Poly(3,4-ethylenedioxythiophene) and method for its preparation, use

Abstract

The present disclosure relates to a kind of poly (3, 4-ethylenedioxythiophene) and its preparation method, application, belongs to conductive polymer material field.The preparation method of the poly (3, 4-ethylenedioxythiophene) includes: nitrogen-containing heterocyclic compound or arylamine compound is added to 3, 4-ethylenedioxythiophene, stirring and obtaining mixed solution;Mixed solution is added to iron salt compound and stirs, under the polymerization regulation of nitrogen-containing heterocyclic compound or arylamine compound and the oxidation of iron salt compound, 3, 4-ethylenedioxythiophene partially polymerized prepolymer is obtained;Prepolymer is heated, so that 3, 4-ethylenedioxythiophene continues to polymerize, and poly (3, 4-ethylenedioxythiophene) containing polymer is obtained.Using the preparation method of the present disclosure, the preparation process is solventized and does not add adhesive, and the poly (3, 4-ethylenedioxythiophene) polymer film prepared can shield 99% electromagnetic interference when 50 μm.

Description

Technical Field

[0001] This disclosure relates to the field of conductive polymer materials, specifically to a poly(3,4-ethylenedioxythiophene) and its preparation method and applications. Background Technology

[0002] With the rapid development of modern industry and communication technology, electromagnetic radiation has become the fourth largest form of pollution after noise pollution, water pollution, and air pollution, seriously endangering people's normal production and life, especially interfering with precision instruments. Therefore, it is essential to take effective measures to reduce or eliminate the hazards of electromagnetic radiation. Electromagnetic shielding materials are a class of materials that can absorb or reflect electromagnetic waves, highlighting the importance of developing such materials. Compared to traditional metal materials, conductive polymer composites are not only lower in cost and density, but also corrosion-resistant and easy to process and mold. Furthermore, the conductivity of the material can be further adjusted by regulating the material structure or the amount or type of conductive filler. These advantages make conductive polymer composites a major research direction. Related technologies typically use metal particles such as silver and copper as conductors and polymer foam as the matrix to form electromagnetic shielding composite foam materials. However, these materials suffer from drawbacks such as complex preparation processes, the need for solvents, and poor conductivity.

[0003] Poly(3,4-ethylenedioxythiophene), as a polymer material with high thermal stability, bending resistance, adjustable conductivity, and low cost, is widely used in electromagnetic shielding. Currently, the polymerization methods for poly(3,4-ethylenedioxythiophene) mainly include electrochemical deposition, vapor polymerization, and in-situ chemical polymerization. Electrochemical deposition, which polymerizes 3,4-ethylenedioxythiophene by passing an electric current through a solution containing 3,4-ethylenedioxythiophene, is only suitable for small-scale preparations. Vapor polymerization uses nitrogen or argon gas to blow 3,4-ethylenedioxythiophene onto the surface of a reaction substrate coated with an oxidant, oxidizing it to form poly(3,4-ethylenedioxythiophene) deposited on the substrate surface. This method is more complex and has poorer controllability. The chemical in-situ polymerization method involves a two-step process: first, an oxidant is coated onto a substrate, and then 3,4-ethylenedioxythiophene is superimposed on it, which then polymerizes to produce poly(3,4-ethylenedioxythiophene). This method is relatively complex, and the poly(3,4-ethylenedioxythiophene) film prepared is relatively thin, which limits the application of this polymer in the field of electromagnetic shielding.

[0004] Therefore, it is necessary to find a polymer material with a simple preparation process and good electrical conductivity to solve the above problems as an electromagnetic wave shielding material. Summary of the Invention

[0005] To address at least one or more of the aforementioned technical problems, this disclosure provides a poly(3,4-ethylenedioxythiophene) and its preparation method and applications, which enables the rapid solvent-free preparation of poly(3,4-ethylenedioxythiophene) and provides a suitable film thickness and electromagnetic shielding performance as a magnetic shielding material.

[0006] To achieve the above objectives, as one aspect of this disclosure, a method for preparing poly(3,4-ethylenedioxythiophene) is provided, comprising: adding a nitrogen-containing heterocyclic compound or an aromatic amine compound to 3,4-ethylenedioxythiophene, stirring and obtaining a mixture;

[0007] The mixture was added to an iron salt compound and stirred. Under the polymerization regulation of nitrogen-containing heterocyclic compounds or aromatic amine compounds and the oxidation of iron salt compounds, a prepolymer of 3,4-ethylenedioxythiophene partially polymerized was obtained.

