Preparation method of degradable transparent conductive polymer film

Abstract

The invention discloses a preparation method of a degradable transparent conductive polymer film, and belongs to the technical field of film preparation. Preparing dispersion liquid I through graphene oxide quantum dots; preparing a dispersion liquid II from polyaniline nanofibers; dissolving pyrrole and toluenesulfonic acid in N, N-dimethylformamide to prepare a reaction solution, adding the dispersion liquid I and the dispersion liquid II, stirring, and adding ferric chloride hexahydrate to obtain a reaction solution; adjusting the pH value of the reaction solution to 1.5, and heating to obtain a polypyrrole solution; preparing cellulose acetate, polyvinyl alcohol and N, N-dimethylformamide to obtain a cellulose acetate solution; mixing the polypyrrole solution and the cellulose acetate solution, adding glutaraldehyde to obtain a mixed solution, and pouring the mixed solution into a mold to prepare a composite wet film; and putting the composite wet film into a hot-pressing forming machine for hot-pressing to generate the polymer film. The conductive polymer film prepared by the invention can be applied to the fields of supercapacitor electrode materials, electromagnetic shielding materials, flexible sensors and the like, and provides a new high-performance material choice for the development of related fields.

Description

Technical Field

[0001] The present invention belongs to the technical field of thin film preparation, and particularly relates to a method for preparing a degradable transparent conductive polymer thin film. Background Art

[0002] The transparent conductive polymer thin film combines high light transmittance and high electrical conductivity, and is the core material for realizing the functions of transparent optoelectronic devices, with broad application prospects. The transparent conductive polymer thin film has excellent flexibility, high transparency and stable electrical conductivity, and can meet the strict requirements for the thin film performance during multiple folding processes of the foldable display screen. Therefore, it can be used as the electrode material of the display screen to achieve high-resolution and high-contrast image display, providing key technical support for the development of electronic devices such as foldable mobile phones and tablet computers. It can also be used to make flexible keyboards and touch panels. Its good electrical conductivity and flexibility make the keyboard keys feel sensitive and the touch panel respond quickly, enabling designs of arbitrary shapes and creating conditions for the appearance innovation of electronic devices and the improvement of user experience. At the same time, it may also be used in the field of flexible solar cells. As the electrode material of flexible solar cells, the new conductive thin film can effectively collect and transport photo-generated carriers, improving the photoelectric conversion efficiency of the battery. In the emerging field of perovskite solar cells, the flexible transparent conductive thin film can promote charge transport and interface stability, further enhancing the performance and stability of flexible solar cells. In addition, the high sensitivity, good flexibility and biocompatibility of the flexible transparent conductive thin film enable it to accurately sense human physiological signals and external environmental changes, and can be used to make various flexible sensors, such as pressure sensors, temperature sensors, and biosensors, providing reliable sensing elements for the applications of smart wearable devices in health monitoring, sports tracking, etc.

[0003] However, the traditional preparation processes of transparent conductive films have many limitations, severely restricting their performance improvement and large-scale applications. For example: 1. It is difficult to balance conductivity and transparency: Under traditional preparation processes, to improve the conductivity of polymer films, a large amount of conductive fillers, such as metal nanoparticles and carbon nanotubes, often need to be added. This results in a decrease in the optical transparency of the film, making it difficult to meet the requirements in application scenarios with extremely high transparency requirements, such as the high-end display field; conversely, if high transparency is pursued by reducing the amount of conductive fillers, the conductivity of the film will be insufficient, and it cannot effectively transmit current. 2. Lack of flexibility and stability: When some transparent conductive films prepared by traditional processes are bent or folded, problems such as the breakage of the conductive network and film delamination are likely to occur, leading to a decrease in conductivity and mechanical properties. This is because the interfacial bonding force between the polymer and the conductive filler is weak, and under external stress, the two cannot work together, seriously affecting the service life and reliability of the film in flexible electronic devices. 3. High raw material costs: Traditional processes often rely on expensive metal nanomaterials or high-performance polymers as raw materials. For example, when preparing transparent conductive films based on silver nanowires, the price of silver nanowires is high, and their synthesis process is complex, further increasing the cost. In addition, some high-performance polymers, such as polyimide, although having good comprehensive properties, have expensive raw materials, restricting large-scale applications. 4. Complex preparation steps: The traditional processes for preparing transparent conductive films often involve multiple steps, such as solution spin-coating, thermal annealing, chemical modification, etc. Each step requires precise control of conditions, and there is a waiting time between steps. For example, after spin-coating, the solvent needs to be waited to volatilize, and thermal annealing requires heating and cooling processes. The process steps are cumbersome, greatly prolonging the production cycle and reducing production efficiency. In addition, many traditional processes are difficult to adapt to continuous production modes. For example, the vacuum evaporation method requires placing substrates one by one in a vacuum chamber for coating, and cannot achieve large-scale and high-efficiency continuous production, restricting the production capacity improvement of transparent conductive films. 5. Environmentally unfriendly: Traditional flexible transparent conductive polymer films use polyethylene terephthalate (PET) films as the base film, and PET cannot be naturally degraded, bringing great pressure to environmental protection. Therefore, developing a new preparation process for flexible transparent conductive polymer films and constructing flexible transparent conductive films with good biocompatibility / environmental compatibility and excellent degradation performance to replace traditional conductive films based on PET has important practical significance. Summary of the Invention

