Conductive thin film material and preparation method and application thereof

Abstract

The invention relates to the technical field of flexible electronic materials and film engineering, in particular to a conductive film material and a preparation method and application thereof. Comprising the following steps: S1, preparing and forming an initial conductive material; s2, performing freeze thawing treatment on the initial conductive material for multiple times; s3, carrying out annealing treatment on the initial conductive material under the temperature condition of 60-100 DEG C, and S4, immersing the initial conductive material subjected to the annealing treatment into an acid solution with the pH value of 1-5 so as to carry out acid treatment on the initial conductive material, and finally obtaining the conductive thin film material. By utilizing the synergistic effect among the steps of freezing and thawing, annealing, acid treatment and the like, double optimization and stabilization of an internal mechanical network and a conductive network of the thin film material are realized, the fracture strain of the conductive thin film is remarkably improved, the conductivity of the conductive thin film is effectively improved, and the conductive thin film material has high stretchability and high conductivity; and therefore, the requirement of the flexible electronic device on the performance in a complex use scene can be better met.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of flexible electronic materials and film engineering, in particular to a conductive film material and a preparation method and application thereof. BACKGROUND

[0002] With the wide application of flexible electronic devices in wearable devices, electronic skin, flexible display screens and many other fields, the market demand for thin film materials with high conductivity and excellent mechanical properties is increasing. Conducting polymers and their hybrid materials, represented by poly(3,4-ethylenedioxythiophene)-poly(styrene sulfonate) (PEDOT:PSS), have great application potential in the field of flexible electronics due to their unique structure and properties, but the development of which is faced with the core contradiction between electrical conductivity and mechanical properties.

[0003] In order to improve the conductivity of the thin film material, the existing technology generally adopts strong doping or post-processing method. Although these methods can increase the charge carrier concentration of the thin film material to some extent, thereby improving its conductivity; but also cause significant changes in the internal structure of the thin film material, leading to material embrittlement phenomenon, making its ductility decrease sharply. When trying to improve the ductility of the thin film material by building a high-elasticity network, it is often difficult to form an effective continuous conductive path, thereby limiting the improvement of its electrical conductivity, which cannot meet the demand of flexible electronic devices for efficient charge transport. At the same time, the traditional single post-processing method has many limitations in improving the performance of conductive polymer thin films. For example, pure annealing treatment, although it can improve the crystallinity of the thin film material to enhance the ordered arrangement of molecular chains, to some extent, improve the performance of the thin film material, but also cause the thin film material to be brittle, reduce its flexibility and processability. Pure physical treatment, such as freeze-thaw treatment, can improve the mechanical properties by increasing the cross-linking degree of the internal structure of the thin film material, but the effect of improving the electrical properties is very limited, which cannot meet the requirements of flexible electronic devices for high conductivity. Pure chemical treatment, such as acid doping, can effectively improve the electrical conductivity of the material, but may damage the integrity of the internal network of the material, adversely affect the mechanical properties, and may affect the environmental stability of the material.

[0004] At present, in the field of post-processing of thin film materials, there is a lack of an effective method that can synergistically control the multi-scale network structure of conductive thin films, which cannot optimize the thin film material from the molecular chain arrangement, crystalline state to the conductive path and other levels, so as to meet the actual application requirements of high-performance flexible electronic devices. Therefore, it is urgent to develop a conductive thin film material and a preparation method to solve the above problems. SUMMARY

[0005] The application aims to provide a preparation method of conductive thin film material, which can improve the mechanical and electrical properties of the conductive thin film material by synergistic effect among steps.

[0006] To achieve the above-mentioned purpose, the application provides the following technical scheme: a preparation method of conductive thin film material, comprising the following steps: S1, preparing a mixed solution including water-soluble polymer, polyanion electrolyte and water-soluble conductive polymer to form an initial conductive material; S2, performing multiple freeze-thaw treatments on the initial conductive material to induce molecular chain rearrangement and form physical crosslinking points of the initial conductive material; S3, performing annealing treatment on the initial conductive material after freeze-thaw treatment under the temperature condition of 60-100 DEG C to promote molecular chain relaxation, crystallization and hydrogen bond recombination of the initial conductive material and stabilize the network structure; S4, immersing the initial conductive material after annealing treatment in an acidic solution with pH value of 1-5 to perform acid treatment on the initial conductive material, further etch amorphous regions and regulate doping level, enhance the connectivity of conductive paths, and finally obtain the conductive thin film material.

