EP0852071A2

EP0852071A2 - Functionalized copoly(m-phenylene)-based solid polymer electrolytes

Info

Publication number: EP0852071A2
Application number: EP96943846A
Authority: EP
Inventors: Rolf Mülhaupt; Torsten Zerfass; Holger Frey; Konstantin Ledjeff-Hey; Roland Nolte
Original assignee: Fraunhofer Gesellschaft zur Forderung der Angewandten Forschung eV
Current assignee: Fraunhofer Gesellschaft zur Forderung der Angewandten Forschung eV
Priority date: 1995-09-21
Filing date: 1996-08-28
Publication date: 1998-07-08
Also published as: WO1997011099A2; WO1997011099A3; DE19535086A1; DE19535086B4; JPH11515040A

Abstract

The invention concerns a solid polymer electrolyte with a hydrophobic backbone which is at least partially functionalized by ionic groups. The invention also concerns a process for preparing th epolymer according to the invention and a preferred use thereof. The invention is characterized in that the polymer backbone comprises a copoly(m-phenylene) which contains at least 20 mol.% m-phenylene units and has structure (a), in which R1 to R8 are hydrogen, aryl, oxyaryl, thioaryl, sulphonaryl, carbonylaryl, oxyaryloxyaryl, hydroxyl or ionically dissociable groups.

Description

Solid polymer electrolytes based on functionalized copoly (m-phenylene) e

Description

Technical field

The invention relates to a polymeric solid electrolyte with a hydrophobic backbone which is at least partially functionalized by ionic groups.

State of the art

Solid polymer electrolytes (polymer electrolytes) are ion-exchange membranes, which consist of polymers with ionic groups. They have high ionic conductivity and, in contrast to liquid systems, mechanical stability. They come in various applications, such as. B. ion exchangers, (water) electrolyzers, batteries or fuel cells are used. The invention relates to polymer electrolytes which are used primarily for use in fuel cells and electrolysers.

Disadvantages of liquid electrolytes, such as, for example, their corrosion, the need for circulation devices and, when used in fuel cells, the diffusion of fuel gas and oxygen through the electrolyte, which leads to a reduced efficiency of the fuel cell, are eliminated in the case of polymer electrolytes. From these For this reason, polymer electrolytes enable a simplified, compact construction of the cells, which also have a longer service life. Polymer electrolytes for use in fuel cells and electrolyzers must have the following properties:

1) high proton conductivity

2) no electron conductivity

3) mechanical stability

4) Long-term chemical and electrochemical stability

5) good thermal stability in aqueous media (low swelling even in the boiling point of water)

6) low gas permeability.

The use of perfluorosulfonated membranes such as Nafion (trademark of DuPont) has been state of the art for many years. Unfortunately, these materials are only available with defined parameters (thickness, ion exchange capacity) and are not thermoplastic or processable from solutions. Furthermore, the high manufacturing costs have a negative impact.

Therefore, other materials have already been investigated as alternatives to Nafion. An overview of this can be found in an article by A.E. Steck, "Proceedings of the first international symposium on new materials for fuel cell systems, 1995, Savadogo, Roberge, Veziroglu, Montreal, Canada.

Membranes based on other fluoropolymers are described, for example, in US 4,469,579, US 4,940,525 and WO 94/03503. Furthermore, sulfonated poly (phenylene ethers) can be found in US 3,259,592, US 3,484,293 or US 3,528,858. In addition, membrane materials are based on aromatic Polyether ketones are known from EP 0 575 807 AI or EP 0 574 791 A2. Polymer electrolytes based on sulfonated poly (p-phenylene) s are described in WO 94/24717.

However, these known materials mostly show insufficient ion conductivity, thermal or long-term stability or require a complex manufacturing process.

The sulfonated polymers with poly (p-phenylene) backbone described by WO 94/24717 must have solubilizing side chains because of their rigid structure and their high degree of crystallinity so that they can be processed.

However, this requires complex reaction steps to introduce these side chains into the starting monomers. Furthermore, the side chains are sometimes not stable during sulfonation and must be specially protected. They also reduce the chemical and thermal stability of the product materials.

The properties of the polymer solid electrolytes known hitherto result in particular from the special chemical constitution of the polymer molecules. In addition to a non-polar backbone, they have functional groups that can be dissociated ionically. The charges generated in the presence of water and the hydrophobic backbone lead to phase separation in ion-rich and ion-depleted areas. Proton-conductive channels filled with water are formed. The aggregated ions act as physical crosslinking points for the polymer molecules. To this This creates a macroscopically elastic, thermally reversible, physical network.

In the case of Nafion, the contrast between the hydrophobicity of the poly (tetrafluoroethylene) backbone and the polar, ionic groups is particularly pronounced. The usability of Nafion at high temperatures should have its cause here. In contrast, the alternative materials mostly have heteroatoms in the backbone, i. H. Polarities, which lead to degradation of the network due to water attack at high temperature, which manifests itself in softening.

