Sulfonated Membranes from Random Aramide Copolyisophtalamides with Increasing Sulfonation Degree: Characterization for Possible Use as Solid Electrolyte in Fuel Cell

Sulfonated aromatic random copolyisophthalamides with increasing sulfonation degree were synthesized using different concentrations of 2,4-diaminobenzenosulfonic acid, DABS, and 4,4′-(9-fluorenylidene)diamine, BFA, by direct polycondensation with isophthalic acid, ISO. Ionic membranes from these copolymers were cast from solution using dimethylacetamide, DMAc. The sulfonation degree was confirmed by FT-IR and 1H NMR. The membranes were thermally stable up 310°C. Water uptake (WU%), Ion Exchange Capacity (IEC) and proton conductive values at room temperature, for the sulfonated membrane with 50 mol.% of DABS (BFAS55), were similar or higher than those obtained for Nafion® 115, tested under the same conditions.