Polymer Composites with 0.98 Transparencies and Small Optical Energy Band Gap Using a Promising Green Methodology:...

In this work, a green approach was implemented to prepare polymer composites using polyvinyl alcohol polymer and the extract of black tea leaves (polyphenols) in a complex form with Co²⁺ ions. A range of techniques was used to characterize the Co²⁺ complex and polymer composite, such as Ultraviolet-visible (UV-Visible) spectroscopy, Fourier transform infrared spectroscopy (FTIR), and X-ray diffraction (XRD). The optical parameters of absorption edge, refractive index (n), dielectric properties including real and imaginary parts (ε, and ε) were also investigated. The FRIR and XRD spectra were used to examine the compatibility between the PVA polymer and Co²⁺-polyphenol complex. The extent of interaction was evidenced from the shifts and change in the intensity of the peaks. The relatively wide amorphous phase in PVA polymer increased upon insertion of the Co²⁺-polyphenol complex. The amorphous character of the Co²⁺ complex was emphasized with the appearance of a hump in the XRD pattern. From UV-Visible spectroscopy, the optical properties, such as absorption edge, refractive index (n), (ε), (ε), and bandgap energy (E) of parent PVA and composite films were specified. The E of PVA was lowered from 5.8 to 1.82 eV upon addition of 45 mL of Co²⁺-polyphenol complex. The N/m* was calculated from the optical dielectric function. Ultimately, various types of electronic transitions within the polymer composites were specified using Tauc's method. The direct bandgap (DBG) treatment of polymer composites with a developed amorphous phase is fundamental for commercialization in optoelectronic devices.