[0007] Further, in step S2, each freeze-thaw treatment comprises freezing the initial conductive material in an environment of-15-25 DEG C and then thawing at room temperature. The freeze-thaw treatment is repeated 1-5 times.

[0008] Further, in step S3, the annealing treatment is performed in air or inert atmosphere.

[0009] Further, in step S4, the concentration of the acidic solution is any value in the range of 0.5-2.0 mol / L, and the treatment temperature of the acid treatment is any value in the range of 10-40 DEG C.

[0010] Further, the acidic substance in the acidic solution is one or more of sulfuric acid, nitric acid, methanesulfonic acid and hydrochloric acid.

[0011] Further, the mixed solution includes water-soluble polymer, polyanion electrolyte and water-soluble conductive polymer; in the mixed solution, the mass ratio of the water-soluble polymer, the polyanion electrolyte and the water-soluble conductive polymer is (3-9):(0.5-3.5):(0.5-3.5).

[0012] Furthermore, the preparation process of the initial conductive material is any one of electrospinning, spin coating, screen printing, hydrogel construction, wet spinning, and dry spinning.

[0013] Furthermore, the water-soluble polymer is one or more of polyvinyl alcohol, polyethylene glycol, tetra-arm polyethylene glycol, polyacrylamide, and polyethylene oxide; The polyanionic electrolyte is one or more of sodium polyacrylate, polyacrylic acid, polyvinyl sulfonic acid, polyvinyl phosphate, sodium hyaluronate, and hyaluronic acid; The water-soluble conductive polymer is one or more of poly(3,4-ethylenedioxythiophene)-poly(styrene sulfonic acid), sulfonated poly(3,4-ethylenedioxythiophene), and aniline-styrene sulfonic acid copolymer.

[0014] This application also provides a conductive thin film material, which is prepared by the above-described preparation method.

[0015] This application also provides the application of the above-mentioned conductive thin film material in flexible electronic devices.

[0016] The beneficial effects of this invention are as follows: The preparation method provided in this application utilizes the synergistic effect between freeze-thaw, annealing, and acid treatment steps, fully leveraging the mutual promotion and connection advantages between each step. This achieves dual optimization and stabilization of the internal mechanical network and conductive network of the conductive film material, significantly increasing its tensile strength and conductivity while effectively improving its tensile strength. This allows the conductive film material to possess both high tensile strength and high conductivity, thus better meeting the material performance requirements of flexible electronic devices in complex application scenarios. Furthermore, the post-processing steps provided in this application are simple, require no complex equipment, and can be integrated with continuous electrospinning production, facilitating large-scale preparation, reducing production costs, and accelerating the industrialization of flexible electronic devices.

[0017] The preparation method provided in this application reconstructs and stabilizes the multi-level network structure of the conductive film step by step through freeze-thaw, annealing and acid treatment, respectively from three levels: physical cross-linking, crystallization improvement and chemical doping. The conductive film is optimized at multiple levels from molecular chain arrangement to conductive pathways, so that it has excellent structural stability and environmental tolerance, and also has high strain and high conductivity. It can maintain stable performance under different humidity and solvent environments, and expand the application scenarios of flexible electronic devices.

[0018] The above description is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention and to implement it in accordance with the contents of the specification, the preferred embodiments of the present invention are described in detail below with reference to the accompanying drawings. Attached Figure Description

[0019] Figure 1 This is a flowchart of the post-processing of the initial conductive thin film material shown in Embodiment 1 of the present invention.

[0020] Figure 2 The images shown are AFM diagrams of the conductive thin film materials shown in Embodiment 1 and Comparative Examples 1 and 2 of the present invention.

[0021] Figure 3 The images shown are SEM images of the surface of the conductive thin film materials shown in Embodiment 1 and Comparative Examples 1 and 2 of the present invention.

[0022] Figure 4 The diagram shows a comparison of the mechanical properties of the conductive thin film materials shown in Embodiment 1 and Comparative Examples 1 and 2 of the present invention.

