Proton-conducting membrane, method for their production and their use in electrochemical cells

Abstract

The present invention relates to a novel proton-conducting polymer membrane based on polyazole polymers which, owing to their outstanding chemical and thermal properties, can be used widely and are suitable in particular as polymer electrolyte membrane (PEM) for producing membrane electrode assemblies or so-called PEM fuel cells.

Claims

1. A proton-conducting polymer membrane based on polyazoles, prepared by a process consisting essentially the steps of A) mixing: one or more aromatic tetraamino compounds selected from the group consisting of 2,3,5,6-tetraaminopyridine, 3,3,4,4-tetraaminodiphenylsulfone, 3,3,4,4-tetraaminodiphenyl ether, 3,3,4,4-tetraaminobiphenyl, 1,2,4,5-tetraaminobenzene, 3,3,4,4-tetraaminobenzophenone, 3,3,4,4-tetraaminodiphenylmethane, 3,3,4,4-tetraaminodiphenyldimethyl-methane; and one or more aromatic carboxylic acids or esters thereof selected from the group consisting of pyridine-2,5-dicarboxylic acid, pyridine-3,5-dicarboxylic acid, pyridine-2,6-dicarboxylic acid, pyridine-2,4-dicarboxylic acid, 4-phenyl-2,5-pyridinedicarboxylic acid, 3,5-pyrazoledicarboxylic acid, 2,6-pyrimidinedicarboxylic acid, 2,5-pyrazinedicarboxylic acid, 2,4,6-pyridinetricarboxylic acid, benzimidazole-5,6-dicarboxylic acid, phthalic acid, isophthalic acid, terephthalic acid, 5-hydroxyisophthalic acid, 4-hydroxyisophthalic acid, 2-hydroxyterephthalic acid, 5-aminoisophthalic acid, 5-N,N-dimethylaminoisophthalic acid, 5-N,N-diethylaminoisophthalic 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, and 1,8-dihydroxynaphthalene-3,6-dicarboxylic acid, in polyphosphoric acid to form a solution and/or dispersion, B) heating the mixture from step A), and polymerizing until an intrinsic viscosity of at least 0.8 dl/g, to obtain polyazole polymer, C) forming a membrane using the polyazole polymer obtained in step B) on a carrier or on an electrode, D) optionally heating the membrane on the carrier or electrode, E) treating the membrane formed in step C) or D) in the presence of water or moisture, and F) removing the membrane from the carrier, wherein the total solid content of the polyazole polymer in the membrane is at least 10% by weight to 25% by weight and said total content includes any acids, and water being present, but excludes any optional additives, the membrane has a Youngs modulus of at least 4.5 MPa.

2. The membrane as claimed in claim 1, wherein the one or more aromatic carboxylic acids are pyridine-2,5-dicarboxylic acid, pyridine-3,5-dicarboxylic acid, pyridine-2,6-dicarboxylic acid, pyridine-2,4-dicarboxylic acid, 4-phenyl-2,5-pyridinedicarboxylic acid, 3,5-pyrazoledicarboxylic acid, 2,6-pyrimidinedicarboxylic acid, 2,5-pyrazinedicarboxylic acid, 2,4,6-pyridinetricarboxylic acid, or benzimidazole-5,6-dicarboxylic acid.

3. The membrane as claimed in claim 1, wherein the polyphosphoric acid is concentrated grades of phosphoric acid (H.sub.3PO.sub.4) above 95% in which the individual PO.sub.4 units are polymerized, and the polyphosphoric acids can be expressed by the formula H.sub.n+2+P.sub.nO.sub.3n+1, where n>1, and has a content calculated as P.sub.2O.sub.5 by acidimetry of at least 70% by weight.

4. The membrane as claimed in claim 3, wherein the polyphosphoric acid has a content calculated as P.sub.2O.sub.5 by acidimetry of not more than 86% by weight.

5. The membrane as claimed in claim 1, wherein the polymers based on polyazole being formed in step B) comprise repeat benzimidazole units of one or more of the formula below ##STR00006## ##STR00007## where n and m are each an integer greater than or equal to 10.

