JP2005520001A - Method for producing plasma polymerized polymer electrolyte membrane and polyazole membrane coated by plasma polymerization - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a suitable method for producing a polymer electrolyte membrane using plasma-assisted deposition in a gas phase.
In the method for producing a plasma polymerized ion conductive electrolyte membrane, the plasma polymerized ion conductive electrolyte membrane comprises a matrix-forming component, preferably a hydrocarbon compound or a fluorinated hydrocarbon compound, and water plasma assisted copolymerization. A plasma-coated polyazole film, characterized in that the plasma-coated polyazole film is coated with a plasma-polymerized ion conductive layer obtained by the manufacturing method. By selecting carbon or fluorocarbon compounds and water as starting materials, it is possible to simplify the process compared to conventional techniques.

Description

  The present invention relates to a method for producing a polymer electrolyte membrane by plasma-assisted deposition from the gas phase, which has succeeded in being considerably simpler than the prior art due to the selection of its starting material. The invention further relates to a plasma-coated polyazole film.

  Plasma polymerized layers generally have a high degree of cross-linking and are also adjustable in degree of cross-linking, which results in high chemical resistance and thermal stability (eg R. Hartmann: “Plasmapolymodification von Kunstoffberflachen) "Techn. Rundschau 17 (1988), pp. 20-23; A. Brunold et al .:" Modify erung von Polymeren im Niederduckplasma ", Part 2, mo51 (1997), 81-84). The use of monomers that lead to the introduction of ion-conducting groups (sulfonic acid, phosphonic acid or carboxylic acid groups) in this process allows the production of ion-conducting polymer membranes, which as a result of a high degree of polymerization. The resulting barrier action against gas or liquid permeation and its stability are suitable for use in fuel cells, in particular direct methanol fuel cells, or electrolyzers. Furthermore, the deposition technique used allows the production of thin films (from tens of nanometers to several tens of micrometers), which can be used in miniaturized fuel cell systems for portable applications (see for example DE19624887A1, DE19916461A1) or conventional. For example, a polybenzimidazole film doped with phosphoric acid or a sulphonic acid group-containing film, as a barrier layer deposited on it (DE 1991 4571 A1).

  Conventional plasma polymerized ion-conducting layers can be obtained from combinations of various fluorinated hydrocarbons and trifluoromethanesulfonic acid (eg DE19513292C1, US5750013A), from combinations containing carboxyl groups (DE19624887A1) or vinylphosphonic acid. (DE 19914681A1) from a combination with a compound containing When using trifluoromethanesulfonic acid, fragmentation of the sulfonic acid also occurs in the plasma as a result of the binding energy comparable to the carbon-sulfur bond in the sulfonic acid and the bonding in the sulfonic acid. This results in a highly crosslinked polymer with very low ionic conductivity or a polymer with sufficient ionic conductivity but low degree of crosslinking and a high proportion of trifluoromethanesulfonic acid that is not covalently bonded to the polymer framework, and thus An electrolyte is obtained that does not have long-term stability (see Ber. Bunsenges, Phys. Chem., Vol. 98 (1994), pages 631-635). In all cases of said acid compounds, plasma polymerization requires vaporization, which not only suffers from the disadvantage of having to handle substances that are harmful to health, but also requires increased costs for the device.

  Plasma polymerization according to the invention of ion-conducting layers using carbon compounds, preferably alkenes and alkynes, or fluorocarbons, preferably fluorinated alkenes, with water provides a significant simplification of the process and a significant reduction in production costs. . The fragmentation of water in the plasma results in the formation of OH radicals, so that the carboxyl groups necessary for ionic conductivity are formed only during the growth of the layer. The use of commercially available liquid flow regulators allows for fractionation by vaporizer, which is necessary with other acid compounds. The high vapor pressure of water also allows the precipitation to be carried out at room temperature, but in the case of the acid compounds, the heating of the gas line from the vaporizer to the reactor and the heating of the electrodes are responsible for the acid in these regions. Required to prevent compound condensation.

That is, the present invention relates to a method for producing a plasma polymerized ion conductive electrolyte membrane, wherein the plasma polymerized ion conductive electrolyte membrane comprises a matrix-forming component, preferably a hydrocarbon compound or a fluorinated hydrocarbon compound, and water plasma. The precursor used for the matrix-forming component is preferably a fluorinated alkene, alkene or alkyne, characterized in that it is produced by copolymerization. By selecting a carbon compound or fluorocarbon compound and water as starting materials, the process can be simplified compared to conventional techniques.
In order to use these novel plasma polymerized electrolyte membranes into fuel cells, especially miniaturized fuel cells, they were produced by thin film technology (eg, catalyzed atomization or plasma assisted deposition from the gas phase). It can be produced by bonding the catalyst layer with a porous or nonporous conductive contact layer (DE 19914681A). The deposition of these layers can be performed in a suitable reactor that allows both sputtering and deposition from the gas phase, or can be performed in separate connected reactors, in each of the reactors the film One component of the electrode unit is deposited by thin film technology, and transport between the reactors takes place under reduced pressure. Depending on the support used, a static deposition step is preferred for plasma polymerized electrolytes, for example for coating of individual suitably constructed glass or silicon supports, and for a large number of items or for deposition. If carried out on a suitable film, a continuous process may be preferred.

  The above process is particularly suitable for the production of a plasma-coated polyazole film due to the special configuration of the present invention.

  Acid doped polyazole membranes can be used extensively due to their excellent chemical, thermal and mechanical properties and are particularly suitable as polymer electrolyte membranes (PEM) in PEM fuel cells.

  The basic polyazole membrane is doped with concentrated phosphoric acid or sulfuric acid and acts as a proton conductor and separator in a polymer electrolyte membrane fuel cell (PEM fuel cell).

  Due to the superior properties of polyazole polymers, such polymer electrolyte membranes, when converted into membrane electrode units (MEUs), can be used in fuel cells at long-term operating temperatures of 100 ° C or higher, especially 120 ° C or higher. Can be used. This high long-term operating temperature can increase the activity of precious metal based catalysts present in the membrane electrode unit (MEU). In particular, when using reforming products from hydrocarbons, significant amounts of carbon monoxide are present in the reformed gas, which is usually a complex gas work-up. Or it should be removed by gas purification. Increasing the operating temperature makes it possible to tolerate significantly higher concentrations of CO for long periods of time.

