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 (T-d10%) over 496 degrees 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.