[0023] Figure 5 This is a comparison diagram of the conductivity of the conductive thin film materials shown in Embodiment 1 and Comparative Examples 1 and 2 of the present invention. Detailed Implementation

[0024] The technical solutions of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention. Furthermore, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0025] A preferred embodiment of this application provides a method for preparing a conductive thin film material, such as... Figure 1 As shown, the preparation method includes preparing an initial conductive material and post-processing the prepared initial conductive material, specifically including the following steps: S1. Prepare an initial conductive material by mixing one or more of water-soluble polymers, polyanionic electrolytes and water-soluble conductive polymers. S2. The initial conductive material is subjected to multiple freeze-thaw cycles to induce molecular chain rearrangement and the formation of physical cross-linking points. S3. Anneal the initial conductive material after freeze-thaw treatment at a temperature of 60℃~100℃ to promote the relaxation, crystallization and hydrogen bond recombination of the molecular chain of the initial conductive material and stabilize the network structure. S4. Immerse the annealed initial conductive material in an acidic solution with a pH of 1 to 5 to acid-treat the initial conductive material, further etch the amorphous region and control the doping level to enhance the conductivity of the conductive path, and finally obtain the conductive thin film material.

[0026] In step S1, the initial conductive material is prepared by using a mixture of water-soluble polymer, polyanionic electrolyte and water-soluble conductive polymer as a precursor solution. This helps to precisely control the composition and properties of the material, making the preparation process more targeted and controllable, and thus obtaining an initial conductive material with the expected performance.

[0027] In step S2, by subjecting the initial conductive material to freeze-thaw treatment, the physical process of ice crystal growth and melting can induce the molecular chains of the initial conductive material to rearrange and aggregate, forming additional physical cross-linking points in the amorphous region, thus initially improving the toughness of the film and the stability of the network structure. By performing multiple freeze-thaw cycles, the molecular chain rearrangement and the formation of physical cross-linking points can be induced more precisely, further enhancing the structural stability of the initial conductive material.

[0028] In step S3, annealing can promote the movement and relaxation of molecular chain segments, making the physical cross-linking points formed by freeze-thaw more stable; at the same time, it can promote the improvement of the crystallization region and drive the recombination of secondary bonds such as hydrogen bonds between polymer chains, further stabilizing the network structure, thereby significantly improving the mechanical strength, modulus and dimensional stability of the film.

[0029] In step S4, immersing the annealed initial conductive material in an acidic solution disrupts the electrostatic interaction between PEDOT and PSS, causing some PSS to dissolve, elute, and rearrange from the film, thereby reducing the insulating barrier in the film. Simultaneously, acid molecules can penetrate the conductive polymer network, acting as a secondary dopant, enhancing the connectivity of conductive pathways, further optimizing carrier transport paths, significantly improving and stabilizing the film's conductivity, thus obtaining a high-performance conductive thin film material. The conductive thin film material obtained in step S4, after laser micromachining or other processing, such as... Figure 1 As shown in (d), conductive thin film products can be processed into various patterns or shapes.

[0030] By sequentially applying specific conditions of freeze-thaw, annealing, and acid treatment to the initial conductive material, the physicochemical effects of these three steps can mutually promote and connect, achieving dual optimization and stabilization of both the internal mechanical and conductive networks of the initial conductive material. Freeze-thaw provides a more easily rearranged chain segment conformational basis for annealing; annealing stabilizes the freeze-thaw structure and provides an etch-resistant framework for acid treatment; and acid treatment ultimately optimizes conductivity on the stabilized network. The absence or reversal of any of these steps will prevent the achievement of the synergistic enhancement effect.

[0031] In one embodiment, step S2 includes two stages of freeze-thaw treatment: freezing and thawing. Specifically, the initial conductive material is frozen in a low-temperature environment of -15°C to -25°C, and the freezing time can be reasonably set according to the material characteristics and actual needs. Subsequently, the initial conductive material is transferred to room temperature (20°C to 25°C) for thawing. The number of freeze-thaw cycles is limited to 1 to 5 times. By limiting the temperature range and number of cycles of freeze-thaw treatment, the entire operation process can be made more precise and standardized, thereby more effectively inducing the rearrangement of the molecular chains of the initial conductive material and promoting the formation of physical cross-linking points, ultimately significantly improving the structural stability of the initial conductive material. In this embodiment or other embodiments, in step S3, the annealing treatment can be carried out in an air atmosphere or an inert atmosphere (such as nitrogen, argon, etc.). Under this specific atmospheric environment, it is helpful to more accurately control the annealing process, promote the orderly relaxation of the molecular chains, and make its crystallization and hydrogen bond recombination more complete, so as to jointly promote the network structure of the initial conductive material to be more stable, thereby comprehensively improving the stability of the performance of the initial conductive material and ensuring that it maintains excellent performance under different working conditions.