6. The membrane as claimed in claim 1, characterized in that the polyazole polymer being formed in step B) is a copolymer of meta-polybenzimidazole and para-polybenzimidazole.

7. The membrane as claimed in claim 1, wherein the membrane is formed on an electrode, and the treatment in step E) is such that the membrane formed is not self-supporting.

8. The membrane as claimed in claim 1, the membrane obtained in step C) having a thickness of 20 and 4000 m.

9. The membrane as claimed in claim 1, wherein the membrane formed by step E) has a thickness between 15 and 3000 m.

10. The membrane as claimed in claim 1, wherein the total solid content of polyazole polymer in the membrane is from 13.8% to 18.9% by weight, and the Youngs modulus is from 4.5 to 25.2 MPa.

11. The membrane of claim 1, wherein the one or more aromatic carboxylic acids includes phthalic acid, isophthalic acid, terephthalic acid, pyridine-2,5-dicarboxylic acid, pyridine-3,5-dicarboxylic acid, pyridine-2,6-dicarboxylic acid, pyridine-2,4-dicarboxylic acid, 4-phenyl-2,5-pyridinedicarboxylic acid, 3,5-pyrazoledicarboxylic acid, 2,6-pyrimidinedicarboxylic acid, 2,5-pyrazinedicarboxylic acid, 2,4,6-pyridinetricarboxylic acid, and any one ester of each dicarboxylic acid thereof.

12. A membrane-electrode unit comprising at least two electrodes and at least one membrane as claimed in claim 1.

13. A fuel cell comprising one or more membrane-electrode units as claimed in claim 12.

14. An electrode with a proton-conducting polymer coating based on polyazoles, prepared by a process comprising essentially the steps of A) mixing: (i) one or more aromatic tetraamino compounds selected from the group consisting of 2,3,5,6-tetraaminopyridine, 3,3,4,4-tetraaminodiphenylsulfone, 3,3,4,4-tetraaminodiphenyl ether, 3,3,4,4-tetraaminobiphenyl, 1,2,4,5-tetraaminobenzene, 3,3,4,4-tetraaminobenzophenone, 3,3,4,4-tetraaminodiphenylmethane, 3,3,4,4-tetraaminodiphenyldimethyl-methane; and (ii) one or more aromatic carboxylic acids or esters thereof selected from the group consisting of pyridine-2,5-dicarboxylic acid, pyridine-3,5-dicarboxylic acid, pyridine-2,6-dicarboxylic acid, pyridine-2,4-dicarboxylic acid, 4-phenyl-2,5-pyridinedicarboxylic acid, 3,5-pyrazoledicarboxylic acid, 2,6-pyrimidinedicarboxylic acid, 2,5-pyrazinedicarboxylic acid, 2,4,6-pyridinetricarboxylic acid, benzimidazole-5,6-dicarboxylic acid, phthalic acid, isophthalic acid, terephthalic acid, 5-hydroxyisophthalic acid, 4-hydroxyisophthalic acid, 2-hydroxyterephthalic acid, 5-aminoisophthalic acid, 5-N,N-dimethylaminoisophthalic acid, 5-N,N-diethylaminoisophthalic 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, 1,8-dihydroxynaphthalene-3,6-dicarboxylic acid, or (iii) one or more aromatic and/or heteroaromatic diaminocarboxylic acids, in polyphosphoric acid to form a solution and/or dispersion, B) heating the mixture from step A), and polymerizing until an intrinsic viscosity of at least 0.8 dl/g, to obtain a polyazole polymer, C) applying a layer using the polyazole polymer obtained in step B) on an electrode, D) optionally heating the layer on the electrode, and E) treating the layer formed in step C) or D) in the presence of water or moisture to form a membrane on the electrode, wherein the total content of all polyazole polymers in the membrane is at least 10% by weight to 25% by weight and said total content includes any acids, and water being present, but excludes any optional additives, the membrane has a Youngs modulus of at least 4.5 MPa.

