A poly(3,4-ethylenedioxythiophene) nanoparticle, its synthesis method and application

Abstract

The present invention discloses a poly(3,4-ethylenedioxythiophene) nanoparticle, its synthesis method and application, belonging to the field of conductive polymer materials. The poly(3,4-ethylenedioxythiophene) nanoparticle comprises the following raw materials: organic solvent A, thiophene monomer, oxidant, dopant, organic solvent B. First, the thiophene monomer is dissolved in organic solvent A to form solution A, and at the same time, the oxidant is dissolved in organic solvent B to form solution B. Then, the dopant is added to solution A and stirred, and then solution B is added dropwise to the mixed system obtained in the previous step. Finally, solid particles are obtained by filtration, and the poly(3,4-ethylenedioxythiophene) nanoparticle is obtained after washing the solid particles. Based on the effective combination of the structural characteristics of the conductive polymer poly(3,4-ethylenedioxythiophene) (PEDOT) and the doping technology, the present invention significantly improves the conductivity and long-term stability in air of the PEDOT nanoparticles by incorporating specific inorganic salt dopants.

Description

Technical Field

[0001] The present invention belongs to the field of conductive polymer materials, and particularly relates to poly(3,4-ethylenedioxythiophene) nanoparticles, a synthesis method thereof, and an application thereof. Background Art

[0002] Poly(3,4-ethylenedioxythiophene) (PEDOT) is a widely used conductive polymer. Due to its unique electrical properties, mechanical flexibility, and chemical stability, it has broad application potential in fields such as transparent electrodes, organic photovoltaics, flexible electronic devices, and sensors. Compared with traditional conductive materials such as indium tin oxide (ITO), PEDOT has better flexibility and processability, thus showing great advantages in flexible electronic devices. However, the conductivity of untreated PEDOT materials is relatively low (usually below 1 S / cm), which limits its application in high-performance electronic devices. In addition, the long-term stability of PEDOT in air is also an issue that needs to be addressed.

[0003] In the prior art, in order to improve the conductivity of PEDOT, chemical doping or post-treatment techniques are usually used to enhance its electrical properties. For example, post-treatment with acid or base solutions can improve the conductivity of PEDOT to a certain extent, but such methods often lead to a decrease in the stability of the material in air. Especially when exposed to a humid environment, the conductivity and optical transparency of PEDOT will rapidly decrease. In addition, traditional treatment methods usually require multiple steps, which not only increases the cost but also increases the burden on the environment.

[0004] To improve the application performance of PEDOT, especially to improve its conductivity and stability, many treatment techniques have been developed by researchers. The most common way is to dope PEDOT with high-boiling solvents such as ethylene glycol or dimethyl sulfoxide (DMSO). However, although these solvents can effectively improve the conductivity, they will reduce the environmental stability of PEDOT. Especially when exposed to air for a long time, the conductivity will decrease.

[0005] The synthesis of PEDOT is usually completed by oxidative polymerization. During the reaction process, the conductivity is mainly affected by the orderliness of the polymer chains and the dopant. One way to improve the conductivity is through post-doping or chemical modification. However, existing doping techniques such as using iodine vapor, nitric acid, etc. will bring additional complexity and potential toxicity risks. At the same time, the use of these dopants usually reduces the stability of PEDOT in practical applications.

[0006] With the increasingly strict environmental protection regulations, the demand for green and environmentally friendly synthesis methods in the chemical industry has become more urgent. Although the traditional process of synthesizing PEDOT using organic solvents is mature, the use of highly volatile solvents has imposed a significant burden on the environment. Therefore, the development of environmentally friendly solvent systems or low-toxicity and low-volatility chemical reagents for the synthesis and treatment of PEDOT has become a research hotspot. Summary of the Invention

[0007] Aiming at the problems of low conductivity and poor long-term stability in the existing PEDOT synthesis technology, the purpose of the present invention is to propose a poly(3,4-ethylenedioxythiophene) nanoparticle, its synthesis method and application. By precisely controlling the reaction conditions and directly doping alkali metal or alkaline earth metal salt materials, highly conductive PEDOT nanoparticles can be effectively synthesized.

[0008] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0009] In the first aspect of the present invention, there is provided a poly(3,4-ethylenedioxythiophene) nanoparticle. By mass, the poly(3,4-ethylenedioxythiophene) nanoparticle comprises the following raw materials: 80-120 parts of organic solvent A, 0.1-10 parts of thiophene monomer, 10-20 parts of oxidant, 0.5-20 parts of dopant, and 30-80 parts of organic solvent B; wherein, the thiophene monomer is 3,4-ethylenedioxythiophene; the dopant is selected from at least one of cesium chloride, potassium chloride, sodium chloride, lithium fluoride, calcium chloride, and magnesium chloride.