[0004] In view of this, the purpose of the present invention is to provide a preparation method of a degradable transparent conductive polymer film to solve the above problems.

[0005] To achieve the above purpose, the present invention provides the following technical solutions:

[0006] The present invention provides a preparation method of a degradable transparent conductive polymer film, including the following steps,

[0007] S1. Disperse graphene oxide quantum dots in N,N-dimethylformamide, and after ultrasonic treatment, obtain dispersion liquid one; separately, add polyaniline nanofibers to N,N-dimethylformamide, and stir evenly to obtain dispersion liquid two;

[0008] S2. Dissolve pyrrole and toluenesulfonic acid in N,N-dimethylformamide, and under ice bath conditions, prepare a reaction solution with a mass fraction of 10%. Then add dispersion liquid one and dispersion liquid two and stir, and add ferric chloride hexahydrate under stirring to obtain a reaction solution;

[0009] S3. Transfer the reaction solution to a three-necked flask, add hydrochloric acid to adjust the pH value to 1.5, and then place it in a water bath and heat to 60 °C for 2 hours. After pyrrole undergoes an in-situ polymerization reaction to form polypyrrole (PPy), obtain a polypyrrole solution;

[0010] S4. Add N,N-dimethylformamide to cellulose acetate (CA) and polyvinyl alcohol (PVA), then seal with plastic wrap and stir magnetically. After cellulose acetate and polyvinyl alcohol are completely dissolved, perform ultrasonic treatment for half an hour to remove bubbles, and then add tributyl citrate and let it stand overnight to obtain a cellulose acetate solution;

[0011] S5. Slowly mix the polypyrrole solution with the cellulose acetate solution, mechanically stir and disperse, then add glutaraldehyde and continue to stir evenly to obtain a mixed solution. Slowly pour the mixed solution into a polytetrafluoroethylene mold, and place the mold in a fume hood to volatilize for 24 h. After the solvent is basically volatilized, prepare a composite wet film;

[0012] S6. Place the composite wet film in a hot press and hot press for 20 - 30 minutes. During the hot press process, the cellulose acetate molecular chains rearrange and orient under the action of pressure, tributyl citrate plasticizes the cellulose acetate molecular chains, and glutaraldehyde reacts with the hydroxyl groups on the polyvinyl alcohol molecular chains to obtain a partially cross-linked structure, forming a degradable flexible transparent conductive polymer film with excellent mechanical properties.

[0013] Further, in step S2, the molar ratio of pyrrole, toluenesulfonic acid, and ferric chloride hexahydrate is 1∶1∶1.

[0014] Further, in step S4, the mass ratio of cellulose acetate to polyvinyl alcohol is 10∶1; the mass fraction of tributyl citrate is 5% - 25% of cellulose acetate.

[0015] Further, in step S5, the mass ratio of polypyrrole to cellulose acetate is 1 - 5%∶100.

[0016] Further, in step S6, the conditions of the hot press are 100 - 150 °C and a pressure of 25 - 40 MPa.

