CZ34652U1 - Carbon material surface modified with poly (3,4-ethylenedioxothiophene) - Google Patents

Description

Field of technology

The technical solution relates to the field of surface treatment, in particular to the carbon material of the surface-modified poly (3,4-ethylenedioxothiophene).

Prior art

Carbon nanostructures and conductive polymers are long-studied materials with a wide range of uses in the field of antistatic or dissipative surface treatment of materials, or their modification. Both materials are also widely used in printing formulations designed for electrode, functional or sensor electronic systems produced by printing processes on flexible substrates. In connection with the development of flexible electronics as well as energy storage systems such as flexible and stationary batteries, both primary and secondary or supercapacitors, the question of the combination of these two materials is increasingly emerging. The aim is to combine the properties of both materials so as to increase their utility and application value.

Carbon nanoparticles (CNPs), especially carbon nanotubes and graphene, show high electrical conductivity, although in this respect they do not reach the parameters of metallic layers. Carbon materials are investigated in terms of their application as transparent conductive electrodes for flexible, printed electronic devices, but also as electrodes for energy storage systems, especially batteries and supercapacitors. In all cases, these materials are expected to be easy to apply on an industrial scale with industrially available printing and coating techniques. These are mainly flexographic printing, screen printing, gravure printing and slot die printing techniques. Newly, these materials are also used in 3D printing or additive production. The aim is to prepare defined electrode structures with the largest possible thickness, which will be at the same time sufficiently homogeneous and permeable for charge transfer in their entire volume. From the point of view of these applications, the considered carbon nanomaterials have the great disadvantage in that they agglomerate easily, forming amorphous clumps, which is a disadvantage of all the above-mentioned printing techniques. Solving this problem with dispersants causes a reduction in the conductivity of the printed layer. Last but not least, the thicker printed layer of carbon nanomaterials does not have sufficient properties in terms of uniform charge mobility throughout its volume.

These shortcomings have been gradually eliminated in recent years. One solution to these problems may be the use of carbon nanomaterials in combination with conductive polymers.

The application of conductive polymers to the surface of carbon nanomaterials is expected to improve their surface properties, reduce agglomeration and at the same time not significantly reduce the conductivity of the whole system. Among the most commercially successful conductive polymers is the ion pair poly (3,4-ethylenedioxothiophene) polystyrene sulfonate (PEDOT / PSS). It is most often supplied in the form of an aqueous dispersion prepared by oxidative polymerization of 3,4-ethylenedioxothiophene in the presence of an excess of polystyrene sulfonate. This creates an ion pair of a long polymer, polystyrene sulfonate, with a short polymer chain, PEDOT. In the conductive oxidized form, every second monomeric unit of the PEDOT is positively charged (it contains a positive electron hole) and its charge is compensated by the negative charge of the anion polystyrene sulfonate. PEDOT / PSS exhibits elements of electronic and ionic conductivity. If the mixture is alkalized or reduced, the ion pair disintegrates, the PEDOT changes to a reduced form, and the conductivity decreases by several orders of magnitude. The advantage of this system is that PEDOT / PSS has excellent film-forming properties, which leads to the formation of homogeneous well-conducting films. If the dispersion is not well prepared or the doping anion is not well set, then despite the very good conductivity of the material itself, a high-quality, well-conducting film is not formed.

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PEDOT / PSS is widely used in the field of flexible and printed electronics as an excellent charge carrier. At the same time, it is widely used to modify dispersions of carbon nanomaterials. The system as a whole exhibits improved properties in terms of dispersion and preparation of thin films by standard application techniques. However, it should still be borne in mind that this is a two-component system in which it is not possible to define exactly the nature of the bond between the carbon material and the conductive polymer. In addition, it is a mixture whose composition can be disturbed by various external influences.

