Method for improving Seebeck coefficient of PEDOT

Abstract

The invention discloses a method for improving Seebeck coefficient of PEDOT (poly (3, 4-ethylenedioxythiophene)), which is characterized by comprising the following specific steps: step 1, synthesizing EDOT and a derivative monomer thereof by utilizing an esterification reaction method; step 2, preparing an oxidation solution required by in-situ oxidative polymerization; 3, adding a monomer and an oxidizing solution system, spin-coating on a glass substrate, and performing in-situ oxidative polymerization to obtain a conductive polymer; and step 4, fully cleaning an in-situ polymerization product with absolute ethyl alcohol, and then drying to obtain the final PEDOT conductive film with the high Seebeck coefficient. The method for improving the Seebeck coefficient of the PEDOT by introducing the side group on the surface of the PEDOT provides a new thought for research and application of the PEDOT in the thermoelectric field, especially in the flexible wearable field.

Description

Technical Field

[0001] The invention relates to the field of polymer thermoelectric material structure design, and in particular to a new method for improving the PEDOT Seebeck coefficient. Technical Background

[0002] With the increase of global energy demand and the depletion of fossil energy, the energy crisis is becoming increasingly serious. Thermoelectric (TE) materials are widely used in energy management and other fields due to their ability to directly convert thermal energy into electrical energy. Compared with traditional inorganic thermoelectric materials such as selenide and bismuth telluride, poly (3,4-ethylenedioxythiophene) (PEDOT) has the advantages of low density, low thermal conductivity, good flexibility, etc., so its application in the field of thermoelectric materials has attracted more and more attention.

[0003] The Seebeck coefficient is a key factor in determining the thermoelectric properties of materials. How to improve the Seebeck coefficient of PEDOT has always been the focus of research in the field of polymer thermoelectric materials. At present, there are two main ways to improve the Seebeck coefficient of PEDOT: first, dedoping it with an original reagent; second, blending PEDOT with nanofillers such as tellurium (Te) with a high Seebeck coefficient. However, most reducing agents are very expensive and toxic. In addition, when the PEDOT film is dedoped and cleaned with a reducing agent, the film is easily destroyed, which is extremely unfavorable for the application of PEDOT in the fields of wearable biomaterials. For the method of improving the Seebeck coefficient by blending PEDOT with inorganic fillers such as Te with a high Seebeck coefficient, the content of nanofillers such as Te generally needs to exceed 50wt% to significantly improve the Seebeck coefficient of PEDOT. Increasing the content of nanofillers or even using nanofillers as a substrate may cause PEDOT to lose its advantages such as light weight and flexibility. Therefore, it is necessary to explore a new method to improve the Seebeck coefficient of PEDOT. Summary of the invention

[0004] The purpose of the present invention is to provide a new method for improving the Seebeck coefficient of PEDOT. This method is expected to solve the problems of high toxicity, high cost and poor mechanical properties of the film in the traditional method. This will further provide new ideas for the design and application of PEDOT thermoelectric materials.

[0005] Technical solution of the present invention:

[0006] In order to solve the above technical problems, the present invention provides a new method for improving the Seebeck coefficient of PEDOT, comprising the following specific steps:

[0007] Step 1, synthesizing EDOT and its derivative monomers by esterification reaction method;

[0008] Step 2, preparing the oxidation solution required for in-situ oxidative polymerization;

[0009] Step 3: Add the monomer into the oxidation solution system, spin-coat it on the glass substrate, and in-situ oxidize and polymerize it into a conductive polymer.

[0010] Step 4: Thoroughly wash the in-situ polymerized product with absolute ethanol, and then dry it to obtain the final PEDOT conductive film with a high Seebeck coefficient.

[0011] Preferably, the step 1 includes monomers such as EDOT, EDOT-MeOH, EDOT-Cn (n is the number of C atoms of the alkyl group, n≥1), and EDOT-MeCl.

[0012] Preferably, the oxidant solution in the step 2 is a n-butanol solution containing 35 wt% iron p-toluenesulfonate with 2 wt% imidazole.

[0013] Preferably, the molar ratio of the monomer to iron p-toluenesulfonate in the step 3 is 1:2.5.

[0014] Preferably, the monomer in the step 3 is at least one of those in the step 1.

[0015] Preferably, the polymerization temperature in the step 3 is 50 °C and the polymerization time is 1 h.

[0016] Preferably, the drying temperature in the step 4 is 50 °C and the drying time is 30 min.

[0017] Advantages of the present invention:

[0018] This method first synthesizes a series of EDOT derivatives by an esterification reaction, and then prepares a PEDOT derivative film by an in-situ polymerization method. The increase in the Seebeck coefficient of PEDOT is achieved by introducing side groups on its surface. Different from the traditional methods of de-doping PEDOT with reducing agents or blending PEDOT with inorganic fillers such as tellurium (Te) with a high Seebeck coefficient to improve the Seebeck coefficient of PEDOT, the method of this application is not only simple in process, but also safer, more economical, and more environmentally friendly.

