By courtesy of:
Donald James Connolly, and William Franklin Gresham
US patent 3282875 1966 assigned to E. I. du Pont de Nemours and Company
The above is the first patent about Nafion. Here is the one about its key intermediate: sultone.
Fluorocarbon sulfonyl fluoride
Hugh Harper Gibbs, Vienna, W. Va., and Richard Norman Griffin
US patent 3041317 1962 assigned to E. I. du Pont de Nemours and Company