Characteristic Vibrational Spectral Change Observed for the π-Conjugated Structure of Sulfonated Polyethylene

Abstract

Infrared-active SO stretching bands [ν(SO)] observed for the sulfonated polyethylene (PE) samples were found to change their vibrational frequencies systematically depending on the degree of the π-conjugated chain structure generated through the sulfonation reaction and also on the sulfonate ion species SO3X in the structure [−CHCHCHCHCHC(SO3X)CC−...], where X = H, Na, Li, K, Ca, and Zn. For the sulfonated PE samples with SO3Na groups, the ν(SO) band was found to shift to the higher frequency side as the conjugated chain length was increased. When the π-conjugated chain structure was modified by bromination reaction (...−CCCCCCCC−... + Br2 → ...−CCCCCBrCBr−...), such a high-frequency shift was canceled. The sulfonated PE samples with SO3H groups, on the other hand, did not show any high-frequency shift even for longer π-conjugated chain structure but gave the ν(SO) bands at the position rather close to those of the SO3Na species coupled with a short π-conjugated chain. These spectral changes were confirmed also by measuring the spectral changes for a series of the model compounds having the π-conjugated structure combined with the SO3Na groups.

Key counter ion parameters governing polluted nafion membrane properties

“…This results in a modification of the sulfonate polarization and thereby to the observed dependence of the SO stretching band location with the nature of the counterion. ν shift due to metal cation has observed in 1990s by different research groups working on polymer containing triflate ions49–58 that are consistent with our results. The symmetrical stretching band of the sulfonate group can be decomposed into several components as follows49, 50 (Table 4): (i) free CF 2 SO, (ii) ion pairs, that is, monodentale co‐ordination cation CF 2 SO···M n + , and (iii) agregrates, that is, biendale or tridentale coordination metal cation (Table 4).…”

Sulfonation of the surface of cordierite monoliths through a novel multi-step wet chemical process

“…5, and Table 5 reports the position of the fitted bands. The four bands regarding the sulfonic groups were assigned according to literature values [62][63][64][65][66][67][68][69]: peaks at around 1030 and 1210 cm À1 are produced by the symmetric and antisymmetric stretching vibrations of the SO À 3 group, respectively. The band at about 1012 cm À1 is produced by vibrations of the phenyl ring substituted with a sulfonate group.…”