Structural and thermal degradation studies on thin films of the nanocomposite system PVP–Ce(SO₄)₂·4H₂O

Newly prepared and well-characterized nanocomposite thin films of polyvinylpyrrolidone (PVP) containing 2, 5, 10, and 15 wt% cerium (IV) sulfate have been subjected to structural and thermal stability investigations using the transmission electron microscopy (TEM), atomic force microscope (AFM), X-ray diffraction (XRD), differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA). The nanostructural nature of the investigated films was confirmed from the estimated average size of the particles. Better crystallinity was achieved with the addition of 15 wt% cerium disulfate to PVP. The thermograms of DSC and its derivative for the investigated composites indicated the development of a new endothermic peak of decomposition nature, and the values of peak position and associated enthalpy were found to be composition dependent, indicating a decrease in thermal stability of PVP with the increase of dopant concentration. Thermograms of TGA and its derivative revealed that the weight loss in the composite samples is composition dependent, and two main steps of degradation were clearly evident, the first assigned mainly to dehydration processes at relatively lower temperature range (30–200 °C) and the second at higher temperatures up to 400 °C attributed to decomposition processes. Thermodynamic parameters, such as activation energy, entropy, enthalpy, and Gibbs free energy, were also determined on the basis of thermogravimetric data.