Flexible MXene Polymer Composite Fiber and Its Preparation Method

Abstract

This application relates to a flexible MXene polymer composite fiber and a preparation method thereof, and pertains to the field of conductive fibers. In this application, dopamine or its derivative: polystyrene sulfonic acid is used as a valence bond donor and a soft interlocker to crosslink and composite MXene with TPU, carbon nanotubes or their derivatives, and silver nanoparticles to construct a stable conductive network structure, and then a flexible MXene polymer composite fiber is prepared through wet spinning technology. This solves the problems that in the wet-spun MXene polymer composite fibers prepared by existing methods, the MXene nanosheets are small and uneven in size, the interaction between layers is weak, the self-supporting structure is poor, it is difficult to combine with polymer flexible materials to construct a conductive network structure, and MXene is prone to oxidation, thus losing its conductive properties.

Description

Technical Field

[0001] The present application relates to the technical field of conductive fibers, and particularly relates to a flexible MXene polymer composite fiber and a preparation method thereof. Background Art

[0002] In recent years, with the improvement of people's living standards and the enhancement of their awareness of self-health protection, the popularization and use of synthetic conductive fibers are bound to become a trend. Therefore, the processing of conductive fibers should develop in the direction of simple process and low cost. The development of nanotechnology and the development and marketization of a series of functional nanomaterials have brought opportunities for the development of synthetic conductive fibers. In particular, MXene, as a two-dimensional layered transition metal carbide, nitride or carbonitride, has a two-dimensional layered graphene-like structure. Thanks to its graphene-like two-dimensional layered structure and chemical composition, it has high electrical conductivity (≈104 S / cm), high specific surface area (≈106 m 2 / g) and excellent mechanical properties (Young's modulus ≈ 330 GPa), and has received extensive attention from researchers at home and abroad. It is one of the core materials for constructing flexible sensor devices. A practical method for macroscopically assembling MXene nanomaterials into one-dimensional fibers is wet spinning, and fibers are formed through the gelation of the spinning solution and the solidification in the coagulation bath. For example, some researchers have tried to prepare highly conductive pure MXene fibers using MXene liquid crystals. Similar to graphite oxide and carbon nanotubes, when MXene nanosheets with a high aspect ratio reach a certain concentration in the dispersion, oriented liquid crystals can be formed, and then highly oriented MXene fibers can be prepared through wet spinning technology. The fibers exhibit high electrical conductivity, but it should be noted that the mechanical strength of these pure MXene fibers is still poor, which makes it difficult to operate and exhibit functions in actual processes. Subsequently, researchers blended MXene nanosheets with polymer spinning solutions such as polyurethane (PU) evenly and then carried out wet spinning to obtain MXene polymer composite fibers. The MXene polymer composite fibers prepared by wet spinning are a relatively simple and scalable method, and MXene can endow polymer fibers with multiple properties such as conductivity, antibacterial, sensing, and energy storage. However, due to the small and uneven size of MXene nanosheets and the weak interlayer interaction and poor self-supporting structure, when it acts with PU, it is difficult to combine with it to form a stable conductive network structure, and the molecular chains of the fibers are prone to slip, resulting in low electrical conductivity of the fibers. Therefore, the preparation of MXene composite fibers with both high electrical conductivity and high tensile strength is crucial for expanding the practical applications of MXene polymer composite fibers.

[0003] In the wet-spun MXene polymer composite fibers prepared by the current method, the MXene nanosheets are small and uneven in size, the interaction between layers is weak, the self-supporting structure is poor, it is difficult to combine with polymer flexible materials to construct a conductive network structure, and MXene is prone to oxidation, thus losing its conductive performance. Functional modification of the MXene surface or the use of cross-linking agents may improve the conductivity of the MXene polymer composite fibers and at the same time improve the tensile strength of the MXene polymer composite fibers. Summary of the Invention

[0004] The purpose of this application is to provide a flexible MXene polymer composite fiber and its preparation method to solve the problems that in the wet-spun MXene polymer composite fibers prepared by the existing method, the MXene nanosheets are small and uneven in size, the interaction between layers is weak, the self-supporting structure is poor, it is difficult to combine with polymer flexible materials to construct a conductive network structure, and MXene is prone to oxidation, thus losing its conductive performance.

[0005] To achieve the above purpose, the technical solution adopted in this application is as follows:

[0006] On the one hand, this application provides a preparation method of a flexible MXene polymer composite fiber, including the following steps:

[0007] S1. Add TPU to the DMF solution and stir with a constant temperature magnetic stirrer to obtain a TPU spinning dope.

