Flexible PEDOT:PSS Conductive Composite Fibers and Their Preparation Method

Abstract

This application relates to a flexible PEDOT:PSS conductive composite fiber and its preparation method, and pertains to the field of conductive fibers. In this application, TPU functionalized with gallic acid or its derivatives and hexamethylenediamine is used as the matrix, and a valence bond cross-linking strategy is adopted to effectively integrate PEDOT, carbon nanotube and its derivatives, MXene and its derivatives, and metal silver nanoparticles to construct a multi-dimensional conductive network. The problems of poor dispersion and easy aggregation of PEDOT in conductive fibers are solved, and at the same time, the problem that it is difficult to simultaneously have both high conductivity and high strength in existing PEDOT:PSS conductive composite fibers is solved.

Description

Technical Field

[0001] This application relates to the technical field of conductive fibers, and particularly to a flexible PEDOT:PSS conductive composite fiber and a preparation method thereof. Background Art

[0002] In recent years, intelligent fibers and textiles have been pursued by numerous research teams. Conductive fibers based on conductive polymers have become an important type of intelligent fiber with good application prospects due to their good electromagnetic shielding, antistatic properties, and the flexible characteristics of polymers. Among the methods for preparing conductive fibers, wet spinning for preparing conductive fibers is simple in operation, has the potential for industrial production, and has good application prospects. In particular, poly(3,4-ethylenedioxythiophene) (PEDOT) fibers have advantages such as high electrical conductivity, good stability, and good optical transparency. However, it is an insoluble polymer itself, resulting in difficult processing and limiting its application. After doping with polystyrene sulfonic acid (PSS), a uniformly dispersed and stable PEDOT:PSS aqueous dispersion can be obtained, solving the problem of difficult processing of PEDOT. Under certain conditions, it can be used to prepare continuous fibers through a simple wet spinning technique, and has broad application prospects in intelligent fabrics, wearable electronic devices, etc. For example: OKUZAKI et al. prepared pure spun PEDOT:PSS fibers with an electrical conductivity of about 0.1 S / cm in an At-IPA coagulation bath system (OKUZAKI H, ISHIHAR A M. Spinning and characterization of conducting microfibers. Macromolecular Rapid Communications[J], 2003, 24(3): 261-264.); The PEDOT:PSS fibers wet-spun by the novel water-ethanol system coagulation bath used by YUAN et al. had an electrical conductivity of 38 S / cm after being treated with EG (YUAN D, LI B, CHENG J, et al. Twisted yarns for fiber-shaped supercapacitors based on wetspun PEDOT:PSS fibers from aqueous coagulation[J]. Journal of Materials Chemistry A, 2016, 4(30): 11616-11624). In addition, the patent (CN106381571A) mentions a PEDOT:PSS fiber and a preparation method thereof. The patent uses a mixed solution of inorganic salts, ethanol, and water as the coagulation bath, and prepares wet-spun PEDOT:PSS fibers with an electrical conductivity of 400-850 S / cm through a simple chemical treatment method.

[0003] However, there are still some problems with the PEDOT:PSS fibers disclosed in the related art: First, the solid content of the PEDOT:PSS aqueous dispersion is low and the viscosity is low, making it difficult and not easy to operate directly for wet spinning. The fibers often break in the coagulation bath or in the air, and it is difficult to obtain continuous fiber filaments. Second, due to the existence of the conjugated structure of the PEDOT molecular chain, the molecular chain has a large rigidity. Therefore, the prepared PEDOT:PSS pure spun fibers are brittle, rigid, poor in toughness, and have poor mechanical properties, which are not suitable for subsequent processing and applications. To solve these problems, researchers blend a fiber-forming polymer material with PEDOT:PSS and prepare composite conductive PEDOT:PSS fibers by wet spinning. Seyedin et al. developed PU / PEDOT:PSS fibers with a conductivity of 9.4 S / cm by wet spinning (Seyedin, S.; Razal, J.M.; Innis, P.C.; Jeiranikhameneh, A.; Beirne, S.; Wallace, G.G. Knitted Strain Sensor Textiles of Highly Conductive All-Polymeric Fibers. ACS Appl. Mater. Interfaces 2015, 7, 21150–21158.). However, the introduction of the fiber-forming polymer material will reduce the uneven dispersion of PEDOT:PSS. At the same time, the conductive PEDOT segments are embedded in the insulating PSS, which hinders the efficient aggregation of the PEDOT segments and is difficult to form a continuous conductive phase, thus limiting the conductivity of the conductive composite fibers. Therefore, how to prepare fibers with strong continuity, high strength, and good conductivity through a simple method is an urgent problem to be solved. Summary of the Invention

[0004] The purpose of this application is to provide a flexible PEDOT:PSS conductive composite fiber and its preparation method to solve the problem that the introduction of a fiber-forming polymer insulating material in the wet-spun PEDOT:PSS conductive composite fiber prepared by the existing method leads to the difficulty of efficient aggregation and uniform dispersion of PEDOT segments, thereby affecting 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 PEDOT:PSS conductive 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 PEDOT:PSS to the mixed solution containing gallic acid or its derivatives, hexamethylenediamine, and Tris buffer. After stirring with a thermostatic magnetic stirrer, a PEDOT:PSS mixed solution is obtained.