An alternative method of modifying carbon materials is to use well-dispersed carbon nanomaterials as an adsorbent material for the starting monomer, 3,4-ethylenedioxothiophene, and then treat the mixture with an oxidizing agent such as ferric chloride, ferric sulfate, ferric tosylate or persulfate. ammonium, potassium or sodium. The so-called in situ polymerization takes place, when the adsorbed monomers are interconnected in short polymer units. The properties of carbon treated in this way do not differ significantly from the two-component system of carbon nanomaterials-PEDOT / PSS. However, the conductive polymer is significantly better fixed in the system.

The above-described methods of modification of carbon materials, in situ polymerization or modification of PEDOT / PSS dispersions do not have a direct effect on the overall character of the printed layer of modified carbon nanomaterials. The addition of PEDOT does not make it possible to prepare electrode layers that have a higher charge transfer and storage capacity than layers of unmodified carbon nanostructures.

The task of the technical solution is therefore to create a carbon material of surface-modified poly (3,4-ethylenedioxothiophene), which would eliminate the above-mentioned drawbacks and which would provide carbon material covered with different thicknesses of firmly fixed conductive polymer as needed on all or only part of the surface. for a wide range of industrial applications.

The essence of the technical solution

The stated task is to solve with the help of a carbon material surface-modified poly (3,4-ethylenedioxothiophene) which can be prepared by in situ polymerization of the reaction mixture. The essence of this technical solution lies in the fact that the reaction mixture contains 0.1 to 7 mmol of 3,4-ethylenedioxothiophene per 1 g of carbon material, further it contains a carbon material with an aromatic compound with a sulfone group and an oxidizing agent. The starting carbon material has in its structure a reactively fixed aromatic compound with at least one negatively charged sulfone group containing 0.6 to 2.5 mmol of sulfone groups per 1 g of carbon material by means of a C-C bond. Thus, the carbon material has in its structure at least one aromatic compound reactively fixed by means of a C-C bond or an aromatic support with at least one negatively charged sulfone group forming an ion pair with a positively charged conductive polymer poly (3,4-ethylenedioxothiophene).

Sulfone groups are a system of negative charge carriers that are reactively fixed to the surface of carbon materials, where this system serves as a dopant for the polymer poly (3,4-ethylenedioxothiophene) (PEDOT). In situ polymerization of the starting monomer, 3,4-ethylenedioxothiophene, in the presence of sulfone-modified carbon materials produces an ion pair of positively charged polymer, PEDOT, and negatively charged sulfonated aromatic structures reactively bonded via a C-C bond to the carbon matrix support matrix. It is thus achieved that the PEDOT is fixed on the surface of the carbon material. However, it is not a two-component system, as is the case with a mixture of PEDOT / PSS and carbon nanomaterials. This method of preparation makes it possible to cover the carbon material in a controlled manner with a conductive polymer PEDOT, as required either on the entire surface or only on a certain part thereof, in addition in different thicknesses. The defined preparation procedure therefore allows the fixing of different amounts of PEDOT on the surface of carbon materials.

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The technical solution is designed primarily for carbon nanotubes, both Single-Walled Carbon Nanotubes (SWCNT) and Multi-Walled Carbon Nanotubes (MWCNT) and other carbon materials such as graphite, graphene or nanographite. Fixation of PEDOT on the matrix of carbon material allows to prepare a new type of material, in which the above-mentioned shortcomings are eliminated. The dispersion of the nano / carbon materials thus prepared is stable and thus has a reduced tendency to agglomerate. The actual preparation of the thin layers is then simpler and does not require large additions of dispersants. In addition, the carbon material modified in this way brings new functional properties in terms of its use, for example as a material for sensors or for the preparation of electrode layers. The PEDOT layer can be understood as an intermediate layer between the individual carbon particles, they do not agglomerate and the charge should migrate better between them. The formation of a conductive intermediate layer of PEDOT units between the individual carbon units thus creates space for better charge mobility and for a higher capacity of the carbon matrix layer.

