Chemical modifications of polystyrene under swift Ar ion irradiation: A study of the energy loss effects

Abstract

Polystyrene (PS) films of about 53 μm in thickness are stacked together and are irradiated with 1.37 GeV Ar ions at room temperature to fluences ranging from 1.1 × 10 10 to 5.5 × 10 12 cm −2. The radiations induced chemical changes are studied by the Fourier transform infrared (FTIR) and ultraviolet/visible (UV/Vis) spectroscopies. It is found that the material undergoes serious degradation under irradiation and the chemical modifications depend strongly on the electronic energy loss. The main chains of PS as well as the phenyl ring are destroyed in the track core simultaneously with a damage cross-section of about 28.6 nm 2. Significant reduction in the absorbance of bands at 1602, 2853 and 3059 cm −1 occurs above about 0.77 keV/nm at an energy deposition of about 6.4 MGy. The stronger reduction in intensity of the band at 706 cm −1 compared to the band at 1602 cm −1 is partly attributed to cross-links outside the track core. Alkynes are produced above a threshold of about 0.77 keV/nm. The progressive shift of the absorption edge from UV towards the visible is attributed to the carbonization of the material.