  The use of polymer electrolyte membranes based on polyazole polymers firstly makes it possible at least partly to omit complicated gas work or gas purification, and secondly to reduce the amount of catalyst present in the membrane electrode unit. to enable. Both are indispensable conditions for the widespread use of PEM fuel cells. This is because otherwise the cost of the PEM fuel cell system would be too high.

［式中、Ａｒは、同じか又は異なるものであり、それぞれ、単環式又は多環式であってよい４価の芳香族又はヘテロ芳香族基であり、
Ａｒ¹は、同じか又は異なるものであり、それぞれ、単環式又は多環式であってよい２価の芳香族又はヘテロ芳香族基であり、
Ａｒ²は、同じか又は異なるものであり、それぞれ、単環式又は多環式であってよい２価又は３価の芳香族又はヘテロ芳香族基であり、
Ａｒ³は、同じか又は異なるものであり、それぞれ、単環式又は多環式であってよい３価の芳香族又はヘテロ芳香族基であり、
Ａｒ⁴は、同じか又は異なるものであり、それぞれ、単環式又は多環式であってよい３価の芳香族又はヘテロ芳香族基であり、
Ａｒ⁵は、同じか又は異なるものであり、それぞれ、単環式又は多環式であってよい４価の芳香族又はヘテロ芳香族基であり、
Ａｒ⁶は、同じか又は異なるものであり、それぞれ、単環式又は多環式であってよい２価の芳香族又はヘテロ芳香族基であり、
Ａｒ⁷は、同じか又は異なるものであり、それぞれ、単環式又は多環式であってよい２価の芳香族又はヘテロ芳香族基であり、
Ａｒ⁸は、同じか又は異なるものであり、それぞれ、単環式又は多環式であってよい３価の芳香族又はヘテロ芳香族基であり、
Ａｒ⁹は、同じか又は異なるものであり、それぞれ、単環式又は多環式であってよい２価又は３価又は４価の芳香族又はヘテロ芳香族基であり、
Ａｒ¹⁰は、同じか又は異なるものであり、それぞれ、単環式又は多環式であってよい２価又は３価の芳香族又はヘテロ芳香族基であり、
Ａｒ¹¹は、同じか又は異なるものであり、それぞれ、単環式又は多環式であってよい２価の芳香族又はヘテロ芳香族基であり、
Ｘは、同じか又は異なるものであり、それぞれ、酸素、硫黄、又は水素原子を有するアミノ基、炭素原子１〜２０個を有する基、好ましくは分枝又は分枝していないアルキル又はアルコキシ基又はもう１つの基としてのアリール基であり、
Ｒは、同じか又は異なるものであり、それぞれ、水素、アルキル基又は芳香族基であり、かつ、
ｎ、ｍは、それぞれ、１０以上の整数、好ましくは１００以上の整数である］
のアゾール単位の繰り返しを任意の組み合わせで含むものである。 Polyazoles have the formulas (I), (II), (III), (IV), (V), (VI), (VII), (VIII), (IX), (X), (XI), (XII). ), (XIII), (XIV), (XV), (XVI), (XVII), (XVIII), (XIX), (XX), (XXI) and (XXII) ,

Wherein Ar is the same or different and each is a tetravalent aromatic or heteroaromatic group that may be monocyclic or polycyclic;
Ar ¹ is the same or different and each is a divalent aromatic or heteroaromatic group that may be monocyclic or polycyclic;
Ar ² is the same or different and each is a divalent or trivalent aromatic or heteroaromatic group that may be monocyclic or polycyclic;
Ar ³ is the same or different and each is a trivalent aromatic or heteroaromatic group that may be monocyclic or polycyclic;
Ar ⁴ is the same or different and each is a trivalent aromatic or heteroaromatic group that may be monocyclic or polycyclic;
Ar ⁵ is the same or different and each is a tetravalent aromatic or heteroaromatic group that may be monocyclic or polycyclic;
Ar ⁶ is the same or different and each is a divalent aromatic or heteroaromatic group that may be monocyclic or polycyclic;
Ar ⁷ is the same or different and each is a divalent aromatic or heteroaromatic group that may be monocyclic or polycyclic;
Ar ⁸ is the same or different and each is a trivalent aromatic or heteroaromatic group that may be monocyclic or polycyclic;
Ar ⁹ is the same or different and each is a divalent, trivalent or tetravalent aromatic or heteroaromatic group which may be monocyclic or polycyclic;
Ar ¹⁰ are the same or different and are each a divalent or trivalent aromatic or heteroaromatic group that may be monocyclic or polycyclic,
Ar ¹¹ is the same or different and each is a divalent aromatic or heteroaromatic group that may be monocyclic or polycyclic;
X is the same or different and each is an amino group having an oxygen, sulfur or hydrogen atom, a group having 1 to 20 carbon atoms, preferably a branched or unbranched alkyl or alkoxy group, or An aryl group as another group,
R is the same or different and each is hydrogen, an alkyl group or an aromatic group, and
n and m are each an integer of 10 or more, preferably an integer of 100 or more]
These repeating azole units are included in any combination.

  Preferred aromatic or heteroaromatic groups are benzene, naphthalene, biphenyl, diphenyl ether, diphenylmethane, diphenyldimethylmethane, bisphenone, diphenylsulfone, quinoline, pyridine, bipyridine, pyridazine, pyrimidine, pyrazine, triazine, tetrazine, pyrrole, pyrazole, anthracene , Benzopyrrole, benzotriazole, benzooxathiadiazole, benzooxadiazole, benzopyridine, benzopyrazine, benzopyrazidine, benzopyrimidine, benzopyrazine, benzotriazine, indolizine, quinolidine, pyridopyridine, imidazopyrimidine, pyrazinopyrimidine, carbazole, acylidine , Phenazine, benzoquinoline, phenoxazine, phenothiazine, acrididine, Nzoputerijin are derived from phenanthroline and phenanthrene, which may be substituted, respectively.

Ar ¹ , Ar ⁴ , Ar ⁶ , Ar ⁷ , Ar ⁸ , Ar ⁹ , Ar ¹⁰ , Ar ¹¹ may have any substitution pattern. For example, in the case of phenylene, Ar ¹ , Ar ⁴ , Ar ⁶ , Ar ⁷ , Ar ⁸ , Ar ⁹ , Ar ¹⁰ , Ar ¹¹ may be ortho-, meta- or para-phenylene. Particularly advantageous groups are derived from benzene and biphenylene, each optionally substituted.

