WO1997011099A9

WO1997011099A9 - Functionalized copoly(m-phenylene)-based solid polymer electrolytes

Info

Publication number: WO1997011099A9
Application number: PCT/DE1996/001599
Authority: WO
Filing date: 1996-08-28
Publication date: 1997-05-01

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

1099 PC17DE96 / 01599

Polymeric solid-state electrolytes based on functionalized copoly (m-phenylene) s

Description

Technical area

The invention relates to a polymer Fest¬ body electrolyte with a hydrophobic backbone, which is at least partially functionalized by ionic groups.

State of the art

Polymeric solid electrolytes (polymer electrolytes) are ion-exchanging membranes consisting of polymers with ionic groups. They have high ionic conductivity and, in contrast to liquid systems, mechanical stability. They come in ver¬ different applications, such. As ion exchangers, (water) electrolyzers, batteries or Brennstoffzel¬ len used. The invention relates to polymer electrolyte, which are mainly used in fuel cells and electrolysers.

Disadvantages of liquid electrolytes, such as their corrosiveness, the need for recirculation 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 polymer electrolytes. From these For reasons, polymer electrolytes allow a simplified, compact design 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 also in the range of 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 available only with well-defined parameters (thickness, ion exchange capacity) and are not thermoplastic or processable from solutions. Furthermore, the high production costs negatively impact.

Therefore, other materials have been studied as alternatives to Nafion. An overview can be found in an article by A.E. Steck, "Proceedings of the First International Symposium on 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) are disclosed in US 3,259,592, US 3,484,293 or US 3,528,858. Moreover, membrane materials are based on aromatic Polyether ketones known from EP 0 575 807 A1 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 usually show inadequate ionic conductivity, thermal or long-term stability or require a complex production process.

The sulfonated poly (p-phenylene) backbone polymers described by WO 94/24717, due to their rigid structure and high degree of crystallinity, must have solubilizing side chains to be processed.

However, this requires elaborate reaction steps to introduce these side chains into the starting monomers. Furthermore, the side chains in the sulfonation are sometimes not stable and must be extra ge protects. In addition, they reduce the chemical and thermal stability of the product materials.

The properties of the polymeric 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 ionically dissociable functional groups. The charges generated in the presence of water and the hydrophobic backbone result in phase separation into ion-rich and ion-depleted regions. There are water-filled, proton-conductive channels. The aggregated ions act as physical crosslinking sites for the polymer molecules. To this The result is 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 ability to use Nafion at high temperatures is probably due to this. In contrast, the alternative materials mostly have heteroatoms in the backbone, i. H. Polarities, which at high Te¬ temperature by water attack lead to the degradation of the network, which manifests itself in softening.

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

US 3,376,235 describes a linear, sulfonated poly (p-phenylene) having 1 to 2 sulfonic acid groups per 10 phenylene rings. Unsubstituted poly (p-phenylene) (PPP) is due to the rigid structure ("rigid rod") hoch¬ crystalline, infusible and extremely insoluble. It is chemically and thermally very stable, but due to the properties mentioned hardly processable. The sulfonation according to US Pat. No. 3,376,235 consequently requires very drastic conditions (oleum, reaction time of 1 to 50 hours at 25 to 200 ° C.). The products obtained are dark brown, still insoluble sulfonated materials. Due to the insolubility, however, no membranes can be produced from it. Moreover, condensation reactions in the synthesis of PPP come to a standstill at the stage of oligomers of from 6 to 10 phenylene units due to the precipitation of the polymer associated with the insolubility. Since the 1950s, the common concept for the solublization of PPP has been known. The introduction of substituents leads to a greatly improved solubility of the substituted poly (p-phenylene) s because of the associated disruption of the crystal structure and improved interaction with the solvent. Extensive investigations were conducted, for. B. employed by Kern, Heitz and Rehahn (see the literators 1 to 10).

Based on such PPP solubilized with substituents, polymer electrolytes are described in WO 94/24717.

