Composite electrochromic fabric and method for preparing the same

Abstract

The application provides a composite electrochromic fabric and a preparation method thereof. First, aniline solution with trichloromethane as a solvent and ammonium persulfate solution with hydrochloric acid solution as a solvent are prepared; then, a mixed solution is prepared by adding a carboxylated multi-walled carbon nanotube solution into the ammonium persulfate solution; finally, the fabric is stirred in the aniline solution, the mixed solution is added dropwise during the stirring, and the composite electrochromic fabric is obtained by stirring and reacting at room temperature. The electrochromic material is synthesized on the surface of the fabric by using a dynamic interfacial polymerization method, the monomer has high activity and the reaction temperature is low during the reaction, small molecular byproducts can be removed in time, and the ordinary fabric is endowed with the performance of both conductivity and color change through the regulation of the polyaniline film and the multi-walled carbon nanotube. The composite electrochromic fabric has good flexibility and stable electrochromic performance, the flexible substrate makes it have potential wearable property, and the composite electrochromic fabric can be used in the field of future smart clothes and implantable display.

Description

Technical Field

[0001] This invention relates to the field of electrochromic fabric technology, and in particular to a composite electrochromic fabric and its preparation method. Background Technology

[0002] Smart textiles have attracted great interest from both academia and industry, with an extremely wide range of applications. Smart textiles include intelligent temperature-regulating textiles, shape-memory textiles, color-changing textiles, and electronic information smart textiles. Among these, color-changing textiles, whose color changes are directly observable by human vision and can serve as an important visual signal, have attracted significant interest from researchers and consumers. Electrochromism refers to the phenomenon where optical properties change in a stable and reversible manner under the influence of an applied electric field, manifesting as reversible changes in color and transparency. Compared to other types of color-changing textiles, electrochromic textiles have the advantages of high controllability and a wide color-changing range.

[0003] In the prior art, research on electrochromic materials has largely focused on thin film materials. For example, an invention patent (application number CN 201810817393.3) discloses a method for preparing a carbon nanotube-polyaniline electrochromic composite film. This method involves carboxylating multi-walled carbon nanotubes in aqua regia, drying them, dispersing them in isopropanol, and preparing a carbon nanotube film on an ITO glass slide to obtain ITO conductive glass. A dilute sulfuric acid solution of ethanol is prepared, and then aniline monomer is added to obtain an electrodeposition polyaniline precursor solution. A three-electrode system is selected, and electroplating deposition is performed using a potentiostat and constant current deposition to electrochemically deposit a polyaniline electrochromic film on the surface of the carbon nanotube film. However, the above method for preparing electrochromic thin film materials is difficult to apply to the preparation of electrochromic fabric materials because ordinary fabrics have low strength. If electrodeposition is used to composite the fabric, it can easily lead to fiber breakage, causing damage to the fabric's fiber structure and hindering subsequent applications.

[0004] The invention patent (application number CN 202110279348.9) discloses a composite electrochromic material, its preparation method, and its application. The material comprises a core layer, an electrochromic skin layer, and a transparent flexible polymer protective layer, arranged sequentially. The core layer material includes a fluid conductive mixture comprising liquid metal and carboxylated carbon nanotubes. A three-channel nozzle co-extrusion spinning method is used to produce hollow double-layer fibers containing the skin layer and protective layer. The conductive mixture is injected into the cavities of the hollow double-layer fibers to obtain the composite electrochromic material. This method relies on the internal liquid metal for conductivity, placing extremely high demands on the subsequent processing of the material into finished products. It is prone to leakage of the conductive mixture and requires the material to be a hollow double-layer fiber, limiting its application in ordinary fabrics and resulting in low versatility.

[0005] In view of this, it is necessary to design an improved composite electrochromic fabric and its preparation method to solve the above problems. Summary of the Invention

[0006] The purpose of this invention is to provide a composite electrochromic fabric and its preparation method. Using a flexible fabric as the substrate, an electrochromic layer is synthesized on the surface of the fabric at room temperature using a dynamic interface polymer method. Under the condition of not damaging the fabric structure and not impairing the mechanical properties of the fabric, an electrochromic fabric with good flexibility and stable electrochromic properties is obtained.

[0007] To achieve the above-mentioned objective, this invention provides a method for preparing a composite electrochromic fabric, comprising the following steps:

[0008] S1. Prepare an aniline solution with chloroform as the solvent, and prepare an ammonium persulfate solution with hydrochloric acid as the solvent;

[0009] S2. Add carboxylated multi-walled carbon nanotube solution to the ammonium persulfate solution prepared in step S1 to obtain a mixed solution. The volume ratio of the carboxylated multi-walled carbon nanotube solution to the ammonium persulfate solution is (0.05-0.1):1, and the mass percentage concentration of the carboxylated multi-walled carbon nanotube solution is 0.02%-0.1%.

