Studies on free volume controlled electrical properties of PVA/NiO and PVA/TiO2 polymer nanocomposites

Abstract

Microstructural characterization of poly(vinyl alcohol)/nickel oxide (PVA/NiO) and titanium dioxide (PVA/TiO2) polymer nanocomposites has been performed by Positron Lifetime Technique (PLT). The increased positron lifetime parameter viz., o-Ps lifetime (τ3) up to 1.0 wt% of NiO and up to 0.4 wt% of TiO2 loading suggests the reduction in overall packing density of the polymer network and the formation of interface between PVA polymer matrix and NiO, TiO2 nanoclusters. The decreased o-Ps lifetime (τ3) at the higher concentration of TiO2 loading indicates the improved interfacial interaction between the surface of TiO2 nanoparticles and side chain of PVA polymer matrix. This is evident from Fourier Transform Infrared Spectroscopy (FTIR) studies. Scanning Electron Microscopy (SEM) studies demonstrate the formation of nanoclusters by the agglomeration of nanoparticles at higher wt% of nanofiller loading. The increased AC/DC conductivity of PVA/NiO and at lower concentration of TiO2 in PVA/TiO2 polymer nanocomposites suggests the increased mobility of ions and electric charge carriers. The decreased conductivity at higher concentration of TiO2 indicates the reduced conducting pathways for the mobility of ions and electric charge carriers due to the increased ion aggregation. The increased dielectric constant and dielectric loss up to 1.0 wt% of NiO and 0.4 wt% of TiO2 suggests the increased dipole polarization. The decreased dielectric constant after 0.4 wt% of TiO2 is attributed to the reduced dipole polarization by the formation of thin immobile nano-layers and hence the polymeric chain mobility.