MXene / polyurethane electromagnetic wave absorption elastomer with environmental stability and light acceleration self-healing function and preparation method thereof

Abstract

The invention discloses an MXene / polyurethane electromagnetic wave absorbing elastomer with environmental stability and a light acceleration self-healing function and a preparation method of the MXene / polyurethane electromagnetic wave absorbing elastomer. The MXene / polyurethane electromagnetic wave absorbing elastomer is used for solving the problems that a traditional wave absorbing material is easy to degrade in a severe environment and is easy to lose efficacy after physical damage. The elastomer is formed by compounding an MXene nanosheet and self-healing polyurethane through physical crosslinking. Due to the rich heterogeneous interface and the high-conductivity MXene nanosheet, broadband electromagnetic wave absorption is achieved through MXene / polyurethane. And the physical crosslinking between the MXene and the polyurethane enhances the environment shielding effect of a polyurethane dynamic network through an interface hydrogen bond, so that the material can maintain the structural integrity in a harsh environment. In addition, the completely cut-off material can recover certain mechanical properties and electromagnetic wave absorption capability within 30 minutes under the irradiation of sunlight. The material is suitable for flexible wave-absorbing coatings in wearable electronic equipment, aerospace systems and marine protection equipment, and the limitation of the prior art on the adaptability of complex working conditions is broken through.

Description

Technical Field

[0001] The present invention belongs to the technical field of design and development of electromagnetic wave absorbing materials, and in particular relates to the design and preparation of a MXene / polyurethane electromagnetic wave absorbing elastomer with both environmental stability and light-accelerated self-healing function. Background Art

[0002] Electromagnetic pollution is becoming increasingly serious with the popularization of modern communication technology. The development of high-performance absorbing materials has become a key path to addressing electromagnetic interference. Traditional magnetic materials such as ferrites have excellent loss tolerance in low-frequency bands, but their high density and significant brittleness make them difficult to meet the deformation adaptability requirements of flexible electronic devices. Carbon-based materials, while lightweight, have a narrow absorption band due to poor impedance matching, limiting their application scenarios. It is particularly noteworthy that emerging two-dimensional materials such as MXene, while exhibiting tunable dielectric properties, are susceptible to oxidative degradation in hot, humid, or corrosive environments. Experiments have shown that their electrical conductivity decays by more than 30% after immersion in seawater, severely limiting their service life in harsh environments such as marine equipment.

[0003] To this end, researchers have attempted to break through the bottleneck through composite strategies: on the one hand, core-shell structures (such as SiO2@MXene) or three-dimensional aerogel frameworks are designed to optimize impedance matching, and on the other hand, flexible matrices such as epoxy resins and silicone rubber are introduced to improve mechanical properties. However, high filler loadings can easily limit the plastic deformation capacity of the matrix, resulting in a decrease in the toughness of the composite material. At the same time, the interfacial compatibility problem between the dynamic cross-linked network and the functional filler has not been fundamentally solved. Existing technologies are unable to maintain stable electromagnetic wave absorption efficiency in extreme environments, and lack the ability to self-heal from physical damage, which hinders the application of materials in fields such as wearable devices and ship radar covers that require long-term resistance to mechanical stress and environmental erosion. Summary of the Invention

[0004] The technical problem addressed by this invention is to develop a MXene / polyurethane elastomer that combines environmental tolerance, light-accelerated self-healing, and broadband absorption. The key to this development lies in constructing a composite structure of a dynamically cross-linked polyurethane network and a fluorinated end-group-modified MXene. By introducing disulfide bonds into the polyurethane, the network is physically cross-linked via hydrogen bonds with the surface-modified MXene nanosheets, forming an interpenetrating network. The increased number of fluorinated end groups on the MXene surface not only facilitates the formation of F-Ti bonds and -CF···HN- hydrogen bonds, but also significantly inhibits oxidative degradation of the MXene.