[0019] Specifically, this method of introducing side groups to improve the Seebeck coefficient of PEDOT is achieved by changing the intrinsic electronic structure and chain structure of PEDOT. When the EDOT derivative completes oxidative polymerization, its polymer has a higher Seebeck coefficient than PEDOT. This method does not require blending PEDOT with other fillers anymore, nor does it need to use any chemical reagents for de-doping treatment. Therefore, it effectively avoids the problem that the PEDOT film may be damaged during the process of high nano-filler content and de-doping treatment; in addition, this method avoids the use of toxic reagents such as strong reducing agents, is safer and more environmentally friendly, and is more conducive to applications in fields such as flexible wearable devices. Brief Description of the Drawings

[0020] To more clearly illustrate the monomer structure, the molecular structure of the monomer is drawn,

[0021] Figure 1 which is the molecular structure diagram of the monomer. Detailed Description of the Invention

[0022] For further illustration, the present invention needs to be further elaborated. All monomers in the present invention are synthesized according to the mature esterification reaction. The specific synthesis method is as follows:

[0023] Synthesis method of EDOT: The transesterification reaction is carried out in toluene solvent, using 3,4 - dimethoxythiophene and ethylene glycol as reactants, and p - toluenesulfonic acid as the catalyst. Add toluene (30 g), 3,4 - dimethoxythiophene (2 g, 13.87 mmol), ethylene glycol (1.72 g, 27.74 mmol) and p - toluenesulfonic acid (0.24 g, 1.39 mmol) into a three - necked flask. Under nitrogen protection, heat the mixture to 100 °C and stir for 24 h. To ensure complete conversion of 3,4 - dimethoxythiophene, add ethylene glycol (0.86 g, 13.87 mmol) into the reaction system and continue to react at 100 °C for 6 h. After the reaction is completed, first remove the catalyst using filter paper, and then remove toluene by vacuum distillation. Finally, purify the product using column chromatography (silica gel, petroleum ether / ethyl acetate = 15 / 2 V / V) to obtain an oily product of EDOT (yield 58.65%). The synthesis steps of other EDOT derivatives are the same as those of EDOT.

[0024] Preparation of oxidant solution: Take 5 g of iron p - toluenesulfonate and 0.286 g of imidazole and add them to 9.014 g of n - butanol. Stir the mixture at 80 °C for 1 h to ensure complete dissolution of iron p - toluenesulfonate and imidazole, and then cool to room temperature to obtain the oxidant solution.

[0025] Example 1: Preparation method of PEDOT - MeCl film

[0026] At room temperature, take 0.071 g of EDOT - MeCl and add it to 1.43 g of the oxidant solution, and spin - coat it on a 2 * 2 cm glass substrate at a speed of 2000 r / min within 30 s. Then react on a hot plate at 50 °C for 1 h. After cooling to room temperature, wash away the residual oxidant and other impurities with anhydrous ethanol. Finally, dry it in a drying oven at 50 °C for 30 min.

[0027] Example 2

[0028] The difference from Example 1 is that the monomer is changed to EDOT - MeOH.

[0029] Example 3

[0030] Differing from Example 1, the monomer was changed to EDOT-C2.

[0031] Example 4

[0032] Differing from Example 1, the monomer was changed to a mixture of EDOT and EDOT-MeCl.

[0033] Comparative Example 1

[0034] Differing from Example 1, the monomer was changed to EDOT.

[0035] To verify the Seebeck coefficient of the thin films prepared by the manufacturing method of the present invention, the Seebeck coefficients of the thin films in the above-mentioned examples and comparative examples were tested, and the specific test results are shown in the following table.

[0036] Seebeck coefficient (μV / K) Example 1 39.62 Example 2 27.98 Example 3 31.57 Example 4 29.65 Comparative Example 1 25.56

[0037] From the data of the above examples and comparative examples, it can be seen that introducing side groups can significantly improve the Seebeck coefficient of PEDOT, especially more significantly after introducing -MeCl. In addition, copolymerizing EDOT derivatives with EDOT can also improve its Seebeck coefficient.

[0038] The specific embodiments are only explanations of the present invention and are not limitations thereof. For example, different monomers can be blended and copolymerized in different proportions. Those skilled in the art can make modifications without creative contributions to the present embodiments after reading this specification, but as long as they are within the scope of the claims of the present invention, they are protected by the patent law.

Claims

1. A method for improving the Seebeck coefficient of PEDOT, characterized in that: The specific steps include: Step 1, synthesizing EDOT and its derivative monomers by esterification reaction method; Step 2, preparing the oxidation solution required for in-situ oxidative polymerization; Step 3, adding the monomers and into an oxidizing solution system, and in-situ oxidatively polymerizing them into a conductive polymer after spin coating on a glass substrate; Step 4: The in-situ polymerized product is fully cleaned with anhydrous ethanol, and then dried to obtain the final high Seebeck coefficient PEDOT conductive film.

2. The method according to claim 1, characterized in that: The monomers in step 1 are EDOT, EDOT-MeOH, EDOT-Cn (n is the number of C atoms of the alkyl group, n≥1), and EDOT-MeCl.

3. The method according to claim 1, characterized in that: The oxidant solution in step 2 is a 35 wt % n-butanol solution of iron p-toluenesulfonate containing 2 wt % imidazole.

4. The method according to claim 1, characterized in that: The molar ratio of the monomer to iron p-toluenesulfonate in step 3 is 1:2.

5.

5. The method according to claim 1, characterized in that: The polymerization temperature in step 3 is 50° C. and the polymerization time is 1 hour.

6. The method according to claim 1, characterized in that: The drying temperature in step 4 is 50° C. and the drying time is 30 min.

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