Polyvinylidene fluoride / polyaniline composite conductive fiber membrane material as well as preparation method and application thereof

Abstract

The invention relates to a polyvinylidene fluoride / polyaniline composite conductive fiber membrane material as well as a preparation method and application thereof. The preparation method comprises the following steps: spinning by adopting an electrostatic spinning method to prepare a PVDF nanofiber membrane; the preparation method comprises the following steps: mixing water, absolute ethyl alcohol and phytic acid, then adding aniline into the mixed solution to obtain an ANI growth solution, and finally immersing the PVDF nanofiber membrane in the ANI growth solution; and adding an oxidizing agent into the ANI growth solution containing the PVDF nanofiber membrane, and polymerizing in a water bath of-5 to 0 DEG C for 6-12 hours. According to the invention, phytic acid (PA) is adopted as mild protonic acid, and a PVDF / PANI-PA nanofiber membrane with a uniform core-shell structure is constructed. The ANI in the multifunctional film can uniformly grow on the surface of the PVDF nanofiber, meanwhile, high porosity, high air permeability and high conductivity of the fiber film are kept, and EMI shielding and human motion monitoring can be achieved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of high polymer materials, and particularly relates to a polyvinylidene fluoride / polyaniline composite conductive fiber membrane material and a preparation method and application thereof. BACKGROUND

[0002] With the development of information technology and artificial intelligence, as a new generation of intelligent devices, wearable smart electronics are rapidly developing to realize human motion sensing and personal health monitoring functions. However, the electromagnetic radiation generated by these electronic devices has an adverse impact on the operation of the devices, human health and the surrounding environment. Therefore, in order to effectively reduce electromagnetic radiation pollution and interference, the development of a new generation of high-performance electromagnetic interference (EMI) shielding materials is crucial for the stable operation of wearable or precision electronic devices and electromagnetic wave protection. Traditional metal materials such as copper, silver and nickel are widely used in electromagnetic wave shielding due to their excellent electrical conductivity. However, the rigidity, high density, corrosion resistance and complex processing of these metal materials, as well as the high cost limit their application in modern integrated electronic devices, and cannot meet the demand for lightweight, intelligent, flexible and miniaturization. In contrast, textile-based electromagnetic shielding materials stand out with their light weight, softness, flexibility and easy processing. Compared with pure metal shielding systems, these materials have lower cost and maintenance requirements, and the skeleton and surface morphology of textiles can be modified by chemical and physical methods, making them competitive in many electromagnetic interference shielding materials.

[0003] Currently, polyaniline (PANI) is a low-cost and conductivity-controllable dielectric material, which has the advantages of easy synthesis, excellent thermal and chemical stability, and low microwave loss, and is considered as one of the most promising functional polymers. Due to the large energy gap of PANI, the intrinsic state of PANI is usually in an insulating state, and the conductivity can be realized by introducing carriers through proton acid doping. Specifically, by introducing acidic or other ionic substances to dope PANI, the dopant will undergo oxidation-reduction reaction with the main chain of PANI, generate charged defects and form charge transfer, so that the electronic structure of PANI changes from insulating state to conductive state. In order to obtain electromagnetic interference shielding materials with lightness, softness and high strength, researchers have developed PANI composite materials with different structures. The common method is to add PANI to the insulating polymer matrix, which can realize various processing and molding processes. Traditional processing methods of polyaniline are commonly coating, mixing, electrochemical polymerization and chemical oxidation polymerization, but there are drawbacks: (1) Polyaniline as a coating, due to poor interfacial interaction between the coating and the matrix, the coating is easy to peel off under mechanical deformation, resulting in unstable performance; (2) Polyaniline as a functional filler mixed in the composite material, the conductive network is easy to be interrupted by the insulating matrix, often needs to increase the filler, usually needs a higher filling load to achieve the ideal efficiency, which limits its application in precision flexible intelligent wearable devices; (3) Electrochemical polymerization and chemical oxidation polymerization are usually carried out on the surface of the matrix to form a dense polyaniline layer with more stable interfacial structure, but the existing technology generally uses strong acid (such as HCl, sulfuric acid) as a proton acid to induce the chemical oxidation polymerization of PANI. But the strong acid will cause the polymerization rate to be too fast, and the PANI is easy to form agglomeration on the surface of the fiber, resulting in: the pores of the nanofiber are blocked, the air and moisture permeability performance decreases significantly; the shell is uneven, the flexibility is reduced; the conductivity fluctuates greatly, it is difficult to form a stable core-shell structure. Chinese patent application CN 115452205 A discloses a conductive flexible pressure sensor based on conjugate orientation electrospinning technology and a preparation method thereof, the conductivity of the oriented conductive nanofiber membrane is only 1×10 -4 ~9×10 -2 S / cm, and the addition amount of proton acid has a significant effect on the performance, but it cannot balance the conductivity and the integrity of the fiber structure.

