DE19919261B4 - Process for the production of ultra-thin compact, adherent and electrically conductive polymer layers on surfaces of oxidic particles, particles produced therewith and their use - Google Patents

Abstract

method for producing ultra-thin, compact, adherent and adjustable in electrical conductivity polymer layers on surfaces oxide particles, characterized in that the particle surfaces before the generation of the polymer layer are cleaned and dried and that the particle surfaces directly with a solution from monomers / oligomers used for the formation intrinsically more conductive Polymers are known to be treated oxidatively, the oxidic Be mixed with the monomer / oligomer solution, which is then a separate solution, the oxidizing agent comprises is added.

Description

The The invention relates to a method for producing ultra-thin, compact, adherent and adjustable in electrical conductivity polymer layers on surfaces oxide particles.

DE 36 30 708 A1 teaches a method for producing a coated ceramic component (not composite) of an electrically conductive polymer and a component of a ceramic material based on monomers of the five-membered heterocycles with nitrogen or sulfur as the heteroatom, wherein is polymerized chemically or by anodic oxidation.

EP 0 206 133 A1 discloses methods for applying layers of electrically conductive polymers of monomers of 5- and 6-membered heterocycles containing nitrogen or sulfur as heteroatoms onto large area substrates such as e.g. B. on slides.

US Re. 35,278 teaches the preparation of electrically conductive composites from a dielectric porous Substance like fiberglass fabric and a pyrrole polymer.

By coating the surface of oxidic particles such as TiO ₂ , Al ₂ O ₃ , SiO ₂ , ZrO ₂ , SnO ₂ , MgO, ZnO or CuO with organic molecules, the surface properties of these particles are modified so as to yield novel systems with economically interesting properties. However, it is problematic to produce a coating of the surfaces of oxide particles which is adherent and compact. In order to build up layers of intrinsically conductive polymers on the surfaces of oxidic particles, coupling agents have hitherto been required, since a direct attachment of the molecules forming these polymers to the particle surface could not be successfully carried out. A coating of oxidic surfaces by such molecules is only possible if adhesion promoters are used which are applied to the oxide particle surface before the polymer layer is produced.

For example, the German patent application describes DE 198 15 220 A1 a process for coating metals and metal oxides such as silicon, aluminum, titanium and magnesium or their oxides with monomers which can form intrinsically conductive polymers. The method comprises a material-dependent pretreatment of the substrate surfaces, followed by the application of an adhesion-promoting substance from the liquid or gaseous phase. The adhesion-promoting substance used is long-chain substituted organic compounds which have silane groups, phosphonic acid groups or phosphoric acid groups. These functional groups, referred to as adhesive groups, are able to attach to the oxidic surfaces by chemical reaction. This forms an ultra-thin film on the substrate surface. Furthermore, the adhesion-promoting substances have head groups such as halogen, methyl, alkoxy, carboxylic acid, ester and other groups to which the actually applied molecule can be attached. The spacer between the adhesive and the head group consists of up to twenty methylene units. The formation of the actual coating by generating an intrinsically conductive polymer layer is carried out by oxidative treatment of the already coated substrate with appropriate monomers.

It it is obvious that that Applying an intermediate layer on which only the actual coating can be applied, associated with a variety of disadvantages is. On the one hand, the production is suitable adhesion-promoting Substances often consuming, so this mostly expensive. On the other hand, the application of this layer technically demanding and time-consuming. Moreover, a sticky one Applying the polymer layers only possible if the adhesion-promoting Substance layer has a sufficient density. Is this layer only poor, the polymer layer is qualitatively insufficient. For this reason, the adhesion-promoting layer after its application to the substrate in terms of quality investigated by suitable methods such as concentration determinations become.

It is therefore an object of the present invention, a technically and temporally less expensive process for producing ultra-thin, compact, adhesive and in electrical conductivity adjustable polymer layers on surfaces of oxide particles to Find. The task is to make this polymer layer more oxidic on surfaces Apply particles on which previously no layer of adhesion-promoting Substances has been generated.