[0009] S3. Add CNTs-DMPA, MXene, and silver powder to the PEDOT:PSS mixed solution in sequence. After stirring with a thermostatic magnetic stirrer, a PEDOT:PSS mixed conductive solution is obtained.

[0010] S4. Slowly pour the PEDOT:PSS mixed conductive solution into the TPU spinning dope. After stirring with a thermostatic magnetic stirrer, a PEDOT:PSS mixed spinning solution is obtained.

[0011] S5. Inject the PEDOT:PSS mixed spinning solution into a syringe. Perform wet spinning at room temperature. Use an injection pump to extrude the PEDOT:PSS mixed spinning solution into a DMF aqueous coagulation bath. After the as-spun fibers solidified in the coagulation bath are subjected to three-fold mechanical drawing, then heat setting treatment is carried out. Finally, the fibers after heat setting treatment are wound onto a uniformly rotating hot roller for collection and drying to obtain flexible PEDOT:PSS conductive composite fibers.

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

[0013] The content of the TPU is 2 - 10 g / L;

[0014] The mass-volume concentration of the DMF is 20 - 200 mg / mL;

[0015] The constant temperature of the thermostatic magnetic stirrer is 40 - 60 °C, the stirring speed is 200 - 660 rpm, and the stirring time is 4 - 10 h.

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

[0017] The concentration of the PEDOT:PSS is 10 - 60 mol / L;

[0018] The concentration of the gallic acid or its derivatives is 15 - 45 mol / L;

[0019] The concentration of the hexamethylenediamine is 15 - 65 mol / L;

[0020] The concentration of the Tris buffer is 0.5 - 4.5 mol / L.

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

[0022] The pH of the solution after adding PEDOT:PSS to the mixed solution containing gallic acid or its derivative, hexamethylenediamine, and Tris buffer is 8 - 10;

[0023] The constant temperature of the constant temperature magnetic stirrer is 40 - 60 °C, the stirring speed is 200 - 660 rpm, and the stirring time is 10 - 40 min.

[0024] In a possible implementation, in step S2:

[0025] The gallic acid or its derivative includes one of pyrogallic acid, gallic acid, (Z)-3,4,5,4'-tetramethoxy-3'-hydroxystilbene, and GA butyl ester.

[0026] In a possible implementation, in step S3:

[0027] The concentrations of CNTs-DMPA, MXene, and silver powder are 5 - 10 mol / L, 2 - 6 mol / L, and 4 - 15 mol / L, respectively.

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

[0029] The constant temperature of the constant temperature magnetic stirrer is 40 - 60 °C;

[0030] The initial stirring speed of the constant temperature magnetic stirrer is set to 200 - 600 rpm and stirred continuously for 0.5 - 4.5 h; then the stirring speed is adjusted to 500 - 800 rpm and stirred continuously for 10 - 60 min; finally, the stirring speed is adjusted to 900 - 2500 rpm and stirred continuously for 4 - 12 h.

[0031] In a possible implementation, in step S4:

[0032] The constant temperature of the constant temperature magnetic stirrer is 40 - 60 °C, the stirring speed is 200 - 660 rpm, and the stirring time is 2 - 12 h.

[0033] In a possible implementation, in step S5:

[0034] The volume capacity of the syringe is 5 - 40 mL, and the inner diameter of the needle is 0.2 - 0.8 mm;

[0035] The spinning rate of the wet spinning is 0.5 - 6.5 mL / h;

[0036] The length of the coagulation bath is 90 cm;

[0037] The temperature of the heat setting treatment is 60 °C;

[0038] In the process of collecting and drying by winding the heat-set fiber around a uniformly rotating hot roller, the drying temperature is 20-40 °C and the drying time is 6-12 h.

[0039] On the other hand, the present application also provides a flexible PEDOT:PSS conductive composite fiber, which is prepared by the preparation method of the above flexible PEDOT:PSS conductive composite fiber.