[0008] The prepolymer solution is heated to allow 3,4-ethylenedioxythiophene to continue polymerizing, resulting in a polymer containing poly(3,4-ethylenedioxythiophene).

[0009] According to embodiments of this disclosure, aromatic amine compounds include aniline; nitrogen-containing heterocyclic compounds include at least one of imidazole and pyridine; and iron salt compounds include at least one of ferric p-toluenesulfonate and ferric halide.

[0010] According to embodiments of this disclosure, the mass ratio of nitrogen-containing heterocyclic compounds or aromatic amine compounds to 3,4-ethylenedioxythiophene is 1:6.8-1:136.

[0011] According to embodiments of this disclosure, the mass ratio of the mixture to the iron salt compound is 1:1 to 10:1.

[0012] According to embodiments of this disclosure, the conditions for forming the prepolymer liquid are: stirring for 10-20 minutes at 5-10°C, with a stirring frequency of 200-300 r / min.

[0013] According to the embodiments of this disclosure, the conditions for obtaining the mixture are: stirring for 1-10 minutes at a stirring frequency of 400-500 r / min.

[0014] According to embodiments of this disclosure, heating the prepolymer liquid includes:

[0015] After the prepolymer solution is cast or coated, the resulting film is heated.

[0016] According to an embodiment of this disclosure, the heating conditions are: heating at 55-75°C for 12-72 hours.

[0017] As another aspect of this disclosure, a poly(3,4-ethylenedioxythiophene) prepared by the preparation method described above is also provided.

[0018] As another aspect of this disclosure, the application of poly(3,4-ethylenedioxythiophene) in electromagnetic shielding is also provided.

[0019] Based on the poly(3,4-ethylenedioxythiophene) and its preparation method and application as described in the above embodiments of this disclosure, 3,4-ethylenedioxythiophene can polymerize with iron salt compounds and release protons during the polymerization reaction. The nitrogen atoms in nitrogen-containing heterocyclic compounds or aromatic amine compounds contain unshared electron pairs. These unshared electron pairs can coordinate with the protons released during the polymerization reaction, resulting in a complexation reaction. This prevents the generated hydrogen ions from enhancing the oxidizing power of the iron salt compound. As the iron salt compound is gradually consumed, its oxidizing power gradually decreases, leading to a decrease in oxidation potential and further slowing down or terminating the reaction rate. Further heating intensifies the electron movement within the combined coordinate bonds, making the coordinate bonds easier to break. Furthermore, the nitrogen-containing heterocyclic compounds or aromatic amine compounds are relatively more volatile, releasing the hydrogen ions bound to them. This enhances the oxidizing power of the iron salt compound, thereby accelerating the polymerization reaction and forming poly(3,4-ethylenedioxythiophene) with a high degree of polymerization. The degree and state of polymerization are controlled by adding nitrogen-containing heterocyclic compounds or aromatic amine compounds, which increases the film thickness of the polymer containing poly(3,4-ethylenedioxythiophene). The preparation method disclosed herein can achieve a film thickness of 2 mm, which greatly improves the conductivity and electromagnetic shielding effect of poly(3,4-ethylenedioxythiophene). Furthermore, it overcomes the dependence on solution in the preparation of poly(3,4-ethylenedioxythiophene) in related technologies and realizes solvent-free preparation. Attached Figure Description

[0020] The present disclosure will be further described in detail below with reference to the accompanying drawings.

[0021] Figure 1 A flowchart of the method for producing poly(3,4-ethylenedioxythiophene) according to an embodiment of this disclosure is shown;

[0022] Figure 2 A schematic diagram of a heated casting mold for poly(3,4-ethylenedioxythiophene) in an embodiment of this disclosure is shown;

[0023] Figure 3 The images show the surface and cross-section of the poly(3,4-ethylenedioxythiophene) film formed in the embodiments of this disclosure.

[0024] Figure 4A schematic diagram of the electromagnetic shielding effectiveness test of poly(3,4-ethylenedioxythiophene) in Embodiment 3 of this disclosure is shown; and

[0025] Figure 5 A schematic diagram illustrating the electromagnetic shielding effect of poly(3,4-ethylenedioxythiophene) of different thicknesses in the range of 30MHz-1.5GHz is shown in Embodiment 3 of this disclosure.

[0026] [Explanation of Labels in the Attached Image]

[0027] 10 - Insulator board, 20 - Spacer. Detailed Implementation

[0028] When iron salt compounds, acting as oxidants, come into contact with 3,4-ethylenedioxythiophene, a polymerization reaction immediately occurs, making it difficult to control the reaction process. In implementing this disclosure, it was discovered that using nitrogen-containing heterocyclic compounds or aromatic amine compounds can complex the protons released during the polymerization reaction, thereby controlling the degree and state of polymerization.