[0017] The beneficial effects of the present invention are:

[0018] 1. In the present invention, ferric chloride hexahydrate is used as an oxidant to capture electrons from pyrrole molecules, triggering an oxidative polymerization reaction of pyrrole monomers to form polypyrrole chains. Polypyrrole has a conjugated π electron structure, which allows electrons to move freely on the molecular chain, thereby giving the material a certain conductivity.

[0019] 2. The graphene oxide quantum dots in the present invention have excellent electrical properties and a large specific surface area, and can form a good electron transmission channel with polypyrrole, further improving the conductivity of the film; polyaniline nanofibers can increase the conductive network inside the film, and synergize with polypyrrole to improve the overall conductive properties.

[0020] 3. In the present invention, under the action of the cross-linking agent glutaraldehyde, the molecular chains of polyvinyl alcohol form covalent cross-links to form a three-dimensional network structure. This structure can not only enhance the mechanical properties of the film, but also firmly fix polypyrrole, graphene oxide quantum dots and polyaniline nanofibers in the network, prevent their agglomeration and migration in the film, and ensure the stability of the film structure and the durability of the performance. Cellulose acetate, as a film-forming aid, can improve the forming properties of the film, so that the film has good flexibility and uniformity, and is also degradable.

[0021] 4. The conductive polymer film prepared by the present invention has excellent conductivity through the synergistic effect of polypyrrole, graphene oxide quantum dots and polyaniline nanofibers, and the square resistance can reach below 50Ω / sq, which is significantly better than the traditional single polypyrrole conductive film. In addition, due to the presence of the polyvinyl alcohol cross-linked network in the present invention, the tensile strength of the film can reach more than 20MPa, and the elongation at break can reach 15%. It has good flexibility and impact resistance, and can meet the needs of a variety of practical application scenarios. The conductive polymer film prepared by the present invention can be used in supercapacitor electrode materials, electromagnetic shielding materials, flexible sensors and other fields, providing a new high-performance material selection for the development of related fields.

[0022] Other advantages, objectives and features of the present invention will be described in the following description and will be apparent to those skilled in the art to some extent, or those skilled in the art may be taught from the practice of the present invention. The objectives and other advantages of the present invention may be realized and obtained through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to make the purpose, technical solution and beneficial effects of the invention clearer, the present invention provides the following drawings for illustration:

[0024] Figure 1The influence of the plasticizer content on the tensile strength of the degradable flexible transparent conductive polymer film in the present invention;

[0025] Figure 2 The influence of the plasticizer content on the elongation at break of the degradable flexible transparent conductive polymer film in the present invention;

[0026] Figure 3 The corresponding curve of the change in film resistance of the degradable flexible transparent conductive polymer film in the present invention versus the number of bending times;

[0027] Figure 4 The ultraviolet-visible light transmission spectra of the pure cellulose acetate film and its conductive composite film in the present invention;

[0028] Figure 5 The relationship curve of the surface resistance and the light transmittance at 550 nm of the degradable films with different polypyrrole contents in the present invention. Detailed implementation manners

[0029] As Figures 1-5 shown, the present invention provides a preparation method of a degradable transparent conductive polymer film.

[0030] Example 1

[0031] S1. Disperse 5 parts of graphene oxide quantum dots in 20 parts of N,N-dimethylformamide, and obtain dispersion liquid one after ultrasonic treatment; separately, add 8 parts of polyaniline nanofibers to 10 parts of N,N-dimethylformamide, and stir evenly to obtain dispersion liquid two;

[0032] S2. Dissolve 10 parts of pyrrole and 10 parts of toluenesulfonic acid in N,N-dimethylformamide, and prepare a reaction solution with a mass fraction of 10% under an ice bath condition. Then add dispersion liquid one and dispersion liquid two and stir, and add 10 parts of ferric chloride hexahydrate under stirring to obtain a reaction solution;

[0033] S3. Transfer the reaction solution to a three-necked flask, add hydrochloric acid to adjust the pH value to 1.5, and then place it in a water bath and heat to 60 °C for reaction for 2 hours. After the pyrrole undergoes an in-situ polymerization reaction to generate polypyrrole, obtain a polypyrrole solution;

[0034] S4. Weigh 10 parts of cellulose acetate and 1 part of polyvinyl alcohol, add 90 parts of N,N-dimethylformamide thereto, then seal with a plastic wrap and stir magnetically. After the cellulose acetate and polyvinyl alcohol are completely dissolved, perform ultrasonic treatment for 30 min for degassing, and then add tributyl citrate accounting for 5% of the total mass of cellulose acetate and stir, and let it stand overnight to obtain a cellulose acetate solution;