[0008] S2. Add MXene or its derivatives and dopamine or its derivative: polystyrene sulfonic acid to the DMF solution in sequence and stir with a constant temperature magnetic stirrer to obtain a MXene mixed solution.

[0009] S3. Add carbon nanotubes or their derivatives and silver powder to the MXene mixed solution in sequence and stir with a constant temperature magnetic stirrer to obtain a MXene mixed conductive solution.

[0010] S4. Slowly pour the MXene mixed conductive solution into the TPU spinning dope and stir with a constant temperature magnetic stirrer to obtain a MXene mixed spinning solution.

[0011] S5. Inject the MXene mixed spinning solution into a syringe, perform wet spinning at room temperature, use an injection pump to extrude the MXene mixed spinning solution into a DMF aqueous coagulation bath, perform three-fold mechanical drawing on the nascent fiber solidified and formed by the coagulation bath, then perform heat setting treatment, and finally wind the fiber after heat setting treatment onto a uniformly rotating hot roller for collection and drying to obtain a flexible MXene polymer composite fiber.

[0012] In a possible implementation, in step S1:

[0013] The content of the TPU is 0.5 - 10.5 g / L;

[0014] The mass - volume concentration of the DMF is 40 - 300 mg / mL;

[0015] The constant - temperature of the constant - temperature magnetic stirrer is 40 - 60 °C, the stirring speed is 150 - 650 rpm, and the stirring time is 3 - 12 h.

[0016] In a possible implementation, in step S2:

[0017] The concentration of the MXene or its derivative is 15 - 75 mol / L;

[0018] The concentration of the dopamine or its derivative: polystyrene sulfonic acid is 0.2 - 10.2 mol / L;

[0019] The mass - volume concentration of the DMF is 10 - 30 mg / mL;

[0020] The constant - temperature of the constant - temperature magnetic stirrer is 40 - 60 °C, the stirring speed is 250 - 850 rpm, and the stirring time is 15 - 55 min.

[0021] In a possible implementation, in step S2:

[0022] The dopamine or its derivative includes one of dopamine hydrochloride, polydopamine - like, and N - 3,4 - dihydroxyphenethyl acrylamide.

[0023] In a possible implementation, in step S2:

[0024] The MXene or its derivative includes one of titanium carbide, dititanium carbide, dinibium carbide, divanadium carbide, titanium carbonitride, and titanium nitride.

[0025] In a possible implementation, in step S3:

[0026] The concentration of the carbon nanotube or its derivative is 0.5 - 12.5 mol / L, and the concentration of the silver powder is 2.5 - 6.5 mol / L;

[0027] The constant - temperature of the constant - temperature magnetic stirrer is 40 - 60 °C, the stirring speed is 100 - 700 rpm, and the stirring time is 4 - 12 h.

[0028] In a possible implementation, in step S3:

[0029] The carbon nanotubes or their derivatives include one of aminated carbon nanotubes, carboxylated carbon nanotubes, hydroxylated carbon nanotubes, and CNTs-AM.

[0030] In a possible implementation, in step S4:

[0031] The constant temperature of the constant temperature magnetic stirrer is 40 - 60 °C, the stirring speed is 150 - 650 rpm, and the stirring time is 4 - 8 h.

[0032] In a possible implementation, in step S5:

[0033] The volume capacity of the syringe is 5 - 40 mL, and the inner diameter of the needle is 0.2 - 0.8 mm;

[0034] The spinning rate of the wet spinning is 0.5 - 10.5 mL / h;

[0035] The length of the coagulation bath is 90 cm;

[0036] The temperature of the heat setting treatment is 60 °C;

[0037] The drying temperature in the process of winding the heat-set fiber onto a uniformly rotating hot roller for collection and drying is 25 - 45 °C, and the drying time is 4 - 8 h.

[0038] On the other hand, the present application also provides a flexible MXene polymer composite fiber, which is prepared by the preparation method of any one of the above flexible MXene polymer composite fibers.