15. The electrode as claimed in claim 14, the membrane after Step E) having a thickness between 2 and 3000 m.

16. The electrode of claim 14, wherein the polyphosphoric acid is a concentrated grade of phosphoric acid (H.sub.3PO.sub.4) above 95% in which the individual PO.sub.4 units are polymerized and the polyphosphoric acids can be expressed by the formula H.sub.n+2+P.sub.nO.sub.3n+1, where n>1, and polyphosphoric acid have a content of at least 70% by weight, but not more than 86% by weight, calculated as P.sub.2O.sub.5 (by acidimetry).

17. The electrode as claimed in claim 14, wherein the total solid content of polyazole polymer in the membrane is from 13.8% to 18.9% by weight, and the Youngs modulus is from 4.5 to 25.2 MPa.

18. The electrode as claimed in claim 14, wherein the one or more aromatic carboxylic acids is selected from the group consisting of pyridine-2,5-dicarboxylic acid, pyridine-3,5-dicarboxylic acid, pyridine-2,6-dicarboxylic acid, pyridine-2,4-dicarboxylic acid, 4-phenyl-2,5-pyridinedicarboxylic acid, 3,5-pyrazoledicarboxylic acid, 2,6-pyrimidinedicarboxylic acid, 2,5-pyrazinedicarboxylic acid, 2,4,6-pyridinetricarboxylic acid, and any one ester of each dicarboxylic acid thereof.

19. A membrane-electrode unit comprising at least one electrode as claimed in claim 14.

20. A proton-conducting polymer membrane based on polyazoles, prepared by a process consisting essentially the steps of A) mixing: one or more aromatic tetraamino compounds selected from the group consisting of 2,3,5,6-tetraaminopyridine, 3,3,4,4-tetraaminodiphenylsulfone, 3,3,4,4-tetraaminodiphenyl ether, 3,3,4,4-tetraaminobiphenyl, 1,2,4,5-tetraaminobenzene, 3,3,4,4-tetraaminobenzophenone, 3,3,4,4-tetraaminodiphenylmethane, 3,3,4,4-tetraaminodipheuldimethyl-methane; and one or more aromatic carboxylic acids selected from the group consisting of pyridine-2,5-dicarboxylic acid, pyridine-3,5-dicarboxylic acid, pyridine-2,6-dicarboxylic acid, pyridine-2,4-dicarboxylic acid, 5-hydroxyisophthalic acid, 4-hydroxyisophthalic acid, 2-hydroxyterephthalic 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, 1,8-dihydroxynaphthalene-3,6-dicarboxylic acid, diphenylsulfone-4,4-dicarboxylic acid, and any one ester of each dicarboxylic acid thereof, in polyphosphoric acid to form a solution and/or dispersion; B) heating the mixture from step A), and polymerizing until an intrinsic viscosity of at least 0.8 dl/g, to obtain polyazole polymer; C) forming a membrane using the polyazole polymer obtained in step B) on a carrier or on an electrode; D) optionally heating the membrane on the carrier or electrode; E) treating the membrane formed in step C) or D) in the presence of water or moisture; and F) removing the membrane from the carrier; wherein the total solid content of the polyazole polymer in the membrane is at least 10% by weight to 25% by weight and said total content includes any acids, and water being present, but excludes any optional additives, the membrane has a Youngs modulus of at least 4.5 MPa.

21. The polyazoles membrane of claim 20, wherein the total solid content of polyazole polymer in the membrane is from 13.8% to 18.9% by weight, and the Youngs modulus is from 4.5 to 25.2 MPa.

Description

EXAMPLES

(1) International patent application WO02/081547

Example 1

(2) 95 g para-PBI/PPA solution (BASF Fuel cell) was obtained in accordance with International patent application WO 02/081547, except that the monomer concentration was raised so that the final para-PBI/PPA solution had a concentration of 5.6 wt % of para-PBI). Such solution was pre-heated at 160 C. under dry nitrogen. 5 ml of 85% phosphoric acid was added dropwise to reduce the solution viscosity. Slight vacuum was applied to remove the bubbles from the system. The temperature was increased to 200 C. for 30 minutes, and then was cast using a 25 mil gap casting blade onto clear glass plates. The cast membrane was hydrolyzed at 25 C., 55% relative humidity (RH) for 24 hours.