[0004] Therefore, it is urgent to develop wearable electromagnetic wave protection composite materials with high comfort and structural stability, which is the key to meet the needs of the next generation of high-performance wearable electronic devices. SUMMARY

[0005] To address the problems of existing technologies, namely: (1) excessive polymerization of PANI induced by strong acid leading to membrane pore blockage; (2) uneven shell structure and difficulty in obtaining a stable core-shell structure; and (3) difficulty in simultaneously achieving conductivity and fiber permeability and flexibility, this invention provides a method for preparing a polyvinylidene fluoride / polyaniline composite conductive fiber membrane material. This method uses phytic acid (PA) as a mild protic acid to construct a PVDF / PANI-PA nanofiber membrane with a uniform core-shell structure.

[0006] Another objective of this invention is to provide a polyvinylidene fluoride / polyaniline composite conductive fiber membrane material prepared by the above method. In this multifunctional film, ANI can be uniformly grown on the surface of PVDF nanofibers, while maintaining the high porosity, high air permeability, and high conductivity of the fiber membrane, enabling EMI shielding and human motion monitoring.

[0007] Another object of the present invention is to provide the application of the above-mentioned polyvinylidene fluoride / polyaniline composite conductive fiber membrane material.

[0008] The objective of this invention is achieved through the following technical solution: A method for preparing a polyvinylidene fluoride / polyaniline composite conductive fiber membrane material includes the following steps: (1) Preparation of PVDF nanofiber membrane: Polyvinylidene fluoride (PVDF) was added to an organic solvent and stirred to dissolve, thus obtaining PVDF spinning solution. Then, electrospinning was performed to obtain PVDF nanofiber membrane. (2) PVDF nanofiber membrane impregnated with ANI solution: water, anhydrous ethanol and phytic acid (PA) are mixed, and then aniline (ANI) is added to the mixed solution to obtain ANI growth solution. Finally, the PVDF nanofiber membrane is immersed in the ANI growth solution. (3) Chemical oxidation polymerization to form a core-shell structure: An oxidant is added to the ANI growth solution containing the PVDF nanofiber membrane, and polymerization is carried out in a water bath at -5 to 0 ℃ for 6–12 h. After the reaction is completed, PA-doped polyvinylidene fluoride / polyaniline composite conductive fiber membrane material (PVDF / PANI-PA nanofiber membrane) is obtained.

[0009] This invention utilizes polyvinylidene fluoride (PVDF) nanofiber membranes prepared by electrospinning as the matrix. Leveraging their high porosity and small-diameter fiber characteristics, PVDF nanofiber membranes impart superior comfort and ultra-high flexibility to wearable smart electronic devices. The PVDF nanofiber membranes prepared by electrospinning are then immersed in an acidic medium containing aniline (PANI) for chemical oxidation polymerization, ultimately forming a core-shell structure PVDF / PANI-PA nanofiber membrane with a PVDF nanofiber core and PANI as the shell. PA is a relatively mild organic acid; using phytic acid (PA) as the protonated acid for polyaniline doping prevents excessively vigorous polymerization, significantly reducing PANI aggregation and avoiding clogging of the nanofiber membrane pores. Simultaneously, the PA-doped PANI-based composite membrane introduces protonated amino groups (-NH4+). 3+ This significantly enhances the hydrophilicity of the membrane and increases its moisture permeability.

[0010] Preferably, the stirring and dissolving in step (1) is carried out by stirring in a hot water bath at 60 °C for 2 h to fully dissolve the PVDF; the organic solvent is N,N-dimethylformamide (DMF).

[0011] Preferably, the mass ratio of aniline to phytic acid in step (2) is controlled at 0.05–0.30, more preferably 0.10–0.20; and the concentration of phytic acid in the mixed solution is controlled at 0.05–0.5 mol / L, more preferably 0.1–0.3 mol / L.

[0012] Preferably, the soaking time in step (2) is 20-40 min.

[0013] Preferably, the molar ratio of the oxidant to aniline in step (3) is 1:1-2:1, more preferably 1:1-1.5:1.