[0039] The beneficial effects brought by the technical solution provided by the present application at least include:

[0040] (1) In this application, dopamine or its derivative, polystyrene sulfonic acid, is used as a valence bond donor and a soft interlocker to crosslink and compound MXene with TPU, carbon nanotubes or their derivatives, and silver nanoparticles to construct a stable conductive network structure. Then, flexible MXene polymer composite fibers are prepared by wet spinning technology. This crosslinking and compounding means that, on the one hand, amino groups, phenolic hydroxyl groups, etc. in dopamine or its derivative, polystyrene sulfonic acid, are intercalated and locked with hydrophilic groups of MXene or its derivative through hydrogen bonds, π-π stacking, electrostatic interactions, etc., inhibiting the oxidation and decomposition of MXene or its derivative and maintaining its conductivity; on the other hand, MXene or its derivative constructs a stable conductive network structure with TPU, carbon nanotubes or their derivatives, and silver nanoparticles through metal chelation, covalent reaction, hydrophobic interaction, etc. The above-mentioned stable conductive network structure means: on the one hand, a two-dimensional conductive network structure between silver nanoparticles and carbon nanotubes or their derivatives; on the other hand, a three-dimensional conductive network structure between MXene or its derivative, carbon nanotubes or their derivative, and silver nanoparticles.

[0041] (2) The method of wet spinning in this application solves the problem of the bonding firmness between MXene or its derivative and other components in conductive fibers. Compared with the prior art, this application provides a simple method for preparing fibers. The spinning process is simple and the production is flexible. The produced fibers not only have a high conductivity, but also have characteristics such as high tensile strength and good hand feeling, and can fully meet the requirements of subsequent processes such as textile. The conductive fibers obtained by the above materials and preparation methods have good conductive properties. In addition to being used as wearable devices and anti-static materials, they can also absorb radar, infrared rays, ultraviolet rays, etc. and are applied to many special fields.

[0042] (3) The tensile strength of the flexible MXene polymer composite fiber prepared by the method of this application is 536.14 MPa, the strain is 986.08%, and after 650 times of friction, the conductivity is within 1762 - 1792 S / cm; after 240 times of water washing, the conductivity is within 1765 - 1792 S / cm, indicating that the conductive synthetic fiber has mechanical reliability and long-term durability. Description of the Drawings

[0043] The drawings are used to provide a further understanding of this application, and constitute a part of the specification. Together with the embodiments of this application, they are used to explain this application and do not constitute a limitation to this application. In the drawings:

[0044] Figure 1 Shows a flowchart of the preparation method of the flexible MXene polymer composite fiber provided by an exemplary embodiment of this application;

[0045] Figure 2Shows the electron microscope image of the flexible MXene polymer composite fiber provided by an exemplary embodiment of the present application;

[0046] Figure 3 Shows the synthesis mechanism and chemical structure schematic diagram between the MXene (Ti3C2Tx) mixed conductive material and the dopamine: polystyrene sulfonic acid of the soft interlocking insert TPU. Detailed implementation manners

[0047] Next, the technical solutions in the embodiments of the present application will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present application.

[0048] Among them, the same components are denoted by the same reference numerals. It should be noted that the terms "front", "rear", "left", "right", "upper" and "lower" used in the following description refer to the directions in the accompanying drawings of the present application specification, and the terms "bottom surface" and "top surface", "inner" and "outer" refer to facing or away from a specific component respectively. In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include one or more of such features. In the description of the present application specification, "a plurality of" means two or more.

[0049] The present application will be further described below in conjunction with the accompanying drawings and embodiments.

[0050] First, a brief introduction to the nouns involved in the embodiments of the present application:

[0051] TPU, short for Thermoplastic Urethane, is a thermoplastic polyurethane elastomer. TPU is a polymer material formed by the copolymerization of diphenylmethane diisocyanate (MDI), toluene diisocyanate (TDI), macromolecular polyols and chain extenders.

[0052] DMF, dimethylformamide (DMF or N,N-dimethylformamide) is a transparent liquid that can be miscible with water and most organic solvents, and it is a commonly used solvent for chemical reactions.

[0053] Tris buffer solution refers to Tris-HCl (tris(hydroxymethyl)aminomethane hydrochloride buffer solution), which is specifically obtained by mixing a tris(hydroxymethyl)aminomethane (Tris) solution with hydrochloric acid and then diluting with water.

[0054] MXene, as a two-dimensional layered transition metal carbide, nitride or carbonitride, has a two-dimensional layered graphene-like structure. Due to its graphene-like two-dimensional layered structure and chemical composition, it has high electrical conductivity (≈104 S / cm), high specific surface area (≈106 m 2 / g) and excellent mechanical properties (Young's modulus ≈ 330 GPa), which has attracted extensive attention from researchers at home and abroad. It is one of the core materials for constructing flexible sensor devices.

[0055] Carboxylated CNTs are obtained by etching and ultrasonic treatment of carbon nanotubes in a mixed acid solution of concentrated sulfuric acid and concentrated nitric acid, and then stirring at 70 - 80 °C.

