A method for preparing a stretchable composite conductive film

Abstract

The application discloses a preparation method of a stretchable composite conductive film, comprising the following steps: rapidly preparing PEG functionalized single-walled carbon nanotubes (PEG-SWCNTs); blending PEG-SWCNTs with PEDOT:PSS and ultrasonically dispersing to form a film by spin coating; and obtaining the stretchable composite conductive film through cross-linking treatment. The preparation time of PEG-SWCNTs is shortened to 4-8 hours by accurately controlling the reaction conditions, and the efficiency is significantly improved. The dispersibility of SWCNTs in PEDOT:PSS is improved through PEG functionalization, a synergistic conductive network is formed by PEG-SWCNTs and PEDOT:PSS, and the stretch stability is further improved through cross-linking treatment. The resistance change rate of the prepared composite film is reduced under a tensile strain of 500%, and the composite film remains stable after 100 times of tensile cycles, and the composite film has high conductivity and excellent stretchability, and is suitable for fields of flexible electronic devices, stretchable sensors, wearable devices and the like.

Description

Technical Field

[0001] This invention belongs to the field of flexible electronic materials technology, specifically relating to a method for preparing a stretchable composite conductive film. Background Technology

[0002] With the rapid development of flexible electronics, the demand for stretchable conductive materials in wearable devices, flexible displays, electronic skin, biomedical sensors, and other fields is increasing. An ideal flexible conductive material needs to simultaneously possess high conductivity, good mechanical flexibility and stretchability, excellent stability, and processability.

[0003] Poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) is one of the most widely used conductive polymers, possessing high transparency, good solution processability, and excellent thermal stability. However, the intrinsic brittleness of PEDOT:PSS limits its application in stretchable devices, as it is prone to cracking under stretching or bending conditions, leading to a sharp decline in conductivity.

[0004] Single-walled carbon nanotubes are often used as conductive fillers to improve the conductivity and mechanical properties of polymer composites due to their excellent electrical, mechanical, and thermal stability. However, pristine carbon nanotubes exhibit poor dispersibility and agglomeration in PEDOT:PSS aqueous solutions, and their compatibility with the PEDOT:PSS matrix is ​​poor, making it difficult to form a uniform conductive network.

[0005] Polyethylene glycol-functionalized carbon nanotubes (PEG-SWCNTs) can significantly improve the dispersibility of carbon nanotubes in aqueous systems, while the flexibility of PEG chains helps to enhance the tensile properties of composite materials. However, current methods for preparing PEG-SWCNTs suffer from problems such as long reaction times, low grafting efficiency, and difficult purification. Furthermore, there are no systematic reports on the preparation of stretchable conductive films by blending PEG-SWCNTs with PEDOT:PSS.

[0006] Furthermore, cross-linking treatment to further enhance the tensile stability and mechanical properties of composite films is currently a hot topic in flexible electronic materials research.

[0007] Therefore, it is necessary to develop a method for preparing stretchable composite conductive films to solve the above problems. Summary of the Invention

[0008] The purpose of this invention is to provide a method for preparing a stretchable composite conductive film. By rapidly preparing PEG-SWCNTs with a high grafting rate, blending them with PEDOT:PSS to spin-coat a film, and then performing a crosslinking treatment, a composite film with both high conductivity and excellent stretchability is obtained.

