FTIR equivalent weight determination of perfluorosulfonate polymers

Abstract

Fourier transform infrared (FTIR) and attenuated total reflectance (ATR) spectroscopy studies of the sulfonyl fluoride, potassium salt, and sulfonic acid forms of long and short side chain perfluorosulfonate polymers revealed bands indicative of the sidegroup and backbone compositions, endgroups on the main chain, water content, monomer concentration, and degree of salt hydrolysis. The equivalent weight (EW) of the polymer was obtained by titration and NMR measurements which were then calibrated to either the CAF/CAOAC absorbance band ratio for thin (<1.1 mil) films or to a CAF/SO 2 F absorbance band ratio for thick films (5 to 25 mils). An FTIR measurement of the film thickness based on the CAF group concentration was found to be both a function of the actual thickness and the EW; a method for compensating for this EW dependence is described. Esterification and fluorination of the polymers yielded FTIR measurements of the endgroup compositions on the polymer backbone which were shown to consist of ACOF, ACOOH, ACO 2 CH 3 , and ACF¼ ¼CF 2 groups. Thermogravimetric Analysis Infrared (TGA-IR) spectroscopy of the acid form polymers indicates that degradation begins by the decomposition of the ASO 3 H group at 320 C followed by bulk deterioration above 400 C. The FTIR techniques detailed herein have been developed for accurate, reproducible, and rapid compositional measurements of Nafion V R and other perfluorosulfonate polymers.

Synthesis and characterization of perfluoro quaternary ammonium anion exchange membranes

“…All spectra were normalized to the high intensity peak at 1200 cm À1 owing to the stability of the CAF backbone throughout the reaction. The precursor material also showed a distinct peak at 1470 cm À1 that is associated with SAF motion 23 or the asymmetric stretch of the SO 2 F group. 16 This peak is drastically reduced upon amination where the SAF bond is replaced by an SAN bond.…”

The reaction between Nafion sulfonyl fluoride precursor membrane and 1,4-dimethylpiperazine does not yield reliable anion-exchange membranes

“…The FT-Raman spectrum of Naon-SO 2 F has bands at 1470, 1250, and 648 cm À1 , that are well demarcated and not present in the spectrum of Naon-SO 3 H; these are therefore diagnostic of the -SO 2 F functional group. A band at 1470 cm À1 in the FTIR spectrum of Naon-SO 2 F was tentatively assigned to the S-F bond motion in a recent prior study 8 and to the asymmetric -SO 2stretch (of the -SO 2 F group) in an earlier prior study. 9 The Raman spectrum of Naon-SO 3 H is well assigned ( Table 2 in ref.…”

Synthesis of perfluorinated ionomers and their anion exchange membranes

“…1A), the sharp peak at 1467 cm À 1 is associated with the asymmetric stretch of the O ¼S¼ O in the -SO 2 F group and the twin peaks at 823 and 796 cm À 1 are ascribed to the stretching vibration of the S-F group. The strong band at 989 cm À 1 is associated with stretching vibration of the C-O-C groups, and the two large bands at 1320 cm À 1 and 1120 cm À 1 represent the -CF 2 group [37,38]. Compared with the S-PFSO 2 F spectrum, in the S-PFSO 2 NH 2 spectrum (Fig.…”