[0005] The technical solution of the present invention is: a method for preparing a MXene / polyurethane electromagnetic wave absorbing elastomer with both environmental stability and light-accelerated self-healing function, comprising the following steps: (1) LiF is dispersed in hydrochloric acid and stirred into a uniform solution. Ti3AlC2 is added, and after stirring, HF stock solution is added. After etching, washing, and stripping, a MXene nanosheet aqueous dispersion is obtained. The MXene nanosheet solvent is exchanged with N,N-dimethylformamide to obtain a DMF dispersion of MXene nanosheets. (2) Under nitrogen atmosphere, polytetrahydrofuran, 4,4'-diisocyanate dicyclohexylmethane and dibutyltin dilaurate were weighed and added to N,N-dimethylacetamide, and the mixture was stirred to cause polymerization. 4,4'-diaminodiphenyl disulfide was added and the stirring was continued. The obtained polymer product was vacuum dried to obtain a self-healing polyurethane; (3) The self-healing polyurethane is dissolved in DMF, and the DMF dispersion of MXene nanosheets is added. After sufficient stirring, vacuum drying is performed to obtain a MXene / polyurethane electromagnetic wave absorbing elastomer with both environmental stability and light-accelerated self-healing function.

[0006] Furthermore, in step (1), the entire process was performed in a fume hood, and the addition ratio of LiF, hydrochloric acid, Ti3AlC2 and HF was 500 mg: (10-15) mL: (300-500) mg: (0-10) mL, wherein the concentrations of hydrochloric acid and HF were 36-38 wt% and 40 wt%.

[0007] Furthermore, in step (1), the stirring time is 10-30 min, the etching time is 24-48 h, the centrifugal speed and time during the washing process are 4000-6000 rpm and 5-10 min, the ultrasonic power and time during the stripping process are required to be 3000w and 5 min, and the washing-stripping process is repeated until the pH of the supernatant is greater than 6. The supernatant is poured out, DMF is added to disperse the precipitate, and the washing-stripping process is repeated until the supernatant turns black. The supernatant and the precipitate are separated to obtain a DMF dispersion with a few layers or a single layer of MXene nanosheets.

[0008] Furthermore, in step (2), the entire process is operated under inert protective gas, and the ratio of the added amounts of polytetrahydrofuran, 4,4'-diisocyanate dicyclohexylmethane, dibutyltin dilaurate and N,N-dimethylacetamide is 20 g: 10 mL: (5-10) μL: (20-50) mL, wherein the average molecular weight of T polytetrahydrofuran is 2000.

[0009] Furthermore, in step (2), the polymerization time is 3-6 h, the polymerization temperature is 70-80 ° C, after the prepolymerization is completed, the temperature is lowered to 40 ° C, 3-5 g of 4,4'-diaminodiphenyl disulfide is added as a chain extender, stirring is continued for 3 h, and the vacuum drying temperature is 80-100 ° C.

[0010] Furthermore, in step (3), the mass ratio of MXene nanosheets to self-healing polyurethane is 10-20 wt%.

[0011] Furthermore, in step (3), the dissolution temperature of the self-healing polyurethane is 70-90°C, the vacuum drying temperature is 70-100°C, and the drying time is 12-24 h.

[0012] The beneficial effects of this invention include: The self-healing behavior of this material is triggered by the photothermal effect of MXene: MXene absorbs light energy within a wide spectral range of 300-2500 nm, converting it into heat energy, which promotes the reorganization of dynamic disulfide bonds at the fracture interface. Experimental results show that completely severed samples can be repaired by irradiating them under standard sunlight (1000 W / m²) for 30 minutes, with a tensile strain recovery rate of 87.5% and an effective absorption bandwidth (RL ≤ -10dB) restored to 72.6% of the original value. This design, which integrates environmental barriers, photothermal conversion, and impedance matching, overcomes the dual limitations of traditional absorbing materials, which suffer from performance degradation and irreversible damage under extreme operating conditions.

[0013] Through research, the present invention discovered that traditional absorbing materials (such as ferrites and carbon-based materials) have problems such as high brittleness, poor flexibility, and insufficient environmental stability, making them difficult to apply to wearable devices or curved structures. Although MXene materials have high conductivity and electromagnetic loss capabilities, they are easily oxidized and inactivated, and a single component cannot achieve both impedance matching and mechanical properties. Existing flexible absorbing materials lack self-healing capabilities, and their performance cannot be restored after damage, which affects their service life. However, the present application utilizes physical cross-linking of MXene and polyurethane to achieve excellent absorbing performance at a low filling ratio. In addition, by utilizing the environmental shielding effect of the polyurethane network and the high photothermal conversion efficiency of MXene, the MXene / polyurethane elastomer also achieves environmental stability and rapid self-healing capabilities.

