Modeling large permittivity of poly(vinylidenefluoride-co-trifluoroethylene) and nanospring single-walled carbon nanotube-polyvinylpyrrolidone nanocomposites

Highly dispersible nanospring single-walled carbon nanotubes (NS-CNTs) were incorporated in a P(VDF-TrFE) copolymer with up to 15 wt.% of nanofiller. The relative dielectric constant (K) of the polymer nanocomposite at 1 kHz was greatly enhanced from 12.7 to 62.5 at 11 wt.% of NS-CNTs, corresponding to a 492% increase over that of pristine P(VDF-TrFE) with only a small dielectric loss tangent (D) of 0.1. Based on two theoretical models, the Bruggeman equation and self-consistent effective medium theory (SC-EMT), experimental permittivity data for the P(VDF-TrFE) and NS-CNTs nanocomposites were simulated to estimate the dielectric constant of the NS-CNTs while changing both the shape of the nanofillers and the volume fraction of the interface when increasing the number of NS-CNTs in piled layers of P(VDF-TrFE). The number of NS-CNTs layers was counted from HR-TEM images to calculate the interfacial volume fraction, and used to infer the Eshelby tensor of the NS-CNTs in the SC-EMT model. The experimental dielectric constants of the composite films fit the Bruggeman equation and SC-EMT theory well for dielectric constants k=240-360, showing that the NS-CNTs nanofillers may be considered electrically semiconductive.