[0014] Preferably, the oxidant in step (3) is at least one of ammonium persulfate, ferric chloride, or copper chloride. Preferably, after the reaction in step (3) is completed, the fiber membrane is taken out, washed with ethanol and deionized water respectively, and dried under vacuum at 60 °C for 6 h.

[0015] The polyvinylidene fluoride / polyaniline composite conductive fiber membrane material prepared by the above method of the present invention combines the excellent properties of PVDF substrate material and PANI, and has good flexibility, thinness, as well as excellent conductivity, mechanical flexibility and EMI shielding performance.

[0016] The polyvinylidene fluoride / polyaniline composite conductive fiber membrane material described in this invention can be applied to wearable electronic devices, electromagnetic interference shielding materials, vibration sensors, and smart textiles.

[0017] Compared with the prior art, the present invention has the following advantages and beneficial effects: (1) This invention uses PA to achieve a uniform core-shell nanofiber structure, which is isotropic and does not clog the pores. PA is a mild organic acid with a polyphosphate structure and moderate protonation ability, which can form a stable hydrogen bond network on the surface of PVDF nanofibers, so that PANI segments grow uniformly along the fiber surface during polymerization. Compared with strong acids such as hydrochloric acid and sulfuric acid, PA does not trigger a violent polymerization reaction, thereby significantly reducing PANI agglomeration and avoiding fiber pore clogging. Experiments show that when PA is used as the doping acid, the air permeability of the PVDF / PANI-PA nanofiber membrane prepared in this invention is maintained at 89–95 mm / s, and the moisture permeability reaches 9600–9800 g / m. 2 • 24h; When using HCl, CH3COOH, or SSA, the air permeability decreases to 36–18 mm / s, and the moisture permeability decreases to 5400–6400 g / m³. 2 • 24h, confirming that PA is irreplaceable in constructing homogeneous core-shell structures.

[0018] (2) This invention determines the optimal range of PA addition. When the PA / PANI mass ratio is 0.1–0.2 and the in-situ polymerization time is 6–12 min, excellent shell thickness can be obtained, resulting in a uniformly coated PANI structure. Under these conditions, the conductivity of the PVDF / PANI-PA nanofiber membrane can reach 0.60–0.88 S / cm. When the PA addition exceeds the range of this invention, the conductivity decreases to 0.1–0.3 S / cm, proving that the parameters of this invention have a significant and repeatable improvement in technical effect.

[0019] (3) The core-shell structured PVDF / PANI-PA nanofiber membrane prepared by this invention simultaneously possesses high conductivity, high air permeability, high flexibility, and excellent EMI shielding performance (22–25 dB). It also achieves stable and sensitive current response in wearable pressure sensing and throat vibration recognition, accurately identifying specific vocal signals such as "Hello" and "Good morning," demonstrating superior comprehensive performance compared to existing technologies. Therefore, this invention, through PA-controlled polymerization interface methods, achieves a synergistic improvement in the conductivity and gas transport capacity of nanofibers, a non-obvious innovation not found in existing technologies. Attached Figure Description

[0020] Figure 1 The image shown is a SEM image of the PVDF / PANI-PA nanofiber membrane from Example 1.

[0021] Figure 2 The image shown is a SEM image of the PVDF / PANI-HCl nanofiber membrane in Comparative Example 3.

[0022] Figure 3 The image shown is a SEM image of the PVDF / PANI-SSA film in Comparative Example 4.

[0023] Figure 4 The image shows the contact angle test results of the PVDF / PANI-PA nanofiber membrane in Example 1, illustrating the improved hydrophilicity of the fibers.

[0024] Figure 5 The graph shows the arm bending monitoring experiment curve of the PVDF / PANI-PA nanofiber membrane in Example 1. The PVDF / PANI-PA nanofiber membrane exhibits an accurate current response by detecting the stress generated by repeated arm bending and straightening movements. When the arm is bent, the applied stress increases the internal contact points of the fiber membrane, resulting in a decrease in resistance and an increase in current; when the arm returns to the straightened state, the stress is relieved, and the current value returns to the initial level.

