Spider-silk-mimic microstructure shape memory polyimide composite material, preparation method and application thereof

Abstract

The application discloses a spider-silk-microstructure-shaped-memory polyimide composite material and a preparation method and application thereof, and the composite material is designed by coupling a spider-silk-microstructure-shaped-memory polyimide, a flame retardant and an electromagnetic shielding two-dimensional intercalation compound.The conductive polyaniline is intercalated with a transition metal carbon / nitride to prepare a Ti3C2T x @PANI intercalation compound, and then the SMPI is compounded to enhance the mechanical strength and electromagnetic shielding property of the spider-silk-microstructure-shaped resin matrix, and when the thickness of the SMPI composite material is 100 microns, the electromagnetic shielding efficiency of the SMPI composite material exceeds 25 dB in the X wave band, and more than 99% of the incident microwaves are effectively shielded.In addition, the flame retardant grade of the composite material reaches V0 level, the limiting oxygen index is 39.1%, the composite material also has high-temperature resistance and shape memory characteristics, the shape fixing rate is 96%, and the shape recovery rate is 97%.The composite material can eliminate electromagnetic interference, is flame-retardant, and can also autonomously deform, and is applied to the fields of self-adapting deformation, thermal management electromagnetic shielding devices and intelligent wearable devices.

Description

Technical Field

[0001] This invention belongs to the field of functional polymer technology. Specifically, it relates to an organic-inorganic hybrid spider silk-inspired shape memory polyimide composite material with flame retardant and electromagnetic shielding properties, its preparation method, and its application. Background Technology

[0002] Currently, electromagnetic pollution is considered the fourth largest form of pollution after air, water, and noise pollution. High-density electromagnetic energy radiated into the air causes severe electromagnetic pollution, endangering not only human health but also information security and the operational reliability of precision instruments. Traditional metal shielding materials, due to their low density, poor flexibility, narrow absorption bandwidth, and low chemical corrosion resistance, have limited their widespread application to some extent. Furthermore, people's demands for lightweight, portable, and wearable electronic products are gradually increasing. Therefore, to meet the needs of people for advanced materials, it is urgent to find alternatives to traditional metal electromagnetic shielding materials. Conductive polymer composites (CPCs) have advantages such as good flexibility, good conductivity, and easy processing, and are widely recognized as the most promising electromagnetic shielding materials. Combining CPCs with smart materials to imbue them with intelligence is also a promising direction for the future development of electromagnetic shielding materials.

[0003] Shape memory polymers, or SMPs for short, are smart materials that actively change shape in response to external environmental stimuli. Due to their lightweight, low cost, large deformability, and ease of processing, they have broad application prospects in aerospace, deployable space structures, biomedical engineering, anti-counterfeiting engineering, and soft robotics. Shape memory polyimide (SMPI) possesses advantages such as high and low temperature resistance, good mechanical properties, flexibility, dimensional stability, corrosion resistance, and radiation resistance, making it widely favored by researchers. However, due to the high resistivity and low dielectric constant of SMPI, modification is necessary to meet the requirements of electromagnetic shielding applications. Transition metal carbon / nitrogen compounds (MXenes) are two-dimensional nanomaterials composed of multiple elements, obtained by selectively etching active metal elements in the MAX phase, including Ti3C2T. x It is currently the most widely studied, with its surface containing abundant -OH, -O, and -F functional groups, exhibiting excellent electrical properties (conductivity as high as 2.4 × 10⁻⁶). 4 It has excellent optical and mechanical properties and is widely used in batteries, sensors, supercapacitors, and electromagnetic radiation protection.

[0004] In summary, electromagnetic pollution not only endangers human health but also jeopardizes information security and the operational reliability of precision instruments. Effective protection against electromagnetic waves, shielding equipment from radiation and interference, is a pressing issue. Furthermore, electromagnetic shielding materials absorb electromagnetic waves and convert them into heat, causing equipment operating temperatures to rise. Therefore, protecting equipment from fire hazards is also a crucial problem that must be addressed. Summary of the Invention

[0005] The purpose of this invention is to address the problems of low electromagnetic shielding effectiveness and inability to simultaneously achieve high flame retardancy in shape memory polyimide composite materials. This invention provides an organic-inorganic hybrid shape memory polyimide composite material with a spider silk-like microstructure, possessing both flame retardant and electromagnetic shielding properties, along with its preparation method and applications. This invention utilizes a smart polymer material and a two-dimensional intercalation composite to design an organic-inorganic hybrid shape memory polyimide composite material with both flame retardant and electromagnetic shielding properties, forming a spider silk-like microstructure. This endows the composite material with excellent mechanical properties and can be applied in future adaptive flexible thermal management electromagnetic shielding devices and smart wearable devices.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] A spider silk-inspired microstructure shape memory polyimide composite material, the structural formula of which is shown below:

[0008]

[0009] The value of n ranges from 100 to 165. In the chemical formula, the left side of the slash represents the polymer matrix resin, and the right side represents the particles; the two form a composite material.