Example 2

(3) 3.214 g tetraaminobiphenyl (TAB, 15 mmol) and 2.492 g terephthalic acid (TPA, 15 mmol) was added to 137 g polyphosphoric acid [PPA concentration 116%], mixed with overhead stirrer, purged with dry nitrogen. The mixture was heated at 150 C. for 3 hours, 170 C. for 3 hours, and then 195 C. for 12 hours. 5 ml of 85% phosphoric acid was added dropwise to reduce the solution viscosity. Temperature increased to 220 C. for half an hour before the casting.

(4) The polymer solution (having a total solids content of PBI of 3.26 wt %) was casted onto clear glass plates. The cast membrane was hydrolyzed in 65% phosphoric acid bath for 24 hours. This example corresponds to the membranes known from International patent application WO 02/081547.

(5) The mechanical properties of the membranes were measured by cutting dumb bell specimens (ASTM D683 Type V) from the bulk membrane using a cutting press. Tensile properties were measured using an Instron Tensile Tester (5543A) with a 10N load cell. All measurements were made at room temperature on samples preloaded to 0.1N with a crosshead speed of 5 mm per minute.

(6) TABLE-US-00001 Strain at Young's Thickness Max. Load Modulus Modulus sample (mm) (mm/mm) (MPa) (MPa) Example 1 0.43 2.334 4.904 1.562 Example 2 0.36 4.908 1.863 0.865

(7) The higher modulus means that higher resistance to flow/creep of the membranes is obtained.

Example 3

(8) 1. 2,5-Pyridine-r-Para-PBI

(9) To a three-necked flask equipped with nitrogen flow and overhead stirrer, a solution of 2,5-pyridinedicarboxylic acid (3.508 g, 2 equiv.), terephthalic acid (1.744 g, 1 equiv.), tetraaminobiphenyl (6.747 g, 3 equiv.), and polyphosphoric acid (88 g) was stirred and heated to 195 C. for 6 hours. Following completion of the polymerization process, the PBI solution was poured onto a glass plate and cast at a thickness of 15mil using a Gardner blade. To form a gel membrane, the glass plates with the cast films were immediately placed into a humidity controlled chamber at 55%5% relative humidity (RH), 252 C. Complete hydrolysis of the membrane occurred over a span of 24 h. The final gel membrane thickness was roughly 444 m.

(10) The composition of acid-doped PBI membranes was determined by measuring the relative amounts of polymer solids, water, and acid in the film. The phosphoric acid (PA) content was determined by titrating a sample of membrane with standardized sodium hydroxide solution (0.1 N) using a Metrohm 716 DMS Titrino autotitrator. The sample was washed with water and dried in a vacuum oven overnight at 120 C. The dried sample was then weighed to determine polymer solids content for the membrane. The amount of water was calculated by subtracting the weights of polymer and PA from the initial PBI membrane sample weight. The final composition of the membrane was 55.89 wt % phosphoric acid, 15.93 wt % polymer, and 28.17% water.

(11) The tensile properties of the membranes were tested at room temperature using an Instron Model 5543A system with a 10 N load cell and crosshead speed of 5 mm/min. Dog-bone shaped specimens were cut according to ASTM standard D683 (Type V specimens) and preloaded to 0.1 N prior to testing. The Young's Modulus of the resulting membrane was 25.17 MPa, and its tensile strain at break was 0.529 mm/mm.

(12) Ionic conductivities were measured via a four-probe through-plane bulk measurement using an AC Zahner IM6e impedance spectrometer that scanned a frequency range from 1 Hz to 100 KHz. A rectangular sample of membrane (3.5 cm7.0 cm) was placed in a glass cell with four platinum wire current collectors. Two outer electrodes set 6.0 cm apart supplied current to the cell, while the two inner electrodes 2.0 cm apart on opposite sides of the membrane measured the voltage drop. To ensure a through-plane bulk measurement of the membrane ionic conductivity, the two outer electrodes are placed on opposite sides of the membrane and the two inner electrodes are arranged in the same manner. The reported conductivities were of preconditioned (dehydrated) membranes that were held at >100 C. for at least two hours. Proton conductivity was calculated using the following equation:
=D/(L*B*R)

(13) Where D was the distance between the two test current electrodes, L was the thickness of the membrane, B was the width of the membrane, and R was the measured resistance. The resulting anhydrous proton conductivity of the membrane was 0.11 S/cm at 180 C.