[0025] Figure 6 The image shows the signal diagrams for "Hello," "Congratulations," and "Good morning" using the PVDF / PANI-PA nanofiber membrane from Example 1, based on laryngeal vibration recognition. Each word exhibited consistent current changes in both tests, producing unique signal patterns. This demonstrates the potential of PVDF / PANI-PA nanofibers for voice recognition based on vocal cord vibrations, potentially serving as an effective means of assisting communication for people with speech disorders in wearable electronic devices. Detailed Implementation

[0026] The present invention will be further described in detail below with reference to embodiments and accompanying drawings, but the embodiments of the present invention are not limited thereto. All raw materials involved in the present invention can be purchased directly from the market. For process parameters not specifically specified, conventional techniques can be referred to.

[0027] In the following embodiments and comparative examples, the performance of the composite membrane was tested according to the following methods: Microstructure analysis: The microstructure of the samples was observed using a field emission scanning electron microscope (FE-SEM, Hitachi S4800). The samples were fixed to the sample stage with conductive adhesive and dried, followed by gold sputtering using an ion sputtering system. The scanning voltage was set to 10 kV during the test.

[0028] Moisture permeability test: The water vapor transmission rate of the sample was measured using a moisture permeability tester (YG501D-2) in accordance with the ASTM E96-2010 standard.

[0029] Air permeability test: The air permeability of the sample was tested using an air permeability tester (YG461DB, Fangyuan Instrument Co., LTD, China). The composite membrane was flatly fixed at the vent, and the test area was 20 cm². 2 Select a pressure drop value of 200Pa and read the data after it stabilizes.

[0030] Conductivity testing: The conductivity of the sample was measured using a four-probe tester (RTS-4, Beijing Shichuang Technology, China). The composite film was cut into strips (25mm × 20mm), the thickness was measured with a micrometer, and it was ensured that the four probes were in close contact with the composite film.

[0031] Sample current test: The sample current (I) was measured using an RST5200 electrochemical workstation with the voltage set to 2 V.

[0032] Shielding effectiveness testing: Using an Agilent E5071C vector network analyzer, the EMI shielding performance of the samples was measured in the 8.2–12.4 GHz (X-band) range using the waveguide method. Samples were cut into 22.5 mm × 10.2 mm pieces, stacked to a thickness of 1 mm, and compacted. Electromagnetic shielding effectiveness was measured. The electromagnetic absorption loss (SE) of the samples was calculated using the measured scattering parameters (S11 and S21). A ), reflection loss (SE) R ) and total shielding (SE) T ).

[0033] Example 1: (1) 0.5 g of PVDF powder was slowly added to 4.5 g of DMF solution and stirred in a 60 ℃ hot water bath for 2 h to completely dissolve it and form a 10 wt% PVDF spinning solution. The prepared PVDF spinning solution was loaded into a 10 mL syringe and electrospinned using an electrospinning method with a liquid supply rate of 1 mL / h, a jet voltage of 17 kV, a jet distance of 16 cm, and a relative humidity of ≤50%. Spinning was continued for 2 h to obtain a uniform PVDF nanofiber membrane with an average fiber diameter of about 250–320 nm.

[0034] (2) Preparation of ANI growth solution: Deionized water, anhydrous ethanol, and PA were mixed in a volume ratio of 1:1:0.1 to obtain a mixed solution with a total volume of 500 mL, wherein the molar concentration of PA in the mixed solution was 0.10 mol / L. 1 g of aniline monomer (ANI) was added to the above 500 mL mixed solution and stirred at room temperature until completely dissolved to obtain the ANI growth solution. At this time, the mass ratio of ANI to PA was approximately 1:0.1, which is near the lower limit of the preferred range of 0.1–0.2 of the present invention.

[0035] (3) The PVDF nanofiber membrane prepared in step (1) is completely immersed in the ANI growth solution prepared in step (2) for 30 min (the preferred immersion time of this invention is 20–40 min), so that the ANI monomer is fully adsorbed on the surface of the PVDF nanofiber and penetrates into the interfiber pores.

[0036] (4) Prepare an ammonium persulfate (APS) oxidant solution and add the APS solution dropwise to the ANI growth solution containing the PVDF nanofiber membrane, so that the molar ratio of APS to ANI is 1:1. After stirring gently and evenly, place the reaction system in a low-temperature water bath at −5 ℃ for chemical oxidation polymerization. The polymerization reaction time is 12 h. After the reaction is completed, take out the fiber membrane, rinse it several times with anhydrous ethanol and deionized water in sequence to remove unreacted monomers and by-products, and then dry it under vacuum at 60 ℃ for 6 h to obtain a PA-doped PVDF / PANI core-shell structure conductive nanofiber membrane (PVDF / PANI-PA nanofiber membrane).