[0014] (1) The novel MXene / polyurethane electromagnetic wave absorbing elastomer provided by the present invention has the advantages of wide bandwidth and low matching thickness. At a low thickness of 1.77 mm, it can achieve wide bandwidth absorption of 5.40 GHz. After long-term exposure to extreme environments such as seawater, strong acid (pH=1), and strong base (pH=14), it can maintain structural integrity. After being completely cut, the material can recover certain mechanical properties and electromagnetic wave absorption capacity within 30 minutes under sunlight irradiation.

[0015] (2) The synthesis process and method of the present invention are novel, simple, and easy to promote to synthesize other types of new composite elastomer materials.

[0016] (3) The MXene and polyurethane in the present invention have many adjustable parameters, which can effectively regulate and optimize the electromagnetic parameters, mechanical properties, self-healing rate, and environmental stability of the materials, thereby achieving multifunctional integration. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 (a) X-ray diffraction spectrum of MXene nanosheets prepared in Example 1 and Comparative Examples 1 and 2; (b) X-ray photoelectron spectroscopy F 1s spectrum; Figure 2 Fourier transform infrared spectroscopy of MXene and MXene / polyurethane elastomers; Figure 3 Transmission electron microscopy images: (a) Example 1, (b) Comparative Example 1, and (c) Comparative Example 2; Figure 4 Example 1 and Comparative Examples 1 to 3 reflection loss value change curve; Figure 5 Example 1 Digital photos and self-healing properties before and after immersion in different solvents for 30 days; Figure 6 . Microscopic self-healing process of Example 1 and Comparative Example 3 under different conditions: (a) Room temperature healing of Comparative Example 3; (b) Room temperature healing of Example 1; (c) Light healing of Example 1. DETAILED DESCRIPTION

[0018] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments. This embodiment is implemented based on the technical solution of the present invention, and provides a detailed implementation method and specific operation process, but the protection scope of the present invention is not limited to the following embodiments.

[0019] The following are examples of the present invention. Unless otherwise specified, raw materials or processing techniques are conventional commercially available raw materials or conventional processing techniques in the art.

[0020] Example 1

[0021] (1) Weigh 500 mg of LiF and add it to a polytetrafluoroethylene beaker containing 10 mL of hydrochloric acid. Stir for 10 minutes to form a uniform solution, and then add 500 mg of Ti3AlC2. After etching for 2 hours, add 5 mL of HF to the above uniform solution and keep it at room temperature for 24 hours. Then wash it with deionized water, centrifuge it (the centrifugal speed and time are 4000 rpm and 5 minutes), and strip it (the ultrasonic power and time require 3000w and 5 minutes). Repeat the washing-stripping process until the pH of the supernatant is greater than 6. Pour out the supernatant, add DMF to disperse the precipitate, and repeat the washing-stripping process until the supernatant turns black. At this time, repeating the washing-stripping process can increase the concentration of the DMF dispersion of MXene nanosheets. The supernatant and the precipitate are separated to obtain a DMF dispersion with few or single-layer MXene nanosheets.

[0022] (2) Under nitrogen atmosphere, 20 g of polytetrahydrofuran was weighed and added to 20 mL of N,N-dimethylacetamide. After heating to 80 °C, 10 mL of 4,4'-diisocyanate dicyclohexylmethane and 10 μL of dibutyltin dilaurate were added. After stirring for 3 h, 3 g of 4,4'-diaminodiphenyl disulfide was added and stirring was continued for another 3 h. The obtained polymer product was vacuum dried at 90 °C to obtain self-healing polyurethane. (3) MXene (the corresponding mass is converted according to the concentration of the obtained MXene dispersion) and self-healing polyurethane are dissolved in 10 mL of DMF at a mass ratio of 15 wt%. After thorough stirring, the mixture is poured into a specific silicone mold and vacuum dried at 90 °C for 20 h to obtain the target product.