The sandwich structure of the carbon material-sulfone group-PEDOT or CNPSO3H / PEDOT allows the formation of thicker layers that are functional throughout their volume, which ultimately brings a reduction in sheet resistance compared to standard layers of carbon materials. In addition, the carbon material modified in this way can be used for the preparation of spatial electrode structures by means of 3D printing.

The actual preparation of the CNP-SO3H / PEDOT composite consists of two steps. First, the aromatic anion carrier, an arylsulfone group, is fixed on a carbonaceous material, and then the actual polymerization of EDOT is performed. Fixation of the aromatic anion carrier, sulfone group, is performed by so-called C-C coupling, radical nucleophilic aromatic substitution. The amino-substituted aromatic sulfone compound is subjected to a so-called diazotization in an aqueous medium containing hydrochloric acid or sulfuric acid by the addition of sodium nitrite at a temperature of 0 to 30 ° C to give the corresponding diazonium salt. Examples of useful sulfonic compounds are: 2-aminobenzene-1-sulfonic acid, 3-aminobenzene-1-sulfonic acid, 4-aminobenzene-1-sulfonic acid, 1-aminonaphthalene-4-sulfonic acid, 1-aminonaphthalene-5-sulfonic acid , 1-aminonaphthalene-6-sulfonic acid, 1-aminonaphthalene-7-sulfonic acid, 1-aminonaphthalene-8-sulfonic acid, 2-aminonaphthalene-1-sulfonic acid, 2-aminonaphthalene-5-sulfonic acid, 2-aminonaphthalene- 6-sulfonic acid, 2-aminonaphthalene-7-sulfonic acid, 2-aminonaphthalene-8-sulfonic acid.

This diazonium salt is then used for C-C coupling. The reaction mechanism of these reactions is schematically shown in the following figure. In the first step of the reaction, a complex is formed between the diazonium salt and the carbonaceous material. Subsequently, nitrogen is released and a radical is formed, which immediately reacts with the surrounding carbon atoms. The formation of a covalent bond between the aryldiazonium radical and these atoms leads to the transformation of the sp2 carbon to sp3. The degree of modification of carbonaceous materials is affected by the amount of diazonium salt used, in a molar ratio of carbonaceous material: salt from 140: 1 to 1: 1. In this way, 0.6 to 2.5 mmol of sulfone groups, -SO3 per 1 g of carbonaceous material, are introduced into the carbonaceous material.

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Scheme of reaction of diazonium salt with carbonaceous material, where R is S (hH

The carbon materials thus modified can then be used as a dopant for the in situ polymerization of 3,4-ethylenedioxothiophene. In situ polymerization of PEDOT is performed in an aqueous medium in the presence of oxidizing agents. Acid-forming salts of ferric ions such as ferric fluoride, ferric chloride, ferric bromide, ferric iodide, ferric sulfate, ferric nitrate, ferric phosphate and ferric tosylate are used as oxidizing agents. Furthermore, the oxidizing properties of the salts of persulphuric acid, such as sodium persulphate, potassium persulphate and ammonium persulphate, are preferably used. Other oxidizing agents used include salts containing a silver ion, such as silver nitrate or silver sulfate, salts containing a cerium ion, such as cerium sulfate, or salts containing a copper ion, such as copper chloride, copper sulfate, copper nitrate, or a combination thereof. In this way, 0.1 to 7 mmol of poly (3,4-ethylenedioxothiophene) per 1 g of carbonaceous material is introduced into the carbonaceous material. The polymerizations are usually carried out at concentrations of oxidizing agents and 3,4-ethylenedioxothiophene monomer from 0.01 mM to 0.1 M, in a wide temperature range from -30 ° C to temperatures approaching 100 ° C.

Example of implementing a technical solution

Example 1: Procedure for diazotization of 4-aminobenzene-1-sulfonic acid - formation of diazonium salt

First, a mixture of sulfanilic acid (0.05 mol) and hydrochloric acid (15 ml) was cooled to -5 ° C. Then, an aqueous saturated sodium nitrite solution (0.06 mol) was slowly added to the reaction mixture so that the temperature did not exceed 0 ° C. After all the amine had reacted, tetrafluoroboric acid (15 mL) was added to the reaction mixture to exchange chloride ions and stabilize the diazonium salt.

