Relaxation processes in side-chain polyazomethine/thermally reduced graphene oxide nanocomposites

Nanocomposites based on side-chain polyazomethine (PAZ) and reduced graphene oxide (rGO) were prepared by solution blending method. They were subjected to broadband dielectric spectroscopy (BDS) analysis to discover the filler effect on the molecular mobility of the polymer chains Low-temperature non-cooperative local gamma- and beta-relaxations and a high-temperature cooperative segmental alpha-relaxation were found and described analytically. The increasing rGO content was shown to retard all kinds of the molecular mobility of the PAZ chains. Because of enhanced attractive rGO/polymer segments interaction and retarded alpha-relaxation, the polymer fragility m and the dielectric glass transition temperature T-g100 of the PAZ/rGO nanocomposite were found to increase strongly with increasing rGO loading phi up to 1 wt%. However, when go exceeds 1 wt%, the rGO nanoparticles form the percolation network resulting in enhanced conductivity of the nanocomposite and weakening the rGO/polymer segments interaction. As a consequence, m decreases and T-g100 tends to decline towards the value of the pristine PAZ. The dielectric relaxation strength was found to increase with increasing phi because of the rGO increment to the total dipole moment of the nanocomposite. Meanwhile, the thermal relaxation strength evaluated from the differential scanning calorimetry (DSC) data was shown to demonstrate other behavior. It decreases dramatically at a low rGO content (< 0.5 wt%) and does not change at higher rGO concentration. Such a behavior correlates with a strong decrease in the polymer degree of crystalliny evaluated from the wide-angle X-ray scattering (WARS) data with increasing phi. This finding confirms the polymer chains intercalation into the rGO stacks in PAZ/rGO nanocomposites.