[0029] Based on this, this disclosure provides a poly(3,4-ethylenedioxythiophene) and its preparation method and application. The nitrogen atoms in the nitrogen-containing heterocyclic compounds or aromatic amine compounds contain unshared electron pairs, which can combine with the protons released in the polymerization reaction through coordinate bonds. This prevents the generated hydrogen ions from further enhancing the oxidation ability of the iron salt compound. However, further heating can intensify the electron movement in the coordinate bonds, making the coordinate bonds easier to break, thereby accelerating the polymerization reaction.

[0030] To make the objectives, technical solutions, and advantages of this disclosure clearer, the following detailed description is provided in conjunction with specific embodiments and the accompanying drawings.

[0031] The following illustrative examples illustrate poly(3,4-ethylenedioxythiophene), its preparation methods, and applications. It should be noted that these examples are merely specific embodiments of this disclosure and do not limit the scope of protection of this disclosure.

[0032] Figure 1 A flowchart of a method for producing poly(3,4-ethylenedioxythiophene) according to an embodiment of this disclosure is shown.

[0033] like Figure 1 As shown, the preparation method of poly(3,4-ethylenedioxythiophene) includes stages S101-S103.

[0034] In stage S101, nitrogen-containing heterocyclic compounds or aromatic amine compounds are added to 3,4-ethylenedioxythiophene and stirred to obtain a mixture.

[0035] In stage S102, the mixture is added to the iron salt compound and stirred. Under the polymerization regulation of nitrogen-containing heterocyclic compounds or aromatic amine compounds and the oxidation of iron salt compounds, a prepolymer of 3,4-ethylenedioxythiophene partially polymerized is obtained.

[0036] In stage S103, the prepolymer liquid is heated to allow 3,4-ethylenedioxythiophene to continue polymerizing, resulting in a polymer containing poly(3,4-ethylenedioxythiophene).

[0037] According to embodiments of this disclosure, firstly, since 3,4-ethylenedioxythiophene polymerizes upon contact with an iron salt compound and releases protons during the polymerization reaction, this disclosure first adds a nitrogen-containing heterocyclic compound or an aromatic amine compound to 3,4-ethylenedioxythiophene to form a mixture, and then adds it to the iron salt compound because the nitrogen atoms in the nitrogen-containing heterocyclic compound or aromatic amine compound contain lone pairs of electrons, which can undergo a complexation reaction with the protons released during the polymerization reaction, preventing the generated hydrogen ions from further enhancing the oxidizing power of the iron salt compound. As the iron salt compound is gradually consumed, its oxidizing power relatively decreases, causing the oxidation potential to gradually decrease, thus further slowing down the reaction rate or even terminating it. This disclosure achieves the desired polymerization state by adding a nitrogen-containing heterocyclic compound or aromatic amine compound with polymerization regulating effect and an iron salt compound with oxidizing effect, thereby forming a prepolymer liquid for partial polymerization of 3,4-ethylenedioxythiophene. By further heating the prepolymer solution, the electron movement in the originally bound coordination bonds intensifies under elevated temperatures, making the coordination bonds relatively easier to break. Furthermore, the nitrogen-containing heterocyclic compounds or aromatic amines are relatively more volatile, releasing the hydrogen ions bound to them. These released hydrogen ions enhance the oxidizing power of the iron salt compounds, thereby accelerating the polymerization reaction and allowing 3,4-ethylenedioxythiophene to continue polymerizing, resulting in a polymer containing poly(3,4-ethylenedioxythiophene). The addition of these nitrogen-containing heterocyclic compounds or aromatic amines controls the degree and state of the polymerization reaction, increasing the film thickness of the prepared poly(3,4-ethylenedioxythiophene) polymer. Using the preparation method disclosed herein, a film thickness of 2 mm can be achieved, significantly improving the conductivity and electromagnetic shielding effect of poly(3,4-ethylenedioxythiophene). Moreover, this method does not involve the addition of a solvent, overcoming the solvent dependence in the preparation of poly(3,4-ethylenedioxythiophene) in related technologies and achieving solvent-free preparation.

[0038] According to embodiments of this disclosure, the mass ratio of nitrogen-containing heterocyclic compound or aromatic amine compound to 3,4-ethylenedioxythiophene is 1:6.8-1:136. By adjusting the amount of nitrogen-containing heterocyclic compound or aromatic amine compound added, the degree and state of polymerization of the partially polymerized 3,4-ethylenedioxythiophene can be further adjusted, thereby adapting to the subsequent film thickness.

