Sulfonate anion, stretching vibrations

For the 1.7 mole X Na-SPS, the absorbance at 1048 Cm is probably due to the symmetric stretch of the SO anion, and the broad band at 1226 cm is attributed to the asymmetric stretch of the SOj anion. The second absorbance due to the asymmetric stretch of the S 2 anion is not easily identified, but it appears that the 1197 cm band in the sulfonated polymer may include a contribution from thij vibration (note Jhe difference between the ratio of the 1197 cm and the 1155 cm intensities in NaSPS jijid polystyrene)j+... 

For the Zn salt, the broad absorbance between 1228 and 1240 cm is due to the asymmetric stretch of the SO anion. The symmetric stretch of the SOj anion appears as a shoulder at 1042 cm. A band at 1009 cm results from the in-plane bending vibrations of a benzene ring substituted with a metal sulfonate group. 

Tbe effect of hydration on the infrared spectrum of a 7.6 mole % H-SPS is shown in figure 3. After 19 hours the sample absorbed about 9% water, which corresponds to 9 moles H O per sulfonic acid group. This was accompanied by a ljirge decrease in the intensity of the absorbance band at 1176 cm and increases in the intensities of the bands at 1126 cm and 1007 cm. This result was expected, since upon hydration the acidic proton of the sulfonic acid is removed from the anion (1176 cm is characteristic of the S 0 symmetric stretch of the -SO.H and 1126 cm and 1007 cm are due to the ln-plane skeleton and the in-plane bending vibrations of a benzene ring with a SO, group attached). An absorbance at 1033 cm in the 19 hour sample is due to the symmetric stretch of the -SO and is further evidence of hydration Similarly, the decrease in intensity of the band at 1100 cm in the hydrated sample indicates that fewer -SO.H groups are present. 

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