Functionalized polyphenylenes based on poly (p-phenylene) are, as already mentioned, described in US 3,376,235 and in PCT WO 94/24717.

US 3,376,235 describes a linear, sulfonated poly (p-phenylene) with 1 to 2 sulfonic acid groups per 10 phenylene rings. Unsubstituted poly (p-phenylene) (PPP) is highly crystalline, infusible and extremely insoluble due to the rigid structure ("rigid rod"). It is chemically and thermally very stable, but can hardly be processed due to the properties mentioned. The sulfonation according to US 3,376,235 consequently requires very drastic conditions (oleum, 1 to 50 hours reaction time at 25 to 200 ° C.). Dark brown, still insoluble sulfonated materials are obtained as products. Due to the insolubility, however, no membranes can be made from it. In addition, condensation reactions in the synthesis of PPP come to a standstill at the oligomer stage of 6 to 10 phenylene units due to the polymer's insolubility. The common concept for the solubilization of PPP has been known since the 1950s. The introduction of substituents leads to a greatly improved solubility of the substituted poly (p-phenylene) e because of the associated disturbance of the crystal structure and improved interaction with the solvent. Extensive investigations have been carried out e.g. B. made by Kern, Heitz and Rehahn (see the specified literary positions 1 to 10).

Polymer electrolytes based on such PPP solubilized with substituents are described in WO 94/24717.

From WO 94/24717 it is known that the substitution of the PPP backbone is a prerequisite for further processing.

Disadvantages of this known concept of solubilization by side groups or chains are the relatively complex monomer syntheses and the significantly reduced thermal stability compared to unsubstituted polyphenylenes, especially when alkyl chains are present in the molecule. The sulfonation of rigid-rod polyphenylenes according to WO 94/24717 also requires reaction times in the range of hours. The side chains can also decompose in an uncontrolled manner during sulfonation and must e.g. T. be protected from sulfonation. The material shows a specific Wider¬ stand of at least about 50 Ω cm- ^■. This value is about a factor of 6-10 higher than that of Nafion. Presentation of the invention

The invention has for its object to develop polymeric solid electrolytes with a preferably hydrophobic backbone, which is at least partially functionalized by ionic groups, in such a way that no side chains or groups to be provided for further processing are required for the production. The materials should also not be produced on the basis of the rigid-rod concept described in WO 94/24717. In addition, the thermal and chemical stability properties of the polymers are to be improved. Finally, it should be achieved that the manufacturing process can be shortened and therefore cheaper. The polymer to be developed should be particularly suitable for use as an electrolyte membrane in electrolysis devices or in fuel cells.

The solution to the problem on which the invention is based is given in claims 1, 10 and 13. Features which further develop the invention in an advantageous manner are contained in the subclaims.

According to the invention, a polymeric solid electrolyte with a preferably hydrophobic backbone, which is at least partially functionalized by ionic groups, is developed in such a way that the backbone of the polymer has a copoly (m-phenylene) which contains at least 20 mol% m-phenylene Contains units and is of the following structure:

where Rl to R8 are hydrogen, aryl, oxyaryl, thioaryl,

Are sulfonaryl, carbonylaryl, oxyaryloxyaryl, hydroxyl or ionically dissociable groups.

The invention is based on the surprising finding that, by incorporating m-phenylene units in PPP, a soluble and fusible poly (m-phenylene-co-p-phenylene) is obtained despite the absence of solubilizing side chains.

The disturbance of the crystal structure required for solubilization is achieved here as it were by "kinks" in the polyphenylene chain and can be further improved with the help of side chains. Such copoly (m-phenylene) s as well as poly (m-phenylene), which are not rigid-rod polymers, can nevertheless be converted into polymer electrolytes by sulfonation.

In contrast to the known rigid-rod polyphenylenes, substitution with side chains is advantageously not absolutely necessary for processability in the new materials. Even without ring substitution, sulfonation and electrolyte production are possible in copolymers with predominantly m-linking of the repeating units. The invention allows for the first time the synthesis of polymer electrolytes whose polymer molecules only have the ionic groups. The advantage of such systems over systems with longer side groups has already been found in WO 94/03503 for fluorinated materials.

The polymeric solid electrolytes of this invention consist of copoly (m-phenylene) s of structure (1) with at least 20 mol% m-phenylene units. A degree of functionalization with ionically dissociable groups should preferably be greater than 0 and less than 1. This degree of functionalization is to be understood as the average number of ionic groups per repeating unit. The ionic groups can be randomly distributed over the polymer or preferably bound to certain repeating units.