[0039] Furthermore, the aromatic amine compounds include aniline, the nitrogen-containing heterocyclic compounds include at least one of imidazole and pyridine, and the iron salt compounds include at least one of ferric p-toluenesulfonate and ferric halide. During preliminary experiments related to this disclosure, it was found that the effect was better when the added nitrogen-containing heterocyclic compound with polymerization regulating effect was imidazole or pyridine, and when the added iron salt compound was ferric p-toluenesulfonate.

[0040] According to embodiments of this disclosure, the conditions for obtaining the mixture are as follows: stirring at a stirring frequency of 400-500 r / min for 1-10 min, for example, 1 min, 5 min, 8 min, or 10 min. Stirring ensures that the nitrogen-containing heterocyclic compound or aromatic amine compound is relatively uniformly dispersed in 3,4-ethylenedioxythiophene, thus preventing localized over-polymerization after the subsequent addition of iron salt compounds.

[0041] According to embodiments of this disclosure, the mass ratio of the mixture to the iron salt compound is 1:1 to 10:1. Preliminary experiments related to this disclosure revealed that when an excessive amount of iron salt compound was added, the polymerization reaction of 3,4-ethylenedioxythiophene was relatively vigorous and difficult to control. Conversely, when too little iron salt compound was added, 3,4-ethylenedioxythiophene could not polymerize sufficiently, which would negatively impact the subsequent film quality. When the mass ratio of the mixture to the iron salt compound was 1:1 to 10:1, the resulting poly(3,4-ethylenedioxythiophene) film had relatively better thickness and quality.

[0042] According to embodiments of this disclosure, the conditions for forming the prepolymer solution are: stirring for 10-20 minutes at 5-10°C, with a stirring frequency of 200-300 r / min. During the experiment, it was found that the polymerization reaction of 3,4-ethylenedioxythiophene under the catalysis of iron salt compounds is quite vigorous and the temperature rises rapidly. Therefore, an ice bath is generally used to further maintain the reaction within the 5-10°C temperature range. This prepolymer solution can solidify at a lower temperature and can be stored for more than 30 days. Therefore, the prepolymer solution can be refrigerated, and further processing steps can be performed as needed.

[0043] According to embodiments of this disclosure, heating the prepolymer liquid includes: casting or coating the prepolymer liquid, and then heating the resulting film layer. Figure 2A schematic diagram of a heated casting mold for poly(3,4-ethylenedioxythiophene) according to an embodiment of this disclosure is shown. Figure 2 The coating process involves casting the coating into a mold of suitable film thickness, followed by further polymerization of 3,4-ethylenedioxythiophene to stabilize the film thickness and polymerization effect. The coating mold can, for example, consist of an insulating plate 10, spacers 20, and dovetail clips (not shown). The insulating plate 10 has a clean and flat surface, and the height of the spacers can be 30 μm to 2 mm, for example, 30 μm, 100 μm, 200 μm, 500 μm, 700 μm, 900 μm, 1.1 mm, 1.3 mm, 1.5 mm, 1.7 mm, 1.9 mm, or 2 mm, and the height of the spacers can be matched to the requirements. Treatment can be performed using wire rods, doctor blades, or slot coating. For example, multiple brushings can be applied to an insulating board using wire rods. The insulating board may include, for example, an epoxy resin board or a glass board. The wire rods may be 40 μm, 50 μm, 60 μm, 70 μm, or 80 μm in size. The number of brushings may be 1 to 5, for example, 1, 2, 3, 4, or 5 times. The coating can be cured at a higher temperature to form poly(3,4-ethylenedioxythiophene), and poly(3,4-ethylenedioxythiophene) can be formed into a suitable shape with the aid of a mold.

[0044] Furthermore, the heating conditions are: heating at 55-75℃ for 12-72 hours. During preliminary experiments related to this disclosure, it was found that while ensuring the stability of the mechanical properties of the film and improving the degree of polymerization, the effects are relatively better when heating at 55-75℃ (e.g., 55℃, 60℃, 65℃, 70℃, or 75℃) and for 12-72 hours (e.g., 12 hours, 22 hours, 32 hours, 42 hours, 52 hours, 62 hours, or 72 hours).

[0045] At the same time, it can maintain a longer storage time at lower temperatures, thus showing good application prospects.

[0046] According to embodiments of this disclosure, a poly(3,4-ethylenedioxythiophene) prepared by the method described above is also provided.

