The Sulfonation of Poly(ether ether ketone) as Investigated by Two-Dimensional FTIR Correlation Spectroscopy

Fourier transform infrared and two-dimensional correlation (2D-COS) spectroscopies were used to follow the structural alteration occurring upon sulfonation of poly(ether ether ketone), in concentrated sulfuric acid at room temperature. With the help of high resolution and high sensitivity 2D-COS, it was possible to locate the aromatic ring in which the substitution has taken place. Two new IR bands at 1288 and 1320 cm(-1) were attributed to substitution occurring on the aromatic ring flanked with two ether groups. Limited oxidation effects of concentrated sulfuric acid manifested itself by the production of new carbonyl species absorbing in the IR at 1720 and 1750 cm(-1) that were attributed to a fluorenone-type structure and to ester groups. The 2D-COS analysis showed that the band at 1470 cm(-1) is not only due to the new substitution by sulfone groups and can not be used in the determination of sulfonation degree. Instead, the intensity of the 1490 cm(-1) band, which can be attributed to skeletal ring vibration, was found to correlate well with the degree of sulfonation calculated from H-1 NMR spectroscopy. The infrared spectroscopy combined with 2D-COS provides a fast and powerful method for qualitative polymer structure verification and help to establish the quantitative analysis. (c) 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41242.