The copoly (m-phenylene) s can be random, alternating, segmented or of another order. Statistically structured copoly (m-phenylene) s are advantageously suitable for use as polymer electrolytes. Furthermore, a method is described with which it is possible for the first time to synthesize such structured Colpoly (m-phenylene) s in a statistical arrangement.

The substituents Rl to R8 can be hydrogen, aryl, oxyaryl, thioaryl, sulfonaryl, carbonylaryl, Oxyaryloxyaryl, hydroxyl or ionically dissociable groups.

Preferred ionically dissociable groups are in particular sulfonyl (-S03H), carboxyl (-C00H) or phosphoryl (-PO (OH) 2).

The substituent pairs R2 / R3 or R3 / R4 and / or R5 / R6 or R7 / R8 can also be fused arylene rings.

The polymer electrolytes according to the invention basically have a copoly (m-phenylene) backbone with a hydrophobicity similar to that of the poly (tetrafluoroethylene) backbone from Nafion.

Surprisingly, it has been found that unsubstituted coply (m-phenylene) s and poly (m-phenylene) can also be converted into polymer electrolytes by functionalization with ionic groups. The need for solubilizing side chains, which is not absolutely necessary in this class of polymers, greatly simplifies the synthesis.

The polymeric solid electrolytes according to the invention have a thermally and chemically extremely resistant, highly hydrophobic backbone made of copoly (m-phenylene) s, which is functionalized by ionic groups. In addition to a high proton conductivity, they show very favorable swelling behavior, which is reflected in good mechanical stability even at about 100 ° C. In addition, the materials can be processed from solutions in dipolar aprotic solvents and are therefore accessible in any layer thickness. The abundance of Known from the literature, and in some cases very well studied phenyl coupling reactions, the copoly (m-phenylene) s could also be made available from inexpensive starting materials.

As a prerequisite for the production of solid electrolytes according to the invention, a sulfonation process using chlorosulfonic acid has also been developed for the treatment of copoly (m-phenylene) s, which can be implemented with little outlay in terms of equipment and materials and short reaction times at room temperature. The invention also includes a method of manufacturing membranes from functionalized copoly (m-phenylene) s.

In principle, copoly (m-phenylene) s can be synthesized in two ways. On the one hand, a copolymer (m-phenylene) without ionic groups can be provided with such groups. This is preferably done by sulfonation. On the other hand, the ionic groups can already be present in the monomers during the polymerization. The copoly (m-phenylene) s can be synthesized by a regioselective or at least predominantly regioselective coupling of bifunctional aromatics according to one of the following principles:

Stem structure (I)

^Q

Depending on the electronegativity of the substituents X and Y, a distinction is made between reductive, oxidative or redox-neutral aromatic couplings. A wealth of reactions are known from the literature.

In redox-neutral processes, the substituent X is more electronegative and the substituent Y is less electronegative than carbon or vice versa. The reaction proceeds with transition metal catalysis to form the salt XY. Processes have been described by T. Yamamoto et al. (see reference 11) (X = MgBr, Y = CI, Br) or by M. Rehahn et al. (Liter positions 9 and 10) (X = B (OH) 2, Y = Br, I). In the case of oxidative processes, X and Y are more electropositive than carbon (hydrogen, metals), but these known processes have insufficient regioselectivity and are less suitable for the targeted synthesis of copoly (m-phenylene) s.

In the case of reductive methods, aromatics with more electronegative substituents X and Y are polymerized in the presence of a reducing agent.

The so-called Suzuki coupling (palladium-catalyzed redox-neutral coupling of arylboronic acids and aryl halides) is particularly suitable for the production of copoly (m-phenylene) s of the above structure (I) (with X = B (0H) 2 and Y = Br or vice versa), see. Rehahn et al (reference 9).

It is characterized by high regioselectivity and tolerates a number of functional groups. This is carried out, for example, in a vigorously stirred two-phase mixture of approximately equal volumes of an aromatic in the boiling range of approximately 80 to 130 ° C. (such as toluene or benzene) and the aqueous solution of a base (eg 1-2) molar sodium carbonate solution). Tetrakis (triphenylphosphine-palladium-O) is preferably used as the catalyst in concentrations of 0.1 to 0.6 mol%, but in particular in concentrations between 0.2 and 0.5 mol%, based on the boronic acid groups. The reaction takes place in a boiling mixture between 1 and 12 hours. The unsubstituted copoly (m-phenylene) s precipitate during the reaction because of their insolubility. The formation of copolymers could be shown spectroscopically (IR and - ³ C solid-state NMR) and with the help of DSC. The actual incorporation ratio of the repeat units in the polymer as a function of the monomer ratio used could be examined using quantitative FT-IR spectroscopy using the example of unsubstituted copoly (m-phenylene) s (R1-R8 = H in structure (1)) It has been shown that about 5-10% fewer meta units were incorporated into the polymer than was used in the monomer mixture.