[0037] Performance test results show that the PVDF / PANI-PA nanofiber membrane obtained in this embodiment has an electrical conductivity of 0.72 S / cm, an electromagnetic interference shielding performance of approximately 23 dB, an air permeability of 95.15 mm / s (200 Pa pressure test), and a moisture permeability of 9800 g / m²·24 h. Compared with undoped or strongly acid-doped samples, the membrane material in this embodiment maintains high conductivity while still exhibiting high porosity and excellent air and moisture permeability.

[0038] Wearable pressure sensing test: After fixing the two sides of the membrane to electrodes with conductive silver paste, it was then fixed to a plastic film substrate. The PVDF / PANI-PA nanofiber membrane and the substrate were combined and fixed in a frame to ensure its stability during the test. Finally, it was connected to an electrochemical workstation with wires. The PVDF / PANI-PA nanofiber membrane showed a stable and repeatable current response to stress changes caused by arm bending / straightening movements. In the laryngeal vibration recognition test, the membrane was attached to the skin of the throat and could recognize different pronunciations such as "Hello," "Congratulation," and "Good morning." The corresponding current signals had stable and distinguishable characteristic waveforms, indicating that the membrane material has application potential in wearable sound recognition and voice assistance.

[0039] Example 2 (1) Weigh 0.6 g of PVDF powder and slowly add it to 4.5 g of DMF solution. Stir in a 60 ℃ water bath for 2 h to completely dissolve the PVDF and obtain a PVDF spinning solution with a mass fraction of 12 wt%. Electrospin the PVDF spinning solution to obtain a PVDF nanofiber membrane. The electrospinning conditions are the same as in Example 1. The average fiber diameter of the PVDF nanofiber membrane is about 300–360 nm.

[0040] (2) Preparation of ANI growth solution: Deionized water: anhydrous ethanol: PA = 1:1:0.2 by volume to prepare 500 mL solution. At this time, the molar concentration of PA in the mixed solution is 0.20 mol / L. Add 1 g of ANI to the above 500 mL mixed solution and stir to dissolve to obtain ANI growth solution; the mass ratio of ANI to PA is about 1:0.2, which is near the upper limit of the preferred range of 0.1–0.2 in this invention.

[0041] (3) Immerse the PVDF nanofiber membrane prepared in step (1) into the ANI growth solution prepared in step (2) for 25 min to ensure sufficient adsorption of ANI monomer. Add APS oxidant solution dropwise to make the molar ratio of APS to ANI 1.5:1, and then place the entire reaction system in a 0 ℃ water bath for polymerization reaction for 10 h. After the reaction is completed, take out the fiber membrane, rinse it with ethanol and deionized water in sequence, and then dry it under vacuum at 60 ℃ for 6 h to obtain the PVDF / PANI-PA nanofiber membrane.

[0042] Performance test results show that the PVDF / PANI-PA nanofiber membrane obtained in this embodiment has an electrical conductivity of 0.63 S / cm, an electromagnetic shielding efficiency of 22 dB, an air permeability of 95.22 mm / s (200 Pa pressure), and a moisture permeability of 9811 g / m²·24h. Compared with Example 1, the PVDF / PANI-PA nanofiber membrane obtained in this embodiment has a slightly higher PA content, a slightly thicker PANI shell, and a slightly lower electrical conductivity, but the air permeability and moisture permeability remain at a high level, indicating that a good balance can still be achieved between conductivity and pore structure when the PANI:PA mass ratio is 1:0.20.

[0043] In wearable pressure sensing tests, the PVDF / PANI-PA nanofiber membrane obtained in this embodiment exhibits good linear response and cyclic stability under different pressure step loading, making it suitable for use as a flexible pressure sensor substrate.

[0044] Example 3 (1) Weigh 0.6 g of PVDF powder and dissolve it in 4.5 g of DMF. Stir at 60 °C for 2 h to obtain a 12 wt% PVDF spinning solution. Electrospin the PVDF spinning solution to obtain a PVDF nanofiber membrane. The electrospinning conditions are the same as in Example 1. The average fiber diameter of the PVDF nanofiber membrane is about 320–380 nm and the porosity is about 73%.

