Preparation method of high-conductivity PEDOT dispersion liquid

Abstract

The invention provides a preparation method of a high-conductivity PEDOT dispersion liquid, which comprises the following steps: (1) dispersing polyanions and a first oxidant into water, passing through an anion exchange column, removing anions, adding an EDOT monomer, fully stirring and uniformly mixing, carrying out high-pressure homogenization, and finally introducing inert gas to expel oxygen in the solution so as to obtain a reaction base solution; and (2) dissolving a second oxidant into purified water, passing through a cation exchange column, removing cations, introducing inert gas to expel oxygen in the solution so as to form a dropwise adding solution, slowly dropwise adding the dropwise adding solution into the reaction base solution, and carrying out polymerization reaction at the reaction temperature of 10-30 DEG C so as to obtain a PEDOT dispersion liquid, wherein redundant anions and cations are removed from the PEDOT dispersion liquid through anion-cation exchange resin. After the high-conductivity PEDOT dispersion liquid prepared by the method disclosed by the invention is prepared into a conductive film, the formed film is uniform, the conductivity of the film is tested by using a double-electric four-probe tester, and the conductivity is high.

Description

Technical Field

[0001] The present invention relates to the technical field of conductive polymer dispersions, and particularly relates to a method for preparing a PEDOT dispersion with high conductivity. Background Art

[0002] The PEDOT dispersion is obtained by oxidatively polymerizing the monomer 3,4-ethylenedioxythiophene (abbreviated as EDOT), doping with polystyrene sulfonic acid (abbreviated as PSS), and dispersing in an aqueous solution. Due to the good connectivity of the intramolecular conjugated electron system of PEDOT and the strong ability of electrons to transport within the molecule, PEDOT can form a conductive band and a hole band under the action of an external electric potential, and the film after spin coating has high conductivity. The conductive polymer PEDOT:PSS dispersion has a wide range of applications. With the continuous development of products and the continuous improvement of the conductivity of the polymer, it is expected to replace ITO in high-conductivity fields such as OLED and touch control. Due to the flexible characteristics of the PEDOT polymer, it is expected to be applied to flexible screens to obtain electronic screens with better performance.

[0003] However, the existing PEDOT dispersion has the problem that the conductivity of the prepared conductive film is relatively low.

[0004] In the existing methods for preparing PEDOT dispersions, the prepared PEDOT dispersion after the reaction is often passed through an ion resin for impurity removal and purification. For example, the Chinese invention patent with the publication number CN104448256B discloses a method for preparing a high-conductive PEDOT:PSS aqueous solution; the Chinese invention patent with the publication number CN102731971B discloses a PEDOT-PSS solution with high conductivity; the Chinese invention patent application with the publication number CN106496528A discloses a method for preparing a PEDOT-PSS aqueous dispersion using a microchannel reactor. The step of passing through an ion resin is used in these patents. However, due to the influence of fixed thinking and conventional thinking, the prepared PEDOT dispersion after the reaction is passed through an ion resin. After the reaction, the PEDOT dispersion has already formed, and passing through the ion resin mainly plays a role in impurity removal and purification, and does not play a key role in improving the conductivity. Summary of the Invention

[0005] The present invention provides a method for preparing a PEDOT dispersion with high conductivity, which solves the defect that the conductivity of the conductive film prepared from the PEDOT dispersion in the prior art is relatively low.

[0006] The technical solution of the present invention is realized as follows:

[0007] A method for preparing a PEDOT dispersion with high conductivity includes the following steps:

[0008] (1) Disperse the polyanion and the first oxidant into water, pass through an anion exchange column to remove anions, add the EDOT monomer, stir well to mix evenly, and perform high-pressure homogenization. The purified mass of the polyanion is 2 to 3.5 times that of the EDOT monomer, and the mass of the first oxidant is 0.001 to 0.2 times that of the EDOT monomer. Finally, introduce an inert gas to expel the oxygen in the solution to obtain the reaction bottom liquid;

[0009] (2) Dissolve the second oxidant in purified water. The mass of the second oxidant is 1.4 to 4 times that of the EDOT monomer. Pass through a cation exchange column to remove cations, introduce an inert gas to expel the oxygen in the solution to form a dropping liquid, slowly drop the dropping liquid into the reaction bottom liquid, and obtain a PEDOT dispersion through a polymerization reaction. The reaction temperature is 10 to 30 °C, and the PEDOT dispersion passes through anion and cation exchange resins to remove excess anions and cations.