  Preferred alkyl groups are short-chain alkyl groups having 1 to 4 carbon atoms, such as methyl, ethyl, n- or i-propyl and t-butyl groups.

  Preferred aromatic groups are phenyl or naphthyl groups. Alkyl groups and aromatic groups may be substituted.

  Preferred substituents are halogen atoms such as fluorine, amino groups, hydroxy groups or short chain alkyl groups such as methyl or ethyl.

  Preference is given to polyazoles comprising recurring units of the formula (I) in which the radicals X in one recurring unit are identical.

  Polyazoles may in principle have different repeating units, for example, whose group X is different. However, it is advantageous that there are only identical groups X in the repeating unit.

  Further preferred polyazole polymers are polyimidazole, polybenzothiazole, polybenzoxazole, polyoxadiazole, polyquinoxaline, polythiadiazole, poly (pyridine), poly (pyrimidine) and poly (tetraazapyrene).

  In another aspect of the invention, the polymer comprising repeating azole units is a copolymer or blend comprising at least two units of formula (I) to (XXII) that are different from one another. The polymer may be in the form of a block copolymer (diblock, triblock), random copolymer, periodic copolymer and / or alternating copolymer.

  In a particularly advantageous embodiment of the invention, the polymer comprising repeating azole units is a polyazole containing only units of the formula (I) and / or (II).

  The number of repeating azole units in the polymer is preferably 10 or more. Particularly advantageous polymers have at least 100 repeating azole units.

［式中、ｎ及びｍは、それぞれ１０以上の整数、有利に１００以上の整数である］
に相当する。 For the purposes of the present invention, polymers containing repeated benzimidazole units are advantageous. Some examples of highly preferred polymers that repeatedly contain benzimidazole units are:

[Wherein n and m are each an integer of 10 or more, preferably an integer of 100 or more]
It corresponds to.

  Preferred polyazoles, especially polybenzimidazoles, have a high molecular weight. When measured as the intrinsic viscosity, this is at least 1.0 dl / g, preferably at least 1.2 or 1.1 dl / g.

  The production of such polyazoles is known. In a known manner, one or more tetraamino compounds are reacted in the melt with one or more aromatic carboxylic acids and / or their esters containing at least two acid groups per carboxylic acid monomer, Form. The resulting prepolymer solidifies in the reactor and is subsequently mechanically ground. The prepolymer consisting of powder particles is usually completely polymerized by solid phase polymerization at a temperature up to 400 ° C.

  Preferred aromatic carboxylic acids include in particular dicarboxylic acids and tricarboxylic acids and tetracarboxylic acids and their esters or anhydrides or acid chlorides. The term “aromatic carboxylic acid” also encompasses heteroaromatic carboxylic acids.

The aromatic dicarboxylic acid is preferably isophthalic acid, terephthalic acid, phthalic acid, 5-hydroxyisophthalic acid, 4-hydroxyisophthalic acid, 2-hydroxyterephthalic acid, 5-aminoisophthalic acid, 5-N, N-dimethylamino. Isophthalic acid, 5-N, N-diethylaminoisophthalic acid, 2,5-dihydroxyterephthalic acid, 2,6-dihydroxyisophthalic acid, 4,6-dihydroxyisophthalic acid, 2,3-dihydroxyphthalic acid, 2,4-dihydroxy Phthalic acid, 3,4-dihydroxyphthalic acid, 3-fluorophthalic acid, 5-fluoroisophthalic acid, 2-fluoroterephthalic acid, tetrafluorophthalic acid, tetrafluoroisophthalic acid, tetrafluoroterephthalic acid, 1,4-naphthalenedicarboxylic Acid, 1,5-naphthalene dicarboxylic 2,6-naphthalenedicarboxylic acid, 2,7-naphthalenedicarboxylic acid, diphenic acid, 1,8-dihydroxynaphthalene-3,6-dicarboxylic acid, bis (4-carboxyphenyl) ether, benzophenone-4,4′- Dicarboxylic acid, bis (4-carboxyphenyl) sulfone, biphenyl-4,4′-dicarboxylic acid, 4-trifluoromethylphthalic acid, 2,2-bis (4-carboxyphenyl) hexafluoropropane, 4,4′- Stilbene dicarboxylic acids, 4-carboxycinnamic acids and their C ₁ -C ₂₀ -alkyl esters or C ₅ -C ₁₂ -aryl esters or their acid anhydrides or acid chlorides.

Aromatic tricarboxylic acids or tetracarboxylic acids and their C ₁ -C ₂₀ -alkyl esters or C ₅ -C ₁₂ -aryl esters or their acid anhydrides or acid chlorides are preferably 1,3,5-benzene Tricarboxylic acid (trimesic acid), 1,2,4-benzenetricarboxylic acid (trimellitic acid), (2-carboxyphenyl) iminodiacetic acid, 3,5,3'-biphenyltricarboxylic acid, 3,5,4'-biphenyltricarboxylic acid It is an acid.

The aromatic tetracarboxylic acids and their C ₁ -C ₂₀ -alkyl esters or C ₅ -C ₁₂ -aryl esters or their anhydrides or acid chlorides are preferably 3,5,3 ′, 5′- Biphenyltetracarboxylic acid, 1,2,4,5-benzenetetracarboxylic acid, benzophenonetetracarboxylic acid, 3,3 ′, 4,4′-biphenyltetracarboxylic acid, 2,2 ′, 3,3′-biphenyltetra Carboxylic acid, 1,2,5,6-naphthalenetetracarboxylic acid, 1,4,5,8-naphthalenetetracarboxylic acid. The heteroaromatic carboxylic acids used are preferably heteroaromatic dicarboxylic acids and tricarboxylic acids and tetracarboxylic acids or their esters or anhydrides. For the purposes of the present invention, a heteroaromatic carboxylic acid is an aromatic system containing at least one nitrogen, oxygen, sulfur or phosphorus atom in the aromatic compound. Pyridine-2,5-dicarboxylic acid, pyridine-3,5-dicarboxylic acid, pyridine-2,6-dicarboxylic acid, pyridine-2,4-dicarboxylic acid, 4-phenyl-2,5-pyridinecarboxylic acid, 3, 5-pyrazole dicarboxylic acid, 2,6-pyrimidine dicarboxylic acid, 2,5-pyrazine dicarboxylic acid, 2,4,6-pyridine tricarboxylic acid, benzimidazole-5,6-dicarboxylic acid and their C ₁ -C ₂₀ - alkyl esters or C ₅ -C ₁₂ - aryl esters or their acid anhydrides or acid chlorides are preferred.

