Protonation of sulfonated polyi(4,4′-diphenylether-1,3,4-oxadiazole) membranes

Abstract

This work describes the effect of sulfuric acid protonation on the properties of SPOD-DPE membranes using FT-IR and impedance spectroscopic analyses. The IR spectra showed the protonation of nitrogen atoms from oxadiazole rings, with a broad band complex in the region 3 000-2100 cm -1 with two centered peaks at 2 590 and 2 440 cm-1. The S=O characteristic absorption bands in SPOD-DPE and sulfuric acid were specially studied in the region of 1800-900 cm-1. The band shifts are associated to the interaction between acid groups and oxadiazole ring nitrogen atoms. The IR spectra evidenced the presence of three absorption species (HSO4-, SO42- and free H 2SO4) depending on the sulfuric acid concentration. For the protonated SPOD-DPE membranes, a proton conductivity around 10 mS · cm 1 was reached at 50 °C. © 2007 WILEY-VCH Verlag GmbH & Co. KGaA.