Structural effects on the nano-scale morphology and conductivity of ionomer blends

Abstract

The role of graft and diblock ionomer architecture on the morphology and properties of ionomer/fluoropolymer blends is examined. The graft copolymer consists of a partially fluorinated backbone of P(VDF-co-CTFE) and partially sulfonated polystyrene (PS) side chains while the diblock copolymer consists of a block of P(VDF-co-HFP) and a partially sulfonated PS block. These ionomers are blended with fluoropolymers possessing a chain length that matches the average sequence length of the fluorous block segment of the ionomer. The results from this study are surprising: graft ionomers are primarily insensitive to blending due to the incorporation of the non-ionic fluorous polymers into the domains of the perfluorinated backbone which does not deleteriously affect the interconnecting proton conducting ionic clusters. In contrast, diblock ionomers are highly sensitive to the addition of fluoropolymers and despite the observation that ionic channels are retained, water sorption is decreased due to the increased volume of the non-ionic domains, which decreases proton mobility and proton conductivity.