| Abstract: | A series of sulfonated polybenzimidazoles (sPBI-SF) were prepared from 2,2-bis(4-carboxyphenyl)hexafluoro-propane (BIS-B-AF), 3,3'-disulfonyl-4,4'-dicarboxyldiphenylsulfone (DSDCDPS) and 3,3'-diaminobenzidine (DAB) atvarious stoichiometric ratio by solution copolycondensation in poly(phosphoric acid). The chemical structure of the resultingsPBI-SF was confirmed by FTIR and 1H-NMR. The sPBI-SFs with high molecular-weights (Mn=39400-65500) weresoluble in DMF, DMSO or DMAc. Therefore, they could form some transparent and flexible membranes easily by solutioncasting. The glass-transition temperatures of the acidic form sPBI-SF were in the range from 222℃ to 269℃. Theextrapolated onset decomposition temperatures were up to 440℃. The sulfonic groups grafted in the PBI chain had higherinitial thermal degradation activation energy and exhibited excellent thermal stability. In addition, these membranes withgood mechanical properties presented the swelling degree below 12% and the water uptake about 16%. The protonconductivities of sPBI-SF membranes measured by alternating-current impedance spectroscopy attained to 1.64×10-3 S/cmat 70℃. |
