Patent ID: 7560497

Claim:
A method of preparing a perfluorocarbon ionomer membrane with aligned nanostructure which comprises: (a) casting a perfluorocarbon ionomer solution; (b) evaporating organic solvents at a temperature below T g of perfluorocarbon ionomer, to form an amorphous membrane; (c) annealing the amorphous membrane at a temperature between T g (glass transition temperature) and T m (crystalline melting temperature) of perfluorocarbon ionomer; (d) applying an electric field on the membrane during annealing; (e) keeping the membrane in an electric field and cooling the membrane from the annealing temperature to a temperature below T g of perfluorocarbon ionomer; and (f) moving the power supply of the electric field after the membrane is cooled to a temperature below T g .