(14) Membrane electrode assemblies consisted of the polymer membrane sandwiched between two electrodes. MEAs were prepared by hot pressing the acid-doped membrane between an anode electrode and a cathode electrode at 150 C. for 90-150 seconds using 4500 lbs of force and compressing to 80% its original width. Electrodes were received from BASF Fuel Cell, Inc. with 1.0 mg/cm.sup.2 platinum (Pt) catalyst loading. Anode electrodes contained only Pt as the catalyst, while the cathode electrodes contain a BASF Fuel Cell standard cathode Pt alloy. The active area of the electrodes was 45.15 cm.sup.2. Fuel cell fabrication was conducted by assembling the cell components as follows: end plate:anode current collector:anode flow field:MEA:cathode flow field:cathode current collector:end plate. Gaskets were used on either side of the MEA to control compression. Following assembly, the cell was evenly clamped to 50 in-lbs of pressure.

(15) Fuel cell performance was measured in 50 cm.sup.2 (active area 45.15 cm.sup.2) single stack fuel cells using test stations obtained from Plug Power or purchased from Fuel Cell Technologies. Polarization curves were obtained at various temperatures (120-180 C.) with hydrogen as a fuel and different oxidants (air or oxygen gas). Fuel cells were operated for at least 100 hours (break-in period) at 0.2 A/cm.sup.2 at 180 C. before measurement of polarization curves. Long term stability testing was performed under static current and temperature conditions of 0.2 A/cm.sup.2 and 180 C. with a constant flow rate of hydrogen and air. Following break-in, the MEA constructed from the 2:1 2,5-Pyridine-r-Para-PBI membrane exhibited a fuel cell performance of 0.65 V.

Example 4

(16) 2,5-Pyridine-r-Meta-PBI

(17) To a three-necked flask equipped with nitrogen flow and overhead stirrer, a solution of 2,5-pyridinedicarboxylic acid (0.527 g, 1 equiv.), isophthalic acid (4.715 g, 9 equiv.), tetraaminobiphenyl (6.758 g, 10 equiv.), and polyphosphoric acid (88 g) was stirred and heated to 195 C. for 9 hours. Following completion of the polymerization process, the PBI solution was poured onto a glass plate and cast at a thickness of 15 mil using a Gardner blade. To form a gel membrane, the glass plates with the cast films were immediately placed into a humidity controlled chamber at 55%5% relative humidity (RH), 252 C. Complete hydrolysis of the membrane occurred over a span of 24 h. The final gel membrane thickness was roughly 300 m. The final composition of the membrane was 52.75 wt % phosphoric acid, 18.90 wt % polymer, and 28.35 wt % water. The Young's Modulus of the membrane was 6.55 MPa, and its tensile strain at break was 3.235 mm/mm. The anhydrous proton conductivity of the membrane was 0.11 S/cm at 180 C., and following break-in, the MEA constructed from the 1:9 2,5-Pyridine-r-Meta-PBI membrane exhibited a fuel cell performance of 0.66 V.

Example 5

(18) 2,5-Pyridine-r-2OH-PBI

(19) To a three-necked flask equipped with nitrogen flow and overhead stirrer, a solution of 2,5-pyridinedicarboxylic acid (4.323 g, 5 equiv.), 2,5-dihydroxyterephthalic acid (1.025 g, 1 equiv.), tetraaminobiphenyl (6.652 g, 6 equiv.), and polyphosphoric acid (88 g) was stirred and heated to 195 C. for 6.5 hours. Following completion of the polymerization process, the PI31 solution was poured onto a glass plate and cast at a thickness of 15 mil using a Gardner blade. To form a gel membrane, the glass plates with the cast films were immediately placed into a humidity controlled chamber at 55%5% relative humidity (RH), 252 C. Complete hydrolysis of the membrane occurred over a span of 24 h. The final gel membrane thickness was roughly 509 m. The final composition of the membrane was 51.68 wt % phosphoric acid, 14.99 wt % polymer, and 33.33 wt % water. The Young's Modulus of the membrane was 12.70 MPa, and its tensile strain at break was 0.458 mm/mm. The proton conductivity of the membrane was 0.16 S/cm at 180 C., and following break-in, the MEA constructed from the 5:1 2,5-Pyridine-r-2OH-PBI membrane exhibited a fuel cell performance of 0.64 V.