[0045] (2) Preparation of ANI growth solution: Deionized water: anhydrous ethanol: PA = 1:1:0.3 by volume to prepare a 500 mL solution of deionized water, anhydrous ethanol and PA. At this time, the molar concentration of PA in the mixed solution is 0.30 mol / L. Add 2 g of ANI to the above 500 mL mixed solution and stir to dissolve to obtain ANI growth solution; the mass ratio of ANI to PA is about 2:0.3 ≈1:0.15, which is still within the recommended range of 0.05–0.2 of this invention.

[0046] (3) Immerse the PVDF nanofiber membrane prepared in step (1) into the ANI solution prepared in step (2) for 20 min, which is within the preferred immersion time range of 20–40 min in this invention, so that ANI can be fully adsorbed onto the fiber surface. Then add APS solution dropwise to make the molar ratio of APS to ANI 2:1, and then place the entire reaction system in a 0 ℃ water bath for polymerization reaction for 6 h. After the reaction is completed, take out the fiber membrane, wash it with ethanol and deionized water in sequence, and vacuum dry it at 60 ℃ for 6 h to obtain the PVDF / PANI-PA nanofiber membrane.

[0047] Performance test results show that the PVDF / PANI-PA nanofiber membrane prepared in this embodiment has the highest electrical conductivity of 0.88 S / cm among the three embodiments, an electromagnetic shielding efficiency of 25 dB, an air permeability of 89.52 mm / s (200 Pa pressure), and a moisture permeability of 9667 g / m²·24 h. The experimental results of Examples 1-3 show that as the PA content further increases, the PANI shell becomes denser, and the electrical conductivity and shielding performance improve. However, the air permeability and moisture permeability decrease slightly, indicating that excessively high PA levels cause the shell to thicken and some pores to shrink.

[0048] In the wearable pressure sensing and throat vibration recognition experiment, the PVDF / PANI-PA nanofiber membrane obtained in this embodiment can also achieve stable and sensitive electrical signal output, proving that when the ANI:PA mass ratio is in the range of 1:0.1 to 1:0.2, better overall performance can be obtained, and when it is close to 1:0.15 to 1:0.2, the conductivity and shielding are even better.

[0049] Example 4 This embodiment is based on the same conditions as Example 2, except that the immersion time of the PVDF nanofiber membrane in the ANI growth solution is changed to 6 h.

[0050] Performance test results show that the PVDF / PANI-PA nanofiber membrane sample obtained in this embodiment has an electrical conductivity of 0.63 S / cm, an air permeability of 95 mm / s (200 Pa pressure), and a moisture permeability of 9810 g / m²·24 h. SEM observation revealed that the PVDF / PANI-PA nanofiber membrane obtained in this embodiment exhibits a continuous and uniformly thick PANI shell on the fiber surface, with clear pore structures between fibers and no obvious agglomeration or pore blockage. This indicates that a soaking time of 6–12 h in the ANI growth solution allows for sufficient ANI adsorption without oversaturation, resulting in a good core-shell structure, which is the preferred soaking time range for this invention.

[0051] Comparative Example 1 This comparative example is based on the same conditions as Example 2, except that the immersion time of the PVDF nanofiber membrane in the ANI growth solution is changed to 4 h.

[0052] Performance test results show that the electrical conductivity of the final fiber membrane sample prepared in this comparative example is 0.41 S / cm, the air permeability is 98 mm / s (200 Pa pressure), and the moisture permeability is 9900 g / m²·24h. SEM observation revealed that the PANI shell of the final fiber membrane prepared in this comparative example is not completely continuous, with some fiber regions having a thinner coating and exposed PVDF fibers in some areas. This indicates that insufficient ANI adsorption due to a short soaking time results in a limited number of PANI nuclei during subsequent polymerization.

[0053] Comparative Example 2 This comparative example is based on the same conditions as Example 2, except that the immersion time of the PVDF nanofiber membrane in the ANI growth solution is changed to 14 h.

[0054] Performance test results show that the final fiber membrane sample prepared in this comparative example has an electrical conductivity of 0.59 S / cm, an air permeability of 82 mm / s (200 Pa pressure), and a moisture permeability of 9310 g / m²·24h. SEM observation revealed a thicker PANI aggregate layer in localized areas of the final fiber membrane, partially filling the pores between fibers. The shell layer appeared slightly rough, with significant agglomeration at the intersections. This indicates that prolonged soaking time easily leads to excessive aggregation in the fiber contact areas and pores. Although it still maintains high electrical conductivity, its air and moisture permeability significantly decreases.

[0055] Comparative Example 3 This comparative example is based on the same conditions as Example 2, except that HCl is substituted for PA.