While solubilizing side chains are known to limit the thermal stability of the polymers to about 350 ° C. (nitrogen atmosphere) by degradation, the unsubstituted copoly (m-phenylenes) have a thermal stability of up to about 550 ° C. (nitrogen atmosphere) and thus make thermally extremely stable materials represents.

Of particular note is a coply (m-phenylene) that can be synthesized from 65% 3-bromophenylboronic acid and 35% 4-bromophenylboronic acid. Surprisingly, it is soluble in nonpolar solvents such as paraffins at about 180 ° C. and has a melting point of 210 ° C. In this way, an unsubstituted, meltable and soluble polyphenylene can be obtained for the first time.

If ionically dissociable groups are not already present in the monomers, they can be introduced into the copoly (m-phenylene) s, preferably by sulfonation. As a rule, the polymer backbone or side groups are sulfonated. Various sulfonation methods are known, such as the reaction with concentrated Sulfuric acid, oleum, a mixture of sulfuric acid and thionyl chloride, sulfur trioxide or treatment with chlorosulfonic acid. The sulfonation conditions suitable for the respective copoly (m-phenylene) can be determined by series of tests with increasingly tougher conditions.

The standard method in the production of polymer electrolytes is sulfonation with concentrated sulfuric acid or oleum (cf. WO 94/24717, EP 0 575 807 A1, EP 0 574 791 A2). However, reaction times in the range of hours are required.

As already known from Nafion chemistry, special synergy effects are expected from the combination of carboxylic acid and sulfonic acid functionalities.

According to the invention, a process for producing a polymeric solid electrolyte is specified in such a way that the polymer is a copoly (m-phenylene) with the structure (I) mentioned above, which is sulfonated with the addition of a sulfonating agent. After the sulfonation has ended, the sulfonated copoly (m-phenylene) is dissolved in an organic solvent. The solution is then applied to a support on which the solvent is evaporated. With the addition of water, the film remaining on the support is then detached and swollen.

The copoly (m-phenylene) s of the above structure can preferably be sulfonated very quickly with the aid of chlorosulfonic acid in chloroform. To this end, the ethanol present in chloroform as a stabilizer is first treated with an excess Chlorosulfonic acid reacted and the chloroform was distilled off. For the sake of simplicity, chloroform obtained in the distillation, air-smoking and saturated with hydrogen chloride is used without further pretreatment. The copoly (m-phenylene) is suspended in this chloroform and treated with vigorous stirring with a solution of chlorosulfonic acid in the same solvent. Reaction times in the range of seconds result.

After the required time, the reaction is quenched with methanol. After working up, soluble, sulfonated copoly (m-phenylene) e are obtained in dipolar aprotic solvents such as N, N-dimethylformamide or dimethyl sulfoxide with heating.

Are sulfonated under tougher conditions, e.g. B. by exposure to undiluted chlorosulfonic acid for several hours, so you get a cross-linked S0 ₂ bridges duromer, which is insoluble. Networking takes place according to the following mechanism:

Ar-H + C1S0 ₃ H> Ar-S0 ₃ H + HCI (1)

Ar-S0 ₃ H + C1S0 ₃ H ^V Ar-S0 ₂ Cl + H ₂ SO, (2) Ar-S0 ₂ Cl + Ar'-H> Ar-S0 ₂ -Ar '+ HCI (3)

In the first step, aromatic rings of the polymer backbone (Ar) are sulfonated by chlorosulfonic acid (equation (1).

In the presence of an excess of chlorosulfonic acid is the aromatic sulfonic acid with the compound Ar-S0 ₂ Cl, which are to be understood as aryl-substituted chlorosulfonic acid leaves, in equilibrium (equation (2)).

Similar to chlorosulfonic acid, the aryl-substituted chlorosulfonic acid should in turn have a sulfonating effect and be able to react with another aromatic ring to form a SO ₂ bridge (equation (3)).

If Ar and Ar 'are repeating units of polyphenylene chains, the reaction according to equation (3) leads to chemical crosslinking. The sulfonation and crosslinking of a copoly (m-phenylene) s could be shown with the help of FT-IR spectra.

Brief description of the drawings

The figures below show the characteristic spectra of the copoly (m-phenylene) e on which the solid-state electrolytes are based. Show it:

Fig. 1 a, b, c FT-IR spectra of various copoly (m-phenylene) e, made from 65% 3-bromophenylboronic acid and 35% 4-bromophenylboronic acid

Fig. 2 FT-IR spectra of various copoly (m-phenylene-co-p-phenylene) e and

Fig. 3 ¹³ C-solid-state NMR spectra of copoly (m-phenylene-co-p-phenylene) en.