  The content of tricarboxylic acid or tetracarboxylic acid (based on the dicarboxylic acid used) is in the range from 0 to 30 mol%, preferably from 0.1 to 20 mol%, in particular from 0.5 to 10 mol%.

  The aromatic and heteroaromatic diaminocarboxylic acids used are preferably diaminobenzoic acid and its monohydrochloride and dihydrochloride derivatives.

  Preference is given to using a mixture of at least two different aromatic carboxylic acids. It is particularly advantageous to use a mixture containing both aromatic and heteroaromatic carboxylic acids. The mixing ratio of aromatic carboxylic acid to heteroaromatic carboxylic acid ranges from 1:99 to 99: 1, preferably from 1:50 to 50: 1.

  These mixtures are in particular mixtures of N-heteroaromatic dicarboxylic acids and aromatic dicarboxylic acids. Non-limiting examples are isophthalic acid, terephthalic acid, phthalic acid, 2,5-dihydroxyterephthalic acid, 2,6-dihydroxyisophthalic acid, 4,6-dihydroxyisophthalic acid, 2,3-dihydroxyphthalic acid, 2,4- Dihydroxyphthalic acid, 3,4-dihydroxyphthalic acid, 1,4-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 2,7-naphthalenedicarboxylic acid, diphenic acid, 1,8 -Dihydroxynaphthalene-3,6-dicarboxylic acid, bis (4-carboxyphenyl) ether, benzophenone-4,4'-dicarboxylic acid, bis (4-carboxyphenyl) sulfone, biphenyl-4,4'-dicarboxylic acid, 4 -Trifluoromethylphthalic acid, pyridine-2,5-dicarboxylic acid, pyridine- , 5-dicarboxylic acid, pyridine-2,6-dicarboxylic acid, pyridine-2,4-dicarboxylic acid, 4-phenyl-2,5-pyridinecarboxylic acid, 3,5-pyrazole dicarboxylic acid, 2,6-pyrimidine dicarboxylic acid Acid, 2,5-pyrazinedicarboxylic acid.

  Preferred aromatic tetraamino compounds are in particular 3,3 ′, 4,4′-tetraaminobiphenyl, 2,3,5,6-tetraaminopyridine, 1,2,4,5-tetraaminobenzene, bis ( 3,4-diaminophenyl) sulfone, bis (3,4-diaminophenyl) ether, 3,3 ′, 4,4′-tetraaminobenzophenone, 3,3 ′, 4,4′-tetraaminodiphenylmethane and 3, 3 ', 4,4'-tetraaminodiphenyldimethylmethane and also their salts, in particular their monohydrochloride, dihydrochloride, trihydrochloride and tetrahydrochloride derivatives.

  A preferred polybenzimidazole is commercially available from Celanese AG under the trade name Celazole.

  Apart from the polymers, it is also possible to use blends containing additional polymers. Blend components inherently have the task of improving the mechanical properties of the material and reducing costs. An advantageous blending component is described in German patent application no. Polyethersulfone described in 10052242.4.

  To produce the polymer film, the polyazole is subsequently dissolved in a polar, aprotic solvent such as dimethylacetamide (DMAc) and the film is produced by traditional methods.

In order to remove the residual solvent, the film obtained in this way can be treated with a washing liquid. This cleaning solution may be halogenated, alcohol, ketone, alkane (aliphatic and alicyclic), ether (aliphatic and alicyclic), ester, carboxylic acid, water, inorganic acid (for example, H ₃ PO ₄ , H ₂ SO ₄ ) and mixtures thereof are advantageously selected.

In particular, C ₁ -C ₁₀ -alcohol, C ₂ -C ₅ -ketone, C ₁ -C ₁₀ -alkane (aliphatic and alicyclic), C ₂ -C ₆ -ether (aliphatic and alicyclic), C ₂ -C ₅ -esters, C ₁ -C ₃ -carboxylic acids, dichloromethane, water, inorganic acids (eg H ₃ PO ₄ , H ₂ SO ₄ ) and mixtures thereof are used. Of these liquids, water is particularly advantageous.

  After washing, the film can be dried to remove the washing solution. Drying conditions depend on the vapor partial pressure of the selected processing liquid. Drying is usually carried out at atmospheric pressure and temperature of 20 ° C to 200 ° C. A milder drying can also be carried out under reduced pressure. As an alternative to drying, the membrane can be dabbed to be free of excess processing solution. The order is not definitive.

  The removal of residual solvent from the polyazole film unexpectedly leads to an improvement in the mechanical properties of the film. These properties include, among other things, elastic modulus, ultimate tensile strength and film fracture toughness.

  Furthermore, the polymer film can be produced in other ways, for example in German It could be modified by cross-linking as described in 10110752.8 or WO00 / 44816. In an advantageous embodiment, the polymer film used is not only the basic polymer and at least one blend component, but also German patent application no. Also includes a cross-linking agent as described in 1014147.7.

  Instead of polymer films produced by traditional methods, German patent application no. It is also possible to use the polyazole-containing polymer film described in 1011177686.4, 101448155.5, or 1011177687.2.

  The thickness of the polyazole film may vary over a wide range. The thickness of the polyazole film before doping with acid is preferably in the range of 5 μm to 2000 μm, particularly preferably in the range of 10 μm to 1000 μm, but is not limited thereto.

  In order to make the film proton conductive, it is doped with an acid. In the present context, the term “acid” includes all known Lewis and Bronsted acids, preferably inorganic Lewis and Bronsted acids.

  It is also possible to use polyacids, in particular isopolyacids and heteropolyacids, and also mixtures of various acids. For the purposes of the present invention, heteropolyacids are inorganic polyacids having at least two different central atoms and are metal (preferably Cr, Mo, V, W) and nonmetal (preferably As, I, P). , Se, Te) are formed as partially mixed anhydrides from weakly polybasic oxoacids. These include in particular 12-molybdophosphoric acid and 12-tungstophosphoric acid.

  The conductivity of the polyazole film can be influenced by the degree of doping. The conductivity increases with increasing dopant concentration until a maximum value is reached. According to the present invention, the degree of doping is recorded as the number of moles of acid per mole of polymer repeating units. For the purposes of the present invention, a degree of doping of 3 to 30, in particular 5 to 18, is preferred.

