Relaxation phenomena and conductivity mechanisms in anion-exchange membranes derived from polyketone

A polyketone-b-poly[N-(4 methyl-methylpyridium)-ethylenepyrrole⁺][X⁻], with X⁻ = I⁻ or OH⁻, is investigated as an example of anion-exchange membrane with potential applications in fuel cells. The polyketone starting material PK and the functionalized polyketones Pyr-FPKmI and Pyr-FPKmOH are investigated via Broadband Electrical Spectroscopy (BES) to understand the conductivity mechanism. BES signals are collected in the frequency range of 10⁻² – 10⁷ Hz and from −100° to 120 °C. BES measurements reveal the presence of up to three interdomain polarizations phenomena, one electrode polarization event and two β dielectric relaxation modes for both wet Pyr-FPKmI and Pyr-FPKmOH. Ion conductivity for Pyr-FPKmI and Pyr-FPKmOH is found to be 0.0086 and 0.0105 S cm⁻¹ at 80 °C, respectively. The overall conductivity mechanism is attributed to the superposition of two conduction pathways, via delocalization bodies and via interdomain percolation pathways, which are associated with two different physical phenomena.