All-organic dielectric nanocomposites using conducting polypyrrole nanoclips as filler

All-organic nanocomposites using conducting polypyrrole (PPy) nano-clips as fillers and poly(vinylidene fluoride-chlorotrifluoroethylene) (PVDF-CTFE) as the matrix are studied. The nanocomposites with a uniform microstructure were fabricated via a combination of a solution casting and a hot pressing process. Due to the uniform microstructure, the composites exhibit a single glass transition process, whose temperature decreases with increasing PPy content. The dielectric properties of the nanocomposites are systemically studied and analyzed over a wide temperature range from -60 degrees C to 140 degrees C and a broad frequency range from 100 Hz to 1 MHz. The nanocomposites have a low percolation threshold (similar to 7.4 wt%) and exhibit a high dielectric constant and a low dielectric loss. For the composites with 7 wt% of PPy at room temperature, the dielectric constant at 1 kHz is 23 times higher than that of the polymer matrix and the dielectric loss over a broad frequency range is less than 0.4 which is lower than the loss reported in other composites with the composition close to the percolation threshold. It is concluded that mixing PPy with P(VDF-Clth) results in a new relaxation process that dominates the observed dielectric loss at low temperatures including room temperature. It is demonstrated that it is the DC conductivity rather than the dielectric constant that should be used to determine the percolation threshold.