[0040] The beneficial effects brought by the technical solution provided by the present application at least include:

[0041] (1) The flexible PEDOT:PSS conductive composite fiber of the present application uses gallic acid or its derivatives and hexamethylenediamine-functionalized TPU as the matrix, and a multi-dimensional conductive network is constructed in the matrix by using a valence bond cross-linking strategy; the gallic acid or its derivatives and hexamethylenediamine functional modification means that the amine group and phenolic hydroxyl group in gallic acid or its derivatives and hexamethylenediamine are associated by hydrogen bonds on the one hand to achieve high phase separation of PSS and PEDOT, optimize the conformation of PEDOT molecular chains, and enable PEDOT to form an ordered conductive continuous phase, and on the other hand, they are bonded to TPU through coordination, electrostatic interaction, hydrophobic interaction and even covalent reaction; the valence bond cross-linking strategy refers to the process of obtaining a stable conductive network structure through dynamic valence bond cross-linking between different substances; the multi-dimensional conductive network structure refers to: on the one hand, a two-dimensional conductive network structure between PEDOT and silver nanoparticles, and on the other hand, a three-dimensional conductive network structure between MXene or its derivatives and carbon nanotube or its derivatives and silver nanoparticles.

[0042] (2) The present application uses the wet spinning method to solve the problems of dispersion and re-agglomeration of conductive nanomaterials. Compared with the prior art, the present application provides a simple method for preparing fibers, which has the advantages of simple equipment, simple spinning process, environmental protection, and significant improvement in effect. It does not require expensive and complex equipment and is easy to realize large-scale production. In addition, the conductive composite fiber prepared by this process has good flexibility, tensile properties and large-scale integration properties, and can be widely used in wearable devices.

[0043] (3) The conductive composite fiber prepared by the valence bond cross-linking strategy of the present application improves the problems of poor dispersion and easy agglomeration of PEDOT. At the same time, the cross-linking of carbon nanotubes and their derivatives and MXene and their derivatives with metal silver nanoparticles further improves the continuity and controllability of the three-dimensional conductive network structure, enabling the conductive fillers to be evenly dispersed, saving raw materials while being beneficial to improving the conductive performance and structural stability of the composite material, and providing new ideas for the development of new conductive fibers.

[0044] (4) The tensile strength of the PEDOT:PSS conductive composite fiber prepared by the method of the present application is 780.62 MPa, the strain is 1204.28%, and after 650 times of friction, the conductivity is within 2369 - 2405 S / cm; after 240 times of water washing, the conductivity is within 2365 - 2405 S / cm. Description of the Drawings

[0045] The drawings are used to provide a further understanding of the present application, and constitute a part of the specification. Together with the embodiments of the present application, they are used to explain the present application, and do not constitute a limitation to the present application. In the drawings:

[0046] Figure 1 shows a flowchart of a method for preparing a flexible PEDOT:PSS conductive composite fiber provided by an exemplary embodiment of the present application;

[0047] Figure 2 shows an electron micrograph of a flexible PEDOT:PSS conductive composite fiber provided by an exemplary embodiment of the present application;

[0048] Figure 3 shows a schematic diagram of the mechanism of the action of gallic acid or its derivatives doped with hexamethylenediamine on the chemical structure of PEDOT:PSS;

[0049] Figure 4 shows a schematic diagram of the synthesis mechanism and chemical structure between a PEDOT conductive composite material and TPU functionally modified with gallic acid or its derivatives. Detailed Embodiments

[0050] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the 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. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present application without creative efforts shall fall within the scope of protection of the present application.

[0051] 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 drawings of the specification of the present application, 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 construed as indicating or implying relative importance or implicitly indicating the number 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 specification of the present application, "a plurality of" means two or more.

[0052] The present application will be further described below in conjunction with the accompanying drawings and embodiments.

[0053] First, a brief introduction to the terms involved in the embodiments of the present application is given:

[0054] TPU, short for Thermoplastic Urethane, is a thermoplastic polyurethane elastomer. TPU is a polymer material formed by the copolymerization reaction of diphenylmethane diisocyanate (MDI), toluene diisocyanate (TDI), macromolecular polyols, and chain extenders.

[0055] DMF, dimethylformamide (DMF or N,N-dimethylformamide) is a transparent liquid that can be miscible with water and most organic solvents. It is a commonly used solvent for chemical reactions.

[0056] Tris buffer refers to Tris-HCl (Tris(hydroxymethyl)aminomethane hydrochloride buffer). Specifically, it is obtained by mixing Tris(hydroxymethyl)aminomethane (Tris) solution with hydrochloric acid and then diluting with water.