According to the invention, this is achieved by a process for producing ultra-thin, compact, adherent and adjustable in electrical conductivity polymer layers on surfaces of oxidic particles, in which the particle surfaces are cleaned and dried before the production of the polymer layer and in which the particle surfaces directly with a solution of monomers / Oligomers known to form intrinsically conductive polymers are oxidatively treated by adding the monomer / oligomer solution to the oxide particles, which is then added to a separate solution comprising oxidizing agents. The oxidative treatment may be chemical, electrochemical and / or photochemical respectively. For this oxidizing agents are preferably used, which are selected from the group, the H ₂ O ₂ , Fe ³⁺ , S ₂ O ₈ ^2- , (NH ₄ ) ₂ S ₂ O ₇ , MnO ₄ ^- , metal oxides, Ce ⁴⁺ and the corresponding lanthanides or organic peracids. By the method according to the invention, the intrinsically conductive polymer layers can be applied to the surface of oxide particles of TiO ₂ , Al ₂ O ₃ , SiO ₂ , ZrO ₂ , SnO ₂ , MgO, ZnO, CuO, BaTiO ₃ and other oxides. The polymer layers thus produced are ordered and chemically bound to the particle surface. The polymer layers produced are ultrathin, but may have a thickness in the nanometer or millimeter range.

• a)
  
  worin X S, O oder NR³ ist, wobei R¹ und/oder R² H oder über eine Alkylkette (0 bis 20 CH₂-Gruppen) verknüpfte Halogen-, Methyl-, Alkoxy-, Carbonsäure- oder Estergruppe sind, R³ H oder über eine Alkylkette (0 bis 20 CH₂-Gruppen) verknüpfte Halogen-, Methyl-, Alkoxy-, Carbonsäure- oder Estergruppe ist und n 1 bis 6 ist;
• b) Anilin oder Anilinderivate und
• c)
  
  oder Derivate davon. Werden diese Monomere/Oligomere polymerisiert, entstehen intrinsisch leitfähige Polymere.

Suitable monomers / oligomers for forming intrinsically conductive polymer layers on oxide particle surfaces are

• a)
  
  wherein X is S, O or NR ³ , wherein R ¹ and / or R ^{2 are} H or via an alkyl chain (0 to 20 CH ₂ groups) linked halogen, methyl, alkoxy, carboxylic acid or ester group, R ³ H or a halogen, methyl, alkoxy, carboxylic acid or ester group linked via an alkyl chain (0 to 20 CH ₂ groups) and n is 1 to 6;
• b) aniline or aniline derivatives and
• c)
  
  or derivatives thereof. When these monomers / oligomers are polymerized, intrinsically conductive polymers are formed.

The Monomer / oligomer solution can be flushed with inert gas before use. The oxidic particles are preferably before treatment with the monomer / oligomer solution ground. Dependent on of the respective material is prior to the generation of the polymer layer a pretreatment of the substrate surfaces required. This is the substrate surface cleaned and dried. The cleaning includes rinsing with chloroform, acetonitrile or Methanol. In the connection become the substrate surfaces in a drying oven at about 100 ° C dried for 20 to 30 min or dried by heated argon.

in the Connection to The oxidative treatment will be the surfaces of the particles with organic solvents such as methanol, chloroform and acetonitrile. The extraction serves to remove monomer / oligomer, oxidant, solvent and salt residues used in the preceding process steps or were formed. Depending on the solvent used, the polymer layer formed in reduced or oxidized form.

By the subsequent thereto Treatment of particle surfaces with redox solutions one defined redox potential to be matched to the substrate, for damages To avoid, the degree of oxidation of the polymer or oligomer layers be set.

The produced by the method according to the invention Composites have an intrinsically conductive, adherent, compact ultrathin polymer layer on. This polymer layer can without the previous application of adhesion-promoting substances are produced on oxidic particle surfaces. The inventive method is therefore suitable for such composites procedurally less expensive and thus more economical to produce.

