Provided is a polymer electrolyte containing a block copolymer comprising
one or more blocks having sulfonic acid groups and one or more blocks
having substantially no sulfonic acid group, and at least one block among
all blocks is a block having aromatic rings in the main chain thereof, and
a method for producing the same. The polymer electrolyte is suitable for a
proton conductive film of a fuel cell due to excellent water resistance
and heat resistance, and high proton conductivity.