[0057] CNTs-DMPA refers to CNTs-DMPA obtained by surface modification of carboxylated CNTs with thionyl chloride (SOCl2) and triethylamine (TEA), and then crosslinking with 2,2-dimethylolpropionic acid (DMPA).

[0058] 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.

[0059] GA butyl ester was prepared by esterifying and modifying GA with concentrated sulfuric acid as the catalyst and n-butanol as the modifier. Gallic acid (GA) is a natural phenolic compound containing three hydroxyl groups, which is extracted from the polyphenol crude extract of fruits, nuts, flowers and other substances; and a significant characteristic of natural polyphenols is their antioxidant activity; therefore, a significant characteristic of GA is its antioxidant property; the three phenolic hydroxyl groups in the GA molecular structure can effectively absorb free hydrogen ions as hydrogen atom acceptors; and GA has certain antibacterial and antiviral properties. GA and other polyphenol compounds have significant antibacterial properties compared with diphenol compounds; there are many ways to reflect its antibacterial properties, such as inhibiting the generation of nucleic acids; causing disorders in the function of the cytoplasmic membrane or dissipating the energy required for metabolism; due to the many excellent properties of GA, GA is widely used in the fields of medicine, organic synthesis, cosmetics, etc.; GA is a phenolic natural compound containing three hydroxyl groups, also known as "gallic acid", which is widely present in plants such as Rheum palmatum and Amaranthus hypochondriacus, and is a naturally occurring polyphenol containing three hydroxyl groups; because its molecular structure contains three phenolic hydroxyl groups and one carboxyl group, and its phenolic hydroxyl groups can provide active hydrogen to react with -NCO, it can be used to prepare bio-based crosslinked polyurethane.

[0060] Figure 1 The flowchart of the preparation method of the flexible PEDOT:PSS conductive composite fiber provided by an exemplary embodiment of the present application is shown. The method includes the following steps:

[0061] Step S1: Add TPU to the DMF solution, and after stirring with a constant temperature magnetic stirrer, obtain the TPU spinning dope.

[0062] In step S1 of this embodiment, the content of TPU is 2 - 10 g / L; the mass-volume concentration of DMF is 20 - 200 mg / mL; the constant temperature of the constant temperature magnetic stirrer is 40 - 60 °C, the stirring speed is 200 - 660 rpm, and the stirring time is 4 - 10 h.

[0063] Step S2: Add PEDOT:PSS to the mixed solution containing gallic acid or its derivative, hexamethylenediamine and Tris buffer solution, and after stirring with a constant temperature magnetic stirrer, obtain the PEDOT:PSS mixed solution.

[0064] In step S2 of this embodiment, the concentration of PEDOT:PSS is 10 - 60 mol / L; the concentration of gallic acid or its derivative is 15 - 45 mol / L; the concentration of hexamethylenediamine is 15 - 65 mol / L; the concentration of Tris buffer solution is 0.5 - 4.5 mol / L. Specifically, after adding PEDOT:PSS to the mixed solution containing gallic acid or its derivative, hexamethylenediamine, and Tris buffer solution, the pH of the solution is 8 - 10; the constant temperature of the constant temperature magnetic stirrer is 40 - 60 °C, the stirring speed is 200 - 660 rpm, and the stirring time is 10 - 40 min. Optionally, the above-mentioned gallic acid or its derivative includes one of pyrogallic acid, gallic acid, (Z)-3,4,5,4'-tetramethoxy-3'-hydroxydiphenylethylene (Combretastatin A-4), and GA butyl ester.

[0065] Step S3: Sequentially add CNTs-DMPA, MXene, and silver powder to the PEDOT:PSS mixed solution, and stir with a constant temperature magnetic stirrer to obtain a PEDOT:PSS mixed conductive solution.

[0066] In step S3 of this embodiment, the concentrations of CNTs-DMPA, MXene, and silver powder are 5 - 10 mol / L, 2 - 6 mol / L, and 4 - 15 mol / L respectively. Additionally, the constant temperature of the constant temperature magnetic stirrer is 40 - 60 °C; the initial stirring speed of the constant temperature magnetic stirrer is set to 200 - 600 rpm, and stirring continues for 0.5 - 4.5 h; then the stirring speed is adjusted to 500 - 800 rpm, and stirring continues for 10 - 60 min; finally, the stirring speed is adjusted to 900 - 2500 rpm, and stirring continues for 4 - 12 h.

[0067] Step S4: Slowly pour the PEDOT:PSS mixed conductive solution into the TPU spinning dope, and stir with a constant temperature magnetic stirrer to obtain a PEDOT:PSS mixed spinning solution.