[0010] Preferably, the polyanion is polystyrene sulfonic acid.

[0011] Preferably, the polystyrene sulfonic acid has a weight-average molecular weight of 50,000 to 500,000. The polystyrene sulfonic acid is a polystyrene sulfonic acid with one weight-average molecular weight, or a combination of two or more polystyrene sulfonic acids with different weight-average molecular weights.

[0012] Preferably, in step (1), the mass of water is 50 to 200 times that of the EDOT monomer.

[0013] Preferably, in step (1), a high-pressure homogenizer is used for homogenization, and the homogenization is performed 1 to 5 times with a homogenization pressure of 50 to 150 Mpa.

[0014] Preferably, the anion exchange resin column is filled with an anion resin, and the anion resin is a strongly acidic anion exchange resin, a weakly acidic anion exchange resin, or a macroporous anion exchange resin; the cation exchange resin column is filled with a cation resin, and the cation resin is a strongly acidic cation exchange resin, a weakly acidic cation exchange resin, or a macroporous cation exchange resin.

[0015] Preferably, the first oxidant is an auxiliary oxidant for catalytic action, and the first oxidant is a divalent iron salt; the second oxidant is a persulfate.

[0016] Preferably, the first oxidant is ferrous chloride or ferrous sulfate; the second oxidant is one of potassium persulfate, sodium persulfate, or ammonium persulfate.

[0017] Preferably, the inert gas is one of helium, argon, or nitrogen.

[0018] Preferably, in step (2), under the protection of an inert gas in a closed environment, the dropping time is 2 to 10 hours, and the total reaction time after dropping and during dropping is 16 to 32 hours.

[0019] Advantages of the present invention: The present invention breaks through the conventional thinking. Instead of simply passing the PEDOT dispersion through anion and cation exchange resin columns for impurity removal and purification after the reaction of the PEDOT dispersion, before the preparation and reaction of the PEDOT dispersion, each component for preparing the PEDOT dispersion is passed through an anion exchange resin column and a cation exchange resin column respectively, which can achieve unexpected effects. For the prepared PEDOT dispersion with high conductivity, 5% dimethyl sulfoxide is added to the dispersion, stirred evenly, then coated and dried to form a 10-μm thin film. When tested with a four-probe tester, the conductivity is high. Specific embodiments

[0020] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0021] Example 1

[0022] A method for preparing a PEDOT dispersion with high conductivity, comprising the following steps:

[0023] (1) Disperse a polyanion and a first oxidant in water, pass through an anion exchange column to remove anions, add EDOT monomer, stir and mix evenly, and perform high-pressure homogenization. The purified mass of the polyanion is 2 to 3.5 times that of the EDOT monomer, and the mass of the first oxidant is 0.001 to 0.2 times that of the EDOT monomer. Finally, introduce an inert gas to drive out the oxygen in the solution to obtain a reaction bottom liquid;

[0024] (2) Dissolve a second oxidant in purified water. The mass of the second oxidant is 1.4 to 4 times that of the EDOT monomer. Pass through a cation exchange column to remove cations, introduce an inert gas to drive out the oxygen in the solution to form a dropping liquid. The dropping liquid is slowly dropped into the reaction bottom liquid, and a polymerization reaction is carried out to obtain a PEDOT dispersion. The reaction temperature is 10 to 30 °C, and the PEDOT dispersion is passed through anion and cation exchange resins to remove excess anions and cations.