Representation of exemplary embodiments

1 shows the FT-IR spectra of the non-sulfonated copoly (m-phenylene) s (see FIG. 1 a), which can be produced with the aid of measure 1b described below. Fig. Lb shows that sulfonated with measure 2 Copoly (m-phenylene) s and Figure lc the copoly (m-phenylene) s, which were extremely strongly sulfonated overnight with pure chlorosulfonic acid, depending on the wave number in the range from 2000 cm-1 to 600 cm-1 (KBr compacts).

At moderate sulfonation (Figure lb) in addition to bands cha¬ acteristic of the copoly (m-phenylene) s four bands at 1214.7 cm- ^1, 1183.7 cm ^{* 1,} 1111.1 cm ^-1 and 1054.3 cm ^{- 1} visible. The band at 1054.3 cm- ¹ stems from the phenyl-sulfur stretching vibration, the other three are due to three characteristic vibrations of the S0 ₃ - groups. A band at 1638.5 cm- ^{1 is also seen} , which is caused by the plane deformation vibration of water. The sulfonated sample has been equilibrated in air so that the sulfonic acid functionalities were available as Ar-S0 ₃ H ₃ 0+. The spectrum shows the sulfonation of the copoly (m-phenylene) s according to equation (1). The spectrum (see FIG. 1c) of the strongly sulfonated sample shows two strong bands at 1302.4 cm ^-1 and 1167.8 cm- ¹ . They correspond to the symmetrical and the asymmetrical vibration of the crosslinking SO ₂ groups that have arisen according to equation (3). The degree of sulfonation can be calculated from elementary analyzes (C, H, S determination).

The electrolyte membrane is produced according to the invention by dissolving the copoly (m-phenylene) functionalized by ionic groups in an organic solvent, preferably a dipolar aprotic solvent, applying it to a glass support and slowly evaporating the solvent. The resulting film is then detached from the base in water, wherein a swollen membrane is created,

To produce an inventive

Solid electrolyte membrane, the following measures should preferably be taken:

1. Measure: Synthesis of copoly (m-phenylene) s without solubilizing side chains according to structure (I) with R1-R8 = H

a) Representation of the monomers 3-bromophenylboronic acid and 4-bromophenylene boronic acid from 1,3-dibromobenzene and 1,4-dibromobenzene, respectively

In a heated and nitrogen-vented 11 three-necked flask with dropping funnel, nitrogen inlet and magnetic stirrer, 30 g (127.2 mmol) of the respective dibromobenzene are placed in 400 ml of absolute diethyl ether and cooled to -78 ° C. 1,4-dibromobenzene precipitates as a fine suspension. 52 ml of a 2.5 molar solution of n-butyllithium in hexane fraction are added dropwise under inert gas through the dropping funnel with stirring and further cooling at a rate of about 2 drops / sec. The mixture is then to be warmed to room temperature and, while stirring in an inert gas atmosphere, transferred to a solution of 75 ml of trimethyl borate in 350 ml of absolute ether, cooled to -78 ° C.

The solution is stirred at room temperature for about 8 hours and 200 ml of 1N hydrochloric acid are added. The initially cloudy becomes clear with vigorous stirring organic phase and a viscous aqueous and a clear organic phase protruding. The organic phase can then be easily decanted. By rinsing with ether and decanting, residues of the product can be removed from the flask. The combined organic phases are extracted with a total of 500 ml of 2N sodium hydroxide solution in portions of 200, 100, 100, 100 ml. The boronic acid passes into the sodium hydroxide solution as boronate. The sodium hydroxide solution is again washed with 150 ml of diethyl ether. The solution is then to be cooled to 0 ° C., while 6N hydrochloric acid is added while cooling until a pH of 2 has been established.

The boronic acid precipitates in crystalline form and can be suctioned off after it has been left to stand. After drying in vacuo, 20 g (78% of theory) of crude product are obtained.

Before being used for the polymerization, the boronic acids must be purified by recrystallization. They are dissolved in as little diethyl ether as possible and precipitated by adding pentane and cooling to -78 ° C. After drying in vacuo, 14.5 g (57%) of pure 3-bromophenyl boronic acid or 15 g (59%) of pure 4-bromophenyl boronic acid remain.

Characterization by ¹ H-NMR (acetone-d6):

- 4-bromophenylboronic acid (4-Br-Cβ H ₄ -B (OH) ₂ ): 6 = 7.3ppm (s, 2H), 7.6ppm (d, 2H), 7.9ppm (d, 2H)

- 3-bromophenylboronic acid (3-Br-Cβ H ₄ -B (0H) ₂ ): δ = 7.35ppm (t, lH), 7.4ppm (s, 2H), 7.6ppm (d, lH), 7 , 85ppm (d, lH), 8.05ppm (s, lH)

b) Preparation of copoly (m-phenylene) s according to structure (1) with R1-R8 = H from 3-bromophenylboronic acid and 4-bromophenylboronic acid.

