A study on the state of PWA in PVDF-based proton conducting membranes by Raman spectroscopy

Polymer composite proton conducting membranes with increasing amount of tungstophosphoric acid (PWA) have been synthesized starting from poly(vinylidene) fluoride and alumina. Membranes could be prepared with an acid loading up to 16.7 wt.%. The conductivity of the membranes increases with acid loading up to 10− 3 Scm− 1 at the highest loading. The membrane matrices have a good thermal stability up to 240 °C, however a loss of water absorbed during the preparation procedure is observed at a considerably lower temperature. Raman spectroscopy showed that in the membrane the polymer adopts a conformation that could promote a separation into hydrophilic/hydrophobic sites. An interaction between alumina and PWA is also found that might limit the conductivity of the membranes.