[0025] As a further technical solution, the polyanion is polystyrene sulfonic acid (abbreviated as PSS). Specifically, the weight-average molecular weight of the polystyrene sulfonic acid is 50,000 to 500,000, and the polystyrene sulfonic acid is a polystyrene sulfonic acid with a single weight-average molecular weight, or a combination of two or more polystyrene sulfonic acids with different weight-average molecular weights.

[0026] As a further technical solution, in step (1), the mass of water is 50 to 200 times the mass of the EDOT monomer. In step (1), a high-pressure homogenizer is used for homogenization, and the number of homogenization times and the pressure are not particularly limited. For the purpose of fully dispersing the monomer in the solution and considering the economic principle, it is preferably homogenized 1 to 5 times, and the homogenization pressure is 50 to 150 Mpa.

[0027] As a further technical solution, the anion exchange resin column is filled with an anion resin, and the anion resin is a strong acid anion exchange resin, a weak acid anion exchange resin or a macroporous anion exchange resin; the cation exchange resin column is filled with a cation resin, and the cation resin is a strong acid cation exchange resin, a weak acid cation exchange resin or a macroporous cation exchange resin.

[0028] As a further technical solution, the first oxidant is an auxiliary oxidant for catalytic action, and the first oxidant is a ferrous salt; the second oxidant is a persulfate. Specifically, the first oxidant is ferrous chloride or ferrous sulfate; the second oxidant is one of potassium persulfate, sodium persulfate or ammonium persulfate.

[0029] As a further technical solution, the inert gas is one of helium, argon or nitrogen. In step (2), under a closed condition and protected by an inert gas, the dropping time is 2 to 10 hours, and the total reaction time after dropping and during dropping is 16 to 32 hours.

[0030] The present invention breaks through the conventional thinking. Instead of passing the PEDOT dispersion through the anion and cation exchange resin columns after the reaction is completed, after the reaction is completed, the length of the PEDOT molecular chain has been fixed, and the length of the PEDOT molecular chain affects the conductivity. At this time, passing through the anion and cation exchange resin columns only plays a role in impurity removal and purification, and has no significant effect on improving the conductivity. However, the method of the present invention is to pass each component for preparing the PEDOT dispersion through the anion exchange resin column and the cation exchange resin column before the PEDOT dispersion is prepared and reacted, which can achieve unexpected effects. The PEDOT molecular chain generated during the reaction of each component can be longer. For the prepared PEDOT dispersion with high conductivity, 5% dimethyl sulfoxide is added to the dispersion, stirred evenly, then coated and dried to form a 10 μm thin film, and the conductivity is measured using a four-probe tester, and the conductivity is high.

[0031] Example 2

[0032] After mixing and dissolving 322 g of 30% polystyrene sulfonic acid with a weight average molecular weight of 250,000, 0.55 g of ferrous sulfate, and 2000 g of water, the mixture was passed through an anion exchange resin column to remove anions. Then, 28 g of 3,4-ethylenedioxythiophene was added to the feed solution. After high-pressure homogenization at 80 Mpa for 2 passes, the mixture was thoroughly stirred and dispersed in a reaction kettle, and nitrogen was introduced to displace the oxygen in the feed solution to obtain a reaction bottom solution. 47 g of sodium persulfate was dissolved in 200 g of pure water, passed through a cation exchange resin column to remove metal cations, and nitrogen was introduced to displace the oxygen in the feed solution to prepare a dropping solution. The dropping solution was slowly added dropwise to the reaction bottom solution over 4 hours at a reaction temperature of 10 °C. After the addition was completed, the reaction was carried out for 24 hours. The completed reaction solution was passed through anion and cation exchange resins to remove the excess anions and cations in the system, obtaining a highly conductive PEDOT dispersion. The conductivity of the dispersion was measured and recorded in Table 1.

