Anomalous Small-Angle X-ray Scattering from Nickel-Neutralized Ionomers. 2. Semicrystalline Polymer Matrices

The ability of anomalous small-angle X-ray scattering (ASAXS) to determine the sign of the electron density difference between the crystalline and amorphous phases in a nickel-neutralized poly(ethylene-co-methacrylic acid) ionomer has been demonstrated. The only a priori knowledge required is which of the phases causing the reflection has a greater concentration of nickel. All observed features of the scattering patterns are consistent with the generally accepted three-phase model incorporating lamellar crystallites, interlamellar amorphous polymeric material, and ionic aggregates distributed within the amorphous lamellae. The change in the intensity of the low-g reflection was in reasonable agreement with that calculated from experimental values of for Ni metal. A nickel-neutralized Nafion perfluorosulfonate ionomer was also studied, but no ionomer peak was visible due to a fortuitous equality of ionic aggregate and amorphous polymer electron densities.