A quaternized diol, 3-(trimethylammonio)-1,2-propanediol neutralized with either bromine or iodine, was used to produce a polyurethane cationomer with a poly(tetramethylene oxide) soft segment and a 4,4'-diphenylmethane diisocyanate hard segment. If these cationomers were annealed at room temperature for a period of approximately Í month in a desiccator filled with dry CaSO*, differential scanning calorimetry (DSC) studies showed an endotherm centered near 70 °C which was not present in the unannealed polymer and did not reappear upon subsequent cooling and heating cycles in the DSC. Some authors have suggested that a very similar endotherm found in other ionomers, mostly notably ethylene-methacrylic acid (E-MAA) copolymer ionomers, was due to an order-disorder transition within the ionic aggregates, i.e. ionic crystallite melting. In order to isolate the origin of this endotherm, the local environment around the anion in compression molded bromine neutralized samples was measured using the extended X-ray absorption fine-structure (EXAFS) technique. By measuring the change in the local environment over the temperature range corresponding to the DSC endotherm, it has been shown that this endotherm corresponds to water leaving the bromine coordination shell, rather than ionic crystallite melting. Other studies which include thoroughly drying the material in a vacuum oven below the transition temperature to remove the water suggest that the endotherm is due to the energetic change associated with water leaving the coordination environment of the anion in combination with water vaporization.

X-ray absorption spectroscopy (EXAFS) was used to characterize zinc-neutralized ionomers made from ethylene−propylene copolymers with grafted maleic anhydride units (Zn-MAn-g-EPM). The structure of the zinc moieties in the dry system consisted of two chelating carboxylate groups around one zinc atoma structure much different than if the carboxylate anions come from acrylic or methacrylic acid. These self-contained zinc−two chelating carboxylate structures assemble into a larger superstructure as shown in a previous SAXS study, which indicated that the microphase-separated ionic aggregates are ∼2 nm. This superstructure must therefore contain significant amounts of nonionic material, consistent with the observation that the superstructure also forms in the unneutralized maleic anhydride precursor. After addition of water, zinc atoms in the sample with 10% of the carboxylate groups neutralized were fully solvated, i.e., zinc was surrounded by six water molecules. Zinc atoms in samples with higher neutralization levels had two carboxylate oxygens replaced by water oxygens, which in turn maintained the zinc coordination number at four.

Extended X-ray absorption fine-structure (EXAFS) spectra were measured for three uniaxially extended lightly sulfonated polystyrenes, each containing 6.1 mol % sulfonate groups. The X-rays were linearly polarized, which enabled changes in local structure to be monitored parallel and perpendicular to the stretch direction. For the zinc-neutralized material, the metal-oxygen first-shell distance increased parallel to the stretch direction. Also, the Zn-0 first-shell bond vectors were aligned in the stretch direction.A simple theoretical description was developed which allowed quantification of the second moment of the orientation function for these bond vectors. In the nickel-neutralized material, the metal-oxygen first-shell distance did not increase, but Ni-0 bond vectors also aligned in the stretch direction. The second coordination shell of sulfur atoms seemed to be unaffected by uniaxial orientation. No changes were found in the local coordination environment of the cadmium-neutralized material after uniaxial extension. The results in this paper are interpreted in light of other orientation studies of ionomers and the structures and composition of the unoriented material.