Broad-Spectrum Enhancement of Polymer Composite Dielectric Constant at Ultralow