Particularly preferred dopants are sulfuric acid and phosphoric acid. A very particularly advantageous dopant is phosphoric acid (H ₃ PO ₄ ). In general, highly concentrated acids are used. According to a special configuration of the invention, the concentration of phosphoric acid is at least 50% by weight, in particular at least 80% by weight, based on the weight of the dopant.

Further, the doped polyazole film has the following steps:
I) Dissolution of polyazole polymer in polyphosphoric acid II) The solution obtained by the method of step I) is heated under inert gas to a temperature of 400 ° C. III) Supporting the solution of polyazole polymer from step II) Use on the body to form a film IV) It can also be obtained by a process comprising a process until the film formed in step III) is self-supporting.

Further, the doped polyazole film has the following steps:
A) In polyphosphoric acid, a mixture of one or more aromatic tetraamino compounds and one or more aromatic carboxylic acids or esters thereof containing at least two acid groups per carboxylic acid monomer, or aromatic and / or hetero The formation of a solution and / or dispersion by mixing one or more aromatic diaminocarboxylic acids,
B) Application of the layer to the support or electrode using the mixture from step A)
C) The planar structure / layer obtained by the process of step B) under inert gas is heated to a temperature of 350 ° C., preferably to 280 ° C., to form a polyazole polymer,
D) treatment of the film formed in step C) (until it becomes self-supporting),
Can be obtained by a process including:

  The aromatic or heteroaromatic carboxylic acids and tetraamino compounds used in step A) have been described previously.

The polyphosphoric acid used in step A) is, for example, polyphosphoric acid commercially available from Riedel-de Haen. Polyphosphoric acid H _{n + 2} P _n O _{3n + 1} (n> 1) usually has a P ₂ O ₅ content of at least 83% (determined by acid titration). Instead of a solution of monomers, it is also possible to produce a dispersion / suspension. The mixture prepared in step A) has a weight ratio of polyphosphoric acid to the sum of all monomers of 1: 10000 to 10,000: 1, preferably 1: 1000 to 1000: 1, in particular 1: 100 to 100: 1. Have

  The layer formation in step B) is carried out by methods known per se from the prior art in the field of polymer film production (casting, spraying, doctor blade application). As a support, it is possible to use all supports that are inert under the relevant conditions. To adjust the viscosity, the solution can be mixed with phosphoric acid (concentrated phosphoric acid, 85%), where appropriate. Thus, the viscosity can be set to a desired value, and the film can be formed more easily.

  The layer prepared in step B) has a thickness of 20 to 4000 μm, preferably 30 to 3500 μm, in particular 50 to 3000 μm.

  If the mixture produced in step A) additionally contains tricarboxylic or tetracarboxylic acids, this leads to branching / crosslinking of the formed polymer. This contributes to improved mechanical properties. The polymer layer produced in step C) is treated in the presence of moisture for a time and temperature sufficient for the layer to have sufficient strength for use in a fuel cell. The treatment can be carried out for a time such that the membrane is self-supporting and can be separated from the support without damage.

  The inert gas used in step C) is known to those skilled in the art. These include in particular nitrogen and noble gases such as neon, argon, helium.

  In a process variant, the mixture from step A) can be heated to a temperature of 350 ° C., preferably to 280 ° C., to form oligomers and / or polymers. Depending on the temperature and time selected, the heating in step C) can then be partly or completely omitted. This variant is also the subject of the present invention.

  The treatment of the membrane in step D) is carried out at a temperature of 0 ° C. or more and less than 150 ° C., preferably at a temperature in the range from 10 ° C. to 120 ° C., in particular from room temperature (20 ° C.) to 90 ° C. It is carried out in the presence of water vapor and / or hydrous phosphoric acid at a concentration up to 85%. The treatment is preferably carried out under overpressure, but can also be carried out under overpressure. It is important to perform the treatment in the presence of sufficient moisture so that the polyphosphoric acid present is partially hydrolyzed to form low molecular weight polyphosphoric acid and / or phosphoric acid, thus Contributes to membrane reinforcement.

  Partial hydrolysis of polyphosphoric acid in step D) results in membrane reinforcement and decreases the layer thickness, with a free-standing membrane having a thickness of 15 to 3000 μm, preferably 20 to 2000 μm, in particular 20 to 1500 μm. Resulting in the formation of. The intramolecular and intermolecular structures (interpenetrating network IPN) present in the polyphosphate layer from step B) are responsible for the ordered film formation which causes the special properties of the formed film, step C). It occurs in.

  The upper temperature limit of the treatment in stage D) is generally 150 ° C. When moisture, such as superheated steam, acts on the membrane for a very short time, the steam can become hotter than 150 ° C. The upper temperature limit is related to the processing time.

  Partial hydrolysis (stage D) can also be carried out in a temperature- and humidity-controlled room where the hydrolysis can be controlled in the presence of a limited amount of moisture. Here, the humidity can be set with a targeted means via temperature, or by saturation of the environment in contact with the membrane, for example a gas such as air, nitrogen, carbon dioxide or other suitable gas or water vapor. Can be set. The processing time depends on the parameters selected previously.

  Furthermore, the processing time depends on the thickness of the film.

  The treatment time is generally from a few seconds to a few minutes, for example in the presence of superheated steam, or up to several days, for example in air, at room temperature and low relative atmospheric humidity. The treatment time is preferably in the range from 10 seconds to 300 hours, in particular from 1 minute to 200 hours.

  When partial hydrolysis is carried out at room temperature (20 ° C.) using ambient air with a relative atmospheric humidity of 40-80%, the treatment time is from 1 hour to 200 hours.

  The membrane obtained according to step D) has been made self-supporting, i.e. it can be removed from the support without damage and then further processed directly if desired.

  The concentration of phosphoric acid, and thus the conductivity of the polymer membrane, can be adjusted by the degree of hydrolysis, ie by time, temperature and ambient humidity. The concentration of phosphoric acid is recorded as the number of moles of acid per mole of repeating units in the polymer. The process comprising steps A) to D) makes it possible to obtain a membrane with a particularly high phosphoric acid concentration. Concentrations of 10 to 50, in particular 12 to 40 (formula (I), for example, mol of phosphoric acid per repeating unit of polybenzimidazole) are advantageous. Such a high degree of doping (concentration) can only be achieved with great difficulty, but if so, it can be achieved by doping polyazoles with commercially available ortho-phosphate.

  Subsequent to the treatment according to step D), the membrane can be further crosslinked on the surface by the action of heat in the presence of atmospheric oxygen. This hardening of the membrane surface additionally improves the properties of the membrane.