[0010] Furthermore, the composite material is composed of polyaniline and MXene intercalation composite (Ti3C2T). x @PANI) and fluorinated, brominated shape memory polyimide (SMPI); wherein, the fluorinated, brominated shape memory polyimide is synthesized from a ternary monomer of 4,4'-diaminodiphenyl ether (ODA), hexafluoroisopropylphthalic anhydride (6FDA), and flame retardant 2,4,6-tribromoaniline (TBA), the total molar ratio of 4,4'-diaminodiphenyl ether and 2,4,6-tribromoaniline to hexafluoroisopropylphthalic anhydride is 1:1-1.05, and the mass of 2,4,6-tribromoaniline accounts for 2wt%-10wt% of the mass of the fluorinated, brominated shape memory polyimide.

[0011] Flame retardant 2,4,6-tribromoaniline (TBA) is chemically grafted into the shape memory polyimide (SMPI) molecular chain, overcoming the drawbacks of physical fillers such as easy precipitation and uneven filling. Additionally, 6FDA contains sulfur (F), which also possesses flame-retardant properties; both components work together to improve the flame retardancy of SMPI. Furthermore, during combustion of the SMPI composite material, Ti3C2T… x Oxidation occurs in air, and Ti-OH gradually transforms into Ti-O-Ti upon heating. It then reacts further with oxygen and water to generate TiO2 and C. The generated TiO2 can form a physical protective layer on the MXene-SMPI interface, encapsulating the residue produced after SMPI carbonization, effectively preventing the material from burning and the further spread of flames, and improving the material's flame retardancy and fire resistance.

[0012] Furthermore, the polyaniline and MXene intercalation composite (Ti3C2T) x The mass ratio of @PANI to fluorinated or brominated shape memory polyimide is 5–20:100.

[0013] Furthermore, in the polyaniline and MXene intercalation composite, the mass percentage of polyaniline is 10%. Ti3C2T x @PANI intercalation composites serve as electromagnetic shielding particles. The lamellar and wrinkled intercalation composites can act as spider silk-like microstructures, improving the mechanical and electromagnetic shielding properties of the SMPI matrix and enhancing the interfacial bonding between the particles and the resin.

[0014] A method for preparing the above-mentioned spider silk-inspired microstructure shape memory polyimide composite material, wherein the method comprises:

[0015] Step S1: Take a few layers or a single layer of Ti3C2T x The sample was dispersed in N,N-dimethylacetamide (DMAc) solvent and stirred thoroughly at 40℃ for 48 h, followed by ultrasonic treatment for 4 h. Then, polyaniline powder was weighed and added to the above DMAc solution, and ultrasonic treatment was continued for 4 h to carry out the intercalation reaction, thus obtaining Ti3C2T. x @PANI intercalation complex suspension;

[0016] Step S2: Dissolve ODA and TBA in DMAc solvent to obtain a mixed solution containing -NH2 groups;

[0017] Step S3: Add 6FDA to the mixed solution containing -NH2 groups in 4-6 portions, react at room temperature under N2 atmosphere for 20 hours to obtain a polyamic acid solution, named PAA;

[0018] Step S4: Place Ti3C2T x@PANI intercalation complex suspension was poured into the PAA solution and stirred until homogeneous to obtain a solution containing Ti3C2T x PAA mixed solution of @PANI intercalation complex;

[0019] Step S5: Pour the above PAA mixed solution onto the substrate and place it in a vacuum oven for vacuum drying to remove air bubbles, thereby obtaining a PAA mixed solution substrate without air bubbles.

[0020] Step S6: Place the bubble-free PAA mixed solution substrate in a high-temperature oven and perform thermal imidization by gradient heating to obtain a substrate containing a polyimide film.

[0021] Step S7: Place the substrate containing the polyimide film in water for 1-2 hours to complete demolding. After drying, an organic-inorganic hybrid spider silk-like microstructure shape memory polyimide composite material with flame retardant and electromagnetic shielding properties is obtained.

[0022] Further, in step S3, the concentration of polyamic acid in the polyamic acid solution is 17-24 wt%.

[0023] Further, in step S5, the vacuum drying process includes: controlling the oven temperature to 50°C and maintaining it for 6 hours, then raising the temperature to 80°C and maintaining it for 6 hours, and then evacuating the vacuum.

[0024] Further, in step S6, the gradient heating includes: heating at a rate of 5℃ / min to 140℃ and holding for 2h; heating at a rate of 5℃ / min to 200℃ and holding for 2h; heating at a rate of 5℃ / min to 260℃ and holding for 2h; and heating at a rate of 5℃ / min to 300℃ and holding for 2h.

[0025] The spider silk-inspired microstructure shape memory polyimide composite material prepared by the above-mentioned method has applications in cutting-edge technology fields such as advanced aircraft with adaptive active deformation, electronic appliances, thermal management electromagnetic shielding devices, and smart wearable devices. For example, an adaptive thermal management electromagnetic shielding protective cover can protect internal equipment from electromagnetic interference. When the equipment temperature becomes too high and reaches the glass transition temperature of the SMPI composite material, the protective cover can actively deform and automatically open a preset heat dissipation path to reduce the equipment temperature and prevent fire hazards.