A Further processing of the coated particles can be achieved by introducing as a filler in polymers or as a pigment additive in paints. A use is also possible in the form that this Polymer powder with conductive additives (Metal powder, carbon powder, soot) and a binder (Teflon powder, polyvinyl alcohol) and subsequently pressed into molds becomes.

The produced by the method according to the invention Composite materials are used as electrode material in sensors and in Batteries, as electrode material with catalytic properties, as conductive Pigments and as a dielectric and conductivity-controllable additive for conductive layers, as filler in electrical insulation technology and suitable for Leiterglättungsschichten.

in the Following, the invention will be explained in more detail with reference to embodiments.

example 1

Coating of barium titanate with polythiophene

Barium titanate (Merck) is ground with a planetary mill for 3 to 4 hours, then rinsed with ethanol and acetonitrile, filtered and dried at 80 to 120 ° C for 30 to 60 min. Thereafter, the ground powder with acetonitrile, water, acetonitrile rinsed and dried in an argon stream or drying oven at 50 to 60 ° C for 20 min. 50 ml and 75 ml acetonitrile (Merck) are placed in two Erlenmeyer flasks and fumigated with dry argon for about 20 minutes.

Preparation of the monomer / oligomer solution

To The 75 ml of acetonitrile are replaced by 10 g of coated barium titanate and 0.300 ml of freshly distilled thiophene (Aldrich, 99%), further rinsed and washed with a magnetic stirrer Stirred for 10 to 20 minutes.

Preparation of the oxidizing agent solution

In 50 ml of acetonitrile are 3 to 5 g of anhydrous iron (III) chloride (Fluka) registered. Subsequently is still purged with argon and stirred.

The Oxidant solution becomes the monomer / oligomer solution added, the reaction vessel sealed and the contents are vigorous for 1 to 2 hours touched. The reaction mixture has first a gray color that gradually turns into a deep black.

The Coating process is terminated by removing the powder from the solvent is separated by filtration. The powder is successively with Washed acetonitrile, methanol and water and sucked dry.

After that the powder shows a deep red color. In the following treatment step The powder is successively 4 hours each with methanol or acetonitrile or Chloroform extracted to residues of the monomer / oligomer, the oxidizing agent and soluble oligomers to remove. Thereafter, the powder is dried. Polythiophene lies within this ceramic-polymer composite in the neutral, the is called semiconducting Form before. By addition of polyvinyl alcohol as plasticizer can pressed the powder into tablets and by redox systems tuned redox potential in its electrical conductivity be set.

Example 2

Coating of titanium oxide with polyethylene dioxythiophene

titanium oxide (Riedel-de Haen) is ground for about 3 to 4 hours, then with Rinsed with ethanol and chloroform, filtered and at 80 to 120 ° C. Dried for 30 to 60 minutes. In two Erlenmeyer flasks, 50 ml or 75 ml of chloroform (Merck, p.a.) and with dry argon fumigated for about 20 minutes.

Preparation of the monomer / oligomer solution

To to the 75 ml of chloroform is added 10 g of dried and ground titanium oxide and 0.300 ml of freshly distilled 3,4-ethylenedioxythiophene (Baytron H, Bayer), further rinsed with argon for 20 min and stirred.

Preparation of the oxidizing agent solution

In 50 ml of chloroform become anhydrous after intensive rinsing with argon 3 to 5 g Iron (III) chloride (Fluka) registered. Subsequently, continue with argon rinsed and stirred.

The Oxidant solution becomes the monomer / oligomer solution added, the reaction vessel sealed and the contents are vigorous for 1 to 2 hours touched. The reaction mixture is first gray colored and then gradually dark blue to deep black.

The Coating process is terminated by removing the powder from the solvent is separated by filtration. The powder is washed successively with chloroform, Washed methanol and water and sucked dry.