[0032] In one embodiment, in step S4, the concentration of the acidic solution is 0.5 mol / L to 2.0 mol / L, and the acid treatment temperature is 10℃ to 40℃. By limiting parameters such as the pH value, concentration, and acid treatment temperature of the acidic solution, a highly precise and controllable operating system can be established for the acid treatment process. Under these conditions, the acidic solution can more effectively etch the amorphous regions of the initial conductive material and precisely control its doping level, thereby significantly enhancing the connectivity of the conductive pathway and ultimately obtaining a high-performance, stable, and reliable conductive thin film material that meets the stringent requirements of high-end electronic devices and other fields for high-performance conductive materials. In this embodiment or other embodiments, the acidic substance in the acidic solution can be selected from one or more of sulfuric acid, nitric acid, methanesulfonic acid, and hydrochloric acid.

[0033] In one embodiment, the mixture comprises a water-soluble polymer, a polyanionic electrolyte, and a water-soluble conductive polymer. Furthermore, the mass ratio of the water-soluble polymer, the polyanionic electrolyte, and the water-soluble conductive polymer in the mixture is (3–9):(0.5–3.5):(0.5–3.5). Precisely defining the proportions of each component helps to clearly define the basic properties of the initial conductive material, thereby laying the foundation for preparing a conductive material with excellent performance and stable quality. In some embodiments, the water-soluble polymer may be selected from one or more of polyvinyl alcohol, polyethylene glycol, tetra-arm polyethylene glycol, polyacrylamide, polyethylene oxide, and glycerol. The polyanionic electrolyte may be selected from one or more of sodium polyacrylate, polyacrylic acid, polyvinyl sulfonic acid, polyvinyl phosphate, sodium hyaluronate, and hyaluronic acid. The water-soluble conductive polymer may be selected from one or more of poly(3,4-ethylenedioxythiophene)-poly(styrene sulfonic acid), sulfonated poly(3,4-ethylenedioxythiophene), and aniline-styrene sulfonic acid copolymers. In this embodiment or other embodiments, the initial conductive material can be in the form of fiber filaments, fiber-cured forms, hydrogel forms, or fiber films. That is, the preparation process of the initial conductive material can be any one of electrospinning, spin coating, screen printing, hydrogel construction, wet spinning, and dry spinning. By limiting the form of the initial conductive material, the corresponding preparation process can be selected, effectively expanding the application field of this preparation method. In actual production, suitable material forms and preparation processes can be flexibly selected according to different application scenarios and performance requirements to meet diverse market demands. Specifically, the preparation of the initial conductive material includes: first, according to the type of the target film, different water-soluble polymers, polyanionic electrolytes and water-soluble conductive polymers are dissolved in a solvent in proportion to prepare a mixed solution, i.e., a precursor solution; then, the initial conductive material is prepared by any one of the following processes: (1) forming a fiber film on the receiver using electrospinning process; the key parameters include: spinning temperature of 15℃~35℃, relative humidity of 50%~80%; the receiver is a roller with aluminum foil on the surface, with a diameter of 5cm~50cm; rotation speed of 100rpm~800rpm, nozzle inner diameter of 0.20mm~1.05mm, feed speed of 1.0mL / h~20.0mL / h, and receiving distance of 5cm~80cm. The electrospinning process uses a high voltage electrostatic field to act on the mixed solution, which can overcome its surface tension to form a charged jet, and solidify on the receiver to form ultrafine fibers, i.e., the initial conductive material.(2) A fiber film is formed on a glass, SiO2, or ITO substrate after plasma cleaning or UV ozone treatment for 10 to 15 minutes using a spin coating process. The key parameters include: spin coating speed of 2000 rpm to 4000 rpm, preferably 3000 rpm; spin coating time of 30 to 60 seconds; concentration of the mixed solution of 5 wt% to 10 wt% or volume ratio of 1% to 5%; and drop volume of 50 μL to 200 μL. The spin coating process utilizes the centrifugal force generated by high-speed rotation to spread the mixed solution evenly on the substrate, and a conductive film is formed after the solvent evaporates. (3) Patterned films formed on PET, PI, PEN, glass or ceramic substrates by screen printing process; key parameters include: using polyester mesh or stainless steel mesh with a mesh size of 100 to 500 mesh, screen tension of 20N to 25N, ink viscosity controlled within the range of 12000mPa / s to 24000mPa / s, squeegee angle of 60° to 80°, printing speed of 10cm / s to 50cm / s; heat curing at 80℃ to 150℃ for 10min to 60min, or at 300 to 500mJ / cm. 2 UV curing under the following conditions. (4) Using a hydrogel construction process, the mixture is injected into a polytetrafluoroethylene mold, glass plate interlayer, or container of a specific shape, and a hydrogel embryo with a three-dimensional network structure is formed through physical or chemical cross-linking; its key parameters include: standing gelation at 25℃~60℃ for 12~48 hours to carry out physical cross-linking or adding 0.1%~5.0%w / v of cross-linking agent for chemical cross-linking, such as genipin, glutaraldehyde, or Ca 2+ Ions, etc., crosslinking time is 0.5h to 6h. (5) Wet spinning process is used to form fiber filaments; the specific operation includes: the mixture is extruded into a coagulation bath at a temperature of 10℃ to 40℃ through a spinneret (inner diameter 0.1mm to 0.5mm) at a feed speed of 0.5mL / h to 5.0mL / h, and then the fiber is solidified and formed by solvent-non-solvent phase separation. Among them, the roller or guide roller take-up speed is 5m / min to 50m / min; the coagulation bath is a poor solvent of water-soluble solvent, including but not limited to ethanol, isopropanol, saturated ammonium sulfate solution or a mixture of acetone and water. (6) The fiber solidification process is formed by dry spinning. The specific operation includes: a high concentration of mixed liquid is extruded into an inert gas channel at a temperature of 80℃ to 180℃ through a spinneret at a feed speed of 0.2 mL / h to 2.0 mL / h; the channel length is 1m to 5m and the gas flow rate is 10L / min to 50L / min. The fiber solidifies and forms through the rapid evaporation of volatile solvent; the winding device takes up the fiber at a speed of 10m / min to 100m / min.

