Block copolymer derived membranes for sustained carbon dioxide-methane separations

Using a reactive block polymer precursor, membranes with a bicontinuous nanostructure containing a poly((N,N-dimethylamino)ethyl methacrylate) phase within a cross-linked poly(cyclooctene) framework were formed. These membranes were evaluated for their CO₂ selectivity over CH₄. Low pressure experiments demonstrated that the CO₂ and CH₄ permeabilities remain the same with pure and mixed gas feeds. This shows that the membranes are able to maintain their selectivity for CO₂. This selectivity was only slightly decreased at moderate temperature (35 °C) and higher pressures (up to 40 bar) using a 50/50 CO₂/CH₄ mixed gas feed. The bicontinuous block polymer membranes resist the plasticization effect by using a cross-linked phase to sustain the properties of the selective block, and not by changing chain mobility through new chemistry. These bicontinuous block polymer membranes may be valuable for CO₂ removal from natural gas streams.