[0026] The advantages of this invention over the prior art are as follows:

[0027] (1) The etched MXene surface is rich in -OH, -O, -F, and -Cl polar groups. After intercalation reaction with conductive polyaniline (PANI), Ti3C2T is obtained. x@PANI intercalation complex, in which Ti3C2T has a lamellar and wrinkled structure x It can be used as a spider silk-like microstructure to enhance the mechanical strength and toughness of the resin matrix and strengthen the interfacial bonding force between the resin and the matrix.

[0028] (2)Ti3C2T x @PANI intercalation compound is combined with polyamic acid, and after thermal imidization, a shape memory polyimide composite material with high electromagnetic shielding effectiveness and flame retardant properties is obtained, in which Ti3C2T x @PANI forms strong hydrogen bond interactions with the imide groups in the SMPI matrix, endowing MXene with excellent dispersibility, compatibility with the matrix resin, and good mechanical and shape memory properties of the composite material. In the future, it can be applied to adaptive flexible thermal management electromagnetic shielding devices and smart wearable devices.

[0029] (3) The smart composite matrix resin and the intercalation compound also have a synergistic flame retardant effect. At the same time, the polyamic acid of chemically grafted flame retardant 2,4,6-tribromoaniline and the F element in 6FDA make the polyimide obtained by thermal imidization have intrinsic flame retardant properties, solving the problem of uneven precipitation and dispersion of physical flame retardant particles. They can work together to improve the flame retardancy and fire resistance of SMPI and expand the application range of smart materials in the field of high temperature resistance. Attached Figure Description

[0030] Figure 1 This is a schematic diagram illustrating the mechanism of the shape memory effect of the polyimide composite material in the embodiments of the present invention.

[0031] Figure 2 This is a schematic diagram of the spider silk-like microstructure of the polyimide composite material and a diagram of the electromagnetic shielding mechanism in an embodiment of the present invention;

[0032] Figure 3 This is a flowchart illustrating the preparation method of an organic-inorganic hybrid spider silk-inspired shape memory polyimide composite material with flame-retardant and electromagnetic shielding properties, as described in this invention.

[0033] Figure 4 This is a synthesis pathway diagram of an organic-inorganic hybrid spider silk-inspired shape memory polyimide composite material with flame retardant and electromagnetic shielding properties, as described in this invention.

[0034] Figure 5 This is a graph showing the storage modulus and loss factor of the organic-inorganic hybrid spider silk-inspired shape memory polyimide composite material with flame retardant and electromagnetic shielding properties in Example 1 of the present invention.

[0035] Figure 6Images and the measured limiting oxygen index of the organic-inorganic hybrid spider silk-like microstructure shape memory polyimide composite material with flame retardant and electromagnetic shielding properties in Example 1 of this invention after a vertical combustion experiment.

[0036] Figure 7 The electromagnetic shielding (EMI) performance of the organic-inorganic hybrid spider silk-inspired shape memory polyimide composite material with flame retardant and electromagnetic shielding properties in Example 1 of this invention is shown in the frequency range of 8.2-12.4 GHz.

[0037] Figure 8 This diagram illustrates the thermally driven shape memory process of the organic-inorganic hybrid spider silk-inspired shape memory polyimide composite material with flame-retardant and electromagnetic shielding properties, as shown in Example 1 of this invention. Detailed Implementation

[0038] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below.

[0039] It should be noted that, unless otherwise specified, the features in the embodiments of this invention can be combined with each other. The terms "comprising," "including," "containing," and "having" are non-limiting, meaning that other steps and other components that do not affect the result can be added. The above terms cover the terms "composed of" and "substantially composed of." Unless otherwise specified, materials, equipment, and reagents are commercially available. Furthermore, it should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in sequences other than those illustrated or described herein.

[0040] This invention involves intercalating conductive polyaniline (PANI) with MXene to prepare Ti3C2T. x @PANI intercalation composites, in which the lamellar and wrinkled structure of the intercalation composite can serve as a spider silk-like microstructure, enhancing the interfacial bonding between the resin and the filler particles, and making a significant contribution to improving the mechanical properties and electromagnetic shielding performance of the composite material. Furthermore, utilizing the terminal amino groups of PANI and Ti3C2T... x The formation of strong hydrogen bonds imparts excellent dispersibility and compatibility with the matrix resin to MXene. Furthermore, Ti3C2T... x@PANI intercalation composites are uniformly mixed with a polyamic acid solution of chemically grafted flame retardant 2,4,6-tribromoaniline, and then thermally imidized to obtain a smart composite material with electromagnetic shielding, flame retardant and shape memory effects. It has broad application prospects in adaptive deformation advanced aircraft, electronic appliances, thermal management electromagnetic shielding devices and smart wearable devices.