[0010] It should be noted that the thiophene monomer can also be one of 3,4-ethylenedioxythiophene derivatives; the dopant can be selected from halides or nitrates of alkali metals or alkaline earth metals.

[0011] In some embodiments, the oxidant is selected from at least one of ferric chloride, potassium persulfate, and ammonium persulfate.

[0012] In some embodiments, both organic solvent A and organic solvent B are selected from at least one of dichloromethane or acetonitrile.

[0013] In the second aspect of the present invention, there is provided a method for synthesizing a poly(3,4-ethylenedioxythiophene) nanoparticle, comprising the following steps:

[0014] S1: Dissolve the thiophene monomer in organic solvent A to form solution A;

[0015] S2: Dissolve the oxidant in organic solvent B and stir to form solution B;

[0016] S3: Add the dopant to solution A and stir;

[0017] S4: Gradually add solution B to the mixed system obtained in S3 and stir.

[0018] S5: Filter the mixed solution obtained in S4 to obtain solid particles, and wash the solid particles to obtain poly(3,4-ethylenedioxythiophene) nanoparticles.

[0019] The conductivity of the poly(3,4-ethylenedioxythiophene) (PEDOT) molecular chain mainly depends on the orderliness and doping state of its molecular chain. When dopants are added to the synthesis process of PEDOT, these inorganic salt dopants can interact with the positive charges in the PEDOT molecule, regulate the arrangement of the molecular chain, and then enhance the mobility of charge carriers, thereby effectively improving the molecular order and conductivity of the material.

[0020] Inorganic salt dopants such as cesium chloride (CsCl), potassium chloride (KCl), sodium chloride (NaCl), lithium fluoride (LiF), and calcium chloride (CaCl2), etc., have relatively large ionic radii and can insert into the PEDOT molecular chain to form a stable charge transfer network. And these salt materials can also interact with the groups of PEDOT to form stable ion pairs, which can effectively improve the molecular order and conductivity of the material.

[0021] In some embodiments, in S1, the reaction temperature is 0 - 80 °C, and it is dissolved to form a uniform and transparent solution.

[0022] In some embodiments, in S2, the reaction temperature is 0 - 50 °C, the stirring time is 60 - 120 min, and it is stirred until a uniform reddish-brown solution is formed.

[0023] In some embodiments, the reaction temperature is 0 - 50 °C, and the stirring time is 10 - 60 min.

[0024] In some embodiments, in S4, the reaction temperature is 0 - 50 °C, the stirring time is 24 h, and it is stirred until a dark blue suspension is formed.

[0025] The third aspect of the present invention is to provide an application of poly(3,4-ethylenedioxythiophene) nanoparticles in the fields of flexible electronic devices, transparent conductive films, or printed electronics.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] 1. The present invention is based on the effective combination of the structural characteristics of the conductive polymer poly(3,4-ethylenedioxythiophene) (PEDOT) and doping technology. By incorporating specific inorganic salt dopants (such as halides or nitrates of alkali metals and alkaline earth metals), the conductivity of PEDOT nanoparticles is significantly improved. At the same time, the inorganic salt dopants have good stability and antioxidant properties, enhancing the long-term stability of the PEDOT material in air. The addition of the dopants can also promote the uniform dispersion of PEDOT nanoparticles, forming a regular nanostructure, which helps to further optimize the electrical properties and optical transparency.

[0028] 2. In the synthesis process of the present invention, these inorganic salt dopants are directly introduced and completed during the polymerization reaction of PEDOT, avoiding the multi-step post-treatment in the traditional process, simplifying the process, reducing the cost, and improving the environmental friendliness of the material while being simple and efficient.

[0029] 3. The PEDOT nanoparticles obtained by the synthesis method of the present invention not only have an ultra-high conductivity (exceeding 550 S / cm), but also possess excellent long-term stability. Even after 270 days, the conductivity of the material can still maintain more than 85% of the initial value.

[0030] 4. The synthesis method provided by the present invention obtains PEDOT nanoparticles with high conductivity and high stability by regulating the reaction temperature, the type and dosage of the dopant, and is applicable to a wide range of application fields such as transparent electrodes, flexible displays, and wearable devices. Detailed implementation mode

[0031] The present invention will be further described in detail below. The description of the embodiments is exemplary and is intended to explain the present invention, and should not be construed as a limitation of the present invention.

[0032] Example 1

[0033] A kind of poly(3,4-ethylenedioxythiophene) nanoparticles, by mass, includes the following raw materials: 2 parts of 3,4-ethylenedioxythiophene (EDOT), 100 parts of dichloromethane, 16 parts of ferric chloride, 50 parts of acetonitrile, and 0.5 part of cesium chloride (CsCl).