[0047] According to embodiments of this disclosure, the poly(3,4-ethylenedioxythiophene) prepared using the method of this disclosure can be cured into a solid at a relatively high temperature. Therefore, poly(3,4-ethylenedioxythiophene) of different thicknesses and shapes can be prepared as needed, and the operation is simple. Furthermore, the film thickness of the obtained poly(3,4-ethylenedioxythiophene) is controllable, and poly(3,4-ethylenedioxythiophene) of different film thicknesses can be prepared according to different requirements. Moreover, this poly(3,4-ethylenedioxythiophene) exhibits good electrical conductivity; even at a thickness in the millimeter range, its conductivity can reach 1.59 S / cm.

[0048] According to embodiments of this disclosure, an application of poly(3,4-ethylenedioxythiophene) in electromagnetic shielding is also provided.

[0049] In the preliminary experiments disclosed herein, it was found that the thicker the poly(3,4-ethylenedioxythiophene) film, the better its electromagnetic shielding effect. When the poly(3,4-ethylenedioxythiophene) film thickness is 50 μm, poly(3,4-ethylenedioxythiophene) can shield 99% of electromagnetic waves; while when the film thickness of the material is 400 μm, the material can shield 99.9% of electromagnetic interference.

[0050] The present disclosure is further illustrated below by way of proportions, embodiments, accompanying drawings, and related test experiments and results. In the following detailed description, numerous specific details are set forth to provide a comprehensive understanding of the embodiments of the present disclosure for ease of explanation. However, it will be apparent that one or more embodiments may be practiced without these specific details. Moreover, the details in the following embodiments can be arbitrarily combined to form other feasible embodiments without conflict.

[0051] It should be noted that the specific embodiments described below are merely illustrative examples, and the scope of protection of this disclosure is not limited thereto. The chemicals and raw materials used in the following embodiments are all commercially available or prepared in-house using recognized methods.

[0052] Example 1

[0053] Poly(3,4-ethylenedioxythiophene) was prepared using pyridine and ferric p-toluenesulfonate, and the preparation method included:

[0054] 10 μL of pyridine was added to 1 mL of 3,4-ethylenedioxythiophene, and the mixture was shaken and mixed at 400 rpm for 10 min to obtain a mixture. This mixture was then added to a reaction flask containing 200 mg of ferric p-toluenesulfonate. Under ice bath conditions (reaction temperature 10 °C), the mixture was magnetically stirred for 10 min until the ferric p-toluenesulfonate was completely dissolved, yielding a prepolymer of partially polymerized 3,4-ethylenedioxythiophene. This prepolymer was then coated into a film using an 80 μm wire rod and incubated at 65 °C for 12 hours to obtain a polymer containing poly(3,4-ethylenedioxythiophene) with a thickness of 30 μm.

[0055] The 30 μm thick polymer film prepared in Example 1 was tested using a four-probe method, and the sheet resistance of the polymer film was found to be 1600 Ω / □.

[0056] It should be noted that, as shown in Equation I below, the mechanism of the polymerization reaction changes after adding pyridine to 3,4-ethylenedioxythiophene and then adding ferric p-toluenesulfonate. Upon introducing pyridine, a nitrogen-containing heterocyclic compound, the nitrogen atom in pyridine possesses a lone pair of electrons, which combines with the generated hydrogen ions to form a coordinate bond. This prevents the generated hydrogen ions from enhancing the oxidizing power of ferric p-toluenesulfonate (Fe(Tos)3). Furthermore, as the oxidant is gradually consumed, the oxidizing power of Fe(Tos)3 gradually decreases, the oxidation potential drops, and the reaction rate slows down or even stops. Upon heating, the hydrogen ions bound to pyridine are released, enhancing the oxidizing power of Fe(Tos)3, thereby accelerating the polymerization reaction and ultimately forming poly(3,4-ethylenedioxythiophene). Therefore, the restriction of hydrogen ions by pyridine can be used to control the polymerization process of 3,4-ethylenedioxythiophene.

[0057]

[0058] Example 2

[0059] Poly(3,4-ethylenedioxythiophene) was prepared using pyridine and ferric p-toluenesulfonate, and the preparation method included:

[0060] 20 μL of pyridine was added to 1 mL of 3,4-ethylenedioxythiophene, and the mixture was shaken and mixed at 400 rpm for 1 min to obtain a mixture. This mixture was then added to a reaction flask containing 300 mg of ferric p-toluenesulfonate, and magnetically stirred for 20 min under ice bath conditions (reaction temperature 10 °C) until the ferric p-toluenesulfonate was completely dissolved, yielding a prepolymer of partially polymerized 3,4-ethylenedioxythiophene. The prepolymer was then coated into a film using a doctor blade and incubated at 70 °C for 24 hours to obtain a polymer containing poly(3,4-ethylenedioxythiophene).

