Preparation and study of the structural, optical, and dielectric properties of composite film PVA: PEO–CuCl2.2H2O through thermal differential scanning calorimetry

Abstract
In this study, solution casting was used to prepare pure polyvinyl alcohol and polyethylene oxide (PVA:PEO) blend films, as well as films reinforced with CuCl₂.2H₂O at varying weight ratios (10–50 wt%). The structural, optical, thermal, and electrical properties of the films were investigated. X-ray diffraction (XRD) revealed broad peaks at 2θ = 19.11°–23.32° in the pure blend, which diminished with increasing content, indicating reduced crystallinity and a shift toward a more amorphous structure. FTIR analysis showed shifts in vibration patterns and bond positions due to interactions between CuCl₂.2H₂O and the PVA:PEO matrix. Peaks in the range of 600–1100 cm⁻¹ indicated single bonds associated with salt reinforcement. O–H, C=O, and C–O–C vibrations were observed, with increased absorption intensity at 1712 cm⁻¹ and changes associated with aldehyde and alcohol groups, suggesting uniform dispersion of the salt within the blend. UV-Vis spectroscopy (190–1100 nm) showed that increasing CuCl₂.2H₂O content reduced the energy gap, indicating enhanced indirect electronic transitions. Differential scanning calorimetry (DSC) analysis revealed irregular changes in the glass transition temperature (Tg) and melting temperature (Tm), with the decomposition temperature (Td) appearing at certain salt ratios. Electrical measurements showed that the dielectric constant (ε') and loss factor (ε'') decreased with increasing frequency, while AC conductivity (σ a.c.) increased with both higher frequency and CuCl₂.2H₂O content. Overall, the addition of CuCl₂.2H₂O significantly influenced the physical properties of the PVA-PEO films, enhancing their potential for various functional applications.