10 g (49.8 mmol) of the monomer mixture in the desired ratio are to be dissolved in 250 ml of 1.5 M aqueous sodium carbonate solution in a 11 three-necked flask with gas supply, KPG stirrer and reflux condenser and the solution is evacuated and aerated several times with nitrogen to degas.

A total of 300 ml of toluene was added under an inert gas atmosphere. A portion of the toluene was used to transfer the catalyst, 160 mg (1.38 * 10 " ^A mol) tetra trais (triphenylphosphine) palladium (0) into the reaction flask. The mixture was stirred in an oil bath with vigorous stirring heated to boiling for 12 hours at 150 ° C. The copoly (m-phenylene) precipitates out. With each monomer ratio, the reaction mixture shows a characteristic color when the boiling point is reached, which changes over time to the color of the polymer. depending on the monomer cold used, a characteristic color and a characteristic consistency. In the range between 70 and 80% meta-monomer they are granular, otherwise they are fine powders. The characteristic colors during the reaction and the colors and consistencies of the copoly (m -phenylene) s are shown in the table below. Polymer color during the color and consistency of the reaction of the product

PPP ¹ light yellow light yellow powder

PMPP 25/75 ² dark yellow ivory powder PMPP 35/65 ² light brown white powder PMPP 50/50 ² brown violet white powder PMPP 60/40 ² brown white powder PMPP 65/35 ² light brown white powder PMPP 70/30 ² red brown light gray grains PMPP 80 / 20 ² gray-gray grains PMP ³ white-white powder

¹ Poly (p-phenylene): Synthesized from 100% para-monomer and

0% meta monomer

² Poly (m-phenylene-co-p-phenylene) m / n: synthesized from m% meta-monomer and n% para-monomer

³ Poly (m-phenylene): Synthesized from 100% meta-monomer and 0% para-monomer

For working up, the reaction mixture is poured into about 11 methanol after cooling and acidified with 6N hydrochloric acid while stirring. If the evolution of carbon dioxide does not begin immediately, water is added in portions of 50 ml until a brisk reaction begins. After the evolution of gas has subsided, the mixture is cooled to 0 ° C. for about 24 hours. The polymer collects on the bottom and is finally sucked off. The unsubstituted copoly (m-phenylene) s are insoluble in normal organic solvents. The cleaning can therefore only be done by washing. To do this, the polymer is mixed with large amounts of water and ethanol washed. Ethanol also serves as a mediator since the polymer is not wetted by water at all. Finally, it is dried in a vacuum at 70 ° C. for 12 hours. The yields are typically 90%.

The formation of copolymers, with the aid of FT-IR spectroscopy (KBr compacts) and ^{l 3} C-solid state NMR spectroscopy are shown. The FT-IR spectra of various poly (m-phenylene-co-p-phenylene) s (nomenclature see table above) are shown in the range from 2000 cm ^-1 to 600 cm ^{* 1} in FIG. 2, exemplary ¹³ C. Solid-state NMR spectra are shown in Fig. 3. The spectra show, depending on the monomer ratio used, continuous changes and document the presence of copolymers.

Measure 2: sulfonation of an unsubstituted copoly (m-phenylene) s

a) Preparation of the solvent

To remove the ethanol contained therein, 100 ml of chloroform are mixed with 5 ml of chlorosulfonic acid and the chloroform is then distilled off via a small Vigreux column. The chloroform, which is saturated with hydrogen chloride and fumes in the air, is used for sulfonation.

b) sulfonation of the copoly (m-phenylene) s

500 mg of an unsubstituted copoly (m-ρhenylene) s acc. Structure (1) (R1-R8 = H), which consists of 65% meta and 35% para-monomer is synthesized and, according to the findings from FT-IR spectroscopy, contains 58% meta repeat units, are suspended in 40 ml of the chloroform prepared according to 2a). A solution of 0.25 ml of chlorosulfonic acid in 20 ml of chloroform is quickly added through a dropping funnel with vigorous stirring. After the addition, the reaction time was measured. In the course of the sulfonation, the initially finely divided polymer aggregates somewhat. After 30 seconds, the reaction is stopped with 40 ml of methanol, the color changing from brown to light green. The polymer is centrifuged off and washed once with methanol and twice with ether and finally dried in vacuo.

The yield is 320 mg of hygroscopic, sulfonated material which is soluble in dipolar aprotic solvents such as N, N-dimethylformamide or dimethyl sulfoxide with heating. It is light yellow.