[0034] This application also provides a conductive thin film material prepared by the above-described preparation method. This conductive thin film material exhibits good structural stability and high conductivity.

[0035] This application also provides the application of the above-mentioned conductive thin film material in flexible electronic devices, such as in flexible sensors, flexible displays and flexible batteries.

[0036] Example 1 S1. Weigh 0.45g of polyvinyl alcohol (PVA) with an average molecular weight of approximately 146,000 Da, 15.0g of PEDOT:PSS aqueous dispersion (1.3wt%), 0.05g of sodium polyacrylate (PANa) with an average molecular weight of approximately 30,000,000 Da, 10g of deionized water, and 5g of dimethyl sulfoxide (DMSO, 99.9% purity), making the water to DMSO mass ratio 2:1. Mix these raw materials thoroughly to prepare a mixture. Then, transfer the mixture into a syringe with a nozzle inner diameter of 0.20mm. Under spinning conditions of 20℃ and 50% relative humidity, and a feed rate of 1.0mL / h, form a fiber film on a 25cm diameter roller covered with aluminum foil. This film serves as the initial conductive material, denoted as RawPPP, and its morphology is shown in the figure below. Figure 2 and Figure 3 As shown.

[0037] S2: Immerse the above-mentioned fiber film in deionized water to allow it to fully swell, and then freeze it in a -20°C environment for 12 hours. Subsequently, remove it and transfer it to a 25°C, 65%RH environment for natural thawing for 6 hours.

[0038] S3. Remove the freeze-thawed fiber film from the water, gently absorb excess moisture from the surface with filter paper, lay it flat on an acrylic plate, and place it in a forced-air drying oven. Anneal it at 80°C for 8 hours in an air atmosphere. After annealing, cool it to room temperature in the oven.

[0039] S4. Immerse the annealed fiber film in a 1.0 mol / L sulfuric acid aqueous solution at 25°C for 30 min. After immersion, remove the film and rinse it three times with plenty of deionized water until the washing solution is neutral. Finally, equilibrate and dry the film at 25°C and 65%RH for 12 hours to obtain a high-performance conductive film material, denoted as PPP-S, with the following morphology. Figure 2 and Figure 3 As shown. And, by Figure 2 It is known that after acid treatment, an interpenetrating network can be formed inside the conductive thin film material, which helps to improve its conductivity.

