Nanostructured Poly(styrene‐b‐butadiene‐b‐styrene) (SBS) Membranes for the Separation of Nitrogen from Natural Gas

The preparation and characterization of new, tailor‐made polymeric membranes using poly(styrene‐ b ‐butadiene‐ b ‐styrene) (SBS) triblock copolymers for gas separation are reported. Structural differences in the copolymer membranes, obtained by manipulation of the self‐assembly of the block copolymers in solution, are characterized using atomic force microscopy, transmission electron microscopy, and the transport properties of three gases (CO 2 , N 2 , and CH 4 ). The CH 4 /N 2 ideal selectivity of 7.2, the highest value ever reported for block copolymers, with CH 4 permeability of 41 Barrer, is obtained with a membrane containing the higher amount of polybutadiene (79 wt%) and characterized by a hexagonal array of columnar polystyrene cylinders normal to the membrane surface. Membranes with such a high separation factor are able to ease the exploitation of natural gas with high N 2 content. The CO 2 /N 2 ideal selectivity of 50, coupled with a CO 2 permeability of 289 Barrer, makes SBS a good candidate for the preparation of membranes for the post‐combustion capture of carbon dioxide.