[0041] In principle, the polyimide of this invention exhibits shape memory effect because its molecular chain segments form a fixed phase and a reversible phase through physical cross-linking. The fixed phase is a physical cross-linked network (i.e., rigid chains) composed of π-π interactions, hydrogen bonds, and molecular chain entanglement between aromatic rings. The function of the fixed phase is to ensure that the molecular chains do not slide as a whole, achieving permanent shape memory. The reversible phase is a mobile phase (i.e., flexible chains) capable of reversible transformation, mainly composed of ether groups and -CF3 groups. Its shape memory transition is provided by the glass transition; the molecular chain segments can be frozen under specific conditions and reactivated under external stimuli, thereby achieving temporary shape fixation and providing driving energy for shape recovery. When the temperature rises to T... g Above the glass transition temperature (Tglass transition temperature), the microscopic Brownian motion of the reversible phase molecular chain segments intensifies, while the stationary phase remains in a solidified state. At this point, applying a certain external force causes the polymer to deform. Maintaining this external force while lowering the temperature "freezes" the motion of the reversible phase molecular chain segments, resulting in a temporary shape. When the temperature rises again to Tglass transition temperature... g At the above point, the reversible phase softens while the stationary phase remains solidified. The molecular chain segments of the reversible phase "thaw" and gradually reach thermodynamic equilibrium under the restoring stress of the stationary phase, which macroscopically manifests as a restored shape.

[0042] The electromagnetic shielding mechanism is as follows: Transition metal carbon / nitrogen compounds (MXenes) are two-dimensional nanomaterials composed of multiple elements, obtained by selectively etching the active metal elements in the MAX phase, among which Ti3C2T x Currently, it is the most widely studied material, possessing excellent electrical properties. Simultaneously, polyaniline is a conductive polymer material, and the intercalation composite Ti3C2T formed by the two... x @PANI also exhibits good electrical conductivity. The incident electromagnetic wave in Ti3C2T x The impedance mismatch between the surface material and air in the PANI / SMPI composite material results in a certain reflection loss, while electromagnetic waves entering the material interior interact with the high charge density of Ti3C2T. x The @PANI molecules interact, attenuating within the material and generating conductive losses. Simultaneously, the unique spider-silk-like microstructure facilitates multiple reflections of electromagnetic waves within the material, further enhancing its electromagnetic wave dissipation capability. Additionally, Ti3C2T... xThe charge asymmetry at the @PANI and SMPI interface, as well as the defects and terminal functional groups of MXene, also contribute to the interface and dipole polarization losses of the incident electromagnetic wave. Therefore, both electromagnetic wave reflection and absorption contribute to providing excellent electromagnetic shielding performance.

[0043] The flame-retardant mechanism is as follows: the synergistic effect between MXene and SMPI gives the SMPI composite film excellent flame-retardant properties. After MXene burns, it undergoes an oxidation reaction in air, and Ti-OH gradually transforms into Ti-O-Ti upon heating, further reacting with oxygen and water to generate TiO2 and C. The generated TiO2 can form a physical protective layer on the MXene-SMPI interface, encapsulating the residue produced after SMPI carbonization, effectively preventing material combustion and further flame propagation. Furthermore, the intrinsic flame-retardant shape memory polyimide is synthesized using a ternary monomer of 4,4'-(hexafluoroisopropene)phthalic anhydride, 4,4'-diaminodiphenyl ether, and 2,4,6-tribromoaniline. In this SMPI, the flame retardant 2,4,6-tribromoaniline is chemically grafted into the SMPI molecular chain segment, and 6FDA contains F element. Br and F elements work together to exert a synergistic flame-retardant function, protecting equipment from fire hazards and thus improving the safety of SMPI use. The invention is further illustrated below with specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention.

[0044] Example 1

[0045] (1) Take 0.2449g of Ti3C2T with few or no layers or monolayers. x The sample was dispersed in 12 mL of N,N-dimethylacetamide (DMAc) solvent and stirred thoroughly at 40 °C for 48 h. It was then sonicated for 4 h. Next, 0.0245 g of polyaniline powder was weighed and added to the DMAc solution, and sonication was continued for another 4 h to carry out the intercalation reaction, thus obtaining Ti3C2T. x @PANI intercalation complex suspension;

[0046] (2) Dissolve 4.8 mmol ODA and 0.4 mmol TBA in 16 mL of DMAc solvent to obtain a mixed solution containing -NH2 groups;

[0047] (3) Add 5 mmol of 6FDA to the mixed solution containing -NH2 groups in 4-6 portions, react at room temperature under N2 atmosphere for 20 h to obtain a polyamic acid solution, named PAA;

[0048] (4) Ti3C2T x The PAI intercalation complex suspension was poured into the PAA solution and stirred at 500 rpm for 2 hours until homogeneous, yielding a solution containing Ti3C2T. xPAA mixed solution of @PANI intercalation complex;

[0049] (5) The above PAA mixed solution is poured onto the substrate and placed in a vacuum oven at 50°C for 6 hours; then at 80°C for 6 hours. Vacuum is then drawn to remove air bubbles, and a PAA mixed solution substrate without air bubbles is obtained.

[0050] (6) The bubble-free PAA mixed solution substrate is placed in a high-temperature oven and subjected to thermal imidization by gradient heating at a rate of 5°C / min, heating to 140°C and holding for 2 hours; heating to 200°C at a rate of 5°C / min and holding for 2 hours; heating to 260°C at a rate of 5°C / min and holding for 2 hours; heating to 300°C at a rate of 5°C / min and holding for 2 hours.