[0010] S3. Place the pretreated fabric in the aniline solution prepared in step S1 and stir for 5-10 minutes. Then add the mixed solution obtained in step S2 and react at room temperature. After cleaning, a composite electrochromic fabric is obtained.

[0011] As a further improvement of the present invention, in step S3, the mixed solution is added slowly dropwise while stirring, and the reaction is also carried out by stirring at room temperature for 2 to 4 hours.

[0012] As a further improvement of the present invention, in step S3, the molar ratio of ammonium persulfate in the added mixed solution to aniline in the aniline solution is 1:(0.9-1.2).

[0013] As a further improvement of the present invention, in step S1, the molar concentration of the hydrochloric acid solution is 1 to 5 mol / L, preferably 2 to 4 mol / L.

[0014] As a further improvement of the present invention, the molar concentration of the aniline solution is 0.005 to 0.05 mol / L, and the molar concentration of the ammonium persulfate solution is 0.005 to 0.05 mol / L.

[0015] As a further improvement of the present invention, in step S3, the pretreatment method of the fabric is to soak the fabric in a sodium hydroxide solution with a concentration of 0.5-1 mol / L, heat it in a water bath at 90-100°C for 30-60 minutes, take it out and then use deionized water and ethanol alternately for ultrasonic treatment for 20-30 minutes, and finally place the fabric at 60°C to dry for 4-6 hours.

[0016] As a further improvement of the present invention, in step S2, before adding the carboxylated multi-walled carbon nanotube solution to the ammonium persulfate solution, the solution is ultrasonically dispersed for 30-40 minutes using a cell disruptor, and after addition, the mixed solution is ultrasonically treated for 20-30 minutes.

[0017] As a further improvement of the present invention, in step S3, the fabric includes one or more of cotton fabric, polyester fabric, and nylon fabric.

[0018] As a further improvement of the present invention, in step S3, the cleaning process is to rinse the prepared fabric with hydrochloric acid solution of the same concentration as in step S1, then rinse it alternately with deionized water and ethanol 2 to 3 times, and then dry it in an oven at 60°C for 4 to 8 hours.

[0019] A composite electrochromic fabric prepared by any one of the above methods, the composite electrochromic fabric comprising a flexible fabric substrate and an electrochromic layer loaded on the surface of the fabric fibers, wherein the morphology of the electrochromic layer is one of a film structure, a tubular stacked network structure, or a sheet-like dense thin film structure.

[0020] The beneficial effects of this invention are:

[0021] 1. The preparation method of the composite electrochromic fabric of the present invention involves first placing the fabric in an aniline solution to adsorb a certain amount of aniline monomers onto its surface, then adding a mixed solution of carboxylated multi-walled carbon nanotubes and ammonium persulfate solution, and stirring the mixture at room temperature for a certain period of time to obtain the composite electrochromic fabric. The composite electrochromic fabric prepared by the present invention uses a flexible fabric as the substrate and polyaniline as both the conductive and color-changing layers. By adding carboxylated multi-walled carbon nanotubes to regulate the formation process and morphology of polyaniline, the electrochromic properties of the conductive fabric are improved. Furthermore, the multi-walled carbon nanotubes possess good mechanical properties and stability, compensating for some of the loss of mechanical properties in the fabric during the reaction. The electrochromic fabric prepared by the present invention exhibits good flexibility and stable electrochromic properties. The flexible substrate makes it potentially wearable and suitable for future smart clothing and implantable display applications.

[0022] 2. In this invention, the aniline solution uses chloroform as a solvent, while the ammonium persulfate solution containing multi-walled carbon nanotubes uses hydrochloric acid as a solvent. The two are immiscible, ensuring that the aniline monomer remains in an oily solvent during the polymerization reaction. Combined with a stirred reaction method, the emulsion undergoes high-speed shearing, resulting in smaller "particles" of the aniline monomer encapsulated by the oily solvent. This increases the total surface area of ​​the reaction interface, making the entire reaction system more uniformly mixed, and accelerating the reaction of the aniline monomer under the oxidation of ammonium persulfate. Simultaneously, the slow dropwise addition of the ammonium persulfate and multi-walled carbon nanotube mixture avoids the aggregation of multi-walled carbon nanotubes, achieving a uniform composite of polyaniline particles and multi-walled carbon nanotubes, thus preventing uneven polymerization caused by the addition of multi-walled carbon nanotubes. The addition of ammonium persulfate provides active oxygen atoms or oxygen free radicals, oxidizing the aniline monomer into free radicals, initiating and accelerating the polymerization reaction. High molecular weight products can be obtained at low reaction levels, shortening the polyaniline formation time.

