EFFECT OF NEUTRALIZING CATION TYPE ON THE MORPHOLOGY AND PROPERTIES OF MODEL POLYURETHANE IONOMERS

The influence of cation type on the morphology and properties of model polyurethane ionomers is investigated in ionomers with different backbone types, pendant anion types and ionic group concentrations. A correlation between the degree of ordering in the local environment of the neutralizing cation and the tensile properties of the ionomers is observed. The geometrical packing constraints of the pendant anion are also seen to be a critical factor in determining the physical properties of ionomers. Differential scanning calorimetry results indicate no significant differences in the extent of phase separation of ionomers neutralized with different cations; however, anion type is shown to have a large influence on the degree of phase separation. Small-angle X-ray scattering analysis of the morphology of the ionomers reveals a correlation between the number of ionic groups per aggregate and the low-temperature storage modulus measured by dynamic mechanical analysis. The importance of the electronic structure and geometrical packing constraints of the ionic groups is emphasized.