Example 6

(20) 3,5-Pyridine-r-Para-PBI

(21) To a three-necked flask equipped with nitrogen flow and overhead stirrer, a solution of 3,5-pyridinedicarboxylic acid (0.878 g, 1 equiv.), terephthalic acid (4.365 g, 5 equiv.), tetraaminobiphenyl (6.756 g, 6 equiv.), and polyphosphoric acid (88 g) was stirred and heated to 195 C. for 13 hours. Following completion of the polymerization process, the PBI solution was poured onto a glass plate and cast at a thickness of 15 mil using a Gardner blade. To form a gel membrane, the glass plates with the cast films were immediately placed into a humidity controlled chamber at 55%5% relative humidity (RH), 252 C. Complete hydrolysis of the membrane occurred over a span of 24 h. The final gel membrane thickness was roughly 294 m. The final composition of the membrane was 56.00 wt % phosphoric acid, 14.87 wt % polymer, and 29.13 wt % water. The Young's Modulus of the membrane was 9.041 MPa, and its tensile strain at break was 0.638 mm/mm. The anhydrous proton conductivity of the membrane was 0.16 S/cm at 180 C., and following break-in, the MEA constructed from the 1:5 3,5-Pyridine-r-Para-PBI membrane exhibited a fuel cell performance of 0.65 V.

Example 7

(22) 3,5-Pyridine-r-2OH-PBI

(23) To a three-necked flask equipped with nitrogen flow and overhead stirrer, a solution of 3,5-pyridinedicarboxylic acid (2.526 g, 1 equiv.), 2,5-dihydroxyterephthalic acid (2.995 g, 1 equiv.), tetraaminobiphenyl (6.478 g, 2 equiv.), and polyphosphoric acid (88 g) was stirred and heated to 195 C. for 10 hours. Following completion of the polymerization process, the PBI solution was poured onto a glass plate and cast at a thickness of 15mil using a Gardner blade. To form a gel membrane, the glass plates with the cast films were immediately placed into a humidity controlled chamber at 55%5% relative humidity (RH), 252 C. Complete hydrolysis of the membrane occurred over a span of 24 h. The final gel membrane thickness was roughly 408 m. The final composition of the membrane was 60.04 wt % phosphoric acid, 13.75 wt % polymer, and 26.21 wt % water. The Young's Modulus of the membrane was 6.538 MPa, and its tensile strain at break was 0.183 mm/mm. The proton conductivity of the membrane was 0.26 S/cm at 180 C., and following break-in, the MEA constructed from the 1:1 3,5-Pyridine-r-2OH-PBI membrane exhibited a fuel cell performance of 0.61 V.

Example 8

(24) 21.426 g tetraaminobiphenyl(TAB, 0.1 mol) and 16.613 g isophthalic acid (IPA, 0.1 mol) were added to 315 g polyphosphoric acid, mixed with overhead stirrer, purged with dry nitrogen. The mixture was heated at 140 C. for 3 hours and then 200 C. for 20 hours. 40 ml of 85% phosphoric acid was added dropwise over 4 hours to reduce the solution viscosity. Temperature increased to 220 C. for half an hour before the casting. The polymer solution was casted onto clear glass plates. The casted membrane was hydrolyzed at R.H. 55% and 25 C. for 24 hours.

