Dielectric characteristics of polyvinylidene fluoride-polyaniline percolative composites up to microwave frequencies

Insulating polyvinylidene fluoride-conductive polyaniline composites were prepared by hot pressing, and their dielectric properties were characterized up to microwave frequencies. The composites exhibited typical percolative dielectric properties in the frequency range of 1–107 Hz, and the room-temperature dielectric constant reached the peak value with polyaniline volume fraction of 0.13. Significant dielectric relaxation was observed, which could be well fitted by Vogel-Fulcher relationship. The composites also exhibited similar percolative dielectric behavior in the frequency range of 3.62–7.30 GHz when polyaniline volume fraction was less than 0.14. This indicated that the interfacial polarization dominated the dielectric properties up to microwave frequencies, although it was usually regarded to be active at frequencies lower than 105 Hz. With further increasing polyaniline volume fraction, the dielectric constant and dielectric loss at microwave frequencies increased significantly. However, the dielectric properties in the frequency range of 1–107 Hz were unmeasurable due to the interconnected polyaniline conductive network.