Structural and optical studies of gamma-irradiated polyvinyl alcohol, polyethylene glycol, and lignosulfonate thin film

Abstract

Thin film of polyvinyl alcohol (PVA), polyethylene glycol (PEG) and lignosulfonate (Lg) were synthesized by solution casting technique. Samples from the synthesized PVA-PEG-Lg thin film were irradiated with different γ doses ranging from 20 to 100 kGy. The resulting effect of the γ-ray irradiation on the structural and optical properties of the blend films was investigated using Fourier transform infrared spectroscopy (FTIR) and ultraviolet spectroscopy (UVs). The FTIR analysis of the blends confirmed the formation of a relatively strong hydrogen bond between the hydroxyl groups of the PVA and the blended polymers. The optical band gap, refractive index, Urbach energy, and optical dielectric parameters were characterized and interpreted based on the γ-ray dose. The optical bandgap decreased from 4.00 to 3.39 eV for a γ-ray dose of 100 kGy, associated with an increase in both Urbach energy and refractive index of the films. This could be attributed to the domination of chain crosslinking caused by γ radiation under the present conditions. Moreover, we used the Commission Internationale de E’Claire (CIE) method to evaluate the change in color between the pristine and irradiated films. The PVA-PEG-Lg film achieved significant color differences during the γ-irradiation.