Preparation and evaluation of microstructure, dielectric and conductivity (ac/dc) characteristics of a polyaniline/poly N-vinyl carbazole/Fe3O4 nanocomposite

A poly N-vinyl carbazole- Fe3O4 hybrid composite was prepared by solid state polymerization of N-vinyl carbazole (NVC) monomer in presence of Fe3O4 powder. This hybrid composite was dispersed in aqueous medium containing a known amount of potassium perdisulfate (KPS) as oxidant under constant sonication. A known amount of aniline (ANI) was injected in the system which started changing color and ultimately a black mass of (PANI-PNVC-Fe3O4) separated out. The composite was characterized by FTIR, FESEM and HRTEM analyses. XRD analyses using Williamson-Hall plot revealed average particle size of the PANI-PNVC-Fe3O4 composite to be around 34 nm. HRTEM analyses confirmed the particle size to be in the range 25–40 nm. The dielectric constants of PNVC–Fe3O4 system was low at 0.1–25 kHz whereas the PANI encapsulated PNVC–Fe3O4 nanocomposites showed significantly higher values of dielectric constant (>5500) at 0.1 kHz implying that the interfaces between grain and grain boundary of the composite play a dominant role for enhancing dielectric properties of the system. The ac conductivity was found to be independent of frequency in the range 102–103 Hz for all the nanocomposites implying contribution of free charges and rise thereafter appreciably in the frequency range of 1–25 kHz due to trapped charges in the grain boundary.