[0068] In step S4 of this embodiment, the constant temperature of the constant temperature magnetic stirrer is 40 - 60 °C, the stirring speed is 200 - 660 rpm, and the stirring time is 2 - 12 h.

[0069] Step S5: Inject the PEDOT:PSS mixed spinning solution into a syringe, perform wet spinning at room temperature, use an injection pump to extrude the PEDOT:PSS mixed spinning solution into a DMF aqueous coagulation bath, perform three-fold mechanical drawing on the as-spun fibers solidified 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 PEDOT:PSS conductive composite fibers.

[0070] In step S5 of this embodiment, the volume capacity of the syringe is 5 - 40 mL, the inner diameter of the needle is 0.2 - 0.8 mm; the spinning rate of wet spinning is 0.5 - 6.5 mL / h; the length of the coagulation bath is 90 cm; the temperature of the heat setting treatment is 60 °C. In addition, the drying temperature during the collection and drying of winding the fibers after the heat setting treatment onto a uniformly rotating hot roller is 20 - 40 °C, and the drying time is 6 - 12 h.

[0071] Figure 2 The electron microscope image of the flexible PEDOT:PSS conductive composite fiber provided by an exemplary embodiment of the present application is shown. The flexible PEDOT:PSS conductive composite fiber is prepared by the preparation method of the above flexible PEDOT:PSS conductive composite fiber.

[0072] In summary, the flexible PEDOT:PSS conductive composite fiber of the present application uses TPU functionalized with gallic acid or its derivatives and hexamethylenediamine as the matrix, and constructs a multi-dimensional conductive network in the matrix by using a valence bond cross-linking strategy; the functional modification of gallic acid or its derivatives and hexamethylenediamine means that on the one hand, the amine group and phenolic hydroxyl group in gallic acid or its derivatives and hexamethylenediamine achieve high phase separation of PSS and PEDOT through hydrogen bond association, optimize the conformation of the PEDOT molecular chain, and enable PEDOT to form an ordered conductive continuous phase. On the other hand, it is bonded to TPU through coordination, electrostatic interaction, hydrophobic interaction and even covalent reaction; the valence bond cross-linking strategy refers to the process of obtaining a stable conductive network structure through dynamic valence bond cross-linking between different substances; the multi-dimensional conductive network structure refers to: on the one hand, a two-dimensional conductive network structure between PEDOT and silver nanoparticles, and on the other hand, a three-dimensional conductive network structure between MXene or its derivatives and carbon nanotubes or their derivatives and silver nanoparticles. In addition, the wet spinning method of the present application solves the problems of dispersion and re-agglomeration of conductive nanometer fillers. Compared with the prior art, the present application provides a simple method for preparing fibers, which has the advantages of simple equipment, simple spinning process, environmental protection, and significant improvement in effect. It does not require expensive and complex equipment and is easy to realize large-scale production. In addition, the conductive composite fiber prepared by this process has good flexibility, tensile properties and large-scale integration characteristics, and can be widely used in wearable devices. The conductive composite fiber prepared by the valence bond cross-linking strategy of the present application improves the problems of poor dispersion and easy agglomeration of PEDOT. At the same time, the cross-linking of carbon nanotubes and their derivatives and MXene and their derivatives with metal silver nanoparticles further improves the continuity and controllability of the three-dimensional conductive network structure, enables the conductive fillers to be evenly dispersed, saves raw materials while being beneficial to improving the conductive performance and structural stability of the composite material, and provides new ideas for the development of new conductive fibers.

[0073] To better understand the present application, a specific embodiment is used below to further illustrate the present application. It should be noted that the embodiments described in this specific embodiment are only a part of the embodiments of the present application and do not limit the scope of protection of the present application.

[0074] A preparation method of a flexible PEDOT:PSS conductive composite fiber includes the following steps:

[0075] Step S1: Add TPU into a DMF solution, and after stirring with a constant-temperature magnetic stirrer, obtain a TPU spinning dope.

[0076] In step S1 of this embodiment, the content of TPU is 5 g / L; the mass-volume concentration of DMF is 150 mg / mL; the constant temperature of the constant-temperature magnetic stirrer is 45 °C, the stirring speed is 300 rpm, and the stirring time is 5 h.

[0077] Step S2: Add PEDOT:PSS into a mixed solution containing gallic acid, hexamethylenediamine, and Tris buffer solution, and after stirring with a constant-temperature magnetic stirrer, obtain a PEDOT:PSS mixed solution.

