Synthesis and characterization of novel sulfonated polyimides derived from naphthalenic dianhydride

4,4'-Ketone dinaphthalene 1, 1',8,8'-tetracarboxylic dianhydride (KDNTDA) was prepared by a new route including six steps with an overall yield of 19%. The structure was confirmed by IR, H-1 NMR and UV spectroscopy. Several novel sulfonated polyimides (SPIs) derived from KDNTDA were synthesized and their structures were characterized by IR and H-1 NMR. Their reduced viscosity ranged from 0.8 to 4.5 dL g(-1) at 35 degrees C. They had good solubility in common aprotic solvents not only in triethylamine salt form but also in proton form. The co-SPIs showed anisotropic membrane swelling with larger swelling in thickness than in plane, while the homo-polymer displayed isotropic membrane swelling. The thermal stability measurements revealed that sulfonic acid group in KDNTDA-based SPIs were stable up to 300 degrees C. They displayed reasonably high proton conductivity, water stability and mechanical properties.