[0023] 3. This invention uses a dynamic interface polymerization method to synthesize electrochromic materials on the surface of fabrics. During the reaction, the monomers have high activity and the reaction temperature is low, which can remove small molecule byproducts in time, so that a thin film with conductive and color-changing capabilities is formed on the fabric surface. After cleaning and drying, electrochromic fabric is obtained. It realizes the growth of conductive polymer composite films on flexible fabric substrates, even without requiring the fabric to be conductive. Through the regulation of polyaniline film and multi-walled carbon nanotubes, ordinary fabrics are endowed with the properties of both conductivity and color change. The dynamic interface polymerization method used in this invention has low synthesis cost and simple synthesis process, and has good prospects for industrial application. Attached Figure Description

[0024] Figure 1 This is a SEM image of the composite electrochromic fabric prepared in Example 1 of the present invention.

[0025] Figure 2 The figure shows the cyclic voltammetric performance test results of the composite electrochromic fabric prepared in Example 1 of the present invention.

[0026] Figure 3 The time-current curve is shown for the composite electrochromic fabric prepared in Example 1 of this invention.

[0027] Figure 4 The ultraviolet-visible-near-infrared reflectance spectra of the composite electrochromic fabric prepared in Example 1 of the present invention in its colored and bleached states.

[0028] Figure 5 SEM image of the electrochromic fabric prepared for Comparative Example 1.

[0029] Figure 6 SEM image of the electrochromic fabric prepared for Comparative Example 2.

[0030] Figure 7 The image shows a SEM image of the composite electrochromic fabric prepared in Example 2.

[0031] Figure 8 The image shows a SEM image of the composite electrochromic fabric prepared in Example 3.

[0032] Figure 9 The image shows a SEM image of the composite electrochromic fabric prepared in Example 4.

[0033] Figure 10 SEM image of the electrochromic fabric prepared in Comparative Example 4.

[0034] Figure 11 The image shows a SEM image of the composite electrochromic fabric prepared in Example 5.

[0035] Figure 12 The image shows a SEM image of the composite electrochromic fabric prepared in Example 6. Detailed Implementation

[0036] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0037] It should also be noted that, in order to avoid obscuring the present invention with unnecessary details, only the structures and / or processing steps closely related to the present invention are shown in the accompanying drawings, while other details that are not closely related to the present invention are omitted.

[0038] Additionally, it should be noted that the terms “comprising,” “including,” or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0039] A method for preparing a composite electrochromic fabric includes the following steps:

[0040] S1. Prepare an aniline solution in chloroform and an ammonium persulfate solution in hydrochloric acid; wherein the molar concentration of the aniline solution is 0.005–0.05 mol / L and the molar concentration of the ammonium persulfate solution is 0.005–0.05 mol / L.

[0041] S2. Add carboxylated multi-walled carbon nanotube solution to the ammonium persulfate solution prepared in step S1 to obtain a mixed solution. The volume ratio of carboxylated multi-walled carbon nanotube solution to ammonium persulfate solution is (0.05~0.1):1, and the mass percentage concentration of carboxylated multi-walled carbon nanotube solution is 0.02%~0.1%.

[0042] S3. Place the pretreated fabric in the aniline solution prepared in step S1 and stir for 5-10 minutes. Then add the mixed solution obtained in step S2 and react at room temperature. After cleaning, the composite electrochromic fabric is obtained.

[0043] Specifically, this preparation method first places the fabric in an aniline solution, allowing a certain amount of aniline monomer to adsorb onto its surface. Then, a mixed solution of carboxylated multi-walled carbon nanotubes and ammonium persulfate is added, and the mixture is stirred and reacted at room temperature for a certain period of time to obtain a composite electrochromic fabric. This composite electrochromic fabric uses a flexible fabric as the substrate and polyaniline as both the conductive and color-changing layers. By adding carboxylated multi-walled carbon nanotubes to regulate the formation process and morphology of polyaniline, the electrochromic properties of the conductive fabric are improved. Furthermore, the multi-walled carbon nanotubes possess good mechanical properties and stability, compensating for some of the loss of mechanical properties in the fabric during the reaction. It also exhibits good flexibility and stable electrochromic properties. The flexible substrate makes it potentially wearable and suitable for future smart clothing and implantable displays.

