Enhancement of electrical properties of ferroelectric polymers by polyaniline nanofibers with controllable conductivities

Conductive nanofibers are adopted to enhance the electric properties of ferroelectric polymers. Polyaniline (PAN[) nanofibers doped by protonic acids have a high dispersion stability in vinylidene fluoride-trifluoroethylene copolymers [P(VDF-TrFE)] and lead to percolative nanocomposites with enhanced electric responses. About a 50-fold rise in the dielectric constant of the ferroelectric polymer matrix has been achieved. Percolation thresholds of the nanocomposites are relevant to doping levels of PAN I nanofibers and can be as low as 2.9 wt% for fully doped nanofibers. The interface between the conductive nanofiber and the polymer matrix plays a crucial role in the dielectric enhancement of the nanocomposites in the vicinity of the percolation threshold. Compared with other dopants, perfluorosulfonic acid resin is better at improving the performance of the nanofibers in that it serves as a surface passivation layer for the conductive fillers and suppresses leakage current at low frequency. The nanofibers drastically reduce the electric field strength required to switch spontaneous polarization of P(VDF-TrFE). The nanocomposites can be utilized for potential applications as high energy density capacitors, thin-film transistors, and non-volatile ferroelectric memories.