Polyelectrolyte/fluorinated polymer interpenetrating polymer networks as fuel cell membrane

Original membranes based on an interpenetrating polymer network (IPN) architecture combining a poly(2-acrylamido-2-methyl-1-propane sulfonic acid) (AMPS) network and a fluorinated network were synthesized. The AMPS weight compositions were varied from 50 to 70 wt%. The first network was achieved by radical copolymerization of AMPS with a fluorinated telechelic diacrylate while the second one was obtained by photoinitiated cationic copolymerization of telechelic fluorinated diepoxide with trimethylol propane triglycidyl ether. The morphologies of these different IPNs were deduced from small-angle X-ray scattering (SAXS) spectra and dynamic thermomechanical analysis (DMTA). The main functional properties related to their use as proton exchange membrane in fuel cells were quantified, such as water vapor sorption, liquid water uptake (22-59 wt%), proton conductivity (1-63 mS/cm), gas permeability (0.06 and 0.80 barrer for dry oxygen and hydrogen, respectively), and oxidative and thermal stabilities. More precisely, the effects of the ionic exchange capacity (IEC) varying from 1.73 to 2.43 meq/g and the cross-linking density of the conducting phase on the morphology and the properties of IPN membranes were studied in detail. Finally, these IPN membranes were tested as fuel cell membrane and a correlation between the ex-situ and in-situ characterizations was established. (C) 2012 Elsevier B.V. All rights reserved.