials.

Images