[0051] (7) Turn off the high-temperature oven and let it cool naturally to room temperature. Take out the glass plate and place it in 100°C deionized water for 1 hour to complete the demolding.

[0052] (8) Place the demolded film material in an oven at 100°C for 6 hours to evaporate the moisture and obtain an organic-inorganic hybrid spider silk-like microstructure shape memory polyimide composite material with flame retardant and electromagnetic shielding properties.

[0053] in, Figure 5 The graph shows the storage modulus and loss factor of the polyimide composite material prepared in this embodiment. Figure 6 Images of the polyimide composite material prepared in this embodiment after a vertical combustion experiment and the measured limiting oxygen index; Figure 7 The electromagnetic shielding (EMI) performance of the polyimide composite material prepared in this embodiment in the frequency range of 8.2-12.4 GHz; Figure 8 This diagram illustrates the thermally driven shape memory process of the polyimide composite material prepared in this embodiment.

[0054] from Figure 5 It can be seen that the T of the polyimide composite material prepared in this embodiment is... g Its shape memory transition temperature is 320℃, and its energy storage modulus at room temperature is 9192 MPa. From Figure 6 As can be seen, the polyimide composite material prepared in this embodiment does not propagate flame when burned vertically, is self-extinguishing upon removal of the flame, produces no molten droplets, cannot ignite absorbent cotton, and turns black on the surface after burning, with white residue forming on the surface. It achieves a UL94 VTM-0 flame retardant rating and a limiting oxygen index of 39.1%. Compared to pure polyimide without intercalation compounds, the limiting oxygen index is increased by 9.7%. Figure 7It can be seen that the polyimide composite material prepared in this embodiment has a total electromagnetic shielding (EMI) effectiveness of 28.4 dB in the frequency range of 8.2-12.4 GHz, which meets the requirements for commercial-grade EMI shielding applications and effectively shields more than 99% of incident microwaves. From Figure 8 It can be seen that the polyimide composite material prepared in this embodiment, when subjected to external force to shape the polyimide in a 340°C thermal environment and then cooled to room temperature, still maintains a bent temporary shape after the external force is removed. When heated to a 340°C thermal environment again, it can recover its original shape after 15 seconds. The shape fixation rate is 96% and the shape recovery rate is 97%.

[0055] Example 2

[0056] (1) Take 0.3314g of Ti3C2T with few or no layers or monolayers. x The sample was dispersed in 12 mL of N,N-dimethylacetamide (DMAc) solvent and stirred thoroughly at 40 °C for 48 h. After ultrasonic treatment for 4 h, 0.0301 g of polyaniline powder was added to the above DMAc solution and ultrasonicated for another 4 h to carry out the intercalation reaction, thus obtaining Ti3C2T. x @PANI intercalation complex suspension;

[0057] (2) Dissolve 4.8 mmol ODA and 0.4 mmol TBA in 16 mL of DMAc solvent to obtain a mixed solution containing -NH2 groups;

[0058] (3) Add 5.01 mmol of 6FDA to the mixed solution containing -NH2 groups in 4-6 portions, react at room temperature under N2 atmosphere for 20 h to obtain a polyamic acid solution, named PAA;

[0059] (4) Ti3C2T x The PAI intercalation complex suspension was poured into the PAA solution and stirred at 500 rpm for 2 hours until homogeneous, yielding a solution containing Ti3C2T. x PAA mixed solution of @PANI intercalation complex;

[0060] (5) The above PAA mixed solution is poured onto the substrate and placed in a vacuum oven at 50°C for 6 hours; then at 80°C for 6 hours. Vacuum is then drawn to remove air bubbles, and a PAA mixed solution substrate without air bubbles is obtained.

[0061] (6) The bubble-free PAA mixed solution substrate is placed in a high-temperature oven and subjected to thermal imidization by gradient heating at a rate of 5°C / min, heating to 140°C and holding for 2 hours; heating to 200°C at a rate of 5°C / min and holding for 2 hours; heating to 260°C at a rate of 5°C / min and holding for 2 hours; heating to 300°C at a rate of 5°C / min and holding for 2 hours.

[0062] (7) Turn off the high-temperature oven and let it cool naturally to room temperature. Take out the glass plate and place it in 100°C deionized water for 1 hour to complete the demolding.

[0063] (8) Place the demolded film material in an oven at 100°C for 6 hours to evaporate the moisture and obtain an organic-inorganic hybrid spider silk-like microstructure shape memory polyimide composite material with flame retardant and electromagnetic shielding properties.

[0064] The T of the polyimide composite material prepared in this embodiment g Its shape memory transition temperature is 323℃, and its energy storage modulus at room temperature is 9252MPa. It has a flame retardant rating of UL94 VTM-0 and a limiting oxygen index of 39.5%. Its total electromagnetic shielding (EMI) effectiveness in the 8.2-12.4GHz frequency range is 28.5dB. Its shape fixation rate is 95%, and its shape recovery rate is 97%.