[0040] Example 2 S1. Weigh 0.5g of polyacrylic acid (PAA) with an average molecular weight of approximately 250,000, 10.0g of PEDOT:PSS aqueous dispersion (1.3wt%), 1.0g of glycerol, and 8.5g of deionized water. Slowly add the weighed PAA to the stirred deionized water until dissolved. Then, add the PEDOT:PSS dispersion and glycerol sequentially, and continue stirring for 12 hours to obtain a homogeneous, viscous mixture. Then, use a spin-coating process to spin-coat the mixture onto a PET substrate that has been treated with oxygen plasma (200W, 2min) at 3500rpm for 30 seconds. Subsequently, pre-dry the mixture on an 80℃ hot plate for 5 minutes to form a uniform initial conductive film, which serves as the initial conductive material.

[0041] S2. Immerse the PET substrate with the initial conductive film into deionized water to allow it to fully swell. Then, freeze it at -18°C for 8 hours. Subsequently, remove it and transfer it to a 25°C, 65%RH environment for natural thawing for 4 hours. Repeat the freezing and thawing operation under the same conditions.

[0042] S3. Carefully peel the initial conductive film after freeze-thaw treatment from the PET substrate, lay it flat on a polytetrafluoroethylene plate, and place it in a forced-air drying oven. Under nitrogen protection, anneal it at 95°C for 6 hours. After annealing, cool it to room temperature in the oven.

[0043] S4. Immerse the annealed initial conductive film in a 0.8 mol / L methanesulfonic acid aqueous solution at 30°C for 30 minutes. After removal, rinse with deionized water until neutral, and dry at room temperature to obtain a flexible conductive film material.

[0044] Example 3 S1. Weigh out 1.0 g of four-arm polyethylene glycol-acrylate (4-arm-PEG-AC) with an average molecular weight of 10000, 0.15 g of aniline monomer, 0.3 g of phytic acid (50 wt% aqueous solution), 0.01 g of photoinitiator (Irgacure 2959), and 8.54 g of deionized water. Dissolve the weighed 4-arm-PEG-AC in the water, and then add the weighed aniline, phytic acid solution, and photoinitiator to the water in sequence. Mix thoroughly by ultrasonication to form a mixture. Then, pour the mixture into a polytetrafluoroethylene mold with dimensions of 10 cm × 10 cm × 2 mm, smooth it, and place it under a 365 nm ultraviolet lamp for 60 seconds to perform photopolymerization, forming an initial hydrogel with both a covalent cross-linked network and a conductive polyaniline (PANI) network, which serves as the initial conductive material.

[0045] S2. Place the initial hydrogel in a -25°C freezer for 24 hours, and then transfer it to a 4°C freezer to thaw slowly for 12 hours.

[0046] S3. Place the freeze-thawed hydrogel in an oven at 60°C and anneal it in air for 12 hours to allow water molecules to escape slowly and uniformly, reduce internal stress, and improve the structural uniformity and dimensional stability of the hydrogel.

[0047] S4. Immerse the annealed hydrogel in a 1.5 mol / L hydrochloric acid (HCl) solution at 10°C for 60 min to deeply dope PANI. Then, transfer it to a large amount of deionized water for 24 h to remove free acid, finally obtaining an ion-conductive hydrogel, i.e., a conductive thin film material.

[0048] Example 4 S1. Weigh 4.75g of polylactic acid (PLA) granules, 10.0g of PEDOT:PSS concentrate (2.5wt%), and 2.5g of DMSO. Premix the PLA granules and DMSO, then add them together with the PEDOT:PSS concentrate into a mixer and blend at 180℃ for 15min to obtain composite masterbatch. Feed the composite masterbatch into a micro twin-screw extruder, setting the feeding, melting, and die head temperatures to 175℃, 180℃, and 185℃, respectively. Extrude through a 1.0mm diameter circular die, cool in a water bath, and wind up with traction rollers to obtain initial composite fibers with a diameter of approximately 1.2mm.

[0049] S2: The initial composite fibers were coiled and then immersed in a 1:1 volume ratio ethanol / water mixture. The mixture was then frozen at -15°C for 16 hours, followed by thawing at room temperature for 8 hours. This freezing and thawing process was repeated under the same conditions. The addition of ethanol lowers the freezing point, causing microphase separation within the initial composite fibers, which in turn helps to form a porous structure.

[0050] S3: The initial composite fibers are suspended in a vacuum oven and annealed at 75°C in a nitrogen atmosphere for 10 hours to eliminate internal stress during the extrusion process and promote the thermally ordered arrangement of PLA crystals and PEDOT phase.

[0051] S4: The annealed initial composite fiber is immersed in a 1.2 mol / L solution of mixed sulfuric acid and nitric acid (volume ratio 5:1), soaked at 40°C for 15 min, and then removed. After that, it is washed with deionized water and ethanol in sequence, and dried to obtain a conductive thin film material.

