Small-angle x-ray scattering investigation of temperature influences on microstructures of an ionomer

Abstract

Ionomer morphology has received extensive studies due to its interesting characteristics in the molecular aggregation of ionic groups. The strong scattering peak in the small-angle X-ray scattering (SAXS) profile has been accounted for by several models. From the multiphase relaxation point of view, Eisenberg et al. proposed that the ionic multiplets were the basic unit of aggregation. The ionic aggregates were surrounded by a spherical region of polymer backbones of restricted mobility. Some overlap of the restricted regions of the ionic phases could be characterized by a high-temperature relaxation relative to the one for the surrounding matrix. The electron density inhomogeneity in a length scale comparable to the average distance between two adjacent multiplets leads to an ionic peak in the SAXS profile. The SAXS profiles of ionomers at different temperatures depended on the counterions and the method of sample preparation. In this paper the authors report SAXS measurements of an ionomer which has undergone different thermal treatment. Extra care was taken in correcting the thermal expansion which was responsible for the primary change in the SAXS profile at different temperatures. The authors used an approach developed by Fischer and Gehrke et al. The modified Porod law and the inversemore » Fourier transform were used to evaluate the microstructure parameters.« less