[0033] Example 3

[0034] After mixing and dissolving 243 g of 30% polystyrene sulfonic acid with a weight average molecular weight of 250,000, 0.55 g of ferrous sulfate, and 2000 g of water, the mixture was passed through an anion exchange resin column to remove anions. Then, 28 g of 3,4-ethylenedioxythiophene was added to the feed solution. After high-pressure homogenization at 80 Mpa for 2 passes, the mixture was thoroughly stirred and dispersed in a reaction kettle, and nitrogen was introduced to displace the oxygen in the feed solution to obtain a reaction bottom solution. 60 g of sodium persulfate was dissolved in 200 g of pure water, passed through a cation exchange resin column to remove metal cations, and nitrogen was introduced to displace the oxygen in the feed solution to prepare a dropping solution. The dropping solution was slowly added dropwise to the reaction bottom solution over 4 hours at a reaction temperature of 20 °C. After the addition was completed, the reaction was carried out for 24 hours. The completed reaction solution was passed through anion and cation exchange resins to remove the excess anions and cations in the system, obtaining a highly conductive PEDOT dispersion. The conductivity of the dispersion was measured and recorded in Table 1.

[0035] Example 4

[0036] After mixing and dissolving 210 g of 30% polystyrene sulfonic acid with a weight average molecular weight of 250,000, 0.55 g of ferrous sulfate, and 2000 g of water, the mixture was passed through an anion exchange resin column to remove anions. Then, 28 g of 3,4-ethylenedioxythiophene was added to the feed solution. After high-pressure homogenization at 80 Mpa for 2 passes, the mixture was thoroughly stirred and dispersed in a reaction kettle, and nitrogen was introduced to displace the oxygen in the feed solution to obtain a reaction bottom solution. 85 g of sodium persulfate was dissolved in 200 g of pure water, passed through a cation exchange resin column to remove metal cations, and nitrogen was introduced to displace the oxygen in the feed solution to prepare a dropping solution. The dropping solution was slowly added dropwise to the reaction bottom solution over 4 hours at a reaction temperature of 30 °C. After the addition was completed, the reaction was carried out for 24 hours. The completed reaction solution was passed through anion and cation exchange resins to remove the excess anions and cations in the system, obtaining a highly conductive PEDOT dispersion. The conductivity of the dispersion was measured and recorded in Table 1.

[0037] Example 5

[0038] After mixing and dissolving 210 g of 30% polystyrenesulfonic acid with a weight-average molecular weight of 250,000, 0.55 g of ferrous sulfate, and 2000 g of water, the anions were removed by passing through an anion exchange resin column. Then, 28 g of 3,4-ethylenedioxythiophene was added to the feed solution. After high-pressure homogenization at 80 Mpa for 2 passes, it was sufficiently stirred and dispersed in a reaction kettle, and nitrogen was introduced to displace the oxygen in the feed solution to obtain the reaction bottom liquid. 60 g of sodium persulfate was dissolved in 200 g of pure water, the metal cations were removed by passing through a cation exchange resin column, and nitrogen was introduced to displace the oxygen in the feed solution to prepare the dropping solution. The dropping solution was slowly added dropwise to the reaction bottom liquid over 4 hours at a reaction temperature of 20 °C. After the addition was completed, the reaction was carried out for 24 hours. The reaction-completed feed solution was treated with anion and cation exchange resins to remove the excess anions and cations in the system, obtaining a highly conductive PEDOT dispersion. The conductivity of the dispersion was measured and recorded in Table 1.

[0039] Example 6

[0040] The same implementation method as in Example 5, except that the amount of ferrous sulfate was 5.5 g, and the rest was the same as in Example 5.

[0041] Example 7

[0042] The same implementation method as in Example 5, except that the amount of water used for the reaction bottom liquid was replaced from 2000 g to 5000 g, and the rest was the same as in Example 5.