Example 9

(25) 10.714 g tetraaminobiphenyl(TAB, 0.05 mol) and 8.307 g isophthalic acid (IPA, 0.05 mol) was added to 199 g polyphosphoric acid, mixed with overhead stirrer, purged with dry nitrogen. The mixture was heated at 140 C. for 3 hours and then 210 C. for 20 hours. 20 ml of 85% phosphoric acid was added dropwise over 3 hours to reduce the solution viscosity. Temperature increased to 220 C. for half an hour before the casting. The polymer solution was casted onto clear glass plates. The casted membrane was hydrolyzed at R.H. 55% and 25 C. for 24 hours.

(26) TABLE-US-00002 Polymer Proton Strain mem- Con- at brane duc- Tensile Max. Young's content IV tivity Strength Load Modulus sample (%) (dL/g) (S/cm) (MPa) (mm/mm) (MPa) Example 8 16.5 1.68 0.172 1.52 1.36 4.23 Example 9 14.3 1.82 0.175 1.45 2.51 3.50

Example 10

(27) 4.500 g tetraaminobiphenyl(TAB, 21 mmol), 2.492 g isophthalic acid (IPA, 15 mmol), and 0.997 g terphthalic acid (TPA, 6 mmol) were added to 106 g polyphosphoric acid, mixed with overhead stirrer, purged with dry nitrogen. The mixture was heated at 150 C. for 3 hours, 170 C. for 3 hours, and then 195 C. for 12 hours. 5 ml of 85% phosphoric acid was added dropwise over one hour to reduce the solution viscosity. Temperature increased to 220 C. for half an hour before the casting. The polymer solution was casted onto clear glass plates. The casted membrane was hydrolyzed at R.H. 55% and 25 C. for 24 hours.

Example 11

(28) 5.143 g tetraaminobiphenyl(TAB, 24 mmol), 3.323 g isophthalic acid (IPA, 20 mmol), and 0.664 g terphthalic acid (TPA, 4 mmol) were added to 121 g polyphosphoric acid, mixed with overhead stirrer, purged with dry nitrogen. The mixture was heated at 150 C. for 3 hours, 170 C. for 3 hours, and then 195 C. for 12 hours. Temperature increased to 220 C. for half an hour before the casting. The polymer solution was casted onto clear glass plates. The casted membrane was hydrolyzed hydrolyzed at R.H. 55% and 25 C. for 24 hours.

Example 12

(29) 6.428 g tetraaminobiphenyl(TAB, 30 mmol), 4.362 g isophthalic acid (IPA, 26.25 mmol), and 0.623 g terphthalic acid (TPA, 3.75 mmol) were added to 103 g polyphosphoric acid, mixed with an overhead stirrer, purged with dry nitrogen. The mixture was heated at 150 C. for 3 hours, 170 C. for 3 hours, and then 195 C. for 12 hours. 5 ml of 85% phosphoric acid was added dropwise over one hour to reduce the solution viscosity. Temperature increased to 220 C. for half an hour before the casting. The polymer solution was casted onto clear glass plates. The casted membrane was hydrolyzed at R.H. 55% and 25 C. for 24 hours.

Example 13

(30) 6.428 g tetraaminobiphenyl(TAB, 30 mmol), 3.987 g isophthalic acid (IPA, 24 mmol), and 0.997 g terphthalic acid (TPA, 6 mmol) were added to 103 g polyphosphoric acid, mixed with overhead stirrer, purged with dry nitrogen. The mixture was heated at 150 C. for 3 hours, 170 C. for 3 hours, and then 195 for 12 hours. 5 ml of 85% phosphoric acid was added dropwise over one hour to reduce the solution viscosity. Temperature increased to 220 C. for half an hour before the casting. The polymer solution was casted onto clear glass plates. The casted membrane was hydrolyzed at R.H. 55% and 25 C. for 24 hours.

(31) TABLE-US-00003 Polymer membrane Proton Tensile Strain at Young's content IV Conductivity Strength Max. Load Modulus sample (%) (dL/g) (S/cm) (MPa) (mm/mm) (MPa) Example 10 14.9 2.45 0.257 3.296 8.65 4.35 Example 11 14.0 2.78 0.260 3.523 7.42 4.20 Example 12 17.5 2.97 0.183 8.414 7.70 10.85 Example 13 17.3 3.77 0.195 8.473 8.39 11.57