[0034] The synthesis method of the above poly(3,4-ethylenedioxythiophene) nanoparticles includes the following steps:

[0035] S1: Dissolve 3,4-ethylenedioxythiophene (EDOT) in dichloromethane, control the reaction temperature at 25°C, and stir until a uniform and transparent solution is formed, which is called solution A.

[0036] S2: Dissolve ferric chloride in acetonitrile, control the reaction temperature at about 25°C, and stir for 60 minutes to obtain a uniform reddish-brown solution, which is called solution B.

[0037] S3: Add cesium chloride (CsCl) to solution A, control the reaction temperature at 25 °C, and continuously stir for 30 minutes to make it evenly dispersed.

[0038] S4: Gradually add solution B to the mixed system obtained in S3, control the dropping rate and reaction temperature (maintain at about 25 °C), and continue to stir and react for 24 hours to obtain a dark blue suspension.

[0039] S5: Filter the suspension after the reaction in S4 to separate out solid particles. Wash the solid particles with deionized water and acetone in turn to remove impurities, and then dry to obtain highly conductive PEDOT nanoparticles.

[0040] Example 2

[0041] The raw material components and synthesis method are the same as those in Example 1, with the only difference being that the amount of cesium chloride (CsCl) is 1 part.

[0042] Example 3

[0043] The raw material components and synthesis method are the same as those in Example 1, with the only difference being that the amount of cesium chloride (CsCl) is 2 parts.

[0044] Example 4

[0045] The raw material components and synthesis method are the same as those in Example 1, with the only difference being that the amount of cesium chloride (CsCl) is 5 parts.

[0046] Example 5

[0047] The raw material components and synthesis method are the same as those in Example 1, with the only difference being that the amount of cesium chloride (CsCl) is 10 parts.

[0048] Example 6

[0049] The raw material components and synthesis method are the same as those in Example 1, with the only difference being that the amount of cesium chloride (CsCl) is 20 parts.

[0050] Example 7

[0051] The raw material components and synthesis method are the same as those in Example 3, with the only difference being that cesium chloride (CsCl) is replaced with potassium chloride (KCl).

[0052] Example 8

[0053] The raw material components and synthesis method are the same as those in Example 3, with the only difference being that cesium chloride (CsCl) is replaced with calcium chloride (CaCl2).

[0054] Example 9

[0055] The raw material components and synthesis method are the same as those in Example 3, with the only difference being that cesium chloride (CsCl) is replaced with lithium fluoride (LiF).

[0056] Example 10

[0057] The raw material components and synthesis method are the same as those in Example 3, with the only difference being that cesium chloride (CsCl) is replaced by magnesium chloride (MgCl2).

[0058] Comparative Example 1

[0059] The raw material components and synthesis method are the same as those in Example 3, with the only difference being that no dopant is added.

[0060] To verify that the prepared poly(3,4-ethylenedioxythiophene) nanoparticles of the present invention have excellent electrical conductivity and long-term stability, as well as the influence of dopants on the size and crystallinity of PEDOT nanoparticles, the PEDOT powders prepared in Examples 1 to 10 and Comparative Example 1 were subjected to electrical conductivity tests and crystallinity tests. The specific operation is as follows: the four-probe method was used to evaluate its electrical conductivity. The test results are summarized in Table 1.

[0061] Table 1 Test results of electrical conductivity and crystallinity

[0062]

[0063]

[0064] As can be seen from Table 1, the type and doping content of rare earth dopants have a significant impact on the electrical conductivity, long-term stability, nanoparticle size and crystallinity of poly(3,4-ethylenedioxythiophene) (PEDOT) nanoparticles.

[0065] First, in terms of conductivity, as the content of cesium chloride (CsCl) dopant increases, the conductivity shows a trend of first increasing and then decreasing. Specifically, when 0.5 to 2 parts of cesium chloride are doped, the conductivity gradually increases, reaching a peak of 550 S / cm (2 parts of cesium chloride). However, when the doping content exceeds 5 parts, the conductivity decreases, which may be due to the destruction of the conductive network caused by excessive dopants; although the conductivity decreases, the conductivity of PEDOT with dopants added is still much higher than that of PEDOT without dopants added. Similarly, other dopants such as calcium chloride (CaCl2), lithium fluoride (LiF), sodium chloride (NaCl) and potassium chloride (KCl) also increase the conductivity of PEDOT, but the best conductivity effect of cesium chloride cannot be achieved.

