Nearly all ionomers (ion-containing polymers) are exposed to solvents either during synthesis, processing, or in their applications. Plasticizers are often added in commercial formulations. Interactions that can occur between solvents and the ionic salt species influence the local arrangement of the ionic groups, which has a profound influence on the properties of the ionomer both in solution and in the solid state. This research program is directed at a phenomenological understanding of the plasticization of ionomers. Spectroscopic methods (electron spin resonance, infrared, and fluorescence) will be used to characterize the specific interactions that occur in ionomers containing low concentrations of organic diluents. This, combined with small angle x-ray scattering and dynamic mechanical analyses, will provide the relationship between these interactions and the structure and properties of these materials. A second aspect of this research is to exploit the variations in the ionomer microstructures obtained by exposure of the material to different solvents to study the mechanism and kinetics of phase separation in ionomers. These studies will also provide a means to unambiguously determine the effects of ionic aggregation on the glass-transition temperature, the radius of gyration, and the viscoelastic behavior of an ionomer.