The degree of sulfonation is calculated from the elementary analysis (C, H, S). This is the sum formula for the sulfonated material

C ₆ HA- _X (SOΓ H ₃ 0 ⁺ ) _X * y H ₂ 0

to take as a basis. FT-IR spectroscopy provides information on S0 ₃ groups and H ₂ 0. For the calculation, an infinite degree of polymerization and a homogeneous distribution of the sulfonic acid groups was assumed. The end groups are negligible. x is the degree of sulfonation, ie the average number of sulfonic acid groups per repeating unit. By y additional water that is drawn from the air by the hygroscopic material is detected. The molasses of a formula unit is (or not equal to):

M _FE = 76.10 + 98.08x + 18.02y

The carbon content x _c (percentage by weight) provided by the elementary analysis is calculated as:

Xc = 72.06 / (76.10 + 98.08x + 18.02y) (1)

the following applies accordingly to the sulfur content xs (percentage by weight) provided by the elementary analysis:

Xs = 32.06x / (76.10 + 98.08x + 18.02y) (2)

With the help of gin. (1) and (2) can now be calculated from the measured values xc and xs

calculate unknown values x and y.

The following result:

y = (4 / x _c ) - 12.24 * (xs / xc) - 4.225

x = (0.7347 / xc) - 0.1837y - 0.7759

In addition, the elementary analysis also provides the hydrogen content X _H (weight fraction). This is used to check the calculated values x and y. The hydrogen content is calculated from x and y and with the actually measured value was compared. It applies to XH:

x _H = (4- x + 3x + 2y) * 1.01 / MFE

= (2 + x + y) / (37.67 + 48.55x + 8.921y)

The following table contains the values for some sulfonation tests, which are mainly carried out with the same reaction times:

Reaction- XC (Z) XS (Z) sulfonia- y XH, expected XH, measured time, (segregation rate) (Z) (Z) x (Z)

20 71.80 6.13 19.21 0.3010 5.02 4.93

30 68.11 8.01 26.45 0.2084 4.72 4.91

35 67.91 8.27 27.39 0.1746 4.66 4.88

3rd measure: Conversion of a sulfonated copoly (m-phenylene) into the Na ⁺ form

A sample of a copoly (m-phenylene) according to Example 2b) which has been sulfonated with a reaction time of 30 seconds (degree of sulfonation 26.45%) is to be stirred for about 7 days with an excess of 0.1N sodium hydroxide solution. It is then filtered off and washed until neutral with distilled water, then with methanol and diethyl ether and then dried in vacuo. The material loses its light yellow color and changes to a gray powder. Based on the empirical formula C ₆ H ₄ . _X (S0 ₃ Na) _x * y H ₂ 0

the values for x and y are calculated from the elementary analysis as in Example 2b). The following result:

y = (4 / x _c ) - 12.7324 * (x _s / x _c ) - 4.223

x = (0.7062 / xc) - 0.1766y - 0.7458

the following also applies to X _H :

x _H = (4- x + 2y) / (75.35 + 101.03x + 17.84y)

measured values: Xc = 66.91%, xs = 6.27%, XH = 4.56%

from this follows: x = 21.03%, y = 0.5623, XH, _e r _w a _r te t = 4.61%

In view of the rather coarse process, the degrees of sulfonation before and after the treatment with sodium hydroxide solution show very good agreement.

4th measure: Production of an electrolyte membrane from a sulfonated copoly (m-phenylene)

400 mg of the copoly (m-phenylene) s sulfonated according to Example 2 with a degree of sulfonation of 26.5% are mixed with 4.5 ml of N, N-dimethylformamide to a paste. With stirring the mixture is heated in a heating bath at 150 ° C until a clear, yellow solution is formed. This is to be placed in a petri dish. The solvent is first evaporated off at 80 ° C. for 2 hours and then at room temperature for 12 hours on an exactly horizontal surface. The resulting film is detached from the base by placing the Petri dish in distilled water, creating a swollen membrane, the thickness of which is approximately 72 μm.

5. Measure: Measurement of the conductivity of the polymer electrolyte membrane according to measure 4

An electrolyte membrane produced according to measure 4 is first equilibrated in IN sulfuric acid for 24 hours. The measurement is carried out in 1 N sulfuric acid in an apparatus consisting of two half cells with platinum electrodes separated by the membrane. Measurements are made with an alternating current with a frequency of 1 kHz. First the resistance is measured several times without a membrane and then several times with a membrane and the two mean values are formed. The installation resistance RMembrane of the membrane is then calculated by forming the difference Rmit - Rohne.

In general, the resistance of the membrane is calculated

RM e m b r a n raw d / A

with raw = specific resistance d = membrane thickness A = cross-sectional area of the measuring cell ======> _rθ h = R _M. _{nb r} . _n * A / d

measured values: RM, _n brarι - 0.09 Ω; d = 72 µm; A = 0.95 cm ²

=> raw = 12.5 Ωcm.

A comparison measurement with Nafion 117 provides a specific resistance of 8.5 Ωcm.

