Three-Component Domains in the Fully Hydrated Nafion Membrane Characterized by Partial Scattering Function Analysis

A fully hydrated Nafion membrane is generally treated as a three-component system comprising the tetrafluoroethylene-like main chain, the fluorinated side chain ending with a sulfonic acid group, and absorbed water. We applied the contrast variation small-angle neutron scattering technique to decompose scattering intensity profiles to partial scattering functions (PSFs) of each component in Nafion quantitatively. In the large scale (>30 nm), structural heterogeneities were observed in the main- and side-chain domains but not in water domains. In the middle scale (5–30 nm), a bicontinuous-like structure of crystalline and amorphous phases with a mean separation distance of 11 nm was observed, as a result of the main-chain semicrystalline templating effect. In the small scale (