[0061] The 30 μm thick polymer film prepared in Example 2 was tested using a four-probe method, and the sheet resistance of the polymer film was found to be 368 Ω / □.

[0062] Example 3

[0063] Poly(3,4-ethylenedioxythiophene) was prepared using pyridine and ferric p-toluenesulfonate, and the preparation method included:

[0064] 40 μL of pyridine was added to 1 mL of 3,4-ethylenedioxythiophene and the mixture was shaken and mixed at 400 rpm for 1 min to obtain a mixture. The mixture was then added to a reaction flask containing 500 mg of ferric p-toluenesulfonate and magnetically stirred for 20 min under ice bath conditions (reaction temperature 10 °C) until the ferric p-toluenesulfonate was completely dissolved, thus obtaining a prepolymer solution for the partial polymerization of 3,4-ethylenedioxythiophene.

[0065] This embodiment 3 uses the following... Figure 2 The mold shown was prepared by placing a 30μm spacer between two clean glass plates and fixing it with a dovetail clamp. The prepolymer solution was then injected into the mold using a dropper and placed at 75°C for 48 hours to obtain a polymer containing poly(3,4-ethylenedioxythiophene).

[0066] The 30 μm thick polymer film prepared in Example 3 was tested using a four-probe method, and the sheet resistance of the polymer film was found to be 83 Ω / □.

[0067] Poly(3,4-ethylenedioxythiophene) of different sizes was prepared using the prepolymer solution prepared in Example 3 and its conductivity was tested. The preparation and testing processes are as follows.

[0068] The prepared prepolymer solution was injected into a mold containing spacers of different sizes (30 μm-2 mm) and placed at 65 °C for 12 hours. Sheet resistance data of the thick film were obtained using a four-probe test, as shown in Table 1. The relative mean deviation (RMD) of conductivity, used to describe the uniformity of the thick film conductivity, was calculated by measuring nine different points on the same conductive thick film. The calculation formula is as follows:

[0069]

[0070] Where n represents the number of data points, x i This represents the conductivity data of the i-th measurement. This represents the average value of the conductivity data.

[0071] Table 1

[0072] Thickness (μm) Conductivity (S cm -1 )]]> Relative average deviation of conductivity 30 4.02 0.268 200 4.07 0.219 400 3.65 0.153 1000 1.59 0.095 2000 0.97 0.072

[0073] As shown in Table 1, when the thickness is between 30 and 200 μm, the conductivity of the poly(3,4-ethylenedioxythiophene) thick film is around 4 S / cm. When the thickness exceeds 400 μm, the conductivity decreases slightly. For a 2 mm thick poly(3,4-ethylenedioxythiophene) film, its conductivity drops to 0.97 S / cm. The relative average deviation of conductivity is negatively correlated with the thickness of the film, indicating that thicker poly(3,4-ethylenedioxythiophene) films are superior to thinner poly(3,4-ethylenedioxythiophene) films in terms of conductivity uniformity. Figure 3 The diagram shows the surface and cross-section of the poly(3,4-ethylenedioxythiophene) film formed in embodiments of this disclosure. Figure 3 As shown, it is demonstrated that the poly(3,4-ethylenedioxythiophene) thick film can exist independently of the substrate, and that the surface and cross-sectional morphology of the poly(3,4-ethylenedioxythiophene) thick film are uniform and smooth, with no internal bubbles.

[0074] The obtained prepolymer liquid was used to prepare an electromagnetic shielding test plate and its shielding effect was tested. The preparation process and testing process are as follows.

[0075] The test board uses a 1mm thick epoxy resin insulating board as the substrate. Prepolymer liquid is evenly brushed onto the epoxy resin insulating board using a wire rod, and then heated at 65℃ for 12 hours to obtain the test board. The coating thickness is controlled by the wire rod size and the number of brushing passes. Figure 4 A schematic diagram illustrating the electromagnetic shielding effectiveness test of poly(3,4-ethylenedioxythiophene) in Embodiment 3 of this disclosure is shown. Figure 4 The flange coaxial method for testing electromagnetic shielding effectiveness is shown. The test plate is fixed in the flange coaxial device. The input and output signals are tested by a vector network analyzer, and then the electromagnetic shielding effectiveness is calculated. The shielding effectiveness data is obtained by connecting to the vector network analyzer. Figure 5 A schematic diagram illustrating the electromagnetic shielding effect of poly(3,4-ethylenedioxythiophene) of different thicknesses in Embodiment 3 of this disclosure between 30 MHz and 1.5 GHz is shown. Figure 5 As shown, when the thickness of the poly(3,4-ethylenedioxythiophene) thick film is 50 μm, the electromagnetic shielding effectiveness exceeds 20 dB, which can shield more than 99% of electromagnetic interference. When the thickness is further increased, the electromagnetic shielding effectiveness of the poly(3,4-ethylenedioxythiophene) thick film is also significantly improved. The shielding effectiveness of a 400 μm thick poly(3,4-ethylenedioxythiophene) thick film exceeds 30 dB, which can shield more than 99.9% of electromagnetic interference.

