Extended x-ray absorption fine-structure studies of the internal aggregate structure in lightly sulfonated polystyrene. 2. Effect of uniaxial orientation

Abstract

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.

EXAFS Studies of Various Sulfonated and Carboxylated Cadmium Ionomers

“…However, it is not clear that the differences shown in Figure 2 are outside of normal experimental error. If the data reduction procedure described in previous papers 3,8 is used, the EXAFS pattern of the 5.7 CdSPS is not outside the experimental error determined previously. 8 Further, differences in peak height are reflected in the quality of the fit and the E 0 value, not in the Debye-Waller factor, which suggests that the local environment in the 5.7 CdSPS is not significantly different from that of the other sulfonate ionomers.…”

“…However, it is not clear that the differences shown in Figure are outside of normal experimental error. If the data reduction procedure described in previous papers , is used, the EXAFS pattern of the 5.7 CdSPS is not outside the experimental error determined previously …”

Imaging and X-ray Microanalysis of a Poly(ethylene-ran-methacrylic acid) Ionomer Melt Neutralized with Sodium

“…A variety of spectroscopic techniques have been used to explore the local (<1 nm) environments of the neutralizing cations in ionomers: solid-state NMR (SSNMR), − FTIR, − dielectric, and EXAFS. ,,− The majority of the data suggests that neutralized acids and their cations exist both in aggregates and as isolated species. For example, dielectric spectroscopy 15 of Na-neutralized noncrystalline EMAA ionomers found two relaxation processes that are ascribed to long chain segments containing Na carboxylates isolated in the matrix and to segments containing Na carboxylates incorporated in ionic aggregates.…”

Morphological Studies of Lightly Sulfonated Polystyrene Using 23Na NMR: Effects of Polydispersity in Molecular Weight

“…One of the most commonly studied ionomers is sulfonated polystyrene (SPS); the morphology − and physical properties ,− of this ionomer have been studied in detail. Many of the previous studies of SPS have been completed using polydisperse ionomers.…”