[0056] Figure 1 The flowchart of the preparation method of the flexible MXene polymer composite fiber provided by an exemplary embodiment of the present application is shown. The method includes the following steps:

[0057] Step S1: Add TPU to the DMF solution and stir with a constant temperature magnetic stirrer to obtain a TPU spinning dope.

[0058] In step S1 of this embodiment, the content of TPU is 0.5 - 10.5 g / L; the mass-volume concentration of DMF is 40 - 300 mg / mL; the constant temperature of the constant temperature magnetic stirrer is 40 - 60 °C, the stirring speed is 150 - 650 rpm, and the stirring time is 3 - 12 h.

[0059] Step S2: Add MXene or its derivatives and dopamine or its derivatives: polystyrene sulfonic acid to the DMF solution in sequence and stir with a constant temperature magnetic stirrer to obtain a MXene mixed solution.

[0060] In step S2 of this embodiment, the concentration of MXene or its derivatives is 15 - 75 mol / L; the concentration of dopamine or its derivatives: polystyrene sulfonic acid is 0.2 - 10.2 mol / L; the mass-volume concentration of DMF is 10 - 30 mg / mL; the constant temperature of the constant temperature magnetic stirrer is 40 - 60 °C, the stirring speed is 250 - 850 rpm, and the stirring time is 15 - 55 min. Optionally, the dopamine or its derivatives include, but are not limited to, one of dopamine hydrochloride (DA·HCl), polydopamine-like (DATA), N-3,4-dihydroxyphenethyl acrylamide (DAA). Optionally, the MXene or its derivatives include, but are not limited to, one of titanium carbide (Ti3C2T x )、titanium dicarbide (Ti2C), niobium dicarbide (Nb2C), vanadium dicarbide (V2C), titanium carbonitride (Ti2CN), titanium dinitride (Ti2N).

[0061] Step S3: Add carbon nanotubes or their derivatives and silver powder into the MXene mixed solution in sequence. After stirring with a constant-temperature magnetic stirrer, a MXene mixed conductive solution is obtained.

[0062] In step S3 of this embodiment, the concentration of carbon nanotubes or their derivatives is 0.5 - 12.5 mol / L, and the concentration of silver powder is 2.5 - 6.5 mol / L; the constant temperature of the constant-temperature magnetic stirrer is 40 - 60 °C, the stirring speed is 100 - 700 rpm, and the stirring time is 4 - 12 h. Optionally, the carbon nanotubes or their derivatives include one of amino-functionalized carbon nanotubes, carboxylated carbon nanotubes, hydroxylated carbon nanotubes, and CNTs-AM.

[0063] Step S4: Slowly pour the MXene mixed conductive solution into the TPU spinning dope. After stirring with a constant-temperature magnetic stirrer, a MXene mixed spinning solution is obtained.

[0064] In step S4 of this embodiment, the constant temperature of the constant-temperature magnetic stirrer is 40 - 60 °C, the stirring speed is 150 - 650 rpm, and the stirring time is 4 - 8 h.

[0065] Step S5: Inject the MXene mixed spinning solution into a syringe. Perform wet spinning at room temperature. Use an injection pump to extrude the MXene mixed spinning solution into a DMF aqueous coagulation bath. After the as-spun fiber solidified in the coagulation bath is subjected to three-fold mechanical drawing, then perform heat setting treatment. Finally, wind the fiber after heat setting treatment onto a uniformly rotating hot roller for collection and drying to obtain a flexible MXene polymer composite fiber.

[0066] In step S5 of this embodiment, the volume capacity of the syringe is 5 - 40 mL, and the inner diameter of the needle is 0.2 - 0.8 mm; the spinning rate of wet spinning is 0.5 - 10.5 mL / h; the length of the coagulation bath is 90 cm; the temperature of the heat setting treatment is 60 °C; the drying temperature for collecting and drying the fiber after heat setting treatment wound onto a uniformly rotating hot roller is 25 - 45 °C, and the drying time is 4 - 8 h.

[0067] Figure 2 The electron micrograph of the flexible MXene polymer composite fiber provided by an exemplary embodiment of the present application is shown. The flexible MXene polymer composite fiber is prepared by the preparation method of the flexible MXene polymer composite fiber described in the above embodiment.