[0023] Example 2

[0024] Without changing other steps, by changing the amount of 4,4'-diaminodiphenyl disulfide added in step (2) to 5 g, a MXene / polyurethane electromagnetic wave absorbing elastomer with lower tensile strength but faster self-healing rate can be obtained.

[0025] Example 3

[0026] Without changing other steps, by changing the mass ratio of MXene to self-healing polyurethane in step (3) to 20wt%, a MXene / polyurethane electromagnetic wave absorbing elastomer with stronger photothermal effect, faster self-healing efficiency and lower electromagnetic wave absorption performance can be obtained.

[0027] Comparative Example 1: Compared with Example 1, HF was not added in step (1), and the remaining steps were the same.

[0028] Comparative Example 2: Compared with Example 1, 10 mL of HF was added in step (1), and the remaining steps were the same.

[0029] Comparative Example 3: Compared with Example 1, only step (2) is performed.

[0030] Figure 1 a is the X-ray diffraction (XRD) analysis of the MXene nanosheets prepared in Example 1 and Comparative Examples 1 and 2. As shown in the figure, both Example 1 and Comparative Examples 1 and 2 show a sharp characteristic peak at 6.6°, corresponding to Ti3C2T x In addition, we use Figure 1 b. Further analysis of the X-ray photoelectron spectroscopy of F 1s shows that the intensity of the C-Ti-F peak at 685.2 eV follows the order of Comparative Example 1 < Example 1 < Comparative Example 2, which proves that the content of fluorine-containing end groups can be effectively adjusted by increasing the HF concentration.

[0031] Figure 2 The Fourier transform infrared spectrum of Example 1 above shows that the typical characteristics of -OH and C=O vibration appear at 3450 and 1650 cm -1 This is attributed to the surface end groups of MXene. In addition, the MXene / polyurethane elastomer has the peaks at 2950 and 1460 cm -1 The peaks at 370 nm correspond to the -CH and CN vibrations of polyurethane, confirming the successful synthesis of MXene / polyurethane elastomer.

[0032] Figure 3 ac are transmission electron micrographs of the MXene nanosheets prepared in Example 1 and Comparative Examples 1 and 2. The MXene nanosheets in Example 1 show a typical two-dimensional morphology with a lateral size of 3-4 μm. Similar morphologies were also observed in Comparative Examples 1 and 2 ( Figure 3 b and 3c). In general, the treatments with different HF concentrations did not have much effect on their morphology.

[0033] Figure 4 The electromagnetic wave absorption performance of the MXene / polyurethane elastomers prepared in Example 1 and Comparative Examples 1-3 is shown. Example 1 achieves a maximum electromagnetic wave absorption bandwidth of 5.40 GHz at a thickness of 1.77 mm, while Comparative Example 2 achieves an effective absorption bandwidth of 4.40 GHz at a thickness of 1.97 mm. However, Comparative Examples 1 and 2 exhibit poor performance due to impedance mismatch caused by excessively high / low conductivity.

[0034] Figure 5 The environmental resistance and self-healing ability of Example 1. Figure 5As shown in Figure a, after Example 1 was immersed in different solvents for 30 days, its morphology and solution color remained unchanged in different solvents, which indicates that it has excellent chemical inertness. Figure 5 b shows the flexibility of Example 1, and after the broken samples were placed in contact with each other and irradiated with a xenon lamp for 30 minutes, the separated Example 1 could be completely repaired and the mechanical properties were restored.

[0035] Figure 6 The microscopic self-healing process of Example 1 and Comparative Example 3. Under room temperature, the scratches on the surface of Comparative Example 3 closed within 3 hours ( Figure 6 a), while Example 1 was only partially healed after 24 hours ( Figure 6 b). In contrast, under xenon lamp irradiation, the scratches of Example 1 completely disappeared within 30 minutes ( Figure 6 c), the repair rate is significantly faster than that of comparative example 3.

[0036] The above description of the embodiments and comparative examples is intended to facilitate understanding and use of the invention by those skilled in the art. Those skilled in the art can readily modify these embodiments and apply the general principles described herein to other embodiments without resorting to creative discovery. Therefore, the present invention is not limited to the above embodiments, and improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the present invention should be within the scope of protection of the present invention.

