Spectroscopic study of Nafion® membrane as a function of water content by Phase-Resolved Photoacoustic Method

Resumo

Nafion® membranes were developed by DuPont, a perfluorosulfonic acid/polytetrafluoroethylene copolymer. These membranes are hydrophilic and the water is preferentially sorbed into the clusters due to the hydrophobic character of fluorocarbon matrix. The sulfonic acid groups are chemically active and fixed within the Teflon polymer matrix. Thus, this first synthetic ionic polymer is chemically resistant and durable, making it useful for Proton Exchange Membrane fuel cells. In order to monitoring the groups -OH of the Nafion®, we used the Photoacoustic Spectroscopy phases. The optical absorption spectrum was determined for wavelengths of 800 to 2600 nm. The procedure was to measure the samples in different hydration times. Using the Phase-Resolved Photoacoustic method, it was possible to separate the contribution of –OH, of C=O and of methylene group. The phase lag as a water function behaviors found may be associated with structural changes induced by membrane hydration.