[0068] In summary, in this application, dopamine or its derivative: polystyrene sulfonic acid is used as a valence bond donor and a soft interlocker to crosslink and compound MXene with TPU, carbon nanotubes or their derivatives, and silver nanoparticles to construct a stable conductive network structure. Then, a flexible MXene polymer composite fiber is prepared by a wet spinning technique. This crosslinking and compounding means that, on the one hand, amino groups, phenolic hydroxyl groups, etc. in dopamine or its derivative: polystyrene sulfonic acid are intercalated and locked with hydrophilic groups of MXene or its derivatives through hydrogen bonds, π-π stacking, electrostatic interactions, etc., inhibiting the oxidative decomposition of MXene or its derivatives and maintaining its conductivity; on the other hand, MXene or its derivatives and TPU, carbon nanotubes or their derivatives, and silver nanoparticles construct a stable conductive network structure through metal chelation, covalent reactions, hydrophobic interactions, etc. The above-mentioned stable conductive network structure means: on the one hand, a two-dimensional conductive network structure between silver nanoparticles and carbon nanotubes or their derivatives; on the other hand, a three-dimensional conductive network structure between MXene or its derivatives, carbon nanotubes or their derivatives, and silver nanoparticles. In addition, this application uses the wet spinning method to solve the problem of the bonding firmness between MXene or its derivatives and other components in the conductive fiber. Compared with the prior art, this application provides a simple method for preparing fibers, with a simple spinning process and flexible production. The produced fibers not only have a high conductivity but also have high tensile strength and good handfeel, fully meeting the requirements of subsequent processes such as textile. The conductive fibers obtained by the above materials and preparation methods have good conductive properties and can not only be used as wearable devices and antistatic materials but also absorb radar, infrared rays, ultraviolet rays, etc., and are applied to many special fields.

[0069] To better understand this application, the following uses a specific embodiment to further illustrate this application. It should be noted that the embodiments described in this specific embodiment are only a part of the embodiments of this application and do not limit the protection scope of this application.

[0070] A method for preparing a flexible MXene polymer composite fiber, the method comprising the following steps:

[0071] Step S1: Add TPU to a DMF solution, and stir with a constant temperature magnetic stirrer to obtain a TPU spinning dope.

[0072] In step S1 of this embodiment, the content of TPU is 4.5 g / L; the mass-volume concentration of DMF is 60 mg / mL; the constant temperature of the constant temperature magnetic stirrer is 45 °C, the stirring speed is 350 rpm, and the stirring time is 8 h.

[0073] Step S2: Add MXene (Ti3C2T x) and dopamine: Polystyrene sulfonic acid was added to the DMF solution in sequence. After stirring with a constant temperature magnetic stirrer, a mixed solution of MXene (Ti3C2T x ) was obtained.

[0074] In step S2 of this embodiment, the mass-volume concentration of DMF was 20 mg / mL; the concentration of MXene (Ti3C2T x ) was 60 mol / L; the concentration of dopamine: polystyrene sulfonic acid was 6.5 mol / L; the constant temperature of the constant temperature magnetic stirrer was 45 °C, the stirring speed was 400 rpm, and the stirring time was 45 min.

[0075] Step S3: CNTs-AM and silver powder were added to the mixed solution of MXene (Ti3C2T x ) in sequence. After stirring with a constant temperature magnetic stirrer, a mixed conductive solution of MXene (Ti3C2T x ) was obtained.

[0076] In step S3 of this embodiment, the concentration of CNTs-AM was 4.8 mol / L, and the concentration of silver powder was 3.2 mol / L; the constant temperature of the constant temperature magnetic stirrer was 45 °C, the stirring speed was 400 rpm, and the stirring time was 4 h.

[0077] Step S4: The mixed conductive solution of MXene (Ti3C2T x ) was slowly poured into the TPU spinning dope. After stirring with a constant temperature magnetic stirrer, a mixed spinning solution of MXene (Ti3C2T x ) was obtained.

[0078] In step S4 of this embodiment, the constant temperature of the constant temperature magnetic stirrer was 45 °C, the stirring speed was 450 rpm, and the stirring time was 6 h.

[0079] Step S5: The mixed spinning solution of MXene (Ti3C2T x ) was injected into a syringe. Wet spinning was carried out at room temperature. The mixed spinning solution of MXene (Ti3C2T x ) was extruded into a DMF aqueous coagulation bath by using an injection pump. The as-spun fibers solidified by the coagulation bath were subjected to three-fold mechanical drawing, and then heat-setting treatment was carried out. Finally, the fibers after heat-setting treatment were wound onto a uniformly rotating hot roller for collection and drying to obtain the flexible MXene polymer composite fiber as shown in Figure 2 Figure.

