Impact of gamma irradiation and DFT simulations on the structural, surface, and thermal characteristics of PVA/Al2O3 nanocomposite films

This study investigates the effects of gamma ray exposure on the structural, surface, and thermal properties of polyvinyl alcohol (PVA)/aluminum oxide (Al 2 O 3 ) nanocomposite films. We employed multiple analytical techniques; including Fourier transform infrared spectroscopy (FTIR), surface roughness analysis, contact angle measurements, and thermogravimetric analysis (TGA) to characterize these effects. FTIR result displays that the gamma energy can be absorbed by the PVA polymer and the embedded nanoparticles. This absorbed energy can lead to the breaking of chemical bonds within the PVA polymer chain and can then reform into new structures, leading to cross-linking. The presence of Al 2 O 3 nanoparticles influences these rearrangements by acting as nucleation sites or by enhancing the interaction between the polymer chains and the radiation, leading to altered structural properties. Surface roughness of the composite films increased with higher gamma doses, while contact angle measurements revealed enhanced surface wettability and hydrophilicity. Thermal stability improved with both the addition of Al 2 O 3 and gamma radiation exposure. Additionally, we applied density functional theory (DFT) using the B3LYP method with a 6-311G(d,p) basis set to explore the relationship between spectral and structural characteristics of PVA and the PVA/Al 2 O 3 nanocomposite. This theoretical approach examined alterations in molecular structure and optical properties following gamma-ray exposure. Our vibrational analysis conducted in the ground state using DFT showed close alignment between experimental infrared spectra and calculated vibrational wave numbers. The molecular energy gap was defined through frontier molecular orbital energies (HOMO-LUMO), with observations indicating intermolecular charge transfer and chemical reactivity within the molecule. Chemical descriptors, including softness and reactivity parameters, provided insights into the nucleophilic and electrophilic behavior of specific molecular sites. The molecular electrostatic potential (MEP) surface highlighted hydrogen bonding and the molecule's reactive nature, while Mulliken atomic charge analysis revealed electron density shifts within the ring structure.