[0044] Specifically, in step S3, the mixed solution is added slowly dropwise while stirring. The reaction is also carried out with stirring at room temperature, and the reaction time is 2–4 hours. This method of slowly adding the ammonium persulfate and multi-walled carbon nanotube mixed solution while stirring avoids the problem of multi-walled carbon nanotubes rapidly adsorbing onto the fabric substrate and easily agglomerating when directly mixed with aniline solution, thus affecting the uniform polymerization of polyaniline on the fabric surface. This method achieves uniform composite of polyaniline particles and multi-walled carbon nanotubes, which is beneficial for forming a uniform electrochromic layer on the fabric surface. Furthermore, the aniline solution uses chloroform as a solvent, while the ammonium persulfate solution containing multi-walled carbon nanotubes uses hydrochloric acid solution as a solvent. Since the two are immiscible, the aniline monomer remains in an oily solvent during the polymerization reaction. Combined with the stirring reaction method, the emulsion undergoes high-speed shearing, resulting in smaller "particles" of aniline monomers encapsulated by the oily solvent, thereby increasing the total surface area of ​​the reaction interface, making the entire reaction system more uniformly mixed, and accelerating the reaction of aniline monomers under the oxidation of ammonium persulfate.

[0045] In step S3, the molar ratio of ammonium persulfate in the added mixed solution to aniline in the aniline solution is 1:(0.9–1.2). The addition of ammonium persulfate provides active oxygen atoms or oxygen free radicals, which oxidize the aniline monomer into free radicals, initiating and accelerating the polymerization reaction. It can also accelerate the initiation of the reaction, providing sufficient energy to activate the polymerization reaction of aniline, so that high molecular weight products can be obtained at a low degree of reaction, thus shortening the formation time of polyaniline.

[0046] In step S1, the molar concentration of the hydrochloric acid solution is 1–5 mol / L, preferably 2–4 mol / L. Besides providing two immiscible solvents to the reaction system, which is beneficial to the reaction, the concentration of the hydrochloric acid solution also affects the density and distribution of the polyaniline film formed on the surface of the fabric fibers. Therefore, by controlling the concentration of the hydrochloric acid solution, it is possible to promote the formation of polyaniline while avoiding damage to the mechanical properties of the fabric.

[0047] In step S3, the fabric pretreatment method involves immersing the fabric in a 0.5–1 mol / L sodium hydroxide solution, heating it in a water bath at 90–100°C for 30–60 minutes, then removing it and subjecting it to alternating ultrasonic treatment with deionized water and ethanol for 20–30 minutes. Finally, the fabric is dried at 60°C for 4–6 hours. This fabric pretreatment method increases the number of surface-active groups on the fabric fibers, which is beneficial for the subsequent composite formation of hydroxylated multi-walled carbon nanotubes and polyaniline on the fabric fiber surface.

[0048] In step S2, before adding ammonium persulfate solution to the carboxylated multi-walled carbon nanotube solution, the mixture is ultrasonically dispersed for 30-40 minutes using a cell disruptor. After addition, the mixture is ultrasonically treated for 20-30 minutes. The purpose of using multi-walled carbon nanotubes in this invention is to control the morphology of polyaniline. Multi-walled carbon nanotubes are tubular structures composed of multiple layers of stacked graphene, which are more conducive to composite with polyaniline than single-layer carbon nanotubes. Furthermore, multi-walled carbon nanotubes possess better mechanical properties and stability, thus ensuring the mechanical properties of the fabric.

[0049] More specifically, in step S3, the fabric includes one or more of cotton, polyester, and nylon fabrics. This invention uses a dynamic interfacial polymerization method to synthesize electrochromic materials on the surface of fabrics. The reaction process involves high monomer activity and a low reaction temperature, which effectively removes small molecule byproducts, resulting in a conductive and color-changing film on the fabric surface. After cleaning and drying, the electrochromic fabric is obtained. This invention achieves the growth of conductive polymer composite films on flexible fabric substrates, even without requiring the fabric to be conductive; ordinary flexible fabrics can be used directly. The polyaniline film and multi-walled carbon nanotubes control the properties of ordinary fabrics, giving them both conductivity and color-changing characteristics. The dynamic interfacial polymerization method used in this invention has low synthesis cost, a simple synthesis process, and good prospects for industrial application.

[0050] In some specific embodiments, in step S3, the cleaning process involves rinsing the prepared fabric with a hydrochloric acid solution of the same concentration as in step S1, then rinsing it alternately with deionized water and ethanol 2 to 3 times, and finally drying it in an oven at 60°C for 4 to 8 hours.