It is known from WO 94/24717 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 complicated monomer syntheses and the unsubstituted polyphenylenes unsubstituted significantly reduced thermal stability, especially in the presence of alkyl chains in the molecule. The sulfonation of the rigid-rod polyphenylenes according to WO 94/24717 also requires reaction times in the range of hours. The side chains can also decompose uncontrollably in the sulfonation and z. T. be protected from sulfonation. The material shows a specific resistance of at least about 50 Ω cm ^-1 . This value is about a factor of 6-10 higher than Nafion. Presentation of the invention

It is an object of the invention to improve polymeric solid electrolyte 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 preparation. In addition, the materials should 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 production process can be shortened and thus cheapened. The polymer to be further developed should be suitable in particular for use as an electrolyte membrane in electrolysis devices or in fuel cells.

The solution of the problem underlying the invention is specified in claims 1, 10 and 13. The invention advantageously further developing features are contained in the subclaims.

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

where R 1 to R 8 are hydrogen, aryl, oxyaryl, thioaryl,

Sulfonaryl, carbonylaryl, oxyaryloxyaryl, hydroxyl or ionically dissociable groups.

The invention is based on the surprising finding that incorporation of m-phenylene units in PPP gives a soluble and meltable poly (m-phenylene-co-p-phenylene) despite the absence of solubilizing side chains.

The disturbance of the crystal structure required for the 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 still be converted by sulfonation in polymer electrolytes.

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

The polymeric solid electrolytes of this invention are copoly (m-phenylene) s of structure (1) having at least 20 mole percent m-phenylene units. Preferably, a degree of functionalization with ionically dissociable groups greater than 0 and less than 1 is to be selected. This degree of functionalization is intended to mean the average number of ionic groups per repeat unit. In this case, the ionic groups can be randomly distributed over the polymer or preferably bound to specific repeat units.

The copoly (m-phenylene) s may be random, alternating, segmented or of a different order. Advantageously, statistically structured copoly (m-phenylene) s are suitable for use as polymer electrolytes. Furthermore, a method is described below which makes it possible for the first time to synthesize such structured colpoly (m-phenylene) s in a statistical arrangement.

The substituents R 1 to R 8 may be hydrogen, aryl, oxyaryl, thioaryl, sulfonaryl, carbonylaryl, Oxyaryloxyaryl, hydroxyl or ionically dissociable groups.

Preferred ionically dissociable groups are, in particular, sulfonyl (-SO 3 H), carboxyl (-COH) or phosphoryl (-PO (OH) 2).

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

The polymer electrolytes of the present invention generally have a copoly (m-phenylene) backbone with similar hydrophobicity, such as the poly (tetrafluoroethylene) backbone of Nafion.

It has surprisingly been found that it is also possible to convert unsubstituted copoly (m-phenylene) s and poly (m-phenylene) into polymer electrolytes by functionalization with ionic groups. The need for solubilizing side chains not necessarily given in this class of polymers greatly simplifies the synthesis.

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

As a prerequisite for the solid-state electrolyte preparation according to the invention, moreover, a sulfonation process using chlorosulfonic acid has been developed for the treatment of copoly (m-phenylene) s, which can be carried out at room temperature with low equipment and material complexity and short reaction times. The invention also includes a method of preparing membranes of functionalized copoly (m-phenylene) s.

The synthesis of copoly (m-phenylene) s can in principle be done in two ways. On the one hand, a copoly (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 contained in the monomers during the polymerization. The synthesis of copoly (m-phenylene) s can be carried out by a regioselective or at least predominantly regioselective coupling of bifunctional aromatics according to one of the following principles:

Structure (I)

w

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 the case of redox-neutral processes, the substituent X is more electronegative and the substituent Y is less electronegative than carbon or vice versa. The reaction proceeds transition metal-catalyzed to form the salt XY. Processes are described, inter alia, by T. Yamamoto et al. (see reference 11) (X = MgBr, Y = CI, Br) or by M. Rehahn et al. (Literature digits 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), however, these known processes have only insufficient regioselectivity and are less suitable for the targeted synthesis of copoly (m-phenylene) s.