[0009] The present invention achieves the above objectives through the following technical solutions: A method for preparing a stretchable composite conductive film, characterized by comprising the following steps: S1. Carboxylated single-walled carbon nanotubes are vacuum dried at 40-60℃ for 1-3 hours to remove adsorbed moisture, and then placed in a desiccator to cool to room temperature for later use. S2. Prepare 0.1M MES buffer, adjust the pH to 6.0±0.1 with 0.1M HCl, and pre-cool at 4℃ for later use; S3. Take methoxy polyethylene glycolamine (mPEG-NH2), with a molecular weight selected from 2000 Da, 5000 Da or 20000 Da, calculate the amount to be used according to the ratio of 1.2-2.0 times the molar amount of carboxyl group, dissolve it in the MES buffer prepared in step S2, and prepare a solution with a concentration of 100-300 mg / mL. Keep it on ice for later use. S4. Disperse the carboxylated single-walled carbon nanotubes pretreated in step S1 at a concentration of 1-3 mg / mL in the MES buffer prepared in step S2. Perform ultrasonic dispersion under ice bath conditions with a probe, ultrasonic power of 200-300 W, ultrasonic for 2 seconds, intermittent for 3 seconds, and a total ultrasonic time of 8-15 minutes to obtain a uniform carbon nanotube dispersion. S5. Add N-hydroxysuccinimide and 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride sequentially to the dispersion obtained in step S4. The amount of each is 15-25 times the molar amount of the carboxyl group. Stir and activate for 25-35 minutes under ice bath and light-protected conditions. S6. Add the methoxy polyethylene glycolamine solution prepared in step S3 to the reaction solution activated in step S5, and control the molar ratio of methoxy polyethylene glycolamine to carboxyl groups to be 1.2-2.0:1. Stir the reaction at room temperature and in the dark for 4-8 hours. S7. After the reaction is complete, add hydroxylamine hydrochloride to quench the unreacted activated ester and stir for 20-40 minutes; then centrifuge at 4℃ and 3000-4000 rpm for 8-12 minutes and take the supernatant. S8. Add the supernatant obtained in step S7 to an ultrafiltration centrifuge tube for purification. Centrifuge and concentrate at 4℃ and 3000-4000 g. Then add ultrapure water to dilute to the original volume. Repeat this concentration and dilution operation 6-10 times until no free PEG can be detected in the filtrate. S9. Centrifuge the purified concentrate from step S8 by inverting to recover the PEG-SWCNTs aqueous dispersion. Freeze-dry the obtained dispersion or vacuum-dry it at 30-45℃ to obtain solid PEG-SWCNTs. S10. Disperse the solid PEG-SWCNTs prepared in step S9 in PEDOT:PSS aqueous solution, wherein the mass fraction of PEG-SWCNTs in PEDOT:PSS is 0.1-5.0 wt%, and disperse with ultrasonic assistance for 10-30 minutes to obtain a uniform composite dispersion. S11. Spin-coat the composite dispersion obtained in step S10 onto the substrate at a spin speed of 1000-5000 rpm for 30-60 seconds, and then anneal at 80-150℃ for 10-30 minutes to form a composite film. S12. The composite film obtained in step S11 is subjected to crosslinking treatment, wherein the crosslinking treatment is selected from at least one of thermal crosslinking, ultraviolet light crosslinking or chemical crosslinking agent crosslinking.

[0010] Preferably, in step S6, the molar ratio of methoxy polyethylene glycolamine to carboxyl groups is 1.5:1, and the reaction time is 6 hours.

[0011] Preferably, in step S8, the concentration and dilution operations are repeated 8 times.

[0012] Preferably, in step S10, the mass fraction of PEG-SWCNTs in PEDOT:PSS is 0.5-2.0 wt%.

[0013] Preferably, in step S11, the spin coating speed is 2000-3000 rpm, the annealing temperature is 120℃, and the annealing time is 15 minutes.

[0014] Further, in step S12, when a chemical crosslinking agent is used for crosslinking, the chemical crosslinking agent used is ethylene glycol glycidyl ether, and the crosslinking treatment conditions are: immersing the film in a 0.1-1.0 wt% ethylene glycol glycidyl ether aqueous solution for 10-30 minutes, and then heat-treating it at 100°C for 10 minutes.

[0015] The beneficial effects of this invention are as follows: (1) Rapid and efficient preparation of PEG-SWCNTs: By precisely controlling the reaction conditions, the reaction time that traditionally requires more than 24 hours is shortened to 4-8 hours, which significantly improves the preparation efficiency.

[0016] (2) Excellent dispersibility: PEG functionalization significantly improves the dispersibility of carbon nanotubes in PEDOT:PSS aqueous solution, forming a uniform and stable composite dispersion.

[0017] (3) Synergistic conductive network: PEG-SWCNTs and PEDOT:PSS form an interpenetrating conductive network, which utilizes the intrinsic conductivity of PEDOT:PSS and leverages the high conductivity and bridging effect of carbon nanotubes, significantly improving the conductivity of the composite film.

[0018] (4) Excellent tensile properties: The introduction of PEG flexible chains and cross-linking treatment work together to enable the composite film to maintain a complete conductive network under tension, with a resistance change rate of less than 30% under 50% tensile strain.