[0051] A composite electrochromic fabric prepared by the aforementioned method is disclosed. The composite electrochromic fabric comprises a flexible fabric substrate and an electrochromic layer loaded on the surface of the fabric fibers. The morphology of the electrochromic layer is one of a film structure, a tubular stacked network structure, or a sheet-like dense thin film structure. This composite electrochromic fabric improves the conductivity and electrochromic properties of the fabric through the composite structure of multi-walled carbon nanotubes (MWCNTs) and polyaniline (PANI), and exhibits a rapid color switching rate with a coloring efficiency reaching 67 cm⁻¹. 2 / C.

[0052] Example 1

[0053] This embodiment provides a method for preparing a composite electrochromic fabric, including the following steps:

[0054] S1. Prepare an aniline solution in chloroform: Dissolve 0.0025 mol of aniline monomer in 50 mL of chloroform and stir for about 5 min to obtain a 0.05 mol / L aniline monomer solution.

[0055] To prepare an ammonium persulfate solution in hydrochloric acid: Dissolve 0.0025 mol of ammonium persulfate in 50 mL of 3 mol / L hydrochloric acid solution and sonicate for 10 min to obtain an ammonium persulfate solution with a concentration of 0.05 mol / L.

[0056] S2. Prepare a multi-walled carbon nanotube (MWCNT) solution with a mass percentage concentration of 0.04%. After ultrasonic dispersion for 30 min using a cell disruptor, take 3 mL of the MWCNT solution and add it to the ammonium persulfate solution prepared in step S1 to obtain a mixed solution. Ultrasonically treat the mixed solution for 30 min to ensure that the MWCNTs are evenly dispersed in the solution.

[0057] S3. Select 2×2cm cotton cloth as flexible substrate and pre-treat it: soak the cotton cloth in 0.5mol / L sodium hydroxide solution, heat it in a water bath at 100℃ for 60min, take it out and use deionized water and ethanol alternately for ultrasonic treatment for 20min, and dry the cleaned cotton cloth at 60℃ for 6h for later use.

[0058] The pretreated fabric was placed in the aniline solution prepared in step S1 and stirred for 10 minutes. Then, the mixed solution obtained in step S2 was added to it by stirring and slowly adding dropwise. The mixture was stirred and reacted at room temperature for 2 hours. After the reaction was completed, the cotton fabric was rinsed with 3 mol / L hydrochloric acid solution, and then rinsed with deionized water and ethanol alternately 2 to 3 times. The fabric was then dried in a 60°C oven for 8 hours to obtain the composite electrochromic fabric.

[0059] Please see Figure 1The image shows a SEM image of the composite electrochromic fabric prepared in Example 1. As can be seen from the image, MWCNTs are attached to the cotton fibers, and polyaniline particles are polymerized on both the MWCNTs and the fibers. The overall structure presents uniform tubular particles attached to the cotton fibers, forming a stacked tubular network structure. This structure provides more active sites for aniline, improving the electrochromic performance.

[0060] Please see Figure 2 The figure shows the cyclic voltammetry test results of the composite electrochromic fabric prepared in Example 1. As can be seen from the figure, the curve shows a reduction peak of PANI at 0.2V and an oxidation peak at 0.6V, indicating that the color change of the electrochromic fabric is mainly caused by the change in the redox state of the electrochromic material. The color of the fabric changes from light yellow to dark green as the voltage increases from 0.2V to 0.6V. The figure also shows that the maximum current value of the electrochromic fabric is 0.53mA.

[0061] Please see Figure 3 The figure shows the time-current curve of the composite electrochromic fabric prepared in Example 1. This curve illustrates the color-changing time of the composite electrochromic fabric in both reduced and oxidized states. The figure shows that the coloring time of the fabric is 3.8 s and the bleaching time is 4.7 s. Its rapid and sensitive color switching time is attributed to the addition of 0.04% MWCNTs, which improves the fabric's conductivity. The tubular structure of the multi-walled carbon nanotubes increases the active sites of aniline, enhancing the H+ ionization. + The embedding and detachment rates of the electrochromic layer indicate that the electrochromic fabric prepared in this embodiment has a relatively fast color switching rate.

[0062] Please see Figure 4 The figure shows the UV-Vis-NIR reflectance spectra of the composite electrochromic fabric prepared in Example 1 in both colored and bleached states. It can be seen from the figure that the maximum contrast is observed at 500 nm. According to the coloring efficiency formula: Where Tb is the transmittance in the bleached state and Tc is the transmittance in the colored state; the calculated coloring efficiency of the composite electrochromic fabric prepared in this embodiment is 67 cm⁻¹. 2 / C.

