Thermal, Optical, and Dielectric Studies of VO2+ Doped PVC Films

Pure and VO2+ doped poly(vinyl chloride) (PVC) films were prepared by using the solution casting method. Various techniques including differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FTIR), ultraviolet-visible spectroscopy (UV-Vis) and electron paramagnetic resonance (EPR) were employed in the characterization of the samples. The thermal properties of these films were investigated by employing DSC and TGA. Using the DSC thermograms, glass transition temperature (Tg) and melting temperature (Tm) of the PVC films were measured. Thermogravimetric curves of pure and VO2+ doped PVC films showed three distinct steps of weight loss. The FTIR results showed that the addition of VO2+ reduces the crystallinity of PVC due to the interaction of vanadium ions with the CH stretching modes of the CH2 groups. Optical absorption edge and indirect band gap showed a decreasing trend with increasing the VO2+ concentration. From the EPR spectra, the Spin – Hamiltonian parameters (g and A) were evaluated. For dielectric studies the films were studied in the frequency range from 10 KHz to 2 MHz at room temperature. It was observed that with the increase in frequency, the value of dielectric constant decreases up to100 kHz, thereafter it becomes almost constant for all the samples.