Investigation of ionomer structure through its dependence on ion exchange capacity (IEC)

The ion exchange capacity (IEC) of conventional ion-exchange perfluorinated membranes based on the so-called Long-Side-Chain (LSC) polymers and their Short-Side-Chain (SSC) Aquivion® derivatives was determined using a series of experimental techniques. Newly developed and already used experimental analyses were compared in terms of sensitivity to the determination of the ion exchange capacity. The use of complementary techniques allows better determination of IEC with an uncertainty of about 3%. This IEC determination method was then applied to membranes with large chemical differences such as copolymers and reinforced membranes. In addition, based on these analyses, relationship between DMA, WAXS, TGA and conductivity parameters and either IEC or the molar number of tetrafluoroethylene (TFE) per comonomer unit are underlined, leading to a more comprehensive approach of architecture in perfluorosulfonic acid (PFSA) polymer membranes.