Example 2: C-C coupling procedure for CNT - formation of a carbon material modified with a sulfone group

To the aqueous suspension of SWCNT (250 mmol) was added the aryldiazonium salt (18 mmol) prepared according to Example 1. The reaction was carried out at room temperature with stirring with a dispersant.

-4GB 34652 UI (ULTRA TURRAX) for 24 hours. The resulting SWCNT-SO3H dispersion was filtered off and washed with distilled water to remove unwanted reactants. Elemental analysis determined the amount of sulfone groups contained to be 2 mmol per 1 g of SWCNT.

Example 3: C-C coupling procedure for CNT - formation of a carbon material modified with a sulfone group

To the aqueous suspension of SWCNT (42 mmol) was added the aryldiazonium salt (1.5 mmol) prepared according to Example 1. The reaction was carried out at room temperature with stirring with a dispersant (ULTRA TURRAX) for 24 hours. The resulting SWCNT-SO3H dispersion was filtered off and washed with distilled water to remove unwanted reactants. The amount of sulfone groups contained was determined by elemental analysis to be 1.5 mmol per 1 g of SWCNT.

Example 4: C-C coupling procedure for CNT - formation of a carbon material modified with a sulfone group

To the aqueous suspension of SWCNT (42 mmol) was added the aryldiazonium salt (0.3 mmol) prepared according to Example 1. The reaction was carried out at room temperature with stirring with a dispersant (ULTRA TURRAX) for 24 hours. The resulting SWCNT-SO3H dispersion was filtered off and washed with distilled water to remove unwanted reactants. The amount of sulfone groups contained was determined by elemental analysis to be 0.6 mmol per 1 g of SWCNT.

Example 5: C-C coupling procedure for CNTs - formation of a carbon material modified with a sulfone group

To the aqueous suspension of MWCNT (300 mmol) was added the aryldiazonium salt (22 mmol) prepared according to Example 1. The reaction was carried out at room temperature with stirring with a dispersant (ULTRA TURRAX) for 24 hours. The resulting MWCNT-SO3H dispersion was filtered off and washed with distilled water to remove unwanted reactants. Elemental analysis determined the amount of sulfone groups contained to be 2.4 mmol per 1 g of MWCNT.

Example 6: C-C coupling procedure for graphites - formation of a carbon material modified with a sulfone group

To the aqueous suspension of graphite or nanographite (15 mmol) was added the aryldiazonium salt (15 mmol) prepared according to Example 1. The reaction was carried out at room temperature with stirring with a dispersant (ULTRA TURRAX) for 24 hours. The resulting dispersion was centrifuged (10,000 rpm, 30 minutes) and the sediment was dispersed in distilled water. This procedure was repeated 5 times to remove unwanted reactants. Elemental analysis determined the amount of sulfone groups contained 2.5 mmol per 1 g of graphite.

Example 7: C-C coupling procedure for graphites - formation of a carbon material modified with a sulfone group

The aryldiazonium salt (11 mmol) prepared according to Example 1 was added to an aqueous suspension of nanographite (250 mmol). The reaction was carried out at room temperature with stirring with a dispersant (ULTRA TURRAX) for 24 hours. The resulting dispersion was centrifuged (10,000 rpm, 30 minutes) and the sediment was dispersed in distilled water. This procedure was repeated 5 times to remove unwanted reactants. Elemental analysis determined the amount of sulfone groups contained to be 0.7 mmol per 1 g of graphite.