[0080] In step S5 of this embodiment, the volume capacity of the syringe is 35 mL, the inner diameter of the needle is 0.5 mm; the spinning rate of wet spinning is 4.2 mL / h; the length of the coagulation bath is 90 cm; the temperature of the heat setting treatment is 60 °C; the drying temperature during the collection and drying of the fibers wound around a uniformly rotating hot roller after the heat setting treatment is 40 °C, and the drying time is 6 h.

[0081] It should be noted that acrylamide (AM) and N,N-dimethylformamide (DMF) used in this embodiment are purchased from Tianjin Damao Chemical Reagent Factory, thionyl chloride (SOCl2) is purchased from Tianjin Tianli Chemical Reagent Co., Ltd., carboxylated carbon nanotubes (CNTs-COOH), nano silver powder and Ti3AlC2MAX are purchased from Nanjing Xianfeng Nano Materials Technology Co., Ltd., lithium fluoride LiF analytical pure (AR) is purchased from Shanghai Macklin Biochemical Technology Co., Ltd., hydrochloric acid HCl analytical pure (AR) is purchased from Zhuhai Huachengda Chemical Co., Ltd., polystyrene sulfonic acid (PSS)-(C8H8O3S) n is purchased from Jiangsu Hongbo Chemical Co., Ltd., dopamine hydrochloride is purchased from Guorui Pharmaceutical Co., Ltd. of China National Pharmaceutical Group, and other solutions not specifically described are water-based solvents.

[0082] Furthermore, the preparation method of CNTs-AM powder in the example includes:

[0083] Place 4.0 g of carboxylated CNTs in 60 mL of DMF, ultrasonically disperse for 30 min, add 120 mL of SOCl2, and magnetically stir and react at 75 °C for 12 h;

[0084] After cooling, filter, wash with DMF to remove the unreacted SOCl2 on its surface;

[0085] Ultrasonically disperse the filter cake in a mixture of 20 mL of ethyl acetate and 160 mL of LEDA, stir and react at 100 °C for 8 h, carry out suction filtration, wash with deionized water, and dry to constant weight at 40 °C to obtain amino-functionalized CNTs;

[0086] Ultrasonically disperse the amino-functionalized CNTs in 50 mL of absolute ethanol, add 60 g of AM, magnetically stir and react at room temperature for 78 h. After the reaction is completed, filter using a Buchner funnel, wash repeatedly with ethanol, and dry the filter cake at 70 °C for 48 h, denoted as CNTs-AM.

[0087] Furthermore, the preparation method of dopamine: polystyrene sulfonic acid, that is, DA:PSS powder in the example includes:

[0088] First, prepare a tris(hydroxymethyl)aminomethane (Tris) buffer solution and adjust its pH to 8.5 with dilute hydrochloric acid;

[0089] Weigh 4 g of sodium polystyrene sulfonate with a molecular weight of 70 kDa and add it to Tris buffer solution, then stir for 5 min;

[0090] Subsequently, add 2 g of dopamine hydrochloride and continue stirring, and react for 12 h under normal temperature and pressure;

[0091] Dopamine hydrochloride monomers are prone to oxidation in the air. The color of the reaction system gradually changes from colorless to light yellow and finally to dark brown;

[0092] The product after the reaction is dialyzed with a dialysis membrane with a molecular weight of 1000 Da to completely remove inorganic salts, unreacted monomers or oligomers of dopamine, and buffer substances;

[0093] The dopamine dispersion system after removing impurities is further freeze-dried to obtain a solid product for characterization. The solid product has good solubility in water (>10 mg / mL) and can also be dissolved in the organic solvent DMSO. The synthesized complex is abbreviated as DA:PSS.

[0094] Furthermore, the preparation method of the MXene nanosheet powder in the example includes:

[0095] MXene (Ti3C2T x ) is prepared by selectively etching the Al layer from the MAX phase (Ti3AlC2) using an aqueous solution of LiF / HCl. First, disperse 2.5 g of LiF in 50 mL of hydrochloric acid solution (12 mol / L) under stirring;

[0096] Then, slowly add 2.5 g of MAX (Ti3AlC2) to the solution;

[0097] Subsequently, react the solution at 40 °C for 48 hours under magnetic stirring to completely etch away the Al layer;

[0098] After 48 hours, dilute the obtained product with deionized water, centrifuge, and repeat several times until the pH of the centrifuged supernatant is greater than 6.0;

[0099] Then, freeze-dry the centrifuged precipitate for 12 hours to obtain MXene nanosheets;

[0100] To obtain few-layer or single-layer MXene nanosheets, the above-obtained MXene nanosheets are further exfoliated. Mix the MXene nanosheets with an intercalating agent, and ultrasonically treat for a period of time in an ice bath using a cell disruptor, and then centrifuge to collect the lower precipitate;

[0101] Mix the above precipitate with deionized water, and then ultrasonically disperse MXene evenly in water. After centrifugation, collect the supernatant, and this supernatant is the few-layer MXene dispersion;

[0102] The dispersion liquid is then freeze-dried to obtain few-layer MXene nanosheet powder.

