Fourier transform infrared spectroscopy of perfluorocarboxylate polymers

Abstract

Perfluorocarboxylate polymers in the carboxylic methyl ester, potassium salt, and carboxylic acid forms have been analyzed by Fourier transform infrared (FT-IR) transmission and attenuated total reflectance (ATR) spectroscopy. Band assignments were made for most of the dominant peaks. An absorbance band ratio, comparing the 555 cm-1 C-F band to the 982 cm-1 C-O-C ether band, was found to be a direct measure of the equivalent weight of the polymers. In addition, the transition from the methyl ester form to the acid form was determined by examining the 2969 cm-1 methyl ester band versus the broad approximately 3200 cm-1 acid band. Quantitative expressions are presented to enable the computation of equivalent weight and acid content based on FT-IR thin-film absorbance measurements.