[0019] (5) Good interfacial compatibility: The PEG chain interacts with the PSS chain segment in PEDOT:PSS through hydrogen bonding, which enhances the interfacial bonding force between the filler and the matrix, and is beneficial to stress transfer and mechanical property improvement.

[0020] (6) Simple process and scalable: The method of the present invention is simple, requires no complex equipment, and is easy to achieve large-scale production. Attached Figure Description

[0021] Figure 1 This is a comparison of the on / off ratios of pure PEDOT:PSS thin-film OECT devices and PEG-SWCNTs / PEDOT:PSS composite thin-film OECT devices.

[0022] Figure 2 The transfer characteristic curves and transconductance curves of pure PEDOT:PSS thin film OECT devices and PEG-SWCNTs / PEDOT:PSS composite thin film OECT devices are shown. Figure 2 (a) shows the absolute value of drain current and transconductance as a function of gate voltage for a pure PEDOT:PSS thin-film OECT device. Figure 2 (b) shows the absolute value of drain current and transconductance as a function of gate voltage for the PEG-SWCNTs / PEDOT:PSS composite thin film OECT device.

[0023] Figure 3 The images show the surface morphology of pure PEDOT:PSS film and PEG-SWCNTs / PEDOT:PSS composite film under different tensile strains. Figure 3 (a) Surface morphology of pure PEDOT:PSS film under 0% tensile strain. Figure 3 (b) shows the surface morphology of a pure PEDOT:PSS film under 70% tensile strain. Figure 3 (c) Surface morphology of PEG-SWCNTs / PEDOT:PSS composite film under 0% tensile strain. Figure 3 (d) shows the surface morphology of the PEG-SWCNTs / PEDOT:PSS composite film under 240% tensile strain. Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below 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.

[0025] The specific embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0026] A method for preparing a stretchable composite conductive film includes the following steps: Step 1: Rapid preparation of PEG-SWCNTs S1. Pretreatment of carboxylated single-walled carbon nanotubes: Vacuum dry the carboxylated single-walled carbon nanotubes at 40-60℃ for 1-3 hours to remove adsorbed moisture, and then cool them to room temperature in a desiccator for later use.

[0027] S2. Preparation and pH adjustment of activation buffer: Prepare 0.1M MES buffer, adjust the pH to 6.0±0.1 with 0.1M HCl, and pre-cool at 4℃ for later use.

[0028] S3. Preparation of amino polyethylene glycol solution: Take methoxy polyethylene glycolamine (mPEG-NH2), with a molecular weight selected from 2000 Da, 5000 Da or 20000 Da, calculate the amount to be used according to the ratio of 1.2-2.0 times the molar amount of carboxyl group, dissolve it in the MES buffer prepared in step (2), and prepare a solution with a concentration of 100-300 mg / mL. Keep it in an ice bath for later use.

[0029] S4. Dispersion of carbon nanotubes: Disperse the COOH-SWCNTs pretreated in step (1) at a concentration of 1-3 mg / mL in the MES buffer prepared in step (2), and perform ultrasonic dispersion under ice bath conditions. The ultrasonic power is 200-300 W, the ultrasonic time is 2 seconds and the interval is 3 seconds, and the total ultrasonic time is 8-15 minutes to obtain a uniform carbon nanotube dispersion.

[0030] S5, Carboxyl activation: N-hydroxysuccinimide (NHS) and 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride (EDC·HCl) are added sequentially to the dispersion obtained in step (4), wherein the amount of NHS and EDC·HCl is 15-25 times the molar amount of carboxyl. The mixture is stirred and activated for 25-35 minutes under ice bath and light-protected conditions.

[0031] S6, PEG grafting reaction: Add the mPEG-NH2 solution prepared in step (3) to the reaction solution after activation in step (5), control the molar ratio of mPEG-NH2 to carboxyl group to be 1.5:1, and stir the reaction for 6 hours at room temperature and in the dark.

[0032] S7. Quenching and preliminary purification: After the reaction is complete, add hydroxylamine hydrochloride to quench the unreacted activated ester and stir for 20-40 minutes; then centrifuge at 4℃ and 3000-4000 rpm for 8-12 minutes and take the supernatant.