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

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

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

While solubilizing side chains by degradation, the thermal stability of the polymers known to limit to about 350 ° C (nitrogen atmosphere), the unsubstituted copoly (m-phenylene) showed a thermal stability up to about 550 ° C (Stickstoffatmos¬ phäre) and thus provide extremely thermally stable materials represents.

Particularly noteworthy is a Coply (m-phenylene) which is synthesized from 65% 3-Bromophenylboronsäure and 35% 4- Bromphenylboronsäure. It is surprisingly soluble in nonpolar solvents such as paraffins at about 180 ° C and has a melting point of 210 ° C. In this way, for the first time, an unsubstituted, fusible and soluble polyphenylene can be obtained.

If ionically dissociable groups are not already present in the monomers, they may 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 which are suitable for the respective copoly (m-phenylene) can be determined by test series with progressively harder conditions.

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

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

According to the invention, a process for producing a polymeric solid electrolyte is specified such that the polymer is a copoly (m-phenylene) having the above ge called structure (I), which is sulfonated with the addition of a sulfonating agent. After completion of the sulfonation, the sulfonated copoly (m-phenylene) is dissolved in an organic solvent. Subsequently, the solution is applied to a support on which the solvent is evaporated off. With the addition of water, the film remaining on the support is then peeled off and swelled.

The copoly (m-phenylene) s of the abovementioned structure can preferably be sulfonated very rapidly with the aid of chlorosulfonic acid in chloroform. For this purpose, the ethanol present in chloroform as a stabilizer is first with an excess of Chlorosulfonic reacted and distilled the chloroform abde¬. For the sake of simplicity, the chloroform obtained in the distillation, which fumes in the air 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. There are reaction times in the range of seconds.

After the required time, the reaction is stopped by quenching with methanol. After working up, sulfonated copoly (m-phenylene) s are obtained in dipolar aprotic solvents such as N, N-dimethylformamide or dimethyl sulfoxide under heating with heat.

Sulfonated under harder conditions, eg. B. by several hours exposure to undiluted chlorosulfonic acid, we obtain a crosslinked via S0 ₂ bridges thermoset, which is insoluble. The networking takes place according to the following mechanism:

Ar-H + C1S0 ₃ H> Ar-S0 ₃ H + HCl (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 '+ HCl (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, the aromatic sulfonic acid is the compound Ar-S0 ₂ Cl, which is considered to be aryl-substituted chlorosulfonic acid leaves, in equilibrium (equation (2)).

Similar to chlorosulfonic acid, the aryl-substituted chlorosulfonic acid should itself be capable of sulfonating again and of reacting with another aromatic ring to form an S0 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 cross-linking of a copoly (m-phenylene) s could be demonstrated by FT-IR spectra.

Brief description of the drawings

The figures below show the characteristic spectra of the copoly (m-phenylene) s underlying the solid-state electrolytes. Show it:

1 a, b, c FT-IR spectra of various copoly (m-phenylene) s prepared 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 ^{l 3} C solid-state NMR spectra of copoly (m-phenylene-co-p-phenylene) s.

Representation of embodiments

1 shows the FT-IR spectra of the non-sulfonated copoly (m-phenylene) s (see FIG. 1 a), which can be prepared by means of the measure lb described below. Fig. Lb shows the sulfonated with the measure 2 Copoly (m-phenylene) s and Figure lc over night with pure chlorosulfonic extremely strongly sulfonated copoly (m-phenylene) s, depending on the wavenumber in the range of 2000 cm-1 to 600 cm-1 (KBr-compacts).