After that the powder shows a gray-blue color. In the following treatment step the powder is extracted successively for 4 hours each time with methanol or chloroform, residues of the monomer / oligomer, the oxidizing agent and soluble oligomers to remove. Thereafter, the powder at 80 to 120 ° C 40 to 60 min dried. Polyethylene dioxythiophene is now within this Ceramic-polymer composite in the neutral, that is semiconducting Form before. By addition of polyvinyl alcohol as plasticizer / binder The powder can be pressed into tablets and tuned by redox systems Redox potential can be adjusted in its electrical conductivity.

Example 3

Coating of zinc oxide with polymethylthiophene

zinc oxide (Merck) is ground for about 3 to 4 hours, then with ethanol and acetonitrile rinsed, filtered and at 80 to 120 ° C. Dried for 30 to 60 minutes. In two Erlenmeyer flasks are 50 ml or 75 ml of acetonitrile (Merck, p. A.) and with dry argon fumigated for about 20 minutes.

Preparation of the monomer / oligomer solution

To The 75 ml of acetonitrile are mixed with 10 g of dried and ground zinc oxide and 0.300 ml of freshly distilled 3-methylthiophene (Aldrich, 98%) added, further rinsed with argon for 20 min and stirred.

Preparation of the oxidizing agent solution

In After thorough rinsing with argon, 50 ml of acetonitrile become 3 to 5 g anhydrous ground ammonium peroxodisulfate (Merck, p. Subsequently, will further flushed with argon and touched. The oxidizer solution becomes the monomer / oligomer solution added, the reaction vessel sealed and the contents stirred vigorously for 1 to 2 h. The Reaction mixture is first gray colored and then gradually deep black.

The Coating process is terminated by removing the powder from the solvent is separated by filtration. The powder is washed successively with chloroform, Washed methanol and water and the filter cake sucked dry. Thereafter, the powder shows a red to reddish brown color. In the following treatment step The powder is successively 4 hours each with methanol or acetonitrile extracted to residues of the monomer / oligomer, the oxidizing agent and soluble To remove oligomers. Thereafter, the powder at 80 to 120 ° C 40 to Dried for 60 min. Polymethylthiophene is now within this Ceramic-polymer composite in the neutral, that is semiconducting Form before. By addition of polyvinyl alcohol as plasticizer / binder The powder can be pressed into tablets or incorporated into polymers and by redox systems tuned redox potential in its electrical conductivity be set.

Example 4:

15 g titanium dioxide (technical, Riedel de Haen, average primary particle size about 200 nm measured under the transmission electron microscope (TEM) and with the Malvern Zetasizer) were treated with ethanol p. a. rinsed, filtered and at 80 to 120 ° C for 45 min dried in a drying oven. The purified and dried powder was subsequently shared with 75 ml of acetonitrile p. a. (Fisher Scientific) and from 0.3 ml of freshly distilled thiophene (Aldrich, 99%) strictly anhydrous solution together in a ball mill over 30 to Milled for 60 minutes.

This Step served to increase the particle surface area to the monomers / oligomers complete adsorption on the particles to enable. To this slurry From oxide particles, acetonitrile and thiophene was then the Oxidizing agent dispersion according to Example 1 added and as explained there continue to proceed.

By Transmission electron microscopic examination (device CM 200 FEG, Phillips, U = 200 kV, magnification 1.100.000x) the coated with polythiophene in the neutral state of red color Particle was an average polymer layer thickness of 5 nm on the Particles determined.

The very good adhesion of the polythiophene layer on the TiO ₂ particles could be detected by treating 5 g of the previously extraction-cleaned particles in 50 ml of ethanol in an ultrasonic bath (Sonorex Super instrument) at a frequency of 35 kHz and at 20 ° C for 30 min become. Due to treatment with ethanol, the polythiophene had been reduced and showed a red color. During the longer ultrasound treatment in ethanol, the dispersion did not show a color change of the red-appearing particles z. B. by spalling of red cladding layers of the white particle cores and showed no separation of oxide core and polymer shell in the subsequent observation of the particles under the TEM, but an orderly, bound directly to the oxide core surface, this enclosing and therefore adherent layer of the polymer.