[0065] Example 3

[0066] (1) Take 0.2336g of Ti3C2T with few or no layers. x The sample was dispersed in 12 mL of N,N-dimethylacetamide (DMAc) solvent and stirred thoroughly at 40 °C for 48 h. It was then sonicated for 4 h. Next, 0.0234 g of polyaniline powder was weighed and added to the DMAc solution, and sonication was continued for another 4 h to carry out the intercalation reaction, thus obtaining Ti3C2T. x @PANI intercalation complex suspension;

[0067] (2) Dissolve 4.8 mmol ODA and 0.4 mmol TBA in 16 mL of DMAc solvent to obtain a mixed solution containing -NH2 groups;

[0068] (3) Add 5.05 mmol of 6FDA to the mixed solution containing -NH2 groups in 4-6 portions, react at room temperature under N2 atmosphere for 20 h to obtain a polyamic acid solution, named PAA;

[0069] (4) Ti3C2T x The PAI intercalation complex suspension was poured into the PAA solution and stirred at 500 rpm for 2 hours until homogeneous, yielding a solution containing Ti3C2T.x PAA mixed solution of @PANI intercalation complex;

[0070] (5) The above PAA mixed solution is poured onto the substrate and placed in a vacuum oven at 50°C for 6 hours; then at 80°C for 6 hours. Vacuum is then drawn to remove air bubbles, and a PAA mixed solution substrate without air bubbles is obtained.

[0071] (6) The bubble-free PAA mixed solution substrate is placed in a high-temperature oven and subjected to thermal imidization by gradient heating at a rate of 5°C / min, heating to 140°C and holding for 2 hours; heating to 200°C at a rate of 5°C / min and holding for 2 hours; heating to 260°C at a rate of 5°C / min and holding for 2 hours; heating to 300°C at a rate of 5°C / min and holding for 2 hours.

[0072] (7) Turn off the high-temperature oven and let it cool naturally to room temperature. Take out the glass plate and place it in 100°C deionized water for 1 hour to complete the demolding.

[0073] (8) Place the demolded film material in an oven at 100°C for 6 hours to evaporate the moisture and obtain an organic-inorganic hybrid spider silk-like microstructure shape memory polyimide composite material with flame retardant and electromagnetic shielding properties.

[0074] The T of the polyimide composite material prepared in this embodiment g Its shape memory transition temperature is 317℃, and its energy storage modulus at room temperature is 8832MPa. It has a flame retardant rating of UL94 VTM-0 and a limiting oxygen index of 36.9%. Its total electromagnetic shielding (EMI) effectiveness in the 8.2-12.4GHz frequency range is 25.5dB. Its shape fixation rate is 97%, and its shape recovery rate is 99%.

[0075] Example 4

[0076] (1) Take 0.4898g of Ti3C2T with few or no layers or monolayers. x The sample was dispersed in 24 mL of N,N-dimethylacetamide (DMAc) solvent and stirred thoroughly at 40 °C for 48 h. It was then sonicated for 4 h. Next, 0.0490 g of polyaniline powder was weighed and added to the DMAc solution, and sonication was continued for another 4 h to carry out the intercalation reaction, thus obtaining Ti3C2T. x @PANI intercalation complex suspension;

[0077] (2) Dissolve 8.2 mmol ODA and 0.8 mmol TBA in 32 mL of DMAc solvent to obtain a mixed solution containing -NH2 groups;

[0078] (3) Add 8.6 mmol of 6FDA to the mixed solution containing -NH2 groups in 4-6 portions, react at room temperature under N2 atmosphere for 20 h to obtain a polyamic acid solution, named PAA;

[0079] (4) Ti3C2T x The PAI intercalation complex suspension was poured into the PAA solution and stirred at 500 rpm for 2 hours until homogeneous, yielding a solution containing Ti3C2T. x PAA mixed solution of @PANI intercalation complex;

[0080] (5) The above PAA mixed solution is poured onto the substrate and placed in a vacuum oven at 50°C for 6 hours; then at 80°C for 6 hours. Vacuum is then drawn to remove air bubbles, and a PAA mixed solution substrate without air bubbles is obtained.

[0081] (6) The bubble-free PAA mixed solution substrate is placed in a high-temperature oven and subjected to thermal imidization by gradient heating at a rate of 5°C / min, heating to 140°C and holding for 2 hours; heating to 200°C at a rate of 5°C / min and holding for 2 hours; heating to 260°C at a rate of 5°C / min and holding for 2 hours; heating to 300°C at a rate of 5°C / min and holding for 2 hours.

[0082] (7) Turn off the high-temperature oven and let it cool naturally to room temperature. Take out the glass plate and place it in 100°C deionized water for 1 hour to complete the demolding.

[0083] (8) Place the demolded film material in an oven at 100°C for 6 hours to evaporate the moisture and obtain an organic-inorganic hybrid spider silk-like microstructure shape memory polyimide composite material with flame retardant and electromagnetic shielding properties.