[0063] Comparative Example 1

[0064] Comparative Example 1 provides a method for preparing an electrochromic fabric. The difference from Example 1 is that in step S2, no MWCNTs solution is prepared, and only ammonium persulfate solution is added. The rest is roughly the same as in Example 1, and will not be repeated here.

[0065] Please see Figure 5The image shown is a SEM image of the electrochromic fabric prepared in Comparative Example 1. Compared with Example 1, the film under these conditions is smoother, but due to the lack of multi-walled carbon nanotubes to regulate the morphology of PANI, the dense PANI film on the fiber surface is not conducive to ion insertion and extraction, which significantly increases the color-changing time.

[0066] Comparative Example 2

[0067] Comparative Example 2 provides a method for preparing an electrochromic fabric. Compared with Example 1, the difference is that in step S1, the solvent for the aniline monomer is replaced with 3 mol / L hydrochloric acid, and the reaction time is increased to 4 h. The rest is roughly the same as in Example 1, and will not be repeated here.

[0068] Please see Figure 6 The image shown is a SEM image of the electrochromic fabric prepared in Comparative Example 2. When chloroform is not added to the aniline solution in the reaction system, and only 3 mol / L hydrochloric acid is used as the solvent, the composite film synthesized by both phases being aqueous solutions (i.e., in-situ polymerization) has an uneven morphology. Furthermore, the sheet-like film structure formed by polyaniline encapsulates the multi-walled carbon nanotubes, resulting in the tubular structure of MWCNTs being covered. This prevents the morphology of the PANI film from being controlled and also affects the electrochemical performance of the fabric.

[0069] Comparative Example 3

[0070] Comparative Example 3 provides a method for preparing an electrochromic fabric. Compared with Example 1, the difference is that in step S1, an ammonium sulfate solution was not prepared, and in step S3, the MWCNTs solution was directly added to the aniline solution. The rest is roughly the same as in Example 1, and will not be repeated here.

[0071] The electrochromic fabrics prepared in Comparative Examples 1 to 3 were tested for cyclic voltammetry, electrochromic properties, and fabric coloring efficiency. The results are shown in the table below.

[0072] Table 1. Performance test results of electrochromic fabrics in Example 1 and Comparative Examples 1-3

[0073] Maximum current value (mA) Coloring time (s) Bleaching time (s) <![CDATA[Coloring efficiency (cm 2 / C)]]> Example 1 0.53 3.8 4.7 67 Comparative Example 1 0.36 3.9 5.1 45 Comparative Example 2 0.28 4.5 6.4 38 Comparative Example 3 0.06 - - 0

[0074] As shown in Table 1, in Comparative Example 3, the reaction could not be completed without ammonium persulfate, and almost no polymerization products were found on the fabric. This is attributed to the fact that ammonium persulfate is both an initiator and oxidant for aniline polymerization. Without ammonium persulfate, polyaniline cannot polymerize in a short time, thus preventing the preparation of polyaniline electrochromic films under these conditions. In Comparative Example 1, without the addition of multi-walled carbon nanotubes (MWCNTs), the lack of carbon nanotube regulation resulted in a dense and irregular film formed on the cotton fibers, leading to a decrease in ion penetration rate. Consequently, bleaching / dyeing times increased, and the dyeing efficiency was worse than in Example 1. In Comparative Example 2, when chloroform was not added to the aniline solution and only 3 mol / L hydrochloric acid was used as the solvent, the composite film synthesized by using aqueous solutions for both phases (i.e., in-situ polymerization) exhibited an uneven morphology. Furthermore, the sheet-like film structure formed by polyaniline encapsulated the MWCNTs, preventing the regulation of the PANI film morphology and affecting the electrochemical properties of the fabric.

[0075] Examples 2-4

[0076] Examples 2-4 provide a method for preparing electrochromic fabric. Compared with Example 1, the difference is that in step S2, the mass percentage concentration of the multi-walled carbon nanotube solution is 0.02%, 0.06%, and 0.08%, respectively. The rest is roughly the same as in Example 1, and will not be repeated here.

[0077] Please see Figure 7 The image shown is a SEM image of the composite electrochromic fabric prepared in Example 2. When only 0.02% MWCNTs were added, the concentration of carbon nanotubes was too low, so it had little effect on the morphology of polyaniline. A polyaniline film was also formed on the surface of the cotton fabric, forming a film structure. However, this film was thinner than the film without MWCNTs. Under the same voltage scanning electron microscope, cracks appeared in the film of this sample, indicating that the film was thinner and had poorer stability.