[0035] S5. Mix the polypyrrole solution and the cellulose acetate solution according to a mass ratio of the solutes (PPy and CA) of 1:100, and disperse them by mechanical stirring. Then, add glutaraldehyde with a mass of 1% of polyvinyl alcohol and continue to stir evenly to obtain a mixed solution. Slowly pour the mixed solution into a polytetrafluoroethylene mold, and place the mold in a fume hood to volatilize for 24 h. After the solvent is basically volatilized, a composite wet film is formed.

[0036] S6. Put the composite wet film into a hot press molding machine, and hot press it at a temperature of 100 - 150 °C and a pressure of 25 - 40 MPa for 20 - 30 minutes. During the hot pressing process, the molecular chains of cellulose acetate are rearranged and oriented under the action of pressure, tributyl citrate plasticizes the molecular chains of cellulose acetate, and glutaraldehyde reacts with the hydroxyl groups on the molecular chains of polyvinyl alcohol to obtain a partially cross-linked structure, forming a degradable flexible transparent conductive polymer film (PPy-1) with excellent mechanical properties.

[0037] Example 2

[0038] The difference between Example 2 and Example 1 is that the mass ratio of polypyrrole (PPy-2) to cellulose acetate is 2:100.

[0039] Example 3

[0040] The difference between Example 3 and Example 1 is that the mass ratio of polypyrrole (PPy-3) to cellulose acetate is 3:100.

[0041] Example 4

[0042] The difference between Example 4 and Example 1 is that the mass ratio of polypyrrole (PPy-4) to cellulose acetate is 4:100.

[0043] Example 5

[0044] The difference between Example 5 and Example 1 is that the mass ratio of polypyrrole (PPy-5) to cellulose acetate is 5:100.

[0045] To prove the superiority of the present invention, Comparative Examples 1 - 2 are set here.

[0046] Comparative Example 1

[0047] The difference between Comparative Example 1 and Example 1 is that the mass ratio of polypyrrole to cellulose acetate is 6:100.

[0048] Comparative Example 2

[0049] The difference between Comparative Example 2 and Example 1 is that the mass ratio of polypyrrole to cellulose acetate is 0.5:100.

[0050] ① Mechanical property test:

[0051] The film was subjected to a tensile test using a universal material testing machine to measure parameters such as its tensile strength and elongation at break. At the same time, a bending test was performed on the film using a bending testing machine, and the resistance change of the film under different numbers of bends was recorded.

[0052] As Figures 1-2 shown, the tensile strength of the film prepared by the present invention is higher than 100 MPa, and the elongation at break is greater than 15%. For a transparent conductive film, mechanical properties such as bend resistance of the film are also crucial to ensure that the film can be used in wearable flexible devices. The surface resistance change rate (ΔR) is calculated using the formula:

[0053] ΔR = (R - R0) / R0

[0054] wherein, R0 is the original resistance value; R is the resistance value after testing.

[0055] As Figure 3 shown, after 1000 bends, the resistance change rate of the film is less than 5%, demonstrating excellent mechanical properties and flexibility.

[0056] ② Optical property test:

[0057] As Figure 4 shown, by comparing Examples 1 - 5, as the polypyrrole content increases, the transmittance of the cellulose acetate conductive film decreases. When the polypyrrole solution content in the cellulose acetate conductive film is 1%, the transmittance of the film at 550 nm is 86.4%, which can meet the requirements for transparency in most optical applications.

[0058] In Comparative Example 1, the mass ratio of polypyrrole to cellulose acetate is 6:100. Excessive addition of polypyrrole will result in too low transparency of the film; in Comparative Example 2, the mass ratio of polypyrrole to cellulose acetate is 0.5:100. Too little addition of polypyrrole will result in insufficient conductivity of the film.

[0059] ③ Electrical property test:

[0060] The sheet resistance of the degradable transparent conductive polymer film was measured using a four-probe tester. As Figure 5 shown, the sheet resistance of the degradable transparent conductive polymer film prepared by the solution polymerization - hot pressing method is 210 Ω / sq, indicating that the film has excellent conductivity. At present, the market's resistive touch screen requires a sheet resistance of 300 Ω / sq and a transmittance of 82% - 92%.