[0084] The T of the polyimide composite material prepared in this embodiment g Its shape memory transition temperature is 318℃, and its energy storage modulus at room temperature is 9200MPa. It has a flame retardant rating of UL94 VTM-0 and a limiting oxygen index of 38.7%. Its total electromagnetic shielding (EMI) effectiveness in the 8.2-12.4GHz frequency range is 27.5dB. Its shape fixation rate is 95%, and its shape recovery rate is 95%.

[0085] Example 5

[0086] (1) Take 0.4898g of Ti3C2T with few or no layers or monolayers. xThe sample was dispersed in 24 mL of N,N-dimethylacetamide (DMAc) solvent, stirred thoroughly at 40 °C for 48 h, and sonicated for 4 h. Then, 0.0490 g of polyaniline powder was weighed and added to the above DMAc solution and sonicated for another 4 h to carry out the intercalation reaction, thus obtaining the Ti3C2Tx@PANI intercalation complex suspension.

[0087] (2) Dissolve 8.2 mmol ODA and 0.8 mmol TBA in 32 mL of DMAc solvent to obtain a mixed solution containing -NH2 groups;

[0088] (3) Add 8.64 mmol of 6FDA to the mixed solution containing -NH2 groups in 4-6 portions, react at room temperature under N2 atmosphere for 20 h to obtain polyamic acid solution, named PAA;

[0089] (4) Ti3C2T x The PAI intercalation complex suspension was poured into the PAA solution and stirred at 500 rpm for 2 hours until homogeneous, yielding a solution containing Ti3C2T. x PAA mixed solution of @PANI intercalation complex;

[0090] (5) The above PAA mixed solution is poured onto the substrate and placed in a vacuum oven at 50°C for 6 hours; then at 80°C for 6 hours. Vacuum is then drawn to remove air bubbles, and a PAA mixed solution substrate without air bubbles is obtained.

[0091] (6) The bubble-free PAA mixed solution substrate is placed in a high-temperature oven and subjected to thermal imidization by gradient heating at a rate of 5°C / min, heating to 140°C and holding for 2 hours; heating to 200°C at a rate of 5°C / min and holding for 2 hours; heating to 260°C at a rate of 5°C / min and holding for 2 hours; heating to 300°C at a rate of 5°C / min and holding for 2 hours.

[0092] (7) Turn off the high-temperature oven and let it cool naturally to room temperature. Take out the glass plate and place it in 100°C deionized water for 1 hour to complete the demolding.

[0093] (8) Place the demolded film material in an oven at 100°C for 6 hours to evaporate the moisture and obtain an organic-inorganic hybrid spider silk-like microstructure shape memory polyimide composite material with flame retardant and electromagnetic shielding properties.

[0094] The T of the polyimide composite material prepared in this embodiment gIts shape memory transition temperature is 321℃, and its energy storage modulus at room temperature is 9176MPa. It has a flame retardant rating of UL94 VTM-0 and a limiting oxygen index of 38.9%. Its total electromagnetic shielding (EMI) effectiveness in the 8.2-12.4GHz frequency range is 28.2dB. Its shape fixation rate is 98%, and its shape recovery rate is 95%.

[0095] Example 6

[0096] (1) Take 0.4858g of Ti3C2T with few or single layers. x The sample was dispersed in 24 mL of N,N-dimethylacetamide (DMAc) solvent and stirred thoroughly at 40 °C for 48 h. It was then sonicated for 4 h. Next, 0.0486 g of polyaniline powder was weighed and added to the DMAc solution, and sonication was continued for another 4 h to carry out the intercalation reaction, thus obtaining Ti3C2T. x @PANI intercalation complex suspension;

[0097] (2) Dissolve 8.2 mmol ODA and 0.8 mmol TBA in 32 mL of DMAc solvent to obtain a mixed solution containing -NH2 groups;

[0098] (3) Add 8.62 mmol of 6FDA to the mixed solution containing -NH2 groups in 4-6 portions, react at room temperature under N2 atmosphere for 20 h to obtain a polyamic acid solution, named PAA;

[0099] (4) Ti3C2T x The PAI intercalation complex suspension was poured into the PAA solution and stirred at 500 rpm for 2 hours until homogeneous, yielding a solution containing Ti3C2T. x PAA mixed solution of @PANI intercalation complex;

[0100] (5) The above PAA mixed solution is poured onto the substrate and placed in a vacuum oven at 50°C for 6 hours; then at 80°C for 6 hours. Vacuum is then drawn to remove air bubbles, and a PAA mixed solution substrate without air bubbles is obtained.

[0101] (6) The bubble-free PAA mixed solution substrate is placed in a high-temperature oven and subjected to thermal imidization by gradient heating at a rate of 5°C / min, heating to 140°C and holding for 2 hours; heating to 200°C at a rate of 5°C / min and holding for 2 hours; heating to 260°C at a rate of 5°C / min and holding for 2 hours; heating to 300°C at a rate of 5°C / min and holding for 2 hours.

[0102] (7) Turn off the high-temperature oven and let it cool naturally to room temperature. Take out the glass plate and place it in 100°C deionized water for 1 hour to complete the demolding.