  Crosslinking is IR or NIR (IR = infrared, ie light having a wavelength longer than 700 nm; NIR = near infrared, ie wavelength in the range from about 700 to 2000 nm, or energy in the range from about 0.6 to 1.75 eV. It can also be carried out by the action of light). Another method is irradiation using β rays. The radiation dose is in this case in the range from 5 to 200 kGy.

In a variation of the above process where doped polyazole films are produced by the use of polyphosphoric acid, these films comprise the following steps:
1) One or more aromatic tetraamino compounds and an aromatic carboxylic acid or ester 1 thereof containing at least two acid groups per carboxylic acid monomer at temperatures up to 350 ° C., preferably up to 300 ° C., in the melt. Reaction with one or more, or reaction with one or more aromatic and / or heteroaromatic diaminocarboxylic acids,
2) Dissolution of the solid prepolymer obtained in step 1) in polyphosphoric acid,
3) The solution obtained by the method of step 2) is heated under inert gas to a temperature of 300 ° C., preferably 280 ° C. to form a dissolved polyazole polymer,
4) Forming a membrane on the support using the solution of the polyazole polymer from step 3)
5) Treatment until the film formed in step 4) becomes self-supporting,
It can also be manufactured by a process including

  The process steps presented in 1) to 5) above are described in detail in the description of steps A) to D) of this specification with respect to particularly preferred embodiments.

  The polyazole film can be provided with a plasma polymerized ion conductive layer before or after acid doping. However, plasma polymerization is preferably performed after doping.

  According to the present invention, a layer that is a plasma polymerization ion conductive electrolyte membrane can be applied to a polyazole film. This layer can also be called a barrier layer because it prevents acid washing-out.

  It has been found that the barrier layer is advantageously located on the cathode side of the polymer electrolyte membrane, since the overvoltage is significantly reduced.

  It is also possible to provide a layer according to the invention on both sides of the polyazole film. This gives a sandwich-like structure, in which the polyazole film, which can be doped with acid, forms the intermediate layer, while at the same time the layer obtainable by the plasma process of the invention is located on the outside.

  Methods for carrying out plasma polymerization are known to those skilled in the art and are disclosed, for example, in the literature. Information on performing plasma polymerization can also be found in CDROM, 5th edition in Ullmann's Encyclopedia of Industrial Chemistry, keywords are Plastics, Processing, Coating Processes, and Boing, H., et al. , Plasma Science and Technology, Carl Hanser Verlag, Munich 1982.

  For the purposes of the present invention, the term “plasma” refers specifically to an ionized gas. Plasma can be produced by exciting a gas using electromagnetic waves. Irradiation can be continuous or pulsed. In addition, a DC or AC voltage source can be used for plasma generation. The plasma generator can obtain what is marketed, for example from GaLa Gabler Laboratorum GmbH.

  Depending on the process, the plasma polymerization can be carried out at a pressure of 0.001 to 1000 Pa, preferably 0.1 to 100 Pa and particularly preferably 1 to 50 Pa. The temperature during plasma coating is preferably in the range of 0 ° C. to 300 ° C., more advantageously 5 to 250 ° C., but is not limited thereto.

  The precursor used for plasma coating includes water and a matrix forming component. The matrix-forming component comprises in particular an unsaturated organic compound. These are in particular alkenes, in particular ethylene, propylene, 1-hexene, 1-heptene, vinylcyclohexane, 3,3-dimethyl-1-propene, 3-methyl-1-diisobutylene, 4-methyl-1-pentene; Alkynes, especially ethyne, propyne, butyne, 1-hexyne; vinyl compounds containing acid groups, especially vinylphosphonic acid, vinylsulfonic acid, acrylic acid and methacrylic acid; vinyl compounds containing basic groups, especially vinylpyridine, 3 -Vinylpyridine, 2-methyl-5-vinylpyridine, 3-ethyl-4-vinylpyridine, 2,3-dimethyl-5-vinylpyridine, N-vinylpyrrolidone, 2-vinylpyrrolidone, N-vinylpyrrolidine and 3- Vinylpyrrolidine; fluorinated alkenes, especially monofluoroethylene, difluoroethylene Includes trifluoroethylene, tetrafluoroethylene, hexafluoropropylene, hexafluoropropylene, trifluoro propylene, hexafluoroisobutylene, trifluorovinyl sulfonic acid, trifluoroacetic vinyl phosphonic acid and perfluoro (vinyl methyl ether).

  The compounds can be used individually or as a mixture.

  The proportion of matrix-forming components is generally from 1 to 99% by weight, preferably from 50 to 99% by weight, particularly preferably from 60 to 99% by weight, based on the gas mixture used for plasma coating.

  The proportion of water is generally from 1 to 99% by weight, preferably from 1 to 50% by weight, particularly preferably from 1 to 40% by weight, based on the gas mixture used for the plasma coating.

  The gas mixture may further comprise an inert carrier gas. Such gases include, for example, noble gases such as helium and neon.

  The components of the gas mixture used for plasma polymerization may be mixed before being introduced into the coating chamber. As another option, the various compounds can be introduced separately into the chamber.

  The processing time can be varied within a wide range. The optionally doped polyazole film is preferably coated under plasma conditions for 10 seconds to 10 hours, preferably 1 minute to 1 hour.

  The flow rate of the gas into the vacuum chamber, the energy used for plasma generation and other process parameters can be varied within a wide range and parameters customary for the process used can be selected. Information about such parameters can generally be found in the operating instructions for each device.

  Advantageous processes for producing the coating according to the invention include both plasma polymerization and plasma impulse chemical vapor deposition process (PICVD) in which power is continuously introduced.

  The PICVD process is described in, for example, Journal of the Ceramic Society of Japan, 99 (10), 894 to 902 (1991), and curved surface coating has also been disclosed (see WO95 / 26427).

  In the PICVD process, the electromagnetic waves that excite the plasma are typically applied in pulses, while the coating gas flows continuously through the coating chamber, so that a thin layer (typically about 1 nm, a single layer region) is applied to each impulse. To deposit on the support. After each power impulse there is a pause, so that a high coating rate can be obtained without any appreciable thermal stress of the support. The amplitude and duration of the power impulse and the duration of the pause between impulses are particularly strict for the generation of the layer. In the PICVD process, impulse amplitude is a measure of power. This corresponds to the impulse power, that is, the product of the voltage and current of the generator during the impulse period. The percentage of power actually engaged in the plasma depends on several parameters, such as the magnitude of the impulse emission component and the dimensions of the reactor.

