Equivalent Weight and Crystallinity Effects on Water Content and Proton Conductivity in Bis[(perfluoroalkyl)sulfonyl]imide-Based Ionomers

Water content and ionic conductivity data were acquired as a function of relative humidity for representative samples of a novel series of perfluorinated ionomers based on bis[(perfluoroalkyl)sulfonyl]imide. The humidity dependence of both water content and mionic conductivity correlates strongly with ionomer equivalent weight (EW); the higher EW ionomer exhibited a much sharper drop in water content and ionic conductivity with diminished humidity than did the lower EW ionomer . This drop in water content and ionic conductivity at low humidity correlates with X‐ray diffraction measurements which indicate a higher poly(tetrafluoroethylene)‐like crystallinity in the higher EW ionomer.