[0078] Please see Figure 8 The image shown is a SEM image of the composite electrochromic fabric prepared in Example 3. Compared with the sample in Example 1, the nanocomposite film at this multi-walled carbon nanotube concentration exhibited slight aggregation. This is attributed to the increased concentration of MWCNTs, which caused aniline to aggregate more at the sites where some carbon nanotubes had aggregated, forming a larger particle structure.

[0079] Please see Figure 9 The image shown is a SEM image of the composite electrochromic fabric prepared in Example 4. With increasing MWCNT concentration, carbon nanotubes aggregate, causing the PANI polymerized on the cotton fibers to exhibit a sheet-like stacked film structure, forming a dense sheet-like thin film structure. This structure is unfavorable for ion insertion and extraction, and has a certain impact on its electrochromic properties.

[0080] Comparative Example 4

[0081] Comparative Example 4 provides a method for preparing an electrochromic fabric. The difference from Example 1 is that in step S2, the mass percentage concentration of the multi-walled carbon nanotube solution is 0.1%, and the rest is roughly the same as in Example 1, which will not be repeated here.

[0082] Please see Figure 10 The image shows a SEM image of the electrochromic fabric prepared in Comparative Example 4. As can be seen from the image, the increased concentration of MWCNTs leads to their extensive adhesion to the cotton fiber surface. Polyaniline forms a thick film covering the fiber surface with large aggregates and uneven morphology, affecting its electrochromic properties.

[0083] Examples 5-6

[0084] Examples 5 and 6 provide a method for preparing electrochromic fabrics. Compared with Example 1, the difference is that in step S1, the concentration of hydrochloric acid is 2 mol / L and 4 mol / L, respectively. The rest is roughly the same as in Example 1, and will not be repeated here.

[0085] Please see Figure 11 The image shown is a SEM image of the composite electrochromic fabric prepared in Example 5. As can be seen from the image, carbon nanotubes are clearly visible on the surface of the PANI-MWCNTS nanocomposite film polymerized at this hydrochloric acid concentration. Polyaniline particles grow by adhering to the tubular structure of the carbon nanotubes, forming a mesh-like structure on the film surface, similar in morphology to Example 1, but less uniform than the film formed in Example 1.

[0086] Please see Figure 12 The image shown is a SEM image of the composite electrochromic fabric prepared in Example 6. Compared with Example 1, the polyaniline film formed under this hydrochloric acid concentration is denser. Although multi-walled carbon nanotubes can be seen attached to the fiber surface, their distribution is uneven. Observation of the overall morphology of the fabric revealed that the hydrochloric acid under this condition is relatively strong and has a certain corrosive effect on cotton fabrics.

[0087] Comparative Example 5

[0088] Comparative Example 5 provides a method for preparing an electrochromic fabric. The difference from Example 1 is that in step S1, the concentration of hydrochloric acid is 6 mol / L. The rest is roughly the same as in Example 1 and will not be repeated here.

[0089] The electrochromic fabrics prepared in Examples 2-6 and Comparative Examples 4-5 were tested for cyclic voltammetry, electrochromic properties, and fabric coloring efficiency. The results are shown in the table below.

[0090] Table 2. Performance test results of electrochromic fabrics in Examples 2-6 and Comparative Examples 4-5

[0091]

[0092]

[0093] Table 2 shows that with increasing concentration of multi-walled carbon nanotubes (WMCNTs) solution, the maximum current value of the prepared polyaniline electrochromic fabric increases, and the coloring / bleaching time also increases. However, the coloring efficiency is maximized at a concentration of 0.04% WMCNTs, which is attributed to the well-integrated morphology of the polyaniline and carbon nanotube network structure, providing more channels for ion penetration and making the color change more obvious. Meanwhile, the acidity of the system also affects the synthesis of polyaniline. When the solution acidity is low, the conductivity of the fabric decreases; when the acidity is too high, the solution corrodes the cotton fibers, thus affecting the performance of the composite electrochromic fabric. The optimal performance is obtained at a hydrochloric acid concentration of 3 mol / L.