In moderate sulfonation (FIG. 1b), in addition to characteristic bands 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 ¹ visible. The band at 1054.3 cm ^{-1 is} due to the phenyl-sulfur stretching vibration, the other three are attributed to three characteristic oscillations of the S0 ₃ - groups. Furthermore, one sees a band at 1638.5 cm ^-1 , which is caused by the flat deformation vibration of water. The sulfonated sample was equilibrated in air such that the sulfonic acid functionalities were present as Ar-S0 ₃ H ₃ O +. The spectrum demonstrates the sulfonation of the copoly (m-phenylene) s according to equation (1). In the spectrum (see FIG. 1c) of the strongly sulfonated sample, one can see two strong bands at 1302.4 er ¹ and 1167.8 cm ^-1 . They correspond to the symmetric and the asymmetric vibration of the crosslinking S0 ₂ groups, which have arisen according to equation (3). The degree of sulfonation can be calculated from elemental analyzes (C, H, S determination).

The electrolyte membrane is produced according to the invention by dissolving the copoly (m-phenylene) s functionalized by ionic groups in an organic solvent, preferably a dipolar aprotic solvent, applying to a glass substrate and slowly evaporating the solvent. The resulting film is subsequently peeled off in water from the base, wherein a swollen membrane is formed.

For the preparation of an inventive

Solid electrolyte membrane are preferably to take the following measures:

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

a) Preparation of the monomers 3-bromophenylboronic acid and 4-bromophenylenboronic acid from 1,3-dibromobenzene or 1,4-dibromobenzene

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

At room temperature, the solution is stirred for about 8 hours and treated with 200 ml of 1 N hydrochloric acid. This is cleared with vigorous stirring the initially cloudy organic phase and there is a viscous aqueous and a supernatant clear organic phase. Thereafter, the organic phase can be easily decanted. By rinsing with ether and decanting, residues of the product are to be removed from the flask. The combined organic phases are extracted with a total of 500 ml of 2N sodium hydroxide in portions of 200, 100, 100, 100 ml. The boronic acid passes as boronate into the sodium hydroxide solution. The sodium hydroxide solution is again to be washed with 150 ml of diethyl ether. Then cool the solution to 0 ° C, adding 6N hydrochloric acid to a pH of 2 with further cooling.

The boronic acid precipitates in crystalline form and can be sucked off after standing. After drying in vacuo, 20 g (78% of theory) of crude product.

Before use for the polymerization, the boronic acids are to be purified by recrystallization. For this they are dissolved in as little as possible diethyl ether and precipitated by addition of pentane and cooling to -78 ° C. After drying in vacuo, 14.5 g (57%) of pure 3-bromophenylboronic acid or 15 g (59%) of pure 4-bromophenylboronic acid remain.

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

4-bromophenylboronic acid (4-Br-CβH ₄ -B (0H) ₂ ): δ = 7,3 ppm (s, 2H), 7,6ρpm (d, 2H), 7, 9 ppm (d, 2H)

3-Bromophenylboronic acid (3-Br-CβH ₄ -B (OH) ₂ ): δ = 7.35 ppm (t, 1H), 7.4 ppm (s, 2H), 7.6 ppm (d, 1H), 7, 85pρm (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 dissolved in 250 ml of 1.5 M aqueous sodium carbonate solution in an 11-necked three-necked flask with gas inlet, KPG stirrer and reflux condenser, and the solution is evacuated several times and purged with nitrogen to degas.

In an inert gas atmosphere, a total of 300 ml of toluene were added. A portion of the toluene was used, the catalyst, 160 mg (1.38 * 10 ^-4 mol) Te¬ tetrakis (triphenylphosphine) to transfer action piston palladium (0) in the Re¬. With vigorous stirring, the mixture was heated to boiling in an oil bath of 150 ° C for 12 hours. The copoly (m-phenylene) precipitates out. At each monomer ratio, when the boiling point is reached, the reaction mixture shows a characteristic color, which later changes to the color of the polymer. Depending on the monomer mixture used, the polymers have 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 copoly (m-phenylene) s are shown in the following table. Polymer color during 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 reddish 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 workup, the reaction mixture is poured into Er¬ cold in about 11 methanol and acidified with 6N hydrochloric acid with stirring. If the carbon dioxide evolution does not start immediately, water is added in portions of 50 ml until a vigorous reaction begins. After the evolution of gas has subsided, the mixture is cooled to 0 ° C. for approximately 24 hours. The polymer collects at 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. For this, the polymer is filled with large amounts of water and ethanol washed. At the same time, ethanol serves as a middle charge since the polymer is not wetted by water at all. Finally, it is dried in vacuo at 70 ° C for 12 hours. The yields are typically 90%.