[0052] Example 5 S1. Weigh 0.5g of polyacrylamide (PAM) with an average molecular weight of approximately 50,000 Da, 0.15g of hyaluronic acid (HA) with an average molecular weight of approximately 10,000 Da, 12.0g of aniline-styrene sulfonic acid copolymer solution (1.9wt.%), 30g of deionized water, and 1g of DMSO. Mix these raw materials thoroughly to form a mixture. Then, transfer the mixture into a syringe with a nozzle inner diameter of 0.20mm. Under spinning conditions of 20℃ and 50% relative humidity, and a feed rate of 1.0mL / h, form an initial PAM / HA / polymer film on a 25cm diameter roller covered with aluminum foil, which serves as the initial conductive material.

[0053] S2. Peel the initial PAM / HA / polymer film from the aluminum foil and immerse it in deionized water to allow it to swell fully. Then, freeze it at -20°C for 12 hours. Subsequently, transfer it to a 25°C, 65%RH environment for natural thawing for 6 hours.

[0054] S3. Remove the initial PAM / HA / polymer film after freeze-thaw treatment, gently absorb excess moisture with filter paper, and then lay it flat on an acrylic plate. Anneal at 75°C for 9 hours in air. After annealing, cool to room temperature in the furnace.

[0055] S4. Immerse the annealed initial PAM / HA / copolymer film in a 1.0 mol / L sulfuric acid aqueous solution, soak at 25°C for 30 min, then remove and rinse repeatedly with deionized water 4 times until the washing solution is neutral (pH≈7). Finally, equilibrate and dry at 25°C and 65%RH for 12 hours to obtain a high-performance and hybrid conductive film material.

[0056] Comparative Example 1 The difference between this comparative example and Example 1 is that only the fiber film obtained in step S1 is subjected to freeze-thaw treatment, and the freeze-thaw treatment conditions are exactly the same as in Example 1. No subsequent annealing and acid treatment are performed to obtain a conductive film material, denoted as FTPPP, whose morphology is shown in the figure below. Figure 2 and Figure 3 As shown.

[0057] Comparative Example 2 The difference between this comparative example and Example 1 is that the fiber film obtained in step S1 is subjected to freeze-thaw treatment and annealing treatment, and the freeze-thaw treatment conditions and annealing treatment conditions are exactly the same as those in Example 1. No subsequent acid treatment is performed to obtain a conductive film material, denoted as PPP, and its morphology is shown in the figure below. Figure 2 and Figure 3 As shown.

[0058] To comprehensively evaluate the performance of the prepared conductive thin film materials, a universal testing machine was used to test the mechanical properties of the conductive thin film materials prepared in Example 1 and Comparative Examples 1-2. Simultaneously, a four-probe resistance meter was used to test the electrical properties of the conductive thin film materials prepared in Example 1 and Comparative Examples 1-2. The test results are as follows: Figure 1 , Figure 2 As shown.

[0059] Comparing the conductive thin film material prepared in Example 1 with the conductive thin film materials prepared in Comparative Examples 1 and 2, it can be seen that... Figure 1 As shown, the conductive thin film materials prepared in Example 1 and Comparative Example 2 exhibit significantly higher fracture strains than the initial conductive material and the conductive thin film material prepared in Comparative Example 1. This result demonstrates that freeze-thaw and annealing treatments on the initial conductive material can significantly improve the fracture strain of the conductive thin film material. The film treated in this way possesses a longer plastic deformation stage and a higher elongation at break. From a microstructural perspective, freeze-thaw treatment creates a more favorable conformational basis for the rearrangement of molecular chain segments during subsequent annealing, allowing the molecular chain segments to arrange and adjust more smoothly during annealing; while annealing further stabilizes the structure formed by freeze-thaw, enhancing the overall integrity and stability of the structure.

