Glassy perfluoropolymers have become an exciting materials platform for membrane gas separation as they define the upper bounds for some gas separations, such as He/H-2, He/CH4, and N-2/CH4. However, due to the difficulty in synthesis, only a few glassy perfluoropolymers are commercially available, including Teflon AF and Hyflon AD derived from dioxoles and Cytop derived from dihydrofuran. In this study, two perfluoropolymers based on dioxolanes, poly(perfluoro-2-methylene-1,3-dioxolane) (poly(PFMD)) and poly(perfluoro-2-methylene-4-methyl-1,3-dioxolane) (poly(PFMMD)), were synthesized by radical polymerization and characterized thoroughly for physical properties such as glass transition temperature (T-g), d-spacing between polymer chains, and fractional free volume (FFV). The gas permeability and solubility were determined at 35 degrees C for a series of pure gases in these perfluorodioxolanes and compared with the commercial perfluoropolymers. Poly(PFMD) and poly(PFMMD) exhibit separation properties of He/H-2, He/CH4, H-2/CH4, H-2/CO2, and N-2/CH4 near or above the upper bounds in Robeson's plots, and superior to the commercial perfluoropolymers, despite their similar T-g and FFV. The underlying reasons for the superior gas separation properties in these dioxolane-based perfluoropolymers are discussed.