Author/Authors :
Utiu، نويسنده , , Lavinia and Filipoi، نويسنده , , Carmen and Demco، نويسنده , , Dan E. and Zhu، نويسنده , , Xiaomin and Vinokur، نويسنده , , Rostislav and Conradi، نويسنده , , Oliver and Graichen، نويسنده , , Andreas and Blümich، نويسنده , , Bernhard and Mِller، نويسنده , , Martin، نويسنده ,
Abstract :
Poly(perfluorosulfonic acid)/silica (PFSA/SiO2) composites were investigated by 129Xe NMR spectroscopy and relaxometry. 129Xe chemical shift extrapolated to zero pressure was used for calculation of average free volume hole size. This quantity reaches a maximum at 2 wt.% SiO2 that could be correlated to the performance of composites proton exchange membrane. 129Xe longitudinal magnetization relaxation revealed a bimodal distribution of the free volume that was explained by the presence of xenon atoms in the backbone and pendant–chain domains. Thus, the free volume is heterogeneous and depends on the content of SiO2. Implications of the free volume changes for the hydrogen crossover through PFSA/SiO2 membranes are also discussed.
