Original Fuel‐Cell Membranes from Crosslinked Terpolymers via a “Sol–gel” Strategy

Hybrid organic/inorganic membranes that include a functionalized (‐SO3H), interconnected silica network, a non‐porogenic organic matrix, and a ‐SO3H‐functionalized terpolymer are synthesized through a sol–gel‐based strategy. The use of a novel crosslinkable poly(vinylidene fluoride‐ter‐perfluoro(4‐methyl‐3,6‐dioxaoct‐7‐ene sulfonyl fluoride)‐ter‐vinyltriethoxysilane) (poly(VDF‐ter‐PFSVE‐ter‐VTEOS)) terpolymer allows a multiple tuning of the different interfaces to produce original hybrid membranes with improved properties. The synthesized terpolymer and the composite membranes are characterized, and the proton conductivity of a hybrid membrane in the absence of the terpolymer is promising, since 8 mS cm−1 is reached at room temperature, immersed in water, with an experimental ion‐exchange‐capacity (IECexp) value of 0.4 meq g−1. Furthermore, when the composite membranes contain the interfaced terpolymer, they exhibit both a higher proton conductivity (43 mS cm−1 at 65 °C under 100% relative humidity) and better stability than the standard hybrid membrane, arising from the occurrence of a better interface between the inorganic silica and the poly[(vinylidene fluoride)‐co‐hexafluoropropylene] (poly(VDF‐co‐HFP)) copolymer network. Accordingly, the hybrid SiO2‐SO3H/terpolymer/poly(VDF‐co‐HFP) copolymer membrane has potential use as an electrolyte in a polymer‐electrolyte‐membrane fuel cell operating at intermediate temperatures.