[0078] In step S2 of this embodiment, the concentration of PEDOT:PSS is 20 mol / L; the concentration of gallic acid is 25 mol / L; the concentration of hexamethylenediamine is 25 mol / L; the concentration of Tris buffer solution is 1 mol / L. Specifically, the pH of the solution after adding PEDOT:PSS into the mixed solution containing gallic acid or its derivative, hexamethylenediamine, and Tris buffer solution is 8.5; the constant temperature of the constant-temperature magnetic stirrer is 45 °C, the stirring speed is 300 rpm, and the stirring time is 30 min.

[0079] Step S3: Add CNTs-DMPA, MXene, and silver powder into the PEDOT:PSS mixed solution in sequence, and after stirring with a constant-temperature magnetic stirrer, obtain a PEDOT:PSS mixed conductive solution.

[0080] In step S3 of this embodiment, the concentrations of CNTs-DMPA, MXene (Ti3C2T x ) and silver powder are 6.5 mol / L, 3.2 mol / L, and 5.5 mol / L respectively. In addition, the constant temperature of the constant-temperature magnetic stirrer is 45 °C; the initial stirring speed of the constant-temperature magnetic stirrer is set to 250 rpm and stirred for 1.5 h; then the stirring speed is adjusted to 600 rpm and stirred for 30 min; finally, the stirring speed is adjusted to 950 rpm and stirred for 6 h.

[0081] Step S4: Slowly pour the PEDOT:PSS mixed conductive solution into the TPU spinning dope. After stirring with a constant-temperature magnetic stirrer, a PEDOT:PSS mixed spinning solution is obtained.

[0082] In step S4 of this embodiment, the constant temperature of the constant-temperature magnetic stirrer is 45°C, the stirring speed is 450 rpm, and the stirring time is 6 h.

[0083] Step S5: Inject the PEDOT:PSS mixed spinning solution into a syringe. Perform wet spinning at room temperature. Use an injection pump to extrude the PEDOT:PSS mixed spinning solution into a DMF aqueous coagulation bath. After the nascent fibers solidified in the coagulation bath are subjected to three-fold mechanical drawing, heat setting treatment is carried out. Finally, the fibers after heat setting treatment are wound onto a uniformly rotating hot roller for collection and drying to obtain the flexible PEDOT:PSS conductive composite fibers as Figure 2 shown.

[0084] In step S5 of this embodiment, the volume capacity of the syringe is 30 mL, and the inner diameter of the needle is 0.28 mm; the spinning rate of wet spinning is 3.6 mL / h; the length of the coagulation bath is 90 cm; the temperature of heat setting treatment is 60°C. In addition, the drying temperature for winding the fibers after heat setting treatment onto a uniformly rotating hot roller for collection and drying is 30°C, and the drying time is 8 h.

[0085] It should be noted that the 2,2-dimethylolpropionic acid (DMPA) used in this embodiment is purchased from Nanjing Runbang Chemical Co., Ltd., N,N-dimethylformamide (DMF) is purchased from Tianjin Damao Chemical Reagent Factory, thionyl chloride (SOCl2) is purchased from Tianjin Tianli Chemical Reagent Co., Ltd., nano silver powder and Ti3AlC2MAX are purchased from Nanjing Xianfeng Nano Materials Technology Co., Ltd., triethylamine (TEA) is purchased from Sinopharm Chemical Reagent Co., Ltd., lithium fluoride LiF analytical pure (AR) is purchased from Shanghai Macklin Biochemical Co., Ltd., hydrochloric acid HCl analytical pure (AR) is purchased from Zhuhai Huachengda Chemical Co., Ltd., and other solutions not specifically described use water as the solvent.

[0086] Furthermore, the preparation method of the MXene nanosheet powder in the example includes:

[0087] MXene (Ti3C2T is prepared by selectively etching off the Al layer from the MAX phase (Ti3AlC2) using an LiF / HCl aqueous solution x) First, 2.5 g of LiF was dispersed in 50 mL of hydrochloric acid solution (12 mol / L) under stirring; then 2.5 g of MAX (Ti3AlC2) was slowly added to the solution; subsequently, the solution was reacted at 40 °C for 48 hours under magnetic stirring to completely etch away the Al layer; after 48 hours, the obtained product was diluted with deionized water, centrifuged, and repeated several times until the pH of the centrifuged supernatant was greater than 6; finally, the centrifuged precipitate was freeze-dried for 12 hours to obtain MXene nanosheets. To obtain few-layer or single-layer MXene nanosheets, the above-obtained MXene nanosheets were further exfoliated; the MXene nanosheets were mixed with an intercalating agent, ultrasonically treated in an ice bath with a cell disruptor for a period of time, and then the lower precipitate was collected by centrifugation; the above precipitate was mixed with deionized water, and then ultrasonically dispersed MXene evenly in water; the supernatant was collected after centrifugation, and this supernatant was the few-layer MXene dispersion; finally, the dispersion was freeze-dried to obtain few-layer MXene nanosheet powder.

