Patent ID: 7749630

Claim:
A composite polymer electrolyte membrane comprising a matrix made of a first sulfonated aromatic polymer having a high ion exchange capacity of 1.0-2.8 meq/g, and a reinforcing material made of a second sulfonated aromatic polymer having a low ion exchange capacity 0.5-1.5 meq/g in the form of fibers or a porous membrane, wherein the ion exchange capacity of the first sulfonated aromatic polymer is at least 0.5 meq/g larger than that of the second sulfonated aromatic polymer, and wherein said first sulfonated aromatic polymer and said second sulfonated aromatic polymer have the same skeleton and yet different ion exchange capacities, and wherein H + in sulfonic groups of said second sulfonated aromatic polymer is substituted by Na + at a degree of 5-50%.