FTIR spectroscopic analysis of ion irradiated poly (ether ether ketone)

Attenuated total reflection Fourier transform infrared (ATR-FTIR) and two dimensional correlation (2D-COS) spectroscopies were used to follow the structural alteration occurring upon ion irradiation (H+ and He2+) of films of poly (ether ether ketone), PEEK. Samples were exposed to ion irradiation doses up to 75 MGy in air atmosphere, and IR spectra were measured after ion irradiation and also for the gels after solvent extraction experiments. With the help of high resolution and high sensitivity 2D COS it was possible to obtain useful information about the different effects, types and mechanisms of reactions accompanying ion irradiation. Three main different effects of ion irradiation were observed. Oxidation manifested itself by the production of new carbonyl species absorbing in the IR at 1715 and 1745 cm−1 that were mainly present in the irradiated samples and attributed to fluorenone structures and to ester groups. Crosslinking occurred with the progressive development of new aromatic species absorbing at 1470, 870 and 810 cm−1 that were mainly present in the gels formed on irradiation. The formation of intermolecular crosslinks resulted in the increase in local ordering within the amorphous phase and orientation was observed to increase after ion irradiation by the progressive development of new bands at 1316, 1288, and 1240 cm−1.The different structures produced on irradiation with proton and helium ions were discussed and the analysis showed that helium ions were more effective in introducing the observed changes than protons. The infrared spectroscopy combined with 2D correlation provides a fast and powerful tool for polymer structure characterization.