[0043] Comparative Example 1

[0044] After mixing and dissolving 200 g of 30% polystyrenesulfonic acid with a weight-average molecular weight of 250,000, 0.55 g of ferrous sulfate, and 2000 g of water, the anions were removed by passing through an anion exchange resin column. Then, 28 g of 3,4-ethylenedioxythiophene was added to the feed solution. It was sufficiently stirred and dispersed in a reaction kettle, and nitrogen was introduced to displace the oxygen in the feed solution to obtain the reaction bottom liquid. 60 g of sodium persulfate was dissolved in 200 g of pure water, the metal cations were removed by passing through a cation exchange resin column, and nitrogen was introduced to displace the oxygen in the feed solution to prepare the dropping solution. The dropping solution was slowly added dropwise to the reaction bottom liquid over 4 hours at a reaction temperature of 50 °C. After the addition was completed, the reaction was carried out for 24 hours. The reaction-completed feed solution was treated with anion and cation exchange resins to remove the excess anions and cations in the system, obtaining a highly conductive PEDOT dispersion. The conductivity of the dispersion was measured and recorded in Table 1.

[0045] Comparative Example 2

[0046] After mixing and dissolving 210 g of 30% polystyrene sulfonic acid with a weight average molecular weight of 250,000, 0.55 g of ferrous sulfate, and 2000 g of water, 28 g of 3,4-ethylenedioxythiophene was added to the feed solution. After high-pressure homogenization at 80 Mpa for 2 passes, it was fully stirred and dispersed in the reaction kettle, and nitrogen was introduced to displace the oxygen in the feed solution to obtain the reaction bottom liquid. 60 g of sodium persulfate was dissolved in 200 g of pure water, and nitrogen was introduced to displace the oxygen in the feed solution to prepare the dropping solution. The dropping solution was slowly added dropwise to the reaction bottom liquid over 4 hours at a reaction temperature of 20 °C, and the reaction was carried out for 24 hours after the addition was completed. The reaction-completed feed solution was treated with anion and cation exchange resins to remove the excess anions and cations in the system, obtaining a highly conductive PEDOT dispersion. The conductivity of the dispersion was measured and recorded in Table 1.

[0047] Comparative Example 3

[0048] After mixing and dissolving 373 g of 30% polystyrene sulfonic acid with a weight average molecular weight of 250,000, 0.55 g of ferrous sulfate, and 2000 g of water, the anions were removed by passing through an anion exchange resin column. 28 g of 3,4-ethylenedioxythiophene was added to the feed solution. After high-pressure homogenization at 80 Mpa for 2 passes, it was fully stirred and dispersed in the reaction kettle, and nitrogen was introduced to displace the oxygen in the feed solution to obtain the reaction bottom liquid. 60 g of sodium persulfate was dissolved in 200 g of pure water, the metal cations were removed by passing through a cation exchange resin column, and nitrogen was introduced to displace the oxygen in the feed solution to prepare the dropping solution. The dropping solution was slowly added dropwise to the reaction bottom liquid over 4 hours at a reaction temperature of 20 °C, and the reaction was carried out for 24 hours after the addition was completed. The reaction-completed feed solution was treated with anion and cation exchange resins to remove the excess anions and cations in the system, obtaining a highly conductive PEDOT dispersion. The conductivity of the dispersion was measured and recorded in Table 1.

[0049] Comparative Example 4

[0050] In Comparative Example 3, the amount of polystyrene sulfonic acid was replaced with 157 g, and the rest was the same as in Comparative Example 3.

[0051] For the highly conductive PEDOT dispersion obtained in the above examples and the PEDOT:PSS dispersion obtained in the comparative examples, using a known method, 5% dimethyl sulfoxide was added, coated and dried, and the conductivity was measured using a four-probe tester to obtain Table 1 below.