The coated particles were compressed into a tablet and this had a conductivity of 10 ^-5 -10 ^-3 S / cm.

Example 5:

15 g Aerosil R 972 (chemically pure, Degussa, average primary particle size about 16 nm determined under the TEM, 110 ± 20 m ² / g BET surface area) were rinsed with ethanol pa, filtered and at 80 ° C to 120 ° C. dried for 45 minutes in a drying oven. The purified and dried powder was then used together with the strictly anhydrous consisting of 150 ml of chloroform pa (Lichrosolv, Merck, max 0.01% H ₂ O) and 0.6 ml of freshly distilled thiophene (Aldrich 99%) Milled together solution in a ball mill for 30 to 60 min to break up particle aggregates and to obtain the largest possible particle surfaces for easier and complete adsorption of the thiophene. The result was a colorless, viscous, water glass-like dispersion. Due to the low tamped density (50 g / l) of the Aerosils R 972 was here worked with the double compared to the already explained examples approach. The further procedure was carried out according to Example 2 with a double approach of the oxidant dispersion.

When average polymer layer thickness on the particles was determined to be 3 nm. The good adhesion of polythiophene on the particle cores was as in Example 4 in an analogous investigation as in Example 4 confirmed.

Example 6:

7.5 g of Aerosil R 972 (chemically pure, Degussa Co., further details cf. Example 5) were rinsed with ethanol pa, filtered and heated at 80 to 120 ° C. dried for 45 minutes in a drying oven and in a vacuum desiccator. The purified and dried powder was then together with the solution consisting of 75 ml of chloroform pa (Lichrosolv, Merck, max 0.01% H ₂ O) and 0.3 ml of 3-methylthiophene (Aldrich) together in a Milled ball mill for 30 to 60 min to break up particle aggregates and to obtain the largest possible particle surfaces for easier and complete adsorption of 3-methylthiophene.

It A colorless, viscous, water glass-like dispersion was formed. The others Processing was carried out according to example 2. As the average layer thickness of the poly-3-methylthiophene on the particles were 3 to 5 nm determined. The exam on adhesive strength and conductivity and their results were as in Example 4.

Comparative Example:

It was as in Example 5, but without prior cleaning and without prior drying of the particles worked, whereby small amounts of water in the dispersion was retained.

Mixing the oxide particle monomer / oligomer dispersion with the oxidizer dispersion containing anhydrous FeCl ₃ particles did not cause the color pit described in Example 2 to appear. The result was a yellow-brown colored dispersion whose color is typical for hydrated ferric ions and in which the particles settle quickly. Upon extraction, no coated particles of reduced coating and red color were obtained as in the previous examples, but the original white particle cores remained uncoated and appeared yellowish white in the dispersion. The polymerization of the hydrophobic thiophene was apparently inhibited by adhering to the hydrophilic oxide particles layers of water. The adsorption of the monomers / oligomers on the particle surfaces was very low.

Claims (15)

Process for producing ultrathin, compact, adherent and electrically conductive polymer layers on surfaces of oxidic particles, characterized in that the particle surfaces are cleaned and dried prior to the production of the polymer layer and that the particle surfaces are treated directly with a solution of monomers / oligomers suitable for the formation of intrinsically conductive polymers are known are oxidatively treated, wherein the oxide particles are added with the monomer / oligomer solution, which is then added to a separate solution comprising oxidizing agent. Process for producing ultrathin, compact, adherent and electrically conductive polymer layers on surfaces of oxidic particles according to Claim 1, characterized in that the oxide particles consist of metal oxides selected from the group consisting of TiO ₂ , Al ₂ O ₃ , SiO ₂ , ZrO ₂ , SnO ₂ , MgO, ZnO, CuO and BaTiO ₃ . Process for the production of ultra-thin, compact, adherent and electrically conductive polymer layers on surfaces of oxide particles according to Claims 1 and 2, characterized in that the monomers / oligomers used to form the polymers are selected from the group consisting of