[0056] When preparing the ANI growth solution, deionized water, anhydrous ethanol and HCl were mixed in a volume ratio of 1:1:0.1 to obtain a mixed solution with a total volume of 500 mL. 1 g of ANI was added to the 500 mL mixed solution and stirred to dissolve to obtain the ANI-HCl growth solution. The PVDF nanofiber membrane (prepared according to step (1) of Example 2) was immersed in the ANI-HCl growth solution and soaked for 30 min.

[0057] A separate APS solution was prepared and added to the ANI-HCl growth solution containing the PVDF nanofiber membrane, making the molar ratio of APS to ANI 2:1. The entire system was placed in a −5 °C water bath for polymerization reaction for 12 h. After the reaction, the fiber membrane was cleaned and dried according to the cleaning and drying steps in Example 2 to obtain the PVDF / PANI-HCl nanofiber membrane.

[0058] Performance testing results showed that the PVDF / PANI-HCl nanofiber membrane had an electrical conductivity of 0.92 S / cm and an EMI shielding performance of approximately 26 dB. However, due to the strong acid HCl, the polymerization reaction was too rapid, and SEM revealed significant PANI agglomeration and blocky deposition. The pores between the fibers were largely blocked, resulting in a significant decrease in air permeability to 36.11 mm / s (200 Pa pressure) and a decrease in moisture permeability to 6374 g / m²·24h. Compared to Examples 1–3, although the PVDF / PANI-HCl nanofiber membrane sample had a slightly higher electrical conductivity, its pore structure was severely damaged, making it unsuitable for use as a wearable sensor material requiring high air permeability and comfort.

[0059] Comparative Example 4 This comparative example is based on the same conditions as Example 2, except that sulfosalicylic acid (SSA) is used instead of PA.

[0060] Deionized water and anhydrous ethanol were mixed at a volume ratio of 1:1, and sulfosalicylic acid (SSA) was added. The ratio of deionized water:anhydrous ethanol:SSA was 1:1:0.2, resulting in a total volume of 500 mL. Then, 1 g of ANI was dissolved in this 500 mL mixed solution to obtain the ANI growth solution. The PVDF nanofiber membrane (prepared according to step (1) of Example 2) was immersed in the ANI growth solution for 30 min to allow ANI to be adsorbed onto the fiber surface. An APS solution was prepared separately and added to the above-mentioned growth solution containing the PVDF nanofiber membrane. The molar ratio of APS to ANI was maintained at 1.5:1. The system was polymerized at 0 °C for 10 h. After the reaction was completed, the fiber membrane was washed with ethanol and deionized water and dried under vacuum at 60 °C to obtain the PVDF / PANI-SSA membrane.

[0061] Performance test results show that the conductivity of the PVDF / PANI-SSA membrane obtained in this comparative example is approximately 0.21 S / cm, significantly lower than that of Examples 1–3; compared with the undoped PVDF membrane, the porosity decreased by approximately 40%, and SEM revealed a large number of PANI particle agglomerates on the fiber surface and uneven PANI shell coating; the air permeability decreased significantly to 23.15 mm / s (200 Pa pressure), and the moisture permeability was only about 5400 g / m³. 2 • 24 h. This indicates that SSA has strong activity, which easily leads to uneven polymerization and makes it difficult to obtain the uniform core-shell structure and excellent comprehensive performance required by this invention.

[0062] Comparative Example 5 This comparative example is based on the same conditions as Example 2, except that sulfuric acid is substituted for PA.

[0063] Deionized water and anhydrous ethanol were mixed at a volume ratio of 1:1, and an appropriate amount of sulfuric acid was added. The ratio of deionized water:anhydrous ethanol:sulfuric acid was 1:1:0.2, resulting in a mixed solution with a total volume of 500 mL. Then, 1 g of ANI was added to the 500 mL mixed solution and stirred to dissolve, thus obtaining the ANI growth solution. The PVDF nanofiber membrane (prepared according to step (1) of Example 2) was immersed in the ANI growth solution for 30 min. An APS solution was prepared separately and added to the above-mentioned growth solution containing the PVDF nanofiber membrane. The molar ratio of APS to ANI was 1.5:1. The system was placed in a 0 °C water bath for polymerization reaction for 10 h. After the reaction was completed, the fiber membrane was washed with ethanol and deionized water and dried under vacuum at 60 °C to obtain a PVDF / PANI-H2SO4 membrane.

