Polyaniline-tungsten oxide metacomposites with tunable electronic properties

Polyaniline (PANI) nanocomposites reinforced with tungsten oxide (WO ₃) nanoparticles (NPs) and nanorods (NRs) are fabricated via a facile surface-initiated-polymerization (SIP) method. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) characterizations reveal the uniform coating of polymer on the filler surface and a good dispersion of the nanofillers within the polymer matrix. Unique negative permittivity is observed in pure PANI and its nanocomposites. The switching frequency (frequency where real permittivity switches from negative to positive) can be easily tuned by changing the particle loading and filler morphology. Conductivity measurements are performed from 50∼290 K, and results show that the electron transportation in the nanocomposites follows a quasi 3-d variable range hopping (VRH) conduction mechanism. The extent of charge carrier delocalization calculated from VRH well explains the dielectric response of the metacomposites. Thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) reveal an enhanced thermal stability of the nanocomposites with the addition of nanofillers as compared to that of pure PANI.