Method of bonding acid-doped membranes and a bonded polybenzimidazole membrane structure

1. A method for bonding together two or more acid-doped polybenzimidazole films, the method comprising, in the following order:

placing a first acid-doped polybenzimidazole film on a first substrate to form a first film/substrate assembly and placing a second acid-doped polybenzimidazole film on a second substrate to form a second film/substrate assembly;

heating the first and second film/substrate assemblies to a temperature sufficient to soften the first and second acid-doped polybenzimidazole films;

positioning the second film/substrate assembly atop the first film/substrate assembly, such that the first acid-doped polybenzimidazole film is in contact with the second acid-doped polybenzimidazole film and such that the polybenzimidazole polymer chains of the first acid-doped polybenzimidazole film interact with polybenzimidazole polymer chains of the second acid-doped polybenzimidazole film; and

re-hydrolyzing the first and second acid-doped polybenzimidazole films, such that the polybenzimidazole polymer chains of the first and second acid-doped polybenzimidazole films are therefore reformed and interlocked with each other to bond together the first and second acid-doped polybenzimidazole films.

2. The method of claim 1 , wherein each of the first and second acid-doped polybenzimidazole films is an acid-doped polybenzimidazole membrane.

3. The method of claim 2 , wherein each acid-doped polybenzimidazole membrane has been fabricated by a sol-gel process.

4. The method of claim 1 , wherein the sol-gel process utilizes polyphosphoric acid.

5. The method of claim 4 , wherein each of the first and second acid-doped polybenzimidazole films is made of poly[2,2′-(p-phenylene)-5,5′-bibenzimidazole] (p-PBI).

6. The method of claim 1 , where each of the first and second porous substrates has pore sizes ranging from 1 nm to 100 cm.

7. The method of claim 1 , wherein the first and second film/substrate assemblies are heated to a temperature of approximately 300° C.

8. The method of claim 1 , further comprising applying a coating of a polymer solvent to an exposed surface of each of the first and second acid-doped polybenzimidazole films after heating of the first and second film/substrate assemblies and prior to positioning the second film/substrate assembly atop the first film/substrate assembly.

9. The method of claim 8 , wherein the polymer solvent is polyphosphoric acid.

10. The method of claim 8 , wherein the first and second film/substrate assemblies are heated to a temperature of approximately 220° C.

11. The method of claim 1 , further comprising applying pressure to the first and second film/substrate assemblies when the second film/substrate assembly is positioned atop the first film/substrate assembly.

12. The method of claim 11 , wherein approximately 0.1 to 10 psi of pressure is applied to the first and second film/substrate assemblies.

13. The method of claim 1 , wherein re-hydrolyzing the first and second acid-doped polybenzimidazole films involves placing the first and second acid-doped polybenzimidazole films in an acid bath.

14. The method of claim 1 , wherein re-hydrolyzing the first and second acid-doped polybenzimidazole films involves placing the first and second acid-doped polybenzimidazole films in a deionized water bath.

15. The method of claim 1 , wherein the first and second substrates are porous substrates.