[0103] (8) Place the demolded film material in an oven at 100°C for 6 hours to evaporate the moisture and obtain an organic-inorganic hybrid spider silk-like microstructure shape memory polyimide composite material with flame retardant and electromagnetic shielding properties.

[0104] The T of the polyimide composite material prepared in this embodiment g Its shape memory transition temperature is 322℃, and its energy storage modulus at room temperature is 9158MPa. It has a flame retardant rating of UL94 VTM-0 and a limiting oxygen index of 37.3%. Its total electromagnetic shielding (EMI) effectiveness in the 8.2-12.4GHz frequency range is 26.9dB. Its shape fixation rate is 94%, and its shape recovery rate is 97%.

[0105] While the disclosure is as stated above, its scope of protection is not limited thereto. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of this disclosure, and all such changes and modifications will fall within the protection scope of this invention.

Claims

1. A method for preparing a spider silk-inspired microstructure shape memory polyimide composite material, characterized in that: The structural formula of the composite material is shown below: Wherein, the value of n ranges from 100 to 165; the method is as follows: Step S1: Take a few layers or a single layer of Ti3C2T x The sample was dispersed in N,N-dimethylacetamide (DMAc) solvent and stirred thoroughly at 40°C for 48 h, followed by ultrasonic treatment for 4 h. Then, polyaniline powder was weighed and added to the above DMAc solution, and ultrasonic treatment was continued for 4 h to carry out the intercalation reaction, thus obtaining Ti3C2T. x @PANI intercalation complex suspension; Step S2: Dissolve ODA and TBA in DMAc solvent to obtain a mixed solution containing -NH2 groups; Step S3: Add 6FDA to the mixed solution containing -NH2 groups in 4 to 6 portions, react at room temperature under N2 atmosphere for 20 h to obtain a polyamic acid solution, named PAA; Step S4: Place Ti3C2T x @PANI intercalation complex suspension was poured into the PAA solution and stirred until homogeneous to obtain a solution containing Ti3C2T x PAA mixed solution of @PANI intercalation complex; Step S5: Pour the above PAA mixed solution onto the substrate and place it in a vacuum oven for vacuum drying to remove air bubbles, thereby obtaining a PAA mixed solution substrate without air bubbles. Step S6: Place the bubble-free PAA mixed solution substrate in a high-temperature oven and perform thermal imidization by gradient heating to obtain a substrate containing a polyimide film. Step S7: Place the substrate containing the polyimide film in water for 1-2 hours to complete demolding. After drying, an organic-inorganic hybrid spider silk-like microstructure shape memory polyimide composite material with flame retardant and electromagnetic shielding properties is obtained.

2. The method for preparing a spider silk-inspired microstructure shape memory polyimide composite material according to claim 1, characterized in that: The composite material is prepared from polyaniline and MXene intercalation complex and fluorinated / bromine-containing shape memory polyimide; wherein, the fluorinated / bromine-containing shape memory polyimide is synthesized from 4,4'-diaminodiphenyl ether, hexafluoroisopropylphthalic anhydride, and 2,4,6-tribromoaniline ternary monomers, the total molar ratio of 4,4'-diaminodiphenyl ether and 2,4,6-tribromoaniline to hexafluoroisopropylphthalic anhydride is 1:1~1.05, and the mass of 2,4,6-tribromoaniline accounts for 2 wt%~10 wt% of the mass of the fluorinated / bromine-containing shape memory polyimide.

3. The method for preparing a spider silk-inspired microstructure shape memory polyimide composite material according to claim 2, characterized in that: The mass ratio of the polyaniline and MXene intercalation composite to the fluorinated, brominated shape memory polyimide is 5~20:

100.

4. The method for preparing a spider silk-inspired microstructure shape memory polyimide composite material according to claim 2 or 3, characterized in that: In the polyaniline and MXene intercalation composite, the mass percentage of polyaniline is 10%.

5. The method for preparing a spider silk-inspired microstructure shape memory polyimide composite material according to claim 1, characterized in that: In step S3, the concentration of polyamic acid in the polyamic acid solution is 17~24 wt%.

6. The method for preparing a spider silk-inspired microstructure shape memory polyimide composite material according to claim 1, characterized in that: In step S5, the vacuum drying process includes: controlling the oven temperature to 50 ℃ and maintaining it for 6 h, then raising the temperature to 80 ℃ and maintaining it for 6 h, and then evacuating the vacuum.

7. The method for preparing a spider silk-inspired microstructure shape memory polyimide composite material according to claim 1, characterized in that: In step S6, the gradient heating includes: heating at a rate of 5 ℃ / min to 140 ℃ and holding for 2 h; heating at a rate of 5 ℃ / min to 200 ℃ and holding for 2 h; heating at a rate of 5 ℃ / min to 260 ℃ and holding for 2 h; and heating at a rate of 5 ℃ / min to 300 ℃ and holding for 2 h.

8. The application of a spider silk-inspired microstructure shape memory polyimide composite material prepared by the preparation method according to any one of claims 1 to 7 in adaptive deformation advanced aircraft, electronic appliances, thermal management electromagnetic shielding devices and smart wearable devices.

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