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Example 8: C-C coupling procedure for graphenes - formation of a carbon material modified with a sulfone group

To the aqueous suspension of graphene (160 mmol) was added the aryldiazonium salt (11 mmol) prepared according to Example 1. The reaction was carried out at room temperature with stirring with a dispersant (ULTRA TURRAX) for 24 hours. The resulting dispersion was dialyzed with distilled water to remove unwanted reactants. Elemental analysis determined the amount of sulfone groups contained to 1.8 mmol per 1 g of graphene.

Example 9: PEDOT in situ polymerization process - formation of surface-modified PEDOT carbon material

500 ml of demineralized water and 50 mg of modified SWCNTs prepared according to Example 2 were introduced into a 1000 ml flask equipped with a magnetic stirrer. The reaction mixture was stirred at room temperature for 24 hours. Then 108 mg (0.40 mmol) of ferric chloride hexahydrate and 50 mg (0.35 mmol) of 3,4-ethylenedioxothiophene were added. The reaction mixture was stirred for 24 hours at room temperature. After the reaction time, the mixture was filtered and washed with 2x20 mL of demi water. The product was dried in an oven and transferred to a vial.

Example 10: PEDOT in situ polymerization process - formation of surface-modified PEDOT carbon material

To a 1000 mL flask equipped with a magnetic stirrer was charged 500 mL of demineralized water, 50 mg of modified SWCNTs prepared according to Example 2, and 25 mg (0.18 mmol) of 3,4-ethylenedioxothiophene. The mixture was sonicated for 2 hours. Then, 46 mg (0.20 mmol) of ammonium persulfate was added to the flask, and the mixture was stirred at 95 ° C and sonicated for 24 hours. After the reaction time, the mixture was filtered and washed with 2x20 mL of demi water. The product was dried in an oven and transferred to a vial.

Example 11: PEDOT in situ polymerization process - formation of surface-modified PEDOT carbon material

To a 1000 mL flask equipped with a magnetic stirrer was charged 500 mL of demineralized water, 50 mg of modified SWCNTs prepared according to Example 2, and 2.8 mg (0.005 mmol) of anhydrous ferric tosylate. The mixture was stirred for 24 hours at 10 ° C. Then 0.5 mg (0.004 mmol) of 3,4-ethylenedioxothiophene was added. The reaction mixture was stirred at 10 ° C for 24 hours. After the reaction time, the mixture was filtered and washed with 2x20 mL of demi water. The product was dried in an oven and transferred to a vial.

Example 12: PEDOT in situ polymerization process - formation of surface-modified PEDOT carbon material

To a 100 mL flask was charged 50 mL of demineralized water, 50 mg of modified SWCNTs prepared according to Example 4, and 0.5 mg (0.004 mmol) of 3,4-ethylenedioxothiophene. The mixture was stirred using a dispersant (ULTRA TURRAX) for 2 hours. Then 0.17 mg (0.001 mmol) of silver nitrate and 0.95 mg (0.004 mmol) of sodium persulfate were added. The reaction mixture was stirred using a dispersant (ULTRA TURRAX) for 24 hours at 50 ° C. After the reaction time, the mixture was filtered and washed with 2x20 mL of demi water. The product was dried in an oven and transferred to a vial.

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Example 13: PEDOT in situ polymerization process - formation of surface-modified PEDOT carbon material

To a 100 mL flask was charged 50 mL of demineralized water, 50 mg of modified SWCNTs prepared according to Example 4, and 57 mg (0.4 mmol) of 3,4-ethylenedioxothiophene. The mixture was sonicated for 2 hours. Subsequently, the flask was cooled to 0 ° C, and 6.4 mg (0.04 mmol) of copper sulfate and all mg (0.4 mmol) of ferric bromide were added thereto. The mixture was stored at -20 ° C for 14 days. After this time, the mixture was filtered and washed with 2x20 mL of demi water. The product was dried in an oven and transferred to a vial.