[0066] In terms of long-term stability, the conductivity retention rates of all doped samples in the table are relatively high after 270 days, generally maintaining between 85% and 95%. This indicates that rare earth dopants not only improve the conductivity of PEDOT but also enhance its stability during long-term use. In particular, the samples doped with a relatively low content of cesium chloride (0.5 to 2 parts) exhibit the highest long-term stability, with a conductivity retention rate reaching 95%, suggesting that appropriate doping is beneficial to maintaining the long-term electrical property stability of the material.

[0067] In terms of nanoparticle size, with the increase in the doping content of cesium chloride, the size of the nanoparticles increases significantly. When doping 0.5 to 2 parts of cesium chloride, the particle size is small and uniform, concentrated in the range of 50 - 100 nm; while when the dopant content increases to 10 parts or 20 parts, the size of the nanoparticles increases to 50 - 500 nm, indicating that high-concentration doping may lead to particle aggregation. In addition, the nanoparticle sizes generated by other rare earth metal dopants such as calcium chloride and lithium fluoride are relatively uniform, remaining in the range of 50 - 100 nm, showing good dispersibility.

[0068] In terms of crystallinity, all doped samples show high crystallinity, indicating that the dopants play a positive role in the ordered arrangement of PEDOT molecular chains. In contrast, the undoped comparative example 1 sample shows a semi-crystalline state, and its conductivity is significantly lower than that of the doped samples, indicating that the conductivity of the undoped PEDOT material is limited due to poor molecular order.

[0069] Finally, all the samples in the table show a consistent dark blue color, indicating that the addition of rare earth dopants does not significantly change the color of PEDOT nanoparticles, and the appearance of all samples is uniform. This shows that rare earth doping has little effect on the optical properties of PEDOT materials but significantly improves their electrical properties. In summary, cesium chloride doping has a particularly significant impact on the conductivity and long-term stability of PEDOT, especially achieving the best effect when doped with 2 parts; excessive doping may cause particle aggregation and reduce the conductivity. Other rare earth metals such as calcium chloride and lithium fluoride can also significantly improve the conductivity and stability, but the effect is slightly inferior to that of cesium chloride.

[0070] The above are only some embodiments of the present invention. For those of ordinary skill in the art, without departing from the inventive concept of the present invention, several modifications and improvements can still be made, and these all belong to the protection scope of the present invention.

Claims

1. A poly(3,4-ethylenedioxythiophene) nanoparticle, characterized in that, By mass parts, the poly(3,4-ethylenedioxythiophene) nanoparticles comprise the following raw materials: 80 - 120 parts of organic solvent A, 0.1 - 10 parts of thiophene monomer, 10 - 20 parts of oxidant, 0.5 - 10 parts of dopant, and 30 - 80 parts of organic solvent B; wherein, the thiophene monomer is 3,4-ethylenedioxythiophene; the dopant is selected from at least one of cesium chloride, potassium chloride, sodium chloride, lithium fluoride, calcium chloride, and magnesium chloride.

2. The poly(3,4-ethylenedioxythiophene) nanoparticles according to claim 1, characterized in that, The oxidant is selected from at least one of ferric trichloride, potassium persulfate, and ammonium persulfate.

3. The poly(3,4-ethylenedioxythiophene) nanoparticles according to claim 2, characterized in that, Both the organic solvent A and the organic solvent B are selected from at least one of dichloromethane or acetonitrile.

4. A method for synthesizing the poly(3,4-ethylenedioxythiophene) nanoparticles according to any one of claims 1-3, characterized in that, It includes the following steps: S1: Dissolve the thiophene monomer in the organic solvent A to form solution A. S2: Dissolve the oxidant in the organic solvent B and stir to form solution B. S3: Add the dopant to solution A and stir. S4: Gradually add solution B to the mixed system obtained in S3 and stir. S5: Filter the mixed solution obtained in S4 to obtain solid particles, and wash the solid particles to obtain the poly(3,4-ethylenedioxythiophene) nanoparticles.

5. The synthesis method according to claim 4, characterized in that, In S1, the reaction temperature is 0 - 80°C and it is dissolved until a uniform and transparent solution is formed.

6. The synthesis method according to claim 4, characterized in that, In S2, the reaction temperature is 0 - 50°C, the stirring time is 60 - 120 min, and it is stirred until a homogeneous brownish-red solution is formed.

7. The synthesis method according to claim 4, characterized in that, In S3, the reaction temperature is 0 - 50°C and the stirring time is 10 - 60 min.

8. The synthesis method according to claim 4, characterized in that In S4, the reaction temperature is 0 - 50°C, the stirring time is 24 h, and it is stirred until a dark blue suspension is formed.

9. Application of the poly(3,4-ethylenedioxythiophene) nanoparticles according to any one of claims 1 - 3 in the fields of flexible electronic devices, transparent conductive films, or printed electronics.

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