Claims

1. A method for preparing a MXene / polyurethane electromagnetic wave absorbing elastomer with both environmental stability and light-accelerated self-healing capabilities, characterized by: The following steps are involved: (1) LiF is dispersed in hydrochloric acid and stirred into a uniform solution. Ti3AlC2 is added, and after stirring, HF stock solution is added. After etching, washing, and stripping, a MXene nanosheet aqueous dispersion is obtained. The MXene nanosheet solvent is exchanged with N,N-dimethylformamide to obtain a DMF dispersion of MXene nanosheets. (2) Under nitrogen atmosphere, polytetrahydrofuran, 4,4'-diisocyanate dicyclohexylmethane and dibutyltin dilaurate were weighed and added to N,N-dimethylacetamide, and the mixture was stirred to cause polymerization. 4,4'-diaminodiphenyl disulfide was added and the stirring was continued. The obtained polymer product was vacuum dried to obtain a self-healing polyurethane; (3) The self-healing polyurethane is dissolved in DMF, and the DMF dispersion of MXene nanosheets is added. After sufficient stirring, vacuum drying is performed to obtain a MXene / polyurethane electromagnetic wave absorbing elastomer with both environmental stability and light-accelerated self-healing function.

2. The method for preparing a MXene / polyurethane electromagnetic wave absorbing elastomer having both environmental stability and light-accelerated self-healing function according to claim 1, characterized in that: In step (1), the entire process was performed in a fume hood, and the addition ratio of LiF, hydrochloric acid, Ti3AlC2, and HF was 500 mg: (10-15) mL: (300-500) mg: (0-10) mL, wherein the concentrations of hydrochloric acid and HF were 36-38 wt% and 40 wt%.

3. The method for preparing a MXene / polyurethane electromagnetic wave absorbing elastomer having both environmental stability and light-accelerated self-healing function according to claim 1, characterized in that: In step (1), the stirring time is 10-30 min, the etching time is 24-48 h, the centrifugal speed and time during the washing process are 4000-6000 rpm and 5-10 min, the ultrasonic power and time during the stripping process are required to be 3000w and 5 min, and the washing-stripping process is repeated until the pH of the supernatant is greater than 6. The supernatant is poured out, DMF is added to disperse the precipitate, and the washing-stripping process is repeated until the supernatant turns black. The supernatant and the precipitate are separated to obtain a DMF dispersion with a few layers or a single layer of MXene nanosheets.

4. The method for preparing a MXene / polyurethane electromagnetic wave absorbing elastomer having both environmental stability and light-accelerated self-healing function according to claim 1, characterized in that: In step (2), the entire process is operated under inert protective gas, and the ratio of the added amounts of polytetrahydrofuran, 4,4'-diisocyanate dicyclohexylmethane, dibutyltin dilaurate and N,N-dimethylacetamide is 20 g: 10 mL: (5-10) μL: (20-50) mL, wherein the average molecular weight of T polytetrahydrofuran is 2000.

5. The method for preparing a MXene / polyurethane electromagnetic wave absorbing elastomer having both environmental stability and light-accelerated self-healing function according to claim 1, characterized in that: In step (2), the polymerization time is 3-6 h, the polymerization temperature is 70-80 ° C. After the prepolymerization is completed, the temperature is lowered to 40 ° C, 3-5 g of 4,4'-diaminodiphenyl disulfide is added as a chain extender, and stirring is continued for 3 h. The vacuum drying temperature is 80-100 ° C.

6. The method for preparing a MXene / polyurethane electromagnetic wave absorbing elastomer having both environmental stability and light-accelerated self-healing function according to claim 1, characterized in that: In step (3), the mass ratio of MXene nanosheets to self-healing polyurethane is 10-20 wt%.

7. The method for preparing a MXene / polyurethane electromagnetic wave absorbing elastomer having both environmental stability and light-accelerated self-healing function according to claim 1, characterized in that: In step (3), the dissolution temperature of the self-healing polyurethane is 70-90°C, the vacuum drying temperature is 70-100°C, and the drying time is 12-24 hours.

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