[0033] S8. Ultrafiltration purification: Add the supernatant obtained in step (7) to an ultrafiltration centrifuge tube for purification: When the molecular weight of mPEG-NH2 is ≤5000 Da, use an ultrafiltration tube with a molecular weight cutoff of 100kDa; when the molecular weight of mPEG-NH2 is 20000 Da, use an ultrafiltration tube with a molecular weight cutoff of 300kDa or 500kDa; centrifuge and concentrate at 4℃ and 3000-4000 g, then add ultrapure water to dilute to the original volume, repeat this “concentration-dilution” operation 8 times until no free PEG can be detected in the filtrate.

[0034] S9. Product collection and drying: The concentrated solution purified in step (8) is centrifuged and recovered to obtain an aqueous dispersion of PEG-SWCNTs; the obtained dispersion is freeze-dried to obtain solid PEG-SWCNTs.

[0035] Step 2: Preparation of PEG-SWCNTs / PEDOT:PSS composite dispersion S10. Disperse the PEG-SWCNTs prepared in step 1 in a PEDOT:PSS aqueous solution. The mass fraction of PEG-SWCNTs in PEDOT:PSS is 0.5-2.0 wt%. Disperse with ultrasonic assistance for 10-30 minutes to obtain a uniform composite dispersion.

[0036] Step 3: Preparation of composite thin films S11. Spin-coat the composite dispersion obtained in step 2 onto the substrate at a spin speed of 2000-3000 rpm for 30-60 seconds; then anneal at 120°C for 15 minutes to form a composite film.

[0037] Step 4: Crosslinking treatment S12. The composite film obtained in step 3 is subjected to crosslinking treatment to improve its tensile properties and stability; the crosslinking treatment is selected from one or more of the following methods: thermal crosslinking (treatment at 100-150℃ for 10-60 minutes), ultraviolet crosslinking (ultraviolet light irradiation for 5-30 minutes), and chemical crosslinking agent crosslinking (immersing the film in a crosslinking agent solution or spin-coating a crosslinking agent followed by heat treatment).

[0038] When using a chemical crosslinking agent, the chemical crosslinking agent is ethylene glycol glycidyl ether. The crosslinking treatment conditions are as follows: immerse the film in a 0.1-1.0 wt% aqueous solution of ethylene glycol glycidyl ether for 10-30 minutes, and then heat-treat at 100°C for 10 minutes.

[0039] The present invention also provides the application of the stretchable composite conductive film prepared by the above method in flexible electronic devices, stretchable sensors, wearable devices, and organic field-effect transistors.

[0040] Example 1: Preparation of PEG2000-SWCNTs Steps S1-S10 were performed to prepare PEG2000-SWCNTs lyophilized powder with a hydrated particle size of 108±15nm, PDI=0.18, and TGA grafting rate of 23.6wt%.

[0041] Example 2: Preparation of PEG5000-SWCNTs Steps S1-S10 were performed to prepare PEG5000-SWCNTs lyophilized powder with a hydrated particle size of 132±20nm, PDI=0.21, and TGA grafting rate of 28.3wt%.

[0042] Example 3: Preparation of PEG20000-SWCNTs Steps S1-S10 were performed to prepare PEG20000-SWCNTs lyophilized powder with a hydrated particle size of 215±35 nm, PDI=0.23, and TGA grafting rate of 32.1 wt%.

[0043] Example 4: Preparation of PEG2000-SWCNTs / PEDOT:PSS composite film (1) Preparation of composite dispersion: The lyophilized PEG2000-SWCNTs powder prepared in Example 1 was dispersed in PEDOT:PSS aqueous solution (Clevios PH1000), with the mass fractions of PEG2000-SWCNTs being 0.1wt%, 0.5wt%, 1.0wt%, 2.0wt%, 3.0wt%, and 5.0wt%, respectively. The mixture was ultrasonicated in an ice bath for 15 minutes (power 100W, ultrasonic 2s / interval 2s) to obtain a uniform composite dispersion.

[0044] (2) Spin coating to form a film: The above composite dispersion is spin-coated onto a pre-cleaned glass substrate at a spin speed of 2000 rpm for 40 seconds. Then, it is annealed on a hot plate at 120°C for 15 minutes to form a composite film.

[0045] (3) Crosslinking treatment: Immerse the annealed composite film in 0.5wt% ethylene glycol glycidyl ether aqueous solution for 15 minutes, take it out and rinse with deionized water, blow dry with nitrogen, and then heat treat it on a hot table at 100℃ for 10 minutes to complete the crosslinking.

