FT-IR spectroscopic studies of ionic interactions in sulfonated: Syndiotactic polystyrene ionomers

The effects of cation and hydration on cation-anion interactions in sulfonated syndiotactic polystyrene (SsPS) ionomers were examined by FTIR spectroscopy. Ionic interactions in SsPS. ionomers are reflected in their FTIR spectra directly, affecting the vibrations of the sulfonate anion. It I is, found that the counterion and hydration have a profound influence on cationanion interactions in the SsPS ionomers containing divalent transition metal cations (such as Mn2+, Zn2+ and Co2+) and alkali metal cations (such as Na+ and K+) In the dry materials, the counterion imposes a strong electrostatic field on the sulfate anion that polarizes the S-O dipole and shifts the asymmetric and symmetric vibrations of the sulfonate anion to higher frequencies. While in the hydrated materials, the polarization by the cation weakens and shifts the cooresponding vibrations to lower frequencies. For the unneutralized sulfonated syndiotactic polystyrene, in the hydrated form, the proton of the sulfonic acid is removed from the anion, yielding the sulfonate anion, SO3-. While in the dry form, the FTIR spectra of the sample exhibit characteristic absorbances of the sulfonic acid, -SO3H, group.