wherein X is S, O or NR ³ , wherein R ¹ and / or R ^{2 are} H or via an alkyl chain (0 to 20 CH ₂ groups) linked halogen, methyl, alkoxy, carboxylic acid or ester group, R ³ H or a halogen, methyl, alkoxy, carboxylic acid or ester group linked via an alkyl chain (0 to 20 CH ₂ groups) and n is 1 to 6; b) aniline or aniline derivatives and c)

or derivatives thereof. Process for producing ultrathin, compact, adherent and electrically conductive polymer layers on surfaces of oxidic particles according to Claims 1 to 3, characterized in that oxidizing agents selected from the group consisting of H ₂ O ₂ are used for the oxidative treatment of the particle surfaces , Fe ³⁺ , S ₂ O ₈ ^2- , (NH ₄ ) ₂ S ₂ O ₇ , MnO ₄ ^- , metal oxides, Ce ⁴⁺ and the corresponding lanthanides or organic peracids. A process for producing ultra-thin, compact, adhesive and in the electrical conductivity adjustable polymer layers on surfaces of oxide particles according to claim 1 to 4, characterized in that the oxidative treatment additional Lich electrochemical and / or photochemical ways. Method of producing ultra-thin, compact, adhesive and adjustable in electrical conductivity Polymer layers on surfaces Oxidic particle according to Claims 1 to 5, characterized that the Monomer / oligomer solution before their use is flushed with inert gas. Method of producing ultra-thin, compact, adhesive and adjustable in electrical conductivity Polymer layers on surfaces Oxidic particle according to Claims 1 to 6, characterized that the oxide particles are ground before treatment with the monomer / oligomer solution become. Method of producing ultra-thin compact, more adhesive and in the electrical conductivity adjustable polymer layers on surfaces of oxidic particles according to claim 1 to 7, characterized in that following the oxidative treatment the extraction of the surfaces of the particles with organic solvents or aqueous acid solvents like sulfuric acid or hydrochloric acid he follows. Method of producing ultra-thin, compact, adhesive and adjustable in electrical conductivity Polymer layers on surfaces Oxidic particle according to Claims 1 to 8, characterized that the organic solvents used for extraction from a group selected which comprises methanol, chloroform and acetonitrile. Method of producing ultra-thin compact, more adhesive and adjustable in electrical conductivity Polymer layers on surfaces Oxidic particles according to Claims 1 to 9, characterized that it Furthermore, the treatment of particle surfaces with coordinated redox solutions to Adjustment of the degree of oxidation of the polymer layers comprises. Oxide particles, characterized in that they are ultra-thin, compact, Adhesive and adjustable in electrical conductivity polymer layers directly on their surface which is produced by the method according to claims 1 to 10 were. Oxidic particles according to Claim 11, characterized that the directly on the surface applied polymer layer a mass fraction of about 10%, based on the total weight of the coated particle, and a thickness between 10 and 100 nm. Use of oxidic particles whose surface is through The method of claim 1 to 10 with ultra-thin, compact, adherent and in the electrical conductivity adjustable polymer layers was coated as electrode material in Sensors, in batteries and as an electrode material with catalytic Properties. Use of oxidic particles whose surface is through The method of claim 1 to 10 with ultra-thin, compact, adherent and in the electrical conductivity adjustable polymer layers was coated as conductive pigments. Use of oxidic particles whose surface is through The method of claim 1 to 10 with ultra-thin, compact, adherent and in the electrical conductivity adjustable polymer layers has been coated as a dielectric and conductivity controllable Addition for conductive Layers, as filler in electrical insulation technology and for conductor smoothing layers.