[0046] Example 5: Preparation of PEG5000-SWCNTs / PEDOT:PSS composite film The PEG5000-SWCNTs prepared in Example 2 were used, and the remaining steps were the same as in Example 4.

[0047] Example 6: Preparation of PEG20000-SWCNTs / PEDOT:PSS composite film The PEG20000-SWCNTs prepared in Example 3 were used, and the remaining steps were the same as in Example 4.

[0048] Example 7: Comparative Experiment of Different Crosslinking Methods Using the composite film with 1.0 wt% PEG2000-SWCNTs added in Example 4 as an example, the following crosslinking methods were adopted: (1) Thermal crosslinking: The film is heat-treated at 120°C for 30 minutes.

[0049] (2) Ultraviolet crosslinking: Place the film in an ultraviolet curing chamber (wavelength 365nm, power 100 mW / cm²) and irradiate for 15 minutes.

[0050] (3) Crosslinking with chemical crosslinking agent: Same as step (3) in Example 4.

[0051] (4) Non-crosslinked control group: No crosslinking treatment was performed.

[0052] Comparative Example 1: Unfunctionalized SWCNTs / PEDOT:PSS composite film The original SWCNTs (unfunctionalized by PEG) were dispersed in PEDOT:PSS at an addition rate of 1.0 wt%, and the remaining steps were the same as in Example 4.

[0053] Comparative Example 2: Pure PEDOT:PSS film Without using any SWCNTs, PEDOT:PSS was directly spin-coated into a film and annealed. The remaining steps were the same as in Example 4.

[0054] Comparative Example 3: Uncrosslinked PEG2000-SWCNTs / PEDOT:PSS composite film A composite film with 1.0 wt% PEG2000-SWCNTs was prepared according to Example 4, but without crosslinking treatment.

[0055] Performance testing and results analysis of the examples 1. OECT device performance testing The PEG-SWCNTs / PEDOT:PSS composite film prepared in this invention and the pure PEDOT:PSS film prepared in Comparative Example 2 were respectively fabricated into OECT devices. Under the same device structure and test conditions, the transfer characteristics, transconductance characteristics and on / off ratio of the two thin film OECT devices were tested.

[0056] like Figure 1 As shown, the on / off ratio of the pure PEDOT:PSS thin film OECT device is 3.61, while that of the PEG-SWCNTs / PEDOT:PSS composite thin film OECT device is 3.91. Compared with the pure PEDOT:PSS thin film device, the composite thin film device with added PEG-SWCNTs has a higher on / off ratio, indicating that the introduction of PEG-SWCNTs is beneficial to improving the switching performance of the device.

[0057] like Figure 2 As shown, Figure 2 (a) shows the absolute value of drain current and transconductance as a function of gate voltage for a pure PEDOT:PSS thin-film OECT device. Figure 2 (b) shows the corresponding curves for the PEG-SWCNTs / PEDOT:PSS composite thin film OECT device. Both devices exhibit obvious gate voltage modulation characteristics, indicating that the composite thin film can still maintain normal organic electrochemical transistor operating characteristics after the addition of PEG-SWCNTs.

[0058] 2. Conductivity testing of composite thin films The conductivity of the composite films prepared in each embodiment and comparative example was measured using a four-probe resistance meter.

[0059] The addition of PEG-SWCNTs significantly improved the conductivity of the composite film. In Example 6 (PEG20000-SWCNTs), the conductivity reached a maximum of 712 S / cm at an addition of 2.0 wt%, which is about 3.2 times that of pure PEDOT:PSS.

[0060] The larger the molecular weight of PEG, the more significant the improvement in conductivity, which may be because long-chain PEG provides better dispersibility and interfacial compatibility.

[0061] The conductivity improvement of Comparative Example 1 (unfunctionalized SWCNTs) was limited and decreased at high addition levels, due to poor dispersibility caused by the aggregation of unfunctionalized SWCNTs.

[0062] The conductivity first increases and then decreases slightly with the addition of PEG-SWCNTs, with the optimal addition amount being 1.0-2.0 wt%.

[0063] 3. Tensile property testing of composite films The composite film was subjected to tensile testing using a universal tensile testing machine to measure its rate of change in resistivity during the stretching process. The sample size was 30 mm × 5 mm, and the stretching rate was 5 mm / min.