[0061] Therefore, the degradable transparent conductive polymer film prepared by the present invention can meet the requirements of market products for transmittance and resistivity.

[0062] Compare the performance of the degradable transparent conductive polymer film prepared by the new process with that of the same type of film prepared by the traditional process. Under the same test conditions, the transmittance of the PEDOT∶PSS film prepared by the traditional process is 75%-80%, the sheet resistance is 150-200 Ω / sq, and the resistance change rate exceeds 15% after 1000 bending times; for the silver nanowire-based film prepared by the traditional process, although it has good conductivity (sheet resistance about 30-50 Ω / sq), its transmittance is only 70%-75%, and the silver nanowires are prone to falling off during the bending process, resulting in a significant increase in resistance. The comparison results fully prove that the degradable transparent conductive polymer film of the present invention has excellent mechanical properties, electrical conductivity and transparency, and the new preparation process proposed by the present invention has significant advantages in improving the comprehensive performance of the film.

[0063] Finally, it should be noted that the above preferred embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail through the above preferred embodiments, those skilled in the art should understand that various changes can be made in form and details without departing from the scope defined by the claims of the present invention.

Claims

1. A preparation method of a degradable transparent conductive polymer film, characterized in that: It includes the following steps: S1. Disperse graphene oxide quantum dots in N,N-dimethylformamide, and after ultrasonic treatment, obtain dispersion liquid one; separately take polyaniline nanofibers and add them to N,N-dimethylformamide, and stir evenly to obtain dispersion liquid two; S2. Dissolve pyrrole and p-toluenesulfonic acid in N,N-dimethylformamide, and prepare a reaction solution with a mass fraction of 10% under an ice bath condition. Then add dispersion liquid one and dispersion liquid two and stir, and add ferric chloride hexahydrate under stirring to obtain a reaction solution; S3. Transfer the reaction solution to a three-necked flask, add hydrochloric acid to adjust the pH value to 1.5, and then place it in a water bath and heat to 60 °C for reaction for 2 hours. After pyrrole undergoes in-situ polymerization reaction, poly-pyrrole is generated to obtain a poly-pyrrole solution; S4. Add N,N-dimethylformamide to cellulose acetate and a small amount of polyvinyl alcohol, then seal it with a plastic wrap and stir magnetically. After cellulose acetate and polyvinyl alcohol are completely dissolved, ultrasonic for half an hour to remove bubbles, and then add tributyl citrate and let it stand overnight to obtain a cellulose acetate solution; S5. Slowly mix the poly-pyrrole solution with the cellulose acetate solution, stir and disperse mechanically, then add glutaraldehyde and continue to stir evenly to obtain a mixed solution. Slowly pour the mixed solution into a polytetrafluoroethylene mold, and place the mold in a fume hood to volatilize for 24 h. After the solvent is basically volatilized, a composite wet film is formed; S6. Put the composite wet film into a hot press and hot press for 20 - 30 minutes. During the hot press process, the molecular chains of cellulose acetate are rearranged and oriented under the action of pressure, tributyl citrate plasticizes the molecular chains of cellulose acetate, and glutaraldehyde crosslinks polyvinyl alcohol to form a degradable flexible transparent conductive polymer film with excellent mechanical properties.

2. The preparation method of a degradable transparent conductive polymer film according to claim 1, characterized in that: In the step S2, the molar ratio of pyrrole, p-toluenesulfonic acid, and ferric chloride hexahydrate is 1∶1∶1.

3. The preparation method of a degradable transparent conductive polymer film according to claim 1, characterized in that: In the step S4, the mass ratio of cellulose acetate to polyvinyl alcohol is 10∶1; the mass fraction of tributyl citrate is 5% - 25% of cellulose acetate.

4. The preparation method of a degradable transparent conductive polymer film according to claim 1, wherein: In the step S5, the mass ratio of poly-pyrrole to cellulose acetate is 1 - 5∶100.

5. The preparation method of a degradable transparent conductive polymer film according to claim 1, wherein: In the step S6, the conditions of the hot press are 100 - 150 °C and the pressure is 25 - 40 MPa.

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