[0052] Table 1

[0053]

[0054]

[0055] In the above Examples 2-7, it can be seen that through the method of this patent, the conductivity is relatively high. Comparing with Example 1, under the conditions of non-homogenization and over-temperature of the reaction temperature, although the raw materials have also been deionized, the final conductivity result is relatively low. From the results of Comparative Example 2, it can be seen that without deionizing the raw materials, the conductivity is also relatively low. Comparing Comparative Example 3 and Comparative Example 4, since the mass ratios of PSS to monomer reach 4:1 and 1.68:1 respectively, the non-conductive PSS component in Comparative Example 3 is too high, which affects the final conductivity. In Comparative Example 4, a lower proportion of PSS is used. Although the content of the conductive monomer EDOT increases and the content of the final conductive polymer PEDOT also increases correspondingly, due to the too low content of PSS, the feed liquid is unstable and forms precipitation, and finally the film formed is uneven and the conductivity is non-uniform.

[0056] From the data of the above examples, it can be known that the high-conductivity PEDOT dispersion prepared by the method of the present invention has a uniform film formation after being made into a conductive film, and the conductivity of the film is measured by a double-probe four-probe tester, and the conductivity is high.

[0057] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for preparing a high conductivity PEDOT dispersion, characterized in that: The following steps are involved: (1) dispersing the polyanion and the first oxidant in water, passing through an anion exchange column to remove anions, adding EDOT monomer, stirring and mixing well, and performing high-pressure homogenization, wherein the weight of the polyanion is 2 to 3.5 times that of the EDOT monomer, and the weight of the first oxidant is 0.001 to 0.2 times that of the EDOT monomer, and finally introducing an inert gas to drive out oxygen in the solution to obtain a reaction base solution; (2) The second oxidant is dissolved in purified water, the mass of the second oxidant is 1.4 to 4 times that of the EDOT monomer, and passed through a cation exchange column to remove cations. An inert gas is introduced to drive out the oxygen in the solution to form a droplet, which is slowly added dropwise to the reaction base solution to obtain a PEDOT dispersion by polymerization reaction. The reaction temperature is 10 to 30°C, and the PEDOT dispersion is passed through an anion and cation exchange resin to remove excess anions and cations.

2. The method for preparing a high conductivity PEDOT dispersion according to claim 1, characterized in that: The polyanion is polystyrene sulfonic acid.

3. The method for preparing a high conductivity PEDOT dispersion according to claim 2, characterized in that: The weight average molecular weight of the polystyrene sulfonic acid is 50,000 to 500,000. The polystyrene sulfonic acid is a single polystyrene sulfonic acid with a weight average molecular weight, or a combination of two or more polystyrene sulfonic acids with a weight average molecular weight.

4. The method for preparing a high conductivity PEDOT dispersion according to claim 1, characterized in that: The mass of water in step (1) is 50 to 200 times the mass of EDOT monomer.

5. The method for preparing a high conductivity PEDOT dispersion according to claim 1, characterized in that: In step (1), a high pressure homogenizer is used for homogenization, and the homogenization is performed 1 to 5 times at a homogenization pressure of 50 to 150 MPa.

6. The method for preparing a high conductivity PEDOT dispersion according to claim 1, characterized in that: The anion exchange resin column is filled with anion resin, which is a strong acid anion exchange resin, a weak acid anion exchange resin or a macroporous anion exchange resin; the cation exchange resin column is filled with cation resin, which is a strong acid cation exchange resin, a weak acid cation exchange resin or a macroporous cation exchange resin.

7. The method for preparing a high conductivity PEDOT dispersion according to claim 1, characterized in that: The first oxidant is an auxiliary oxidant used for catalysis, and the first oxidant is a divalent iron salt; the second oxidant is a persulfate.

8. The method for preparing a high conductivity PEDOT dispersion according to claim 7, characterized in that: The first oxidant is ferrous chloride or ferrous sulfate; the second oxidant is one of potassium persulfate, sodium persulfate or ammonium persulfate.

9. The method for preparing a high conductivity PEDOT dispersion according to claim 1, characterized in that: The inert gas is one of helium, argon or nitrogen.

10. The method for preparing a high conductivity PEDOT dispersion according to claim 1, characterized in that: In step (2), the dropping time is 2 to 10 hours in a closed environment under the protection of an inert gas, and the total reaction time after the dropping is 16 to 32 hours.

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