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 re lative humidity for representative samples of a novel series of perfluorina ted ionomers based on bis[(perfluoroalkyl)sulfonyl]imide. The humidity depe ndence of both water content and ionic conductivity correlates strongly wit h ionomer equivalent weight (EW); the higher EW ionomer (1205 g equiv(-1)) exhibited a much sharper drop in water content and ionic conductivity with diminished humidity than did the lower EW ionomer (1095 g equiv(-1)). This drop in water content and ionic conductivity at low humidity correlates wit h X-ray diffraction measurements which indicate a higher poly(tetrafluoroet hylene)-like crystallinity in the higher EW ionomer. (C) 1999 The Electroch emical Society. S1099-0062(99)04-030-4. All rights reserved.