Small‐angle X‐ray and neutron scattering studies of the morphology of ionomers

Abstract

AbstractPreliminary small‐angle neutron scattering (SANS) studies have been made of different ionomers in the dry state and after saturation with water. Scattering from the dry samples arises from differences in the neutron scattering cross sections of the ionic and nonionic units in the polymer. The SANS technique is complementary to previous small‐angle x‐ray scattering (SAXS) studies since the SANS contrast differences are generally quite different than those for SAXS. A quantitative comparison is made of SANS and SAXS intensities for a dry cesium salt of an ethylene‐methacrylic acid (E‐MAA) copolymer. For water‐saturated samples the technique of isotopic replacement can be used in conjunction with SANS since saturation can be effected with either H2O or D2O. In this case information about the chemical composition of the phases is obtained from an analysis of the intensity ratio I/I. Results are consistent with the presence of a separate phase containing water molecules and ions in a matrix of the nonionic units. A Guinier analysis gives a radius of gyration of 17 Å for a water‐saturated cesium salt of an E‐MAA copolymer.