[0076] Example 4

[0077] Poly(3,4-ethylenedioxythiophene) was prepared using pyridine and ferric p-toluenesulfonate, and the preparation method included:

[0078] 100 μL of pyridine was added to 1 mL of 3,4-ethylenedioxythiophene and the mixture was shaken and mixed at 400 rpm for 1 min to obtain a mixture. The mixture was then added to a reaction flask containing 600 mg of ferric p-toluenesulfonate and magnetically stirred for 20 min under ice bath conditions (reaction temperature 10 °C) until the ferric p-toluenesulfonate was completely dissolved, thus obtaining a prepolymer solution for the partial polymerization of 3,4-ethylenedioxythiophene.

[0079] This embodiment 4 uses the following... Figure 2 The mold shown was prepared by placing a 30μm spacer between two glass plates and fixing it with a dovetail clamp. The prepolymer liquid was then injected into the mold using a dropper and placed at 75°C for 60 hours to obtain a polymer containing poly(3,4-ethylenedioxythiophene).

[0080] The obtained 30 μm thick polymer film was tested using a four-probe method, and the sheet resistance of the polymer film was found to be 124 Ω / □.

[0081] Example 5

[0082] Poly(3,4-ethylenedioxythiophene) was prepared using pyridine and ferric p-toluenesulfonate, and the preparation method included:

[0083] 100 μL of pyridine was added to 1 mL of 3,4-ethylenedioxythiophene and the mixture was shaken and mixed at 400 rpm for 1 min to obtain a mixture. The mixture was then added to a reaction flask containing 800 mg of ferric p-toluenesulfonate and magnetically stirred for 20 min under ice bath conditions until the ferric p-toluenesulfonate was completely dissolved, thus obtaining a prepolymer solution for the partial polymerization of 3,4-ethylenedioxythiophene.

[0084] This embodiment 5 uses the following... Figure 2 The mold shown was prepared by placing a 30μm spacer between two glass plates and fixing it with a dovetail clamp. The prepolymer liquid was then injected into the mold using a dropper and placed at 75°C for 72 hours to obtain a polymer containing poly(3,4-ethylenedioxythiophene).

[0085] In Example 5, the amount of pyridine added reached 10% of the volume of 3,4-ethylenedioxythiophene. The excessive addition of pyridine caused the polymerization reaction to be excessively inhibited, and the prepolymer liquid could not be completely polymerized and solidified in the mold. Therefore, the corresponding sheet resistance could not be measured.

[0086] Example 6

[0087] Poly(3,4-ethylenedioxythiophene) was prepared using pyridine and ferric p-toluenesulfonate, and the preparation method included:

[0088] 200 μL of pyridine was added to 1 mL of 3,4-ethylenedioxythiophene and the mixture was shaken and mixed at 400 rpm for 1 min to obtain a mixture. The mixture was then added to a reaction flask containing 900 mg of ferric p-toluenesulfonate and magnetically stirred for 20 min under ice bath conditions until the ferric p-toluenesulfonate was completely dissolved, thus obtaining a prepolymer solution for the partial polymerization of 3,4-ethylenedioxythiophene.

[0089] This embodiment 6 uses the following... Figure 2 The mold shown was prepared by placing a 30μm spacer between two glass plates and fixing it with a dovetail clamp. The prepolymer liquid was then injected into the mold using a dropper and placed at 75°C for 72 hours to obtain a polymer containing poly(3,4-ethylenedioxythiophene).

[0090] In Example 6, the pyridine content exceeded 10% of the volume of 3,4-ethylenedioxythiophene, which is the same as in Example 5. As a result, the polymerization reaction was excessively inhibited, and the prepolymer could not be completely polymerized and solidified in the mold. Therefore, the corresponding sheet resistance could not be measured.