The formation of copolymers can be demonstrated by FT-IR spectroscopy (KBr compacts) and ^{1 3} C solid-state NMR spectroscopy. The FT-IR spectra of different poly (m-phenylene-co-p-phenylene) s (nomenclature, see the table above) are shown in the range from 2000 cπr 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.

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

a) Preparation of the solvent

100 ml of chloroform are added to remove ent¬ contained ethanol with 5 ml of chlorosulfonic acid and the chloroform is then distilled off through a small Vigreux column. For sulfonation, saturated with hydrogen chloride, used in the air chloroform.

b) Sulfonation of copoly (m-phenylene) s

500 mg of an unsubstituted copoly (m-phenylene) gem. Structure (1) (R1-R8 = H), which consists of 65% meta- and 35% Para-monomer is synthesized and according to the findings from the FT-IR spectroscopy contains 58% meta-repeat units are suspended in 40 ml of the prepared according to 2a) chloroform. Through a dropping funnel, a solution of 0.25 ml of chlorosulfonic acid in 20 ml of chloroform is added rapidly with vigorous stirring. After the addition, the reaction time has been measured. In the course of the sulfonation, the initially finely divided polymer gathers slightly. After 30 seconds, the reaction is stopped with 40 ml of methanol, turning the color 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 elemental analysis (C, H, S). This is the empirical formula for the sulfonated material

C ₆ H ₄ -x (SO ₃ H ₃ O ⁺ ) _X * y H ₂ O

taken as a basis. The FT-IR spectroscopy gives the indication of S0 ₃ groups and H ₂ 0. For the calculation, an infinite degree of polymerization and a homogeneous distribution of the sulfonic acid groups has been assumed. The end groups are negligible in each case. x is the degree of sulfonation, ie the average number of sulfonic acid groups per repeat unit. By y additional water attracted to the hygroscopic material from the air is detected. The molecular weight of a formula unit is (o.w. d. M.):

M _FE = 76.10 + 98.08x + 18.02 yards

The carbon content x _c (weight fraction), which the elemental analysis provides, is calculated as:

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

correspondingly applies to the sulfur content xs (weight fraction), which provides the elemental analysis:

Xs = 32.06x / (76.10 + 98.08x + 18.02 yards) (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.

It follows:

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

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

In addition, the elemental analysis still provides the hydrogen content X _H (wt.). This is used to check the calculated values x and y. From x and y the hydrogen content is calculated and with compared to the actually measured value. It applies to X _H :

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 a few sulfonation experiments, which are carried out predominantly at the same reaction times:

Reaction x _c (Z) xs (Z) Sulphonie y XH, expects XB, g «..>. Tn time, (see) degree (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 0.1 N sodium hydroxide solution. It is then filtered off and washed to neutrality with distilled water, then with methanol and diethyl ether and then dried in vacuo. The material loses its light yellow color and turns into a gray powder. Based on the molecular formula C ₆ H ₄ . _X (S0 ₃ Na) _x * y H ₂ 0

As in Example 2b), the values for x and y are calculated from the elemental analysis. It follows:

y = (4 / x _c) - 12.7324 * (x _s / x c) - 4,223

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

furthermore, for X _H :

x _H = (4- x + 2y) / (75,35 + 101,03x + 17,84y)

measured values: xc = 66.91%, xs = 6.27%, x _H = 4.56%

hence: x = 21.03%, y = 0.5623, X _H , expect t = 4.61%

In view of the rather crude procedure, the degrees of sulphonation before and after treatment with caustic soda show a fairly good agreement.

