A method of fabricating low EW, water insoluble electrolyte materials includes providing a perfluorinated polymer resin that includes perfluorinated carbon-carbon backbone chain and sulfonyl fluoride ended perfluorinated side chains, extending from the perfluorinated backbone chains via an ether linkage, exposing the perfluorinated polymer resin to ammonia gas to convert the sulfonyl fluoride groups to sulfonamide groups, -SO2-NH2, which reacts with sulfonyl fluoride containing chemical agent(s) to form sulfonimide groups, and at the same time, generates low EW, 3-dimensional cross-linked, water-insoluble perfluorinated polymer electrolyte materials.