Example 14: PEDOT in situ polymerization process - formation of surface-modified PEDOT carbon material

To a 100 mL flask was charged 50 mL of demineralized water, 50 mg of modified SWCNTs prepared according to Example 4, and 13 mg (0.04 mmol) of cerium sulfate. The mixture was sonicated with stirring using a dispersant (ULTRA TURRAX) for 2 hours. Then 5.7 mg (0.04 mmol) of 3,4-ethylenedioxothiophene was added. While stirring with a disperser (ULTRA TURRAX) and sonication, the reaction mixture was polymerized at 37 ° C for 24 hours. After the reaction time, the mixture was filtered and washed with 2x20 mL of demi water. The product was dried in an oven and transferred to a vial.

Example 15: PEDOT in situ polymerization process - formation of surface-modified PEDOT carbon material

To a 100 mL flask equipped with a magnetic stirrer was charged 50 mL of demineralized water, 50 mg of modified SWCNTs prepared according to Example 3, and 25 mg (0.18 mmol) of 3,4-ethylenedioxothiophene. The mixture was sonicated for 2 hours. Then, 46 mg (0.20 mmol) of ammonium persulfate was added to the flask, and the mixture was stirred at 95 ° C and sonicated for 24 hours. After the reaction time, the mixture was filtered and washed with 2x20 mL of demi water. The product was dried in an oven and transferred to a vial.

Example 16: Procedure for preparing a tablet for measuring electrical resistance

A tablet with a diameter of 10 mm and a thickness of 2 mm was prepared from 50 mg of dried sample in a hand-held tablet press at a pressure of 15 kN. The electrical resistance was measured using a two-point probe with the measuring tips 1 cm apart, using a Keithley 2701 measuring instrument.

Molar ratio of SO3H group fixed to CNT: PEDOT [mol / mol] 25: 1 1.8: 1 1: 13.3 Electrical resistance (Ω) 0.1 1 10

Example 17: Characteristics of the PEDOT layer on the CNT

The distribution of PEDOT in the sample and its degree of nanotube coverage was defined by AFM. All samples containing CNTs showed a fibrous character with a fiber length of more than 10 μm. Thus, they did not break during the polymerization. PEDOT alone was not found on the mica as a substrate in any sample, it is all bound to CNT. The sample with a minimum amount of PEDOT (according to Example 11) contained fibers with a diameter below 10 nm. For an equivalent amount of PEDOT (according to Example 10), the fibers reached diameters in the range of 10 to 60 nm. In several excesses (according to Example 9), the fiber diameters are in the range from 30 to 60 nm.

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Example Moth. ratio CNP: diazonium salt -SO3H [mmol] EDOT [mmol] Fiber diameter Example 11 14 1 2 0.1 <10 nm Example 10 14 1 2 3.6 10 - 60 nm Example 9 14 1 2 7.0 30 - 60 nm

Industrial applicability

The carbon material surface-modified with poly (3,4-ethylenedioxothiophene) according to this technical solution can be used as a material for sensors, for preparation of electrode layers by printing techniques, for preparation of spatial electrode structures by 3D printing or for antistatic and dissipative surface treatment.

Claims (2)

CLAIMS FOR PROTECTION A carbon material surface modified with poly (3,4-ethylenedioxothiophene), preparable by 5 in situ polymerization of a reaction mixture, wherein the reaction mixture comprises 3,4-ethylenedioxothiophene, a carbon material with a sulfone-aromatic compound and an oxidizing agent, the starting carbon material having reactively fixed aromatic compound with at least one negatively charged sulfone group containing 0.6 to 2.5 mmol of sulfone groups per 1 g of carbon material, the carbon material containing 0.1 to 7 mmol to poly (3.4 -ethylenedioxothiophene) per 1 g of carbon material. The carbon material according to claim 1, wherein the poly (3,4-ethylenedioxothiophene) is deposited on the carbon material in a surface layer with a thickness of 8 to 60 nm. The carbon material of claim 1 or 2, wherein the carbon material is selected from the group: single-layer carbon nanotubes, multilayer carbon nanotubes, graphite, graphene or nanographite.