Highly permeable polymers for gas separation membranes

For gas separation membranes, materials are required that offer high permeability as well as good selectivity for a desired separation. For glassy polymers, the gas transport properties depend on the amount and distribution of free volume and on chain mobility. The most highly permeable polymers have rigid, twisted macromolecular backbones that give rise to microvoids. Examples include substituted polyacetylenes, perfluoropolymers, addition-type polynorbornene, polymers of intrinsic microporosity (PIMs) and some polyimides. High permeability membranes may also be produced by thermal rearrangement of precursor polymers.