[0103] Next, the performance of the flexible MXene polymer composite fiber obtained above is tested:

[0104] 1. Mechanical property test

[0105] At room temperature, the fiber is subjected to a tensile fracture test using a UTM2203 servo-controlled universal testing machine from Shenzhen Sansi Zongheng Technology Co., Ltd. The tensile rate is 10 mm / min, and at least 5 samples of each content are tested and their average value is calculated.

[0106] 1.1. The tensile strength of the specimen is calculated using the following formula (1):

[0107]

[0108] In the formula, σ is the tensile strength (Pa); P is the maximum load (N); S is the cross-sectional area of the specimen (m 2 ²).

[0109] 1.2. The elongation at break of the specimen is calculated using the following formula (2):

[0110]

[0111] In the formula: ε is the elongation at break; L0 is the initial length of the specimen (mm); L is the length of the specimen after stretching (mm).

[0112] 1.3. The Young's tensile modulus of the specimen is calculated using the following formula (3):

[0113]

[0114] In the formula, E is the Young's tensile modulus of the specimen (MPa); ε is a certain strain in the elastic region of the specimen; σ is the tensile strength corresponding to the strain ε in the elastic region of the specimen (MPa).

[0115] 2. Conductivity test

[0116] A 5-cm-long fiber is intercepted, silver paste is coated at both ends and copper tape is connected. At least 5 specimens of each content are tested, and their average value is obtained. The volume conductivity of the specimen is calculated using the following formula (4):

[0117]

[0118] In the formula, σ is the volume conductivity of the specimen (S / cm -1 ²); R is the volume resistance of the specimen (Ω / cm); L is the length of the specimen strip between the two electrodes (cm); S is the cross-sectional area of the specimen (cm2 )

[0119] 3. Friction resistance test

[0120] The test is carried out with reference to the national standard GB / T21196.

[0121] 4. Water resistance test

[0122] The test is carried out with reference to the literature (Dca B, Xue B, Jpa B, et al. In situ hydrothermal growth of CuNPs on knitted fabrics through polydopamine templates for heating and sensing[J]. Chemical Engineering Journal, 382.).

[0123] The test results are as follows:

[0124] Figure 3 Shows the synthesis mechanism and chemical structure schematic diagram between the MXene (Ti3C2T x ) mixed conductive material and the dopamine: polystyrene sulfonic acid of the soft interlocking insert TPU. From Figure 3 it can be seen that:

[0125] On the one hand, the amino groups, phenolic hydroxyl groups, etc. in dopamine 1: polystyrene sulfonic acid 2 are intercalated and locked with the hydrophilic groups of MXene (Ti3C2T x )5 through hydrogen bonds 3, 4 and other interactions, inhibiting the oxidative decomposition of MXene or its derivatives and maintaining its conductivity; on the other hand, MXene (Ti3C2T x ) constructs a stable conductive network structure with TPU 8, CNTs-AM 9, and silver nanoparticles 10 through metal chelation 6, covalent reaction, hydrogen bond interaction 7, etc.

[0126] After testing, the tensile strength of the flexible MXene polymer composite fiber is 536.14 MPa, the strain is 986.08%, and the conductivity is 1792 S / cm.

[0127] The test results of the friction resistance and water washing resistance of the MXene polymer composite fiber prepared by the preparation method of this application are shown in Table 1 and Table 2 below. After 650 times of friction, the conductivity of the flexible fabric-based strain sensor is within 1762 - 1792 S / cm; after 240 times of ultrasonic water washing, the conductivity is only within 1765 - 1792 S / cm.

[0128] Table 1. Test results of friction resistance performance

[0129] Number of friction resistance / times Conductivity / S / cm 0 1792 50 1789 150 1782 250 1778 350 1772 450 1769 550 1767 650 1762

[0130] Table 2, Test results of wash resistance

[0131] Ultrasonic water washing / minutes Conductivity / S / cm 0 1792 20 1790 40 1788 80 1782 120 1775 160 1771 200 1769 240 1765

[0132] The above are only the preferred embodiments of the present application. It should be pointed out that for those of ordinary skill in the art, without departing from the principle of the present application, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present application.

