Enhanced optical properties, thermal transitions, temperature-dependent electrical properties and modelling studies of poly(diphenylamine)/NiO nanocomposites

Conducting polymer nanocomposites with magnificent optical properties, thermal stability, high dielectric constant and electrical conductivity are of paramount importance in the fabrication of electronic devices. In this spotlight of applications, polymer nanocomposites based on nickel oxide (NiO) nanoparticles and poly(diphenylamine) (PDPA) were prepared and characterised. The UV–Vis spectroscopy analysis illustrates the minimum optical bandgap energy and maximum refractive index values obtained for 7 wt.% loaded nanocomposites. The FT-Raman, X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM) and energy-dispersive X-ray (EDX) studies confirm the presence of crystalline NiO nanoparticles in the PDPA matrix. The differential scanning calorimetry (DSC) emphasises the shifts in glass transition temperatures to higher domains with the incorporation of nanoparticles. The magnitude of dielectric constant and loss tangent decreases sharply with frequency and increases with temperature. As a function of temperature, the AC conductivity increases with increase in frequencies and the frequency-dependent AC conductivity obeys Jonscher’s universal power law. The activation energy obtained from Arrhenius plots decreases as a function of frequency. The impedance studies and decreasing radius of semicircles in the Nyquist plot with temperature affirm the temperature-dependent relaxation process. The DC conductivity values of composites increase with increase in filler concentration, and the percolation threshold was found to be around 5 wt.% loadings. The experimental values of DC conductivity were compared with theoretical models like Bueche, Scarisbrick and McCullough. It was observed that the experimental conductivity values match the DC conductivity predicted by the McCullough model.