Orientation of drawn Nafion at molecular and mesoscopic scales

The structural orientation in Nafion films in an ambient environment and under stretching is analyzed using small/wide-angle X-ray scattering. On the basis of the absolute values of Hermans' orientation factor, we characterize the structural anisotropy at different length scales (between angstroms and several hundreds of angstroms) in agreement with a previously proposed fibrillar model of the Nafion membrane. Bundles of elongated polymeric aggregates orient at small draw ratios, together with an orientation of the aggregates within such a bundle. The crystal structure of this semicrystalline polymer is analyzed, and we show that the crystallinity of the Nafion film does not change as a function of the draw ratio.