High dielectric permittivity and low loss tangent of polystyrene incorporated with hydrophobic core-shell copper nanowires

We reported a low-cost strategy to improve dielectric performance of polystyrene (PS) by incorporating core-shell copper nanowires (CuNWs). The hydrothermally synthesized nanowires had a fresh copper core coated with a hydrophobic insulating layer. Compared with pure PS, CuNW/PS nanocomposites exhibited drastically improved dielectric performance, as manifested by their large dielectric permittivity (30) and low loss tangent (tan delta). At 16 wt% CuNWs loading, dielectric permittivity of the composite reaches 37 at 1 MHz, which was about 14 times larger than that of neat PS (epsilon' = 2.5), while the loss tangent of this composite was maintained at a low level (tan delta = 0.04). The pronounced dielectric improvement was ascribed to a large electrical conductivity of the fresh core of CuNWs, which provided the composites with a higher amount of mobile charge carriers participating in the interfacial polarization. The low loss tangent was attributed to the presence of insulating layer on the CuNWs, which impaired the formation of an electrically conductive network, thus suppressing dielectric loss. This simple strategy may open a new avenue to increasing dielectric permittivity of polymers while maintaining relatively low loss tangent.