a process for separating components of a gas mixture using gas - separation copolymer membranes . these membranes use a selective layer made from copolymers of partially fluorinated or perfluorinated dioxolane monomers and a second monomer , such as dioxane or a partially fluorinated dioxolane . the resulting membranes have superior selectivity performance for gas pairs of interest while maintaining fast gas permeance compared to membranes prepared using conventional perfluoropolymers , such as teflon ® af , hyflon ® ad , and cytop ®.