Sulfonated aromatic polyamides containing nitrile groups as proton exchange fuel cell membranes

A series of sulfonated aromatic polyamides containing nitrile groups (SPA-xx) were prepared by the phosphorylation polyamidation using 2,6-bis(4-aminophenoxy)benzonitrile, 5-sulfoisophthalic acid sodium salt and terephthalic acid as starting materials. The intrinsic viscosities of these polymers were between 1.23 and 2.16 dL/g. All the sulfonated polymers have good solubility and could afford flexible proton exchange membranes by solution-casting. Their chemical structures were characterized by fourier transformation infrared spectrum (FTIR) and nuclear magnetic resonance spectrum (NMR). Their properties, including water uptake, dimensional change, proton conductivity and thermal and chemical stability, were also investigated in detail. The results indicated that these sulfonated aromatic polyamides had good dimensional stability and chemical stability, proton conductivity and thermal stability. The representative SPA-100 membrane with IEC values of 1.87 mequiv./g, showed swelling ratio of 16.5% and proton conductivity of 141 mS/cm at 80 °C, respectively.