Thermo-mechanical and opto-electrical study of Cr-doped-ZnO-based polyvinyl chloride nanocomposites

Polymer nanocomposites exhibit unique physical properties inaccessible from their individual constituents, which are tunable through the type of the polymer matrix, the type and size of the incorporated nanoparticles, and the doping level, and therefore, can be utilized in a wide range of potential applications. Here, we report the fabrication of pure Polyvinyl chloride (PVC) and PVC-based nanocomposites containing different loadings of pure and Cr-doped ZnO nanoparticles, using solvent casting method. Scanning electron microscopy images of the obtained nanocomposite films confirmed the successful incorporation of nanoparticles within the PVC matrix, with higher dispersion quality for the Cr-doped ZnO samples. The prepared nanocomposite samples were found to possess higher thermo-mechanical stability, compared to pure PVC, resulting from the strong interaction between the nanoparticles and polymeric chains, as inferred from their thermogravimetric and dynamic mechanical analysis (TGA and DMA) profiles. Specifically, the temperatures corresponding to the onset and 50% weight loss as well as the glass transition temperature are increased by ~ 88, ~ 34, and ~ 16 °C, respectively, after loading selected amounts of the nanoparticles. In addition to the thermo-mechanical stability, the nanocomposites revealed potentially relevant dielectric response, where the dielectric permittivity exhibits remarkable enhancement, by 400%, compared to pristine PVC. The optical transmission of the PVC is strongly suppressed over the entire visible spectral regime, upon loading the nanoparticles, and its optical band gap (~ 4.1 eV) is red shifted toward the value of pristine ZnO nanoparticles (~ 3.3 eV), while the distinct Cr3+ and Cr6+ optical transitions are preserved for the nanocomposites. The obtained thermo-mechanical stability, required for working devices, together with the here reported improvements in the dielectric response for the nanocomposite samples may alter the typical applications of PVC polymers from being insulating materials to be utilized in energy storage and capacitors manufacture, while the preserved optical properties of the incorporated nanoparticles render these nanocomposites suitable candidates for optoelectronic devices.