POXINAR Membrane Family for Gas Separation

Abstract

Poly(oxindolylidene arylene)s (POXINARs), a family polymers with high performance in terms of thermal stability properties and with ether-bond-free aromatic backbones alternating with bulky, torsion resistant oxindolylidene fragments, have been synthesized by superacid catalyzed polyhydroxyalkylation, and their useful physical properties have been assessed to determine their performance as gas separation membranes. The room temperature synthesis allows a variety of fully soluble, high-molecular-weight polymers in a single pot "click" reaction. These polymers can form flexible and transparent films, and they possess high glass transition temperatures (>500 °C); high decomposition temperatures (ranging from 500 to 524 °C); and FFVs (0.130–0.194) comparable to those reported for the polysulfone, polycarbonate, and polyarylate families. However, their selectivity–permeability combinations are very attractive because some fall close to the 2008 upper-bound limits. Membranes made from isatin and 9,9-dimethyl-9H-fluorene (2aD) display P(O2) = 15.4 Barrer for the O2/N2 gas pair and an O2/N2 selectivity of 6.4, whereas for the H2/CH4 gas pair, they display P(H2) = 170 Barrer and a H2/CH4 selectivity of 77.