Depending on the impulse amplitude,
a) Various excitations and reactions occur in the plasma above the threshold characteristic of each gas,
b) Various thicknesses of the plasma zone are set.

  When using the PICVD process, elemental layers (single layers) of different compositions can be deposited from impulse to impulse by appropriate selection of impulse amplitude. This is achieved in particular by the fact that the same gas composition is present at each impulse, for example by a clear separation of the off-gas from the new gas, with a suitable selection of the pause between the impulses. Similar results are not possible when using conventional PCVD processes.

The following range of power parameters is particularly advantageous:
Impulse duration: 0.01 to 10 milliseconds, especially 0.1 to 2 milliseconds;
Pause between impulses: 1-1000 milliseconds, especially 5-500 milliseconds Impulse amplitude: 10-100,000 Watts

  The PICVD process is carried out using AC voltage impulses with frequencies from 50 kHz and 300 GHz, particularly preferably with frequencies from 13.56 MHz and 2.45 GHz.

The gas flow rate in the PICVD process is generally selected such that the gas can be considered stationary for the duration of the impulse. Accordingly, mass flow is generally in the range of 1 to 200 standard cm ³ / min, preferably in the range of 5 to 100 standard cm ³ / min.

  The intrinsic conductivity of the plasma polymerized ion conductive layer is in the range of 0.001 S / cm to 0.3 S / cm at 80 ° C. depending on the mixing ratio of the matrix-forming component and water in the plasma. However, this is not a limitation. The measurement of these values is carried out in a simple manner by impedance spectroscopy using a plasma polymerized layer deposited on a dielectric support, depending on the measurement technique, 2 or 4 electrodes, preferably a thin film A platinum or gold electrode deposited using the technique was previously applied. Temperature-dependent conductivity measurements can be done by heating the specimen, for example, with a hot plate with temperature adjustment by means of a thermal sensor located near the middle of the layer to be measured, or heating the specimen with a suitable measuring cell in an oven To implement.

  Due to its manufacturing process and the resulting high degree of crosslinking, the plasma polymerized ion conducting layer has a high stability. The aging and stability test can be performed, for example, by heating to a temperature range of 100 ° C to 500 ° C. Examination of the structure of the plasma polymerized layers, for example by infrared spectroscopy, allows to draw conclusions taking into account the structural changes that occur as a result of heating and thus taking into account the stability of these layers.

  A polyazole film provided with a layer obtained by plasma polymerization exhibits an unexpectedly high conductivity over a wide temperature range. Therefore, the film obtained by the present invention exhibits unexpectedly high conductivity both at a low temperature in the range of 0 ° C. to 50 ° C. and at a high temperature of 120 ° C. or higher.

  According to a special configuration of the invention, a polyazole film obtained by plasma polymerization and comprising an acid doped layer is at least 0.005 S / cm, in particular at least 0.01 S / cm, particularly preferably at least at 120 ° C. It has a high conductivity of 0.02 S / cm, but is not limited thereto. These values are determined using impedance spectroscopy.

  The conductivity can be measured by impedance spectroscopy with a four-pole arrangement in a constant voltage mode using a platinum electrode (wire, diameter 0.25 mm). The distance between the current collecting electrodes is 2 cm. The resulting spectrum is evaluated by a simple model consisting of a parallel arrangement of ohmic resistance and capacitance. The specimen cross-sectional area of the membrane doped with phosphoric acid is measured immediately before attaching the specimen. In order to measure the temperature dependence, the measuring cell is brought to a predetermined temperature in the oven, and the temperature is adjusted by a Pt-100 resistance thermometer located in the immediate vicinity of the specimen. After the temperature reached, the specimen was held at this temperature for 10 minutes, after which the measurement was started.

  Furthermore, the acid present in the polyazole film is surprisingly retained in the film by the coating according to the invention, so that the acid is not washed away by operation at low temperatures.

  For example, in the case of a film doped with phosphoric acid, the barrier action of the layer obtained by plasma polymerization according to the present invention can be measured as follows.

  The barrier action is measured in a simple way by the change in the pH of the water as a function of time. This is carried out using a measuring cell comprising two chambers separated by a plasma polymerization layer according to the invention. The water and pH electrodes to be measured are located in one chamber, while a solution of known concentration, preferably a phosphoric acid solution, or a polyazole membrane doped with phosphoric acid in direct contact with the plasma polymerized layer, Put it in the room.

  In order to separate the two chambers, the plasma polymerized layer according to the invention is preferably deposited on a porous support, such as a porous film or a porous ceramic. The coated support is placed in a suitable holder that separates the two chambers of the measuring cell and allows access to the limited surface area of the plasma polymerized layer on the support from both sides.

  Furthermore, polyazole films coated according to the invention and doped with acid exhibit very low overvoltages. This property is retained even over long periods of operation and multiple start-up cycles.

  Furthermore, the polyazole film coated with the present invention exhibits an unexpectedly high durability observed when operating at both low and high temperatures.

  The invention also provides a membrane electrode unit comprising a polymer membrane based on at least one polyazole according to the invention.

  Other information regarding membrane electrode units can be found in the technical literature, in particular in patents, US-A-4191618, US-A-4221714 and US-A-4333805. The structure and manufacture of the membrane electrode unit selected in the above references [US-A-4191618, US-A-4221714 and US-A-4333805] and also the disclosure regarding electrodes, gas diffusion layers and catalysts This is incorporated herein by reference.

  In another variation, a catalytically active layer can be applied to the membrane of the present invention, which can be coupled to a gas diffusion layer.

  The invention likewise provides a membrane electrode comprising at least one polymer membrane according to the invention, if desired in combination with another polymer membrane or polymer blend membrane based on polyazole.

  An advantage of MEUs that include polyazole membranes is that this allows fuel cells to be operated at temperatures above 120 ° C. Gaseous and liquid fuels, such as hydrogen-containing gases, are used and applied to fuel cells, which are produced from hydrocarbons, for example, in a prior reforming stage. For example, oxygen or air can be used as the oxidizing agent.

  Another advantage of MEUs containing polyazole membranes is that they are highly resistant to carbon monoxide even when using pure platinum catalysts (ie, without other alloying components) in operation above 120 ° C. It is. At a temperature of 160 ° C., for example, more than 1% CO may be present in the fuel gas, but this does not reduce the fuel cell performance appreciably.