[0064] The resistivity of pure PEDOT:PSS film increases by 15.2 times under 50% strain, indicating that its tensile stability is very poor.

[0065] The addition of PEG-SWCNTs significantly improved the tensile stability of the composite film. Among them, Example 6 (PEG20000-SWCNTs) showed the best performance, with the resistance increasing by only 1.48 times at 50% strain.

[0066] The larger the molecular weight of PEG, the better the tensile stability, because long-chain PEG can better transfer stress and maintain the conductive network during stretching.

[0067] Comparative Example 1 (unfunctionalized SWCNTs) showed a sharp increase in resistance under high strain, indicating that the unfunctionalized SWCNTs had weak interfacial bonding with the matrix and were prone to slippage and debonding during stretching.

[0068] Comparing Example 4 and Comparative Example 3, it can be seen that the crosslinking treatment significantly improves the tensile stability of the composite film, and the resistance change rate at 50% strain decreases from 2.43 times to 1.76 times.

[0069] 4. Tensile Cycle Stability Test Example 6 (PEG20000-SWCNTs, 1.0wt% addition) was subjected to 100 tensile cycles at 50% strain, and the change in resistance was recorded.

[0070] After 100 stretching cycles, the film resistance increased only to 1.09 times the initial value, demonstrating excellent cycle stability.

[0071] 5. Comparison of the effects of different crosslinking methods Based on Example 4 (PEG2000-SWCNTs, 1.0 wt% addition), the effects of different crosslinking methods on the performance of composite films were compared.

[0072] All three crosslinking methods can improve the tensile stability of the composite film, with chemical crosslinking showing the best effect.

[0073] Crosslinking treatment has little effect on conductivity; the slight decrease is acceptable.

[0074] Chemical cross-linking forms a covalent network, which more effectively restricts the slippage of PEDOT:PSS segments during stretching, thereby maintaining the integrity of the conductive network.

[0075] 6. Microscopic morphology observation of thin films like Figure 3 As shown, Figure 3 (a) shows the surface morphology of pure PEDOT:PSS film under 0% tensile strain. The film surface is relatively intact. Figure 3 (b) shows the surface morphology of pure PEDOT:PSS film under 70% tensile strain. After stretching, a large number of obvious crack structures appeared on the surface of the film, indicating that pure PEDOT:PSS film is prone to cracking under large tensile strain.

[0076] Figure 3 (c) shows the surface morphology of the PEG-SWCNTs / PEDOT:PSS composite film under 0% tensile strain. The surface of the composite film is relatively uniform. Figure 3 (d) shows the surface morphology of the PEG-SWCNTs / PEDOT:PSS composite film under 240% tensile strain. Under 240% tensile strain, the surface of the composite film remains relatively intact, without the large number of dense cracks that are present in the pure PEDOT:PSS film.

[0077] The above results indicate that the addition of PEG-SWCNTs can improve the structural integrity and crack resistance of PEDOT:PSS films under high tensile strain. This may be because the flexible PEG chains can alleviate the local stress generated during stretching, while the conductive network formed by SWCNTs can play a bridging and stress transfer role when the film deforms.

[0078] Conclusion of the Implementation Example Based on the above experimental results, the PEG-SWCNTs / PEDOT:PSS composite conductive film prepared by this invention has the following advantages: PEG functionalization significantly improved the dispersibility of SWCNTs in PEDOT:PSS; the larger the molecular weight of PEG, the better the dispersibility.

[0079] The addition of PEG-SWCNTs significantly improves the conductivity of the composite film. The optimal addition amount is 1.0-2.0 wt%, and the conductivity can be more than 3 times that of pure PEDOT:PSS.

[0080] The addition of PEG-SWCNTs and the crosslinking treatment work synergistically to significantly improve the tensile stability of the composite film. The resistance change rate is less than 1.5 times under 50% strain, and it remains stable after 100 tensile cycles.

[0081] Chemical crosslinking is the best crosslinking method, which can effectively improve tensile properties while having the least impact on electrical conductivity.

[0082] The prepared composite film has both high conductivity and excellent tensile properties, making it suitable for applications in flexible electronic devices, stretchable sensors, and other fields.