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

400 mg of the sulfonated according to Example 2 copoly (m-phenylene) s with 26.5% degree of sulfonation are stirred with 4.5 ml of N, N-dimethylformamide to a pulp. While stirring The mixture is heated in a heating bath of 150 ° C until a clear, yellow solution is formed. This is to be brought into a Petri dish. On an exactly horizontal surface, the solvent is first evaporated for 2 hours at 80 ° C and then for 12 hours at room temperature. The resulting film is peeled off by placing the Petri dish in distilled water from the pad, creating a swollen membrane whose thickness is about 72 microns.

5th measure: Measurement of the conductivity of the Polymerelek¬ trolyt membrane according to measure 4

An electrolyte membrane prepared 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 separated by the membrane with platinum electrodes. It is measured with alternating current of frequency 1 kHz. First, the resistance is measured several times without membrane and then several times with membrane and the two mean values are formed. By calculating the difference Rmit - Rohne, the insertion resistance RH.-bi.o of the membrane is calculated.

In general, the resistance of the membrane is calculated

with raw = specific resistance d = membrane thickness A = cross-sectional area of the measuring cell ======> _r0 h = R _M emb ran * A / d

measured values: RMembrar. = 0.09 Ω; d = 72 μm; A = 0.95 cm ²

^: > raw = 12.5 Ωcm.

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

6th measure: Examination of the swelling behavior of a polymer electrolyte membrane prepared in Example 4 in water:

A piece of a membrane prepared according to measure 4 is dried in a vacuum drying oven for 30 min at 110 ° C and 30O hPa. The mass is 33.3mg. The membrane is then swollen ge in water at room temperature for 30 min. For reweighing the membrane is removed after removal from the water bath briefly with a filter paper of adhering water and weighed quickly. It then swells at 80 ° C for 20 minutes and then at 90 ° C for 30 minutes. Finally, it is again dried for 30 minutes at 110 ° C and 30O hPa. Thereafter, 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

Noteworthy is the fact that the membrane shows no significant loss of mechanical stability even in boiling water.

L i t e r a t e r i a n d i n t s

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

1951, 7, 46.

(2) Wirth, H. 0 .; Müller, R.; Core, W, macromol.

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.J. Rehahn, M. Polymer Comm. 1993, 34,

2889th

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

194, 2225.

(8) Rehahn, M.; Schlüter, A. D .; Wegner, G. Makromol.

Chem. 1990, 191, 1991.

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Claims

P at β ntanspr che che

A polymer solid electrolyte having a backbone at least partially functionalized by ionic groups, characterized in that the backbone of the polymer comprises a copoly (m-phenylene) containing at least 20 mole percent m-phenylene units and the structure shown below is:

where R 1 to R 8 are hydrogen, aryl, oxyaryl, thioaryl,

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

3. Polymeric solid electrolyte according to claim 1 or 2, characterized 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 random, alternating or segmented order.

5. Polymeric solid electrolyte according to one of claims 1 to 4, characterized in that the substituents R 2 / R 3 or R 3 / R 4 and / or R 5 / R 6 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 Rl to R8

Is hydrogen.

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

8. Polymeric solid electrolyte according to any one of An¬ claims 1 to 7, characterized in that the polymer contains mixed sulfonic acid and carboxylic acid functionalities.

9. Polymeric solid electrolyte according to one of claims 1 to 8, characterized in that the copoly (m-phenyl) s from 65% 3-Bromophenylboronsäure and 35% 4-Broπ.phenylboronsäure is synthesized.

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

11. A process for the preparation of a polymeric solid electrolyte according to the preamble of An¬ 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 is removed with the addition of water, the ver¬ on the carrier remaining film and swelled.

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