Aromatic polyimides containing pyridine and spirocyclic units: Preparation, thermal and gas separation properties

Six polyimides, containing pyridine and spirocyclic units, were successfully synthesized by chemical imidization. Structure-dependent properties such as thermal decomposition temperatures and gas permeabilities of the high-performance polymers were explicitly investigated. Results showed that all polyimide films exhibited good solubility in common organic solvents and non-polar solvents such as chloroform and tetrahydrofuran. The polymers exhibited good thermal stability, all demonstrating thermal decomposition temperatures (Td10%) over 496 °C in nitrogen. Important from a commercial viewpoint, the permeability coefficients of these for the acidic gas CO2 showed an increase over other tested gases by virtue of the basic group pyridine (C–N linkages) in their structures.