Novel fluorinated aromatic polymers with ether-bond-free aryl backbones for pure and mixed gas separation

Abstract

Three novel fluorinated polymers with ether-bond-free aryl backbones were obtained by one-pot, metal-free, room temperature superacid catalyzed non-stoichiometric step polymerization of 1,1,1-trifluoromethyl acetone with carbazole (CBZ), fluorene (FLN) and 9,9-dimethylfluorene (DFL). 1H and 13C NMR analyses of the polymers revealed their linear structure and high regioselectivity of the polymer forming reaction. The polymers also possess high thermostability with decomposition temperature up to 387 °C for CBZ and up to 530 °C for FLN and DFL as well as reasonable mechanical properties. The gas transport properties of six pure gases and binary gas mixture CO2/CH4 (10/90 mol%) are reported. These polymers present a good combination of permeability and selectivity up to 10 bar at 35 °C for CO2/CH4 mixed-gas feed. DFL exhibits the best pure-gas permeability and selectivity (PCO2 = 78.0, PH2 = 151.5, CO2/CH4 = 22.3 and H2/CH4 = 43.3) and mixed-gas permeability and selectivity CO2/CH4 (PCO2 = 71.3, CO2/CH4 = 23.7) at 35 °C and 2 bar with a slight decrease in selectivity at 10 bar. The highest permselectivity is obtained for FLN (CO2/CH4 = 36.7 and H2/CH4 = 88.4) with a separation performance close to the 2008 upper bound trade off.