[0088] Furthermore, the preparation method of CNTs-DMPA powder in the example includes:

[0089] 3.0 g of carboxylated CNTs was placed in a 500 mL four-necked flask, 30 mL of DMF was added, ultrasonically dispersed for 30 min, stirring was started, and then 100 mL of SOCl2 was slowly added, and the mixture was heated to 70 °C and stirred for reaction for 16 h. After cooling, suction filtration was carried out, and it was washed 3 times with DMF to remove the unreacted SOCl2 on its surface. The filter cake was transferred to a 500 mL conical flask, 80 g of DMPA (using DMF as the solvent) and 20 mL of TEA were added respectively, heated to 50 °C, and magnetically stirred for reaction for 24 h. After cooling, suction filtration was carried out, and the filter cake was washed 5 times with deionized water and then dried to constant weight in an oven at 60 °C to obtain chemically modified CNTs, denoted as CNTs-DMPA.

[0090] Next, the performance of the above-obtained flexible PEDOT:PSS conductive composite fiber was tested:

[0091] 1. Mechanical property test

[0092] At room temperature, the fiber was subjected to a tensile break test using a UTM2203 type servo-controlled universal testing machine of Shenzhen SANS Technology Co., Ltd., the tensile rate was 10 mm / min, and at least 5 samples of each content were tested and their average value was calculated.

[0093] 1.1. The tensile strength of the specimen was calculated using the following formula (1):

[0094]

[0095] Where, σ is the tensile strength (Pa); P is the maximum load (N); S is the cross-sectional area of the specimen (m 2 ).

[0096] 1.2. The elongation at break of the specimen is calculated using the following formula (2):

[0097]

[0098] Where: 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).

[0099] 1.3. The Young's tensile modulus of the specimen is calculated using the following formula (3):

[0100]

[0101] Where, 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).

[0102] 2. Conductivity test

[0103] Fibers with a length of 5 cm are cut and silver paste is coated at both ends and copper tape is connected. At least 5 specimens for each content are tested, and their average value is obtained. The volume conductivity of the specimen is calculated using the following formula (4):

[0104]

[0105] Where, σ is the volume conductivity of the specimen (S / cm -1 ); R is the volume resistance of the specimen (Ω / cm); L is the length of the specimen bar between the two electrodes (cm); S is the cross-sectional area of the specimen (cm 2 ).

[0106] 3. Friction resistance test

[0107] The test is carried out with reference to the national standard GB / T21196.

[0108] 4. Water resistance test

[0109] 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.).

[0110] The test results are as follows:

[0111] Figure 3 The schematic diagram of the mechanism of action of gallic acid or its derivatives doped with hexamethylenediamine on the chemical structure of PEDOT:PSS is shown. From Figure 3 it can be seen that:

[0112] On the one hand, the amino group and phenolic hydroxyl group in gallic acid 1 and hexamethylenediamine 2 are associated through hydrogen bonds 5 and 6 to achieve high phase separation of PSS 3 and PEDOT 4, optimize the conformation of the PEDOT molecular chain, and enable PEDOT to form a continuous phase of an ordered conductive body.

[0113] On the other hand, Figure 4 The schematic diagram of the synthesis mechanism and chemical structure between the PEDOT conductive composite material and the TPU functionally modified with gallic acid or its derivatives is shown. PEDOT 1 is bonded to TPU 2 through hydrogen bond interaction 3. At the same time, the process of obtaining a stable conductive network structure through the dynamic valence bond crosslinking 7 and 8 between PEDOT, CNTs-DMPA 4, MXene (Ti3C2T x ) 5 and metal silver nanoparticles 6. The multi-dimensional conductive network structure refers to: on the one hand, the two-dimensional conductive network structure between PEDOT and silver nanoparticles; on the other hand, the three-dimensional conductive network structure between MXene (Ti3C2T x ) and CNTs-DMPA and silver nanoparticles.

[0114] The tensile strength of the flexible PEDOT:PSS conductive composite fiber prepared by the preparation method of the present application is 780.62 MPa, the strain is 1204.28%, and the conductivity is 2405 S / cm. As shown in Table 1 and Table 2 below, the test results of the friction resistance and water washing resistance of the PEDOT:PSS conductive composite fiber are shown. It can be seen from Table 1 and Table 2 that after 650 times of friction, the conductivity of the PEDOT:PSS conductive composite fiber is within 2369 - 2405 S / cm; after 240 times of water washing, the conductivity is within 2365 - 2405 S / cm.