[0064] Performance testing results showed that the PVDF / PANI-H2SO4 membrane achieved a conductivity of approximately 0.65 S / cm, but its porosity decreased significantly, with an air permeability of only about 18 mm / s (200 Pa pressure). SEM revealed a large area of ​​dark polymer deposition on the fiber surface, with some areas exhibiting a "film-like coverage," and the fiber structure boundaries were blurred. This indicates that the strong acidity and oxidizing properties of sulfuric acid made the polymerization process too intense, damaging the original three-dimensional fiber skeleton. Although the membrane sample exhibited acceptable conductivity, its poor air permeability and insufficient flexibility made it unsuitable for wearable pressure sensing applications.

[0065] Comparative Example 6 Under the same conditions as Example 2, this comparative example uses an electrospun polyurethane (PU) membrane instead of a PVDF nanofiber membrane to prepare a PU / PANI-PA composite membrane.

[0066] Preparation of PU nanofiber membrane: 0.8 g of PU particles were slowly added to 5.9 g of DMF solution and stirred in a 60 ℃ hot water bath for 2 h to completely dissolve and form a 12 wt% PU spinning solution. The prepared PU spinning solution was loaded into a 10 mL syringe, and electrospinning was performed using a solution supply rate of 1 mL / h, a jet voltage of 17 kV, a jet distance of 16 cm, and a relative humidity of ≤50%. Spinning was continued for 2 h to obtain a uniform PU nanofiber membrane. The preparation of the ANI growth solution and the polymerization reaction steps and process conditions of the PU nanofiber membrane in the ANI growth solution were the same as in Example 2.

[0067] In this comparative example, the PU / PANI-PA composite membrane exhibited certain degradation after polymerization in a PA environment due to the limited stability of PU in acidic environments. This resulted in brittleness of the fiber membrane, significantly reducing its mechanical properties. During subsequent wearable pressure sensing tests, the fiber membrane fractured, interrupting the testing process. Furthermore, the PU / PANI-PA composite membrane had a conductivity of only 0.41 S / cm. This is because PU has low conductivity, leading to a lower conductivity of the PU substrate membrane compared to the PVDF substrate membrane. Therefore, PU materials are less advantageous than PVDF materials in this application.

[0068] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A method for preparing a polyvinylidene fluoride / polyaniline composite conductive fiber film material, characterized by, The method comprises the following steps: (1) adding PVDF into an organic solvent, stirring and dissolving to obtain a PVDF spinning solution, and then spinning by electrospinning to obtain a PVDF nanofiber membrane; (2) mixing water, anhydrous ethanol and phytic acid, adding aniline into the mixed solution to obtain an ANI growth solution, and finally immersing the PVDF nanofiber membrane in the ANI growth solution for soaking; (3) adding an oxidizing agent into the ANI growth solution containing the PVDF nanofiber membrane, polymerizing at -5-0 ℃ in a water bath for 6-12 h, and obtaining a PA-doped polyvinylidene fluoride / polyaniline composite conductive fiber membrane material after the reaction is completed.

2. The production method according to claim 1, characterized by, In step (1), the stirring and dissolving is performed in a hot water bath at 60 ℃ for 2 h to fully dissolve the PVDF; and the organic solvent is N,N-dimethylformamide.

3. The production method according to claim 1, characterized by, In step (2), the mass of aniline and phytic acid is 0.05-0.30; and the concentration of phytic acid in the mixed solution is 0.05-0.5 mol / L.

4. The method of claim 1, wherein, In step (2), the mass ratio of aniline to phytic acid is 0.10-0.20; and the concentration of phytic acid in the mixed solution is 0.1-0.3 mol / L.

5. The preparation method according to claim 1, characterized in that, In step (2), the soaking time is 20-40 min.

6. The method of claim 1, wherein, In step (3), the molar ratio of the oxidizing agent to aniline is 1:1-2:

1.

7. The preparation method according to claim 1, characterized in that, In step (3), the molar ratio of the oxidizing agent to aniline is 1:1-1.5:

1.

8. The method of claim 1, wherein, In step (3), the oxidizing agent is at least one of ammonium persulfate, ferric chloride or copper chloride.

9. A polyvinylidene fluoride / polyaniline composite conductive fiber membrane material prepared by the preparation method of any one of claims 1-8.

10. Application of the polyvinylidene fluoride / polyaniline composite conductive fiber membrane material of claim 9 in the field of wearable electronic devices, electromagnetic interference shielding materials, vibration sensors or smart textiles.

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