6. Measure: Examination of the swelling behavior of a polymer electrolyte membrane produced according to Example 4 in water:

A piece of a membrane produced according to measure 4 is dried in a vacuum drying oven at 110 ° C. and 300 hPa for 30 minutes. The mass is 33.3 mg. The membrane is then swollen in water for 30 minutes at room temperature. For re-weighing, the membrane is briefly freed of adhering water after removal from the water bath with a filter paper and quickly weighed. It then swells at 80 ° C for 20 minutes and then at 90 ° C for 30 minutes. Finally, it is dried again at 110 ° C and 300 hPa for 30 min. Then the mass is again 33.3 mg. The specific values can be found in the following table. The water absorption is calculated in% of the dry weight. Temperature mass water absorption water absorption

(° C) (mg) (mg) (*)

Room temp. 43.0 9.7 29.1

80 44.7 11.4 34.2

90 46 12.7 38.1

It is remarkable that the membrane shows no noticeable loss of its mechanical stability even in boiling water.

L i t e r a t u r u b e r s i c h t

(1) Claesson, S .; Gehm, r .; Kern, W. Makromol Chem.

1951, 7, 46.

(2) Wirth, H. 0 .; Müller, R .; Kern, W, Makromol.

Chem. 1963, 77, 90.

(3) Land, H.T .; Hatke, W.; Greiner, A.; Schmidt,

H, W .; Heitz, W. Makromol. Chem. 1990, 191, 2005.

(4) Noll, A.; Siegfried, N .; Heitz, W. Makromol.

Chem., Rapid Commun. 1990, 11, 485.

(5) Heitz, W .; Ullrich, R. Makromol. Chem. 1966, 98, 29

(6) Rau, I. U. Rehahn, M. Polymer Comm. 1993, 34,

2889.

(7) Rau, I. U. Rehahn, M. Makromol. Chem. 1993, 194, 2225.

(8) Rehahn, M. Schlueter, A. D .; Wegner, G. Makromol Chem. 1990 191, 1991.

(9) Rehahn, M. Schlueter, A. D .; Wegner, G. Polymer

1989, 30, 1060.

(10) Rehahn, M.; Schlueter, A. D .; Wegner, G. Polymer

1989, 30, 1054.

(H) Yamamoto, T .; Hayashi, Y .; Yamamoto, A. Bull.

Chem. Soc. Yep 1978, 51 (7), 2091.

Claims

Patent claims

1. Solid polymer electrolyte with a backbone which is at least partially functionalized by ionic groups, characterized in that the backbone of the polymer has a copoly (m-phenylene) which contains at least 20 mol% m-phenylene units and of the structure below is:

where Rl to R8 are hydrogen, aryl, oxyaryl, thioaryl,

2. Solid polymer electrolyte according to claim 1, characterized in that the dissociable groups are sulfonyl, carboxyl or phosphoryl.

3. Solid polymer electrolyte according to claim 1 or 2, characterized in that that m + n corresponds to the degree of polymerization and is at least 15.

4. Polymeric solid electrolyte according to one of claims 1 to 3, characterized in that the structure of the copoly (m-phenylene) corresponds to a statistical, alternating or segmented order.

5. Polymeric solid electrolyte according to one of claims 1 to 4, characterized in that the substituents R2 / R3 or R3 / R4 and / or R5 / R6 or

R7 / R8 are fused arylene rings.

6. Polymeric solid electrolyte according to one of claims 1 to 5, characterized in that at least one of the 8 substituents R 1 to R 8

Is hydrogen.

7. Solid polymer electrolyte according to one of claims 1 to 6, characterized in that the polymer backbone is a terpolymer.

8. Solid polymer electrolyte according to one of claims 1 to 7, characterized in that the polymer contains mixed sulfonic acid and carboxylic acid functionalities.

9. Solid polymer electrolyte according to one of claims 1 to 8, characterized in that the copoly (m-phenyl) is synthesized from 65% 3-bromophenylboronic acid and 35% 4-bromophenylboronic acid.

10. Solid polymer electrolyte according to one of claims 1 to 9, characterized in that the backbone of the polymer is hydrophobic.

11. A method for producing a polymeric solid electrolyte according to the preamble of claim 1, characterized in that the polymer is a copoly (m-phenylene), which is sulfonated with the addition of a sulfonating agent, that the sulfonated copoly (m-phenylene) in is dissolved in an organic solvent and applied to a support on which the solvent is evaporated, that the film remaining on the support is detached and swollen with the addition of water.

12. The method according to claim 11, characterized in that a dipolar aprotic solvent is used as the organic solvent, for example. N, N-dimethylformamide or dimethyl sulfoxide.

13. The method according to claim 11 or 12, characterized in that the sulfonating agent chlorosulfonic acid, oleum, concentrated sulfuric acid, a mixture of Sulfuric acid and thionyl chloride or sulfur trioxide is used.

14. Use of the polymeric solid electrolyte according to one of claims 1 to 9 as a polymer electrolyte membrane in fuel or in electrolyte cells.