[0115] Table 1. Test results of friction resistance performance

[0116] Number of friction resistance / times Conductivity / S / cm 0 2405 50 2403 150 2398 250 2392 350 2387 450 2379 550 2373 650 2369

[0117] Table 2. Test results of water washing resistance

[0118]

[0119]

[0120] The above are only the preferred embodiments of the present application. It should be noted 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 PEDOT:PSS conductive composite fiber, characterized in that, It includes the following steps: S1. Add TPU into the DMF solution, and after stirring with a constant-temperature magnetic stirrer, obtain the TPU spinning dope; S2. Add PEDOT:PSS into the mixed solution containing gallic acid or its derivative, hexamethylenediamine, and Tris buffer solution, and after stirring with a constant-temperature magnetic stirrer, obtain the PEDOT:PSS mixed solution; The pH of the solution after adding PEDOT:PSS into the mixed solution containing gallic acid or its derivative, hexamethylenediamine, and Tris buffer solution is 8 - 10; The gallic acid or its derivative includes one of pyrogallic acid, gallic acid, (Z)-3,4,5,4'-tetramethoxy-3'-hydroxydiphenylethylene, and GA butyl ester; S3. Add CNTs-DMPA, MXene, and silver powder into the PEDOT:PSS mixed solution in sequence, and after stirring with a constant-temperature magnetic stirrer, obtain the PEDOT:PSS mixed conductive solution; The concentrations of CNTs-DMPA, MXene, and silver powder are 5 - 10 mol / L, 2 - 6 mol / L, and 4 - 15 mol / L respectively; S4. Slowly pour the PEDOT:PSS mixed conductive solution into the TPU spinning dope, and after stirring with a constant-temperature magnetic stirrer, obtain the PEDOT:PSS mixed spinning solution; S5. Inject the PEDOT:PSS mixed spinning solution into a syringe, perform wet spinning at room temperature, use an injection pump to extrude the PEDOT:PSS mixed spinning solution into the DMF aqueous coagulation bath, perform three-fold mechanical drawing on the as-spun fibers solidified in 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 PEDOT:PSS conductive composite fibers.

2. The preparation method of the flexible PEDOT:PSS conductive composite fiber according to claim 1, characterized in that, In step S1: The content of the TPU is 2 - 10 g / L; The mass-volume concentration of the DMF is 20 - 200 mg / mL; The constant temperature of the constant-temperature magnetic stirrer is 40 - 60 °C, the stirring speed is 200 - 660 rpm, and the stirring time is 4 - 10 h.

3. The preparation method of the flexible PEDOT:PSS conductive composite fiber according to claim 1, wherein In step S2: The concentration of the PEDOT:PSS is 10 - 60 mol / L; The concentration of the gallic acid or its derivative is 15 - 45 mol / L; The concentration of the hexamethylenediamine is 15 - 65 mol / L; The concentration of the Tris buffer solution is 0.5 - 4.5 mol / L.

4. The preparation method of the flexible PEDOT:PSS conductive composite fiber according to claim 1, characterized in that, In step S2: The constant temperature of the constant-temperature magnetic stirrer is 40 - 60 °C, the stirring speed is 200 - 660 rpm, and the stirring time is 10 - 40 min.

5. The preparation method of the flexible PEDOT:PSS conductive composite fiber according to claim 1, characterized in that, In step S3: The constant temperature of the constant-temperature magnetic stirrer is 40 - 60 °C; The initial stirring speed of the constant-temperature magnetic stirrer is set at 200 - 600 rpm, and stirring is continued for 0.5 - 4.5 h; then the stirring speed is adjusted to 500 - 800 rpm, and stirring is continued for 10 - 60 min; finally, the stirring speed is adjusted to 900 - 2500 rpm, and stirring is continued for 4 - 12 h.

6. The preparation method of the flexible PEDOT:PSS conductive 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 200 - 660 rpm, and the stirring time is 2 - 12 h.

7. The preparation method of the flexible PEDOT:PSS conductive composite fiber according to claim 1, characterized in that, 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 - 6.5 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 fiber after the heat setting treatment onto a uniformly rotating hot roller for collection and drying, the drying temperature is 20 - 40 °C and the drying time is 6 - 12 h.

8. A flexible PEDOT:PSS conductive composite fiber, which is prepared by the preparation method of the flexible PEDOT:PSS conductive composite fiber according to any one of claims 1 to 7.

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