  MEUs containing doped polyazole films can be used in fuel cells without the fuel gas and oxidant to be moistened, despite the high operating temperatures possible. Nevertheless, the fuel cell operates in a stable manner and the membrane does not lose its conductivity. This simplifies the entire fuel cell system and saves additional costs because the water circuit is simplified. Moreover, this also improves the performance of the fuel cell system at temperatures below 0 ° C.

  Surprisingly, MEUs including doped polyazole films can allow the fuel cell to cool to room temperature and below without problems and then resume operation without degrading performance. In contrast, conventional fuel cells based on phosphoric acid must always be kept at a temperature above 80 ° C. even when the fuel cell system is shut down to avoid irreversible damage.

  Furthermore, MEUs including polyazole membranes have very high long-term stability. The fuel cell according to the invention operates continuously at a temperature of 120 ° C. or higher for a long period of time, for example longer than 1000 hours, preferably longer than 2000 hours, particularly preferably longer than 5000 hours, using a dry reaction gas. It was found that no appreciable degradation in performance was observed. The power density obtained under these conditions remains very high even after such a long time.

Claims (18)

  In the method for producing a plasma polymerized ion conductive electrolyte membrane, the plasma polymerized ion conductive electrolyte membrane is produced by plasma assisted copolymerization of a matrix forming component, preferably a hydrocarbon compound or a fluorinated hydrocarbon compound, and water. The manufacturing method characterized by the above-mentioned.   2. A method for producing a plasma polymerized ion conducting electrolyte membrane according to claim 1, characterized in that the precursor used for the matrix-forming component is a fluorinated alkene, preferably tetrafluoroethylene.   2. A method for producing a plasma polymerized ion conducting electrolyte membrane according to claim 1, characterized in that the precursor used for the matrix-forming component is an alkene, preferably ethylene.   2. A method for producing a plasma polymerized ion conducting electrolyte membrane according to claim 1, characterized in that the precursor used for the matrix-forming component is an alkyne, preferably acetylene.   The method for producing a plasma-polymerized ion-conducting electrolyte membrane according to any one of claims 1 to 4, wherein the layer is deposited in a parallel plate plasma reactor.   The method for producing a plasma-polymerized ion-conducting electrolyte membrane according to any one of claims 1 to 5, wherein the coating for forming the membrane is carried out by placing the support on a support.   The method for producing a plasma-polymerized ion-conducting electrolyte membrane according to any one of claims 1 to 5, wherein the coating for forming the membrane is performed by a method in which a support is passed through a coating chamber.   The usage method of the fuel cell which has a plasma polymerization ion conductive electrolyte membrane manufactured by the method of any one of Claims 1-7.   A thin barrier for preventing permeation of a gas or liquid on a polymer electrolyte membrane not produced by plasma polymerization of the plasma polymerized ion conductive electrolyte membrane produced by the method according to any one of claims 1 to 7. Usage as a layer.   The usage method for the electrolytic cell of the plasma polymerization ion conductive electrolyte membrane manufactured by the method of any one of Claims 1-7.   A plasma-coated polyazole film, wherein the polyazole film is coated with a plasma-polymerized ion conductive layer obtained by the production method according to claim 1.   The polyazole film according to claim 11, wherein the polyazole film is doped with an acid.   The polyazole film according to claim 12, wherein the degree of doping is in the range of 3-15.   The polyazole film according to claim 11, wherein the plasma-polymerized ion conductive layer has a thickness in a range of 10 mm to 20 μm. The polyazole film has the formula (I), (II), (III), (IV), (V), (VI), (VII), (VIII), (IX), (X), (XI) , (XII), (XIII), (XIV), (XV), (XVI), (XVII), (XVIII), (XIX), (XX), (XXI) and (XXII) At least one or more:

Wherein Ar is the same or different and each is a tetravalent aromatic or heteroaromatic group that may be monocyclic or polycyclic;
Ar ¹ is the same or different and each is a divalent aromatic or heteroaromatic group that may be monocyclic or polycyclic;
Ar ² is the same or different and each is a divalent or trivalent aromatic or heteroaromatic group that may be monocyclic or polycyclic;
Ar ³ is the same or different and each is a trivalent aromatic or heteroaromatic group that may be monocyclic or polycyclic;
Ar ⁴ is the same or different and each is a trivalent aromatic or heteroaromatic group that may be monocyclic or polycyclic;
Ar ⁵ is the same or different and each is a tetravalent aromatic or heteroaromatic group that may be monocyclic or polycyclic;
Ar ⁶ is the same or different and each is a divalent aromatic or heteroaromatic group that may be monocyclic or polycyclic;
Ar ⁷ is the same or different and each is a divalent aromatic or heteroaromatic group that may be monocyclic or polycyclic;
Ar ⁸ is the same or different and each is a trivalent aromatic or heteroaromatic group that may be monocyclic or polycyclic;
Ar ⁹ is the same or different and each is a divalent, trivalent or tetravalent aromatic or heteroaromatic group which may be monocyclic or polycyclic;
Ar ¹⁰ are the same or different and are each a divalent or trivalent aromatic or heteroaromatic group that may be monocyclic or polycyclic,
Ar ¹¹ is the same or different and each is a divalent aromatic or heteroaromatic group that may be monocyclic or polycyclic;
X is the same or different and each is an amino group having an oxygen, sulfur or hydrogen atom, a group having 1 to 20 carbon atoms, preferably a branched or unbranched alkyl or alkoxy group, or An aryl group as another group,
R is the same or different, and each is hydrogen, an alkyl group or an aromatic group, and n and m are each an integer of 10 or more, preferably an integer of 100 or more.
15. The polyazole film according to claim 11, comprising a polymer containing repeating azole units.   The polyazole film is made of polybenzimidazole, poly (pyridine), poly (pyrimidine), polyimidazole, polybenzothiazole, polybenzoxazole, polyoxadiazole, polyquinoxaline, polythiadiazole and poly (tetraazapyrene). The polyazole film according to claim 11, comprising a polymer selected from the group. The polyazole film has the following steps:
A) Dissolution of polyazole polymer in polyphosphoric acid B) Heat the solution obtained by the method of step A) under inert gas to a temperature of 400 ° C. C) Support the solution of polyazole polymer from step B) A polyazole according to any one of claims 12 to 16, characterized in that it is obtained by a process comprising a treatment until the film formed in step D) is self-supported. film.   A membrane electrode unit comprising at least one plasma-coated polyazole film according to any one of claims 11 to 16.