Modification of Optical Bandgap and Formation of Carbonaceous Clusters Due to 1.75 MeV N5+ Ion Irradiation in PET Polymers and Search for Chemical Reaction Mechanisms

Abstract

The effects of 1.75 MeV N5+ ion beams of varying fluences, ranging from 1x1011 to 5x1014 ions/cm2 on structural, optical, and chemical properties of polyethylene terephthalate (PET) polymer, have been investigated by x-ray diffraction (XRD), UV–Visible spectroscopy, and Fourier transform infrared (FTIR) spectroscopy. The XRD patterns of PET samples show that the crystallinity increases with ion irradiation of fluences 4x1011 and 5x1012 ions/cm2. Optical bandgap energy decreases more at the ion fluences of 5x1014 ions/cm2. Absorption maxima shifted towards a higher wavelength value due to the formation of extended conjugation. Acetylenic (-C≡C-) group formation and free CO2 group are confirmed by FTIR spectroscopy. The reaction mechanism of the degradation product formation chemistry is discussed.