[0060] like Figure 2 As shown, the conductive thin film material prepared in Example 1 exhibits a significantly higher conductivity than the conductive thin film materials prepared in Comparative Examples 1 and 2. This demonstrates that acid treatment of the initial conductive material after annealing can significantly improve the conductivity of the conductive thin film material. Annealing provides a stable and etch-resistant framework structure for subsequent acid treatment, allowing the acid treatment to proceed on a robust network foundation. Acid treatment further modulates the network, and acid molecules can also penetrate the conductive polymer network, acting as a secondary dopant, further enhancing the connectivity of conductive pathways, optimizing carrier transport paths, and significantly improving the conductivity of the conductive thin film material. Annealing also provides an etch-resistant framework for acid treatment, which ultimately optimizes conductivity on a robust network. Therefore, the sequential application of specific conditions to the initial conductive material through freeze-thaw cycles, annealing, and acid treatment creates a mutually reinforcing and interconnected physical and chemical process, forming an organic and synergistic system that jointly reconstructs and optimizes the internal multi-level network structure of the conductive thin film material, thereby simultaneously improving both its mechanical and electrical properties.

[0061] The mechanical properties of the conductive thin film materials prepared in Examples 1-5 were tested using a universal testing machine. At the same time, the electrical properties of the conductive thin film materials prepared in Examples 1-5 were tested using a four-probe resistance tester. The test results are shown in Table 1.

[0062] Table 1. Electromechanical properties of conductive thin film materials prepared in Examples 1-5 and Comparative Examples 1-2

[0063] As shown in Table 1, regardless of the method used to prepare the initial conductive material, its conductivity and mechanical properties are significantly improved after freeze-thaw treatment, annealing, and acid treatment. This demonstrates that the post-processing steps for the initial conductive thin film material provided in this application, namely freeze-thaw, annealing, and acid treatment, have broad applicability and can be applied to initial conductive materials prepared by various methods.

[0064] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0065] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A method for preparing a conductive thin film material, characterized in that, Includes the following steps: S1. Prepare an initial conductive material by mixing any one or more of water-soluble polymers, polyanionic electrolytes, and water-soluble conductive polymers. S2. The initial conductive material is subjected to multiple freeze-thaw cycles to induce molecular chain rearrangement and the formation of physical cross-linking points. S3. Anneal the initial conductive material after freeze-thaw treatment at a temperature of 60℃~100℃ to promote the relaxation, crystallization and hydrogen bond recombination of the molecular chains of the initial conductive material and stabilize the network structure. S4. The annealed initial conductive material is immersed in an acidic solution with a pH of 1 to 5 to perform acid treatment on the initial conductive material, further etching the amorphous region and adjusting the doping level to enhance the connectivity of the conductive pathway, and finally obtaining a conductive thin film material.

2. The preparation method according to claim 1, characterized in that, In step S2, each of the freeze-thaw processes includes: freezing the initial conductive material in an environment of -15°C to -25°C, and then thawing it at room temperature; The freeze-thaw cycle is repeated 1 to 5 times.

3. The preparation method according to claim 1, characterized in that, In step S3, the annealing process is carried out in air or an inert atmosphere.

4. The preparation method according to claim 1, characterized in that, In step S4, the concentration of the acidic solution is any value between 0.5 mol / L and 2.0 mol / L, and the treatment temperature of the acid treatment is any value between 10℃ and 40℃.

5. The preparation method according to claim 4, characterized in that, The acidic substance in the acidic solution is one or more of sulfuric acid, nitric acid, methanesulfonic acid, and hydrochloric acid.

6. The preparation method according to claim 2, characterized in that, The mixture comprises a water-soluble polymer, a polyanionic electrolyte, and a water-soluble conductive polymer; the mass ratio of the water-soluble polymer, the polyanionic electrolyte, and the water-soluble conductive polymer in the mixture is (3-9):(0.5-3.5):(0.5-3.5).

7. The preparation method according to claim 2, characterized in that, The preparation process of the initial conductive material is any one of electrospinning, spin coating, screen printing, hydrogel construction, wet spinning, and dry spinning.

8. The preparation method according to claim 2, characterized in that, The water-soluble polymer is one or more of polyvinyl alcohol, polyethylene glycol, tetra-arm polyethylene glycol, polyacrylamide, and polyethylene oxide; The polyanionic electrolyte is one or more of sodium polyacrylate, polyacrylic acid, polyvinyl sulfonic acid, polyvinyl phosphate, sodium hyaluronate, and hyaluronic acid; The water-soluble conductive polymer is one or more of poly(3,4-ethylenedioxythiophene)-poly(styrene sulfonic acid), sulfonated poly(3,4-ethylenedioxythiophene), and aniline-styrene sulfonic acid copolymer.

9. A conductive thin film material, characterized in that, It is prepared by the preparation method described in any one of claims 1 to 8.

10. The application of the conductive thin film material of claim 9 in flexible electronic devices.

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