Research on the Physical Properties and Internal Structure of PVP/Nb₂O₅ Nanocomposite Coatings

The subject of this study is the effects of various concentrations of niobium pentoxide nanoparticles (Nb₂O₅ NPs) on the physical, optical, and thermal properties of thin films of poly(N-vinylpyrrolidone) (PVP). The obtained results indicate that the addition of nanoparticles significantly affects the physical properties of the investigated materials, limiting their optical UV transmittance in the range of 300-500 nm by approximately 20-40% and increasing the material's resistance to moisture that is present in the surrounding environment. Based on the thermal measurements performed using differential scanning calorimetry (DSC) and variable temperature spectroscopic ellipsometry (VASE), two distinct glass transition temperatures T_g for pure PVP and its Nb₂O₅ composites were revealed, with an additional intermediate T_g appearing in the composites, varying in the range of 135-168 °C (ellipsometric temperature cycle). This intermediate transition indicates the formation of an interfacial region with modified polymer chain mobility due to the interactions occurring between Nb₂O₅ nanoparticles and the PVP matrix. The results obtained from the scanning electron microscopy (SEM), Energy Dispersive Spectroscopy (EDS), and detailed Attenuated Total Reflectance-Fourier Transform Infrared Spectroscopy (ATR-FTIR) analyses also confirmed the presence of this interfacial area and indicated that it arises from nanoparticle agglomeration and surface cluster formation. The contact angle measurements revealed that the composites containing 15% and 25% Nb₂O₅ exhibited greater hydrophobicity. These results suggest that the investigated composite coatings could be employed as surface coverings to protect against external, environmental influences, such as moisture and UV radiation.