[0083] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a stretchable composite conductive film, characterized in that, Includes the following steps: S1. Carboxylated single-walled carbon nanotubes are vacuum dried at 40-60℃ for 1-3 hours to remove adsorbed moisture, and then placed in a desiccator to cool to room temperature for later use. S2. Prepare 0.1M MES buffer, adjust the pH to 6.0±0.1 with 0.1M HCl, and pre-cool at 4℃ for later use; S3. Take methoxy polyethylene glycolamine (mPEG-NH2), with a molecular weight selected from 2000 Da, 5000 Da or 20000 Da, calculate the amount to be used according to the ratio of 1.2-2.0 times the molar amount of carboxyl group, dissolve it in the MES buffer prepared in step S2, and prepare a solution with a concentration of 100-300 mg / mL. Keep it on ice for later use. S4. Disperse the carboxylated single-walled carbon nanotubes pretreated in step S1 at a concentration of 1-3 mg / mL in the MES buffer prepared in step S2. Perform ultrasonic dispersion under ice bath conditions with a probe, ultrasonic power of 200-300 W, ultrasonic for 2 seconds, intermittent for 3 seconds, and a total ultrasonic time of 8-15 minutes to obtain a uniform carbon nanotube dispersion. S5. Add N-hydroxysuccinimide and 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride sequentially to the dispersion obtained in step S4. The amount of each is 15-25 times the molar amount of the carboxyl group. Stir and activate for 25-35 minutes under ice bath and light-protected conditions. S6. Add the methoxy polyethylene glycolamine solution prepared in step S3 to the reaction solution activated in step S5, and control the molar ratio of methoxy polyethylene glycolamine to carboxyl groups to be 1.2-2.0:

1. Stir the reaction at room temperature and in the dark for 4-8 hours. S7. After the reaction is complete, add hydroxylamine hydrochloride to quench the unreacted activated ester and stir for 20-40 minutes; then centrifuge at 4℃ and 3000-4000 rpm for 8-12 minutes and take the supernatant. S8. Add the supernatant obtained in step S7 to an ultrafiltration centrifuge tube for purification. Centrifuge and concentrate at 4℃ and 3000-4000 g. Then add ultrapure water to dilute to the original volume. Repeat this concentration and dilution operation 6-10 times until no free PEG can be detected in the filtrate. S9. Centrifuge the purified concentrate from step S8 by inverting to recover the PEG-SWCNTs aqueous dispersion. Freeze-dry the dispersion or vacuum-dry it at 30-45℃ to obtain solid PEG-SWCNTs. S10. Disperse the solid PEG-SWCNTs prepared in step S9 in PEDOT:PSS aqueous solution, wherein the mass fraction of PEG-SWCNTs in PEDOT:PSS is 0.1-5.0 wt%, and disperse with ultrasonic assistance for 10-30 minutes to obtain a uniform composite dispersion. S11. Spin-coat the composite dispersion obtained in step S10 onto the substrate at a spin speed of 1000-5000 rpm for 30-60 seconds, and then anneal at 80-150℃ for 10-30 minutes to form a composite film. S12. The composite film obtained in step S11 is subjected to crosslinking treatment, wherein the crosslinking treatment is selected from at least one of thermal crosslinking, ultraviolet light crosslinking or chemical crosslinking agent crosslinking.

2. The method for preparing a stretchable composite conductive film according to claim 1, characterized in that, In step S6, the molar ratio of methoxy polyethylene glycolamine to carboxyl groups is 1.5:1, and the reaction time is 6 hours.

3. The method for preparing a stretchable composite conductive film according to claim 1, characterized in that, In step S8, the concentration and dilution operations are repeated 8 times.

4. The method for preparing a stretchable composite conductive film according to claim 1, characterized in that, In step S10, the mass fraction of PEG-SWCNTs in PEDOT:PSS is 0.5-2.0 wt%.

5. The method for preparing a stretchable composite conductive film according to claim 1, characterized in that, In step S11, the spin coating speed is 2000-3000 rpm, the annealing temperature is 120℃, and the annealing time is 15 minutes.

6. The method for preparing a stretchable composite conductive film according to claim 1, characterized in that, In step S12, when a chemical crosslinking agent is used for crosslinking, the chemical crosslinking agent used is ethylene glycol glycidyl ether, and the crosslinking treatment conditions are: immersing the film in a 0.1-1.0 wt% ethylene glycol glycidyl ether aqueous solution for 10-30 minutes, and then heat-treating it at 100°C for 10 minutes.

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