Gas separation membranes prepared with copolymers of perfluoro(2-methylene-4,5-dimethyl-1,3-dioxlane) and chlorotrifluoroethylene

• A new polyfluorinated copolymer is synthesized and characterized.
• Composite membranes based on the new fluoropolymers have been fabricated.
• The gas separation performance of the membranes depends strongly on the copolymer composition.
• The membranes have far superior gas separation performance compared to the commercial perfluoropolymers.

Several families of hydrocarbon polymers (polysulfones, polycarbonates, cellulose acetates, polyamides, and polyimides) have been established as common industrial gas separation membranes over the past three decades. Fluoropolymer membranes have found commercial use because of their unique gas separation properties in addition to their extraordinary chemical resistance and thermo-oxidative stability. To date, studies of gas transport in fluoropolymers have been limited largely to variants of the commercially available perfluoropolymers: Teflon® AF, Cytop™, and Hyflon® AD. Here, we describe gas transport in composite membranes fabricated from copolymers of perfluoro(2-methylene-4,5-dimethyl-1,3-dioxolane) (PFMDD) and chlorotrifluoroethlyene (CTFE). This poly(PFMDD-co-CTFE)-based membranes have far superior gas separation performance compared to the commercial perfluoropolymers for a number of gas pairs, including H2/CH4, He/CH4, and CO2/CH4. The gas separation performance of the membranes depends strongly on the copolymer composition. Increasing the amount of CTFE up to 30 mol% in the copolymer increases the membrane selectivity and reduces permeance. The membranes based on 70 mol% PFMDD-30 mol% CTFE poly(PFMDD-co-CTFE) show H2/CH4 and He/CH4 selectivities of 210 and 480, respectively, values that far exceed those possible with the known commercial perfluoropolymers.

A new fluoropolymer, the copolymer of perfluoro(2-methylene-4,5-dimethyl-1,3-dioxolane) (PFMDD) and chlorotrifluoroethlyene (CTFE) has been prepared with different compositions. The composite membranes fabricated from the poly(PFMDD-co-CTFE) demonstrate far superior gas separation performance compared to the commercial perfluoropolymers for the separation of gas pairs of H2/CH4, He/CH4, and CO2/CH4.Figure optionsDownload as PowerPoint slide