Claims

1. A preparation method of a flexible MXene polymer composite fiber, characterized in that, It includes the following steps: S1. Add TPU into the DMF solution, and stir it with a constant temperature magnetic stirrer to obtain a TPU spinning dope; S2. Add MXene or its derivative, and dopamine or its derivative: polystyrene sulfonic acid into the DMF solution in sequence, and stir it with a constant temperature magnetic stirrer to obtain a MXene mixed solution; S3. Add carbon nanotubes or their derivatives and silver powder into the MXene mixed solution in sequence, and stir it with a constant temperature magnetic stirrer to obtain a MXene mixed conductive solution; S4. Slowly pour the MXene mixed conductive solution into the TPU spinning dope, and stir it with a constant temperature magnetic stirrer to obtain a MXene mixed spinning solution; S5. Inject the MXene mixed spinning solution into a syringe, perform wet spinning at room temperature, extrude the MXene mixed spinning solution into a DMF aqueous coagulation bath with an injection pump, perform three-fold mechanical drawing on the nascent fibers solidified and formed by the coagulation bath, then perform heat setting treatment, and finally wind the fibers after heat setting treatment onto a uniformly rotating hot roller for collection and drying to obtain flexible MXene polymer composite fibers.

2. The preparation method of the flexible MXene polymer composite fiber according to claim 1, characterized in that, In the step S1: The content of the TPU is 0.5 - 10.5 g / L; The mass-volume concentration of the DMF is 40 - 300 mg / mL; The constant temperature of the constant temperature magnetic stirrer is 40 - 60 °C, the stirring speed is 150 - 650 rpm, and the stirring time is 3 - 12 h.

3. The preparation method of the flexible MXene polymer composite fiber according to claim 1, wherein, In the step S2: The concentration of the MXene or its derivative is 15 - 75 mol / L; The concentration of the dopamine or its derivative: polystyrene sulfonic acid is 0.2 - 10.2 mol / L; The mass-volume concentration of the DMF is 10 - 30 mg / mL; The constant temperature of the constant temperature magnetic stirrer is 40 - 60 °C, the stirring speed is 250 - 850 rpm, and the stirring time is 15 - 55 min.

4. The preparation method of the flexible MXene polymer composite fiber according to claim 1, characterized in that, In the step S2: The dopamine or its derivative includes one of dopamine hydrochloride, polydopamine-like, and N-3,4-dihydroxyphenethyl acrylamide.

5. The preparation method of the flexible MXene polymer composite fiber according to claim 1, characterized in that, In the step S2: The MXene or its derivative includes one of titanium carbide, dititanium carbide, dinbium carbide, divanadium carbide, titanium carbonitride, and titanium nitride.

6. The preparation method of the flexible MXene polymer composite fiber according to claim 1, characterized in that, In the step S3: The concentration of the carbon nanotubes or their derivatives is 0.5 - 12.5 mol / L, and the concentration of the silver powder is 2.5 - 6.5 mol / L; The constant temperature of the constant temperature magnetic stirrer is 40 - 60 °C, the stirring speed is 100 - 700 rpm, and the stirring time is 4 - 12 h.

7. The preparation method of the flexible MXene polymer composite fiber according to claim 1, wherein, In the step S3: The carbon nanotubes or their derivatives include one of amino-functionalized carbon nanotubes, carboxyl-functionalized carbon nanotubes, hydroxyl-functionalized carbon nanotubes, and CNTs-AM.

8. The preparation method of the flexible MXene polymer composite fiber according to claim 1, wherein, In the step S4: The constant temperature of the constant temperature magnetic stirrer is 40 - 60 °C, the stirring speed is 150 - 650 rpm, and the stirring time is 4 - 8 h.

9. The preparation method of the flexible MXene polymer composite fiber according to claim 1, wherein In the step S5: The volume capacity of the syringe is 5 - 40 mL, and the inner diameter of the needle is 0.2 - 0.8 mm; The spinning rate of the wet spinning is 0.5 - 10.5 mL / h; The length of the coagulation bath is 90 cm; The temperature of the heat setting treatment is 60 °C; In the step of winding the fibers after the heat setting treatment onto a uniformly rotating hot roller for collection and drying, the drying temperature is 25 - 45 °C, and the drying time is 4 - 8 h.

10. A flexible MXene polymer composite fiber, which is prepared by the preparation method of the flexible MXene polymer composite fiber according to any one of claims 1 to 9.

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