[0094] In summary, this invention provides a composite electrochromic fabric and its preparation method. First, the fabric is placed in an aniline solution to adsorb a certain amount of aniline monomers onto its surface. Then, a mixed solution of carboxylated multi-walled carbon nanotubes and ammonium persulfate is added, and the mixture is stirred at room temperature for a certain time to obtain the composite electrochromic fabric. An electrochromic material is synthesized on the fabric surface using a dynamic interfacial polymerization method. During the reaction, the monomer activity is high and the reaction temperature is low, allowing for the timely removal of small molecule byproducts, resulting in a conductive and color-changing film on the fabric surface. After cleaning and drying, the electrochromic fabric is obtained. This invention achieves the growth of a conductive polymer composite film on a flexible fabric substrate, even without requiring the fabric to be conductive. Through the regulation of the polyaniline film and multi-walled carbon nanotubes, ordinary fabrics are endowed with both conductive and color-changing properties. Furthermore, the synthesis cost is low, the synthesis process is simple, and it has good prospects for industrial application. The composite electrochromic fabric of this invention uses a flexible fabric as the substrate and polyaniline as the conductive and color-changing layers. By adding carboxylated multi-walled carbon nanotubes to regulate the formation process and morphology of polyaniline, the electrochromic properties of the conductive fabric are improved. Moreover, the multi-walled carbon nanotubes have good mechanical properties and stability, which compensates for some of the loss of mechanical properties of the fabric during the reaction. This fabric has good flexibility and stable electrochromic properties. The flexible substrate makes it potentially wearable and can be used in the fields of future smart clothing and implantable displays.

[0095] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention.

Claims

1. A method for preparing a composite electrochromic fabric, characterized in that, Includes the following steps: S1. Prepare an aniline solution with chloroform as the solvent, and prepare an ammonium persulfate solution with hydrochloric acid as the solvent; S2. Add carboxylated multi-walled carbon nanotube solution to the ammonium persulfate solution prepared in step S1 to obtain a mixed solution. The volume ratio of the carboxylated multi-walled carbon nanotube solution to the ammonium persulfate solution is (0.05-0.1):1, and the mass percentage concentration of the carboxylated multi-walled carbon nanotube solution is 0.02%-0.1%. S3. Place the pretreated fabric in the aniline solution prepared in step S1 and stir for 5-10 minutes. Then add the mixed solution obtained in step S2 and react at room temperature. After cleaning, a composite electrochromic fabric is obtained.

2. The method for preparing the composite electrochromic fabric according to claim 1, characterized in that, In step S3, the mixed solution is added slowly dropwise while stirring. The reaction is also carried out by stirring at room temperature, and the reaction time is 2 to 4 hours.

3. The method for preparing the composite electrochromic fabric according to claim 1, characterized in that, In step S3, the molar ratio of ammonium persulfate in the added mixed solution to aniline in the aniline solution is 1:(0.9-1.2).

4. The method for preparing the composite electrochromic fabric according to claim 1, characterized in that, In step S1, the molar concentration of the hydrochloric acid solution is 1 to 5 mol / L.

5. The method for preparing the composite electrochromic fabric according to claim 4, characterized in that, The concentration of the hydrochloric acid solution is 2–4 mol / L.

6. The method for preparing the composite electrochromic fabric according to claim 3, characterized in that, The molar concentration of the aniline solution is 0.005–0.05 mol / L, and the molar concentration of the ammonium persulfate solution is 0.005–0.05 mol / L.

7. The method for preparing the composite electrochromic fabric according to claim 1, characterized in that, In step S3, the pretreatment method of the fabric is to soak the fabric in a sodium hydroxide solution with a concentration of 0.5-1 mol / L, heat it in a water bath at 90-100°C for 30-60 minutes, take it out and then use deionized water and ethanol alternately for ultrasonic treatment for 20-30 minutes, and finally place the fabric at 60°C to dry for 4-6 hours.

8. The method for preparing the composite electrochromic fabric according to claim 1, characterized in that, In step S2, before the carboxylated multi-walled carbon nanotube solution is added to the ammonium persulfate solution, it is ultrasonically dispersed for 30-40 minutes using a cell disruptor. After addition, the mixed solution is ultrasonically treated for 20-30 minutes.

9. The method for preparing the composite electrochromic fabric according to claim 1, characterized in that, In step S3, the fabric includes one or more of cotton, polyester, and nylon fabrics.

10. The method for preparing the composite electrochromic fabric according to claim 1, characterized in that, In step S3, the cleaning process involves rinsing the prepared fabric with a hydrochloric acid solution of the same concentration as in step S1, then rinsing it alternately with deionized water and ethanol 2 to 3 times, and finally drying it in an oven at 60°C for 4 to 8 hours.

11. A composite electrochromic fabric prepared by the preparation method according to any one of claims 1 to 10, characterized in that, The composite electrochromic fabric includes a flexible fabric substrate and an electrochromic layer loaded on the surface of the fabric fibers. The morphology of the electrochromic layer is one of a film structure, a tubular stacked network structure, or a sheet-like dense thin film structure.

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