Synthesis of Sulfonated Aromatic Poly(ether amide)s and Their Application to Proton Exchange Membrane Fuel Cells

A series of wholly aromatic sulfonated poly(ether amide)s (SPEAs) containing a sulfonic acid group on the dicarbonyl aromatic ring were prepared via a polycondensation reaction of sulfonated terephthalic acid (STA), terephthalic acid (TA), and aromatic diamine monomers. The degree of sulfonation was readily controlled by adjusting the monomer feed ratio of STA and TA in the polymerization process, and randomly sulfonated polymers with an ion exchange capacity (IEC) of 1.0-1.8 mequiv/g were prepared using this protocol. The chemical structures of randomly sulfonated polymers were characterized using NMR and FT-IR spectroscopies. Gel permeation chromatography analysis of SPEAs indicated the formation of high-molecular-weight sulfonated polymer. Tough and flexible SPEA membranes were obtained from solution of N,N-dimethylacetamide, and thermogravimetric analysis of these membranes showed a high degree of thermal stability. Compared with previously reported sulfonated aromatic polyamides, these new SPEAs showed a significantly lower water uptake of 10-30%. In proton conductivity measurements, ODA-SPEA-70 (IEC = 1.80 mequiv/g), which was obtained from polycondensation of 4,4'-oxydianiline and 70 mol % STA, showed a comparable proton conductivity (105 mS/cm) to that of Nafion 117 at 80 degrees C. (C) 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 485-496, 2009