[0091] The experimental results from Examples 1-6 show that the conductivity of poly(3,4-ethylenedioxythiophene) is closely related to the amount of pyridine added. Excessive pyridine makes polymerization difficult, while the prepolymer solution ratio in Example 3 yields a thick film with better conductivity. A more detailed study of the prepolymer solution in Example 3 revealed that its polymerization rate is closely related to temperature. At 10°C, the polymerization rate is relatively slow; after about 2 hours, the dark red prepolymer solution begins to show a significant color change and gradually turns into a black solid. When the prepolymer solution is heated to 30°C or higher, this change can occur within 1 minute, indicating a significantly faster polymerization rate. It is noteworthy that when the temperature is lowered from 10°C to 0°C, a dark red solid is obtained. This is because the freezing point of 3,4-ethylenedioxythiophene is approximately 10°C, and the prepolymer solution contains a relatively large amount of 3,4-ethylenedioxythiophene, causing it to solidify at low temperatures. During the experiments conducted according to this disclosure, it was found that this solidification state does not affect the application performance of the prepolymer solution. Upon thawing, the prepolymer solution reverts to a deep red liquid, and the conductivity of the prepared poly(3,4-ethylenedioxythiophene) is similar to that of the solution before solidification. Furthermore, low temperature is beneficial for the storage of the prepolymer solution. The frozen prepolymer solution can be stored at 0°C for more than 5 days, and at -20°C, the storage time can be further extended to more than 30 days.

[0092] Comparative Example 1

[0093] Poly(3,4-ethylenedioxythiophene) was prepared using 3,4-ethylenedioxythiophene and ferric p-toluenesulfonate. The preparation method includes:

[0094] 200 mg of ferric p-toluenesulfonate was added to 1 mL of 3,4-ethylenedioxythiophene, and the mixture was magnetically stirred for 20 min in an ice bath (reaction temperature 10 °C). The resulting mixture contained a large amount of black solid. Adding only 3,4-ethylenedioxythiophene and the iron salt compound resulted in a rapid reaction, producing only a powdery polymer that could not form a film, making it difficult to control the reaction process.

[0095] The polymerization mechanism of 3,4-ethylenedioxythiophene is shown in Equation II below. Ferric p-toluenesulfonate (Fe(Tos)3) reacts with 3,4-ethylenedioxythiophene. 3+Attacking the α-position of the thiophene ring generates a cationic radical, which, through coupling and dehydrogenation, yields a dimer of 3,4-ethylenedioxythiophene. The release of hydrogen ions during the reaction lowers the pH of the system, enhancing the oxidizing power of Fe(Tos)3 and thus accelerating the polymerization reaction. During the reaction, the poly(3,4-ethylenedioxythiophene) chain length continuously increases, and the hydrogen ion concentration in the system also rises, ultimately forming a long-chain poly(3,4-ethylenedioxythiophene). Intrinsic poly(3,4-ethylenedioxythiophene) forms a doped poly(3,4-ethylenedioxythiophene) under the influence of Fe(Tos)3.

[0096]

[0097] The specific embodiments described above further illustrate the purpose, technical solutions, and beneficial effects of this disclosure. It should be understood that the above descriptions are merely specific embodiments of this disclosure and are not intended to limit this disclosure. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this disclosure should be included within the protection scope of this disclosure.

Claims

1. A method for preparing poly(3,4-ethylenedioxythiophene), comprising the following steps: Nitrogen-containing heterocyclic compounds or aromatic amine compounds are added to 3,4-ethylenedioxythiophene and stirred to obtain a mixture; The mixture is added to the iron salt compound and stirred. Under the polymerization regulating effect of the nitrogen-containing heterocyclic compound or aromatic amine compound and the oxidation effect of the iron salt compound, the mixture is stirred for 10-20 minutes at 5-10°C and the stirring frequency is 200-300 r / min to obtain a prepolymer solution of 3,4-ethylenedioxythiophene partially polymerized. The prepolymer liquid is heated to allow 3,4-ethylenedioxythiophene to continue polymerizing, resulting in a polymer containing poly(3,4-ethylenedioxythiophene). The preparation method does not involve the addition of a solvent; heating the prepolymer liquid includes: After the prepolymer liquid is cast or coated, the resulting film is heated at 55-75°C for 12-72 hours. The aromatic amine compounds include aniline; The nitrogen-containing heterocyclic compound includes at least one of imidazole and pyridine; The iron salt compound includes at least one of ferric p-toluenesulfonate and ferric halide.

2. The method according to claim 1, wherein, The mass ratio of the nitrogen-containing heterocyclic compound or aromatic amine compound to 3,4-ethylenedioxythiophene is 1:6.8-1:

136.

3. The method according to claim 1, wherein, The mass ratio of the mixture to the iron salt compound is 1:1 to 10:

1.

4. The method according to claim 1, wherein, The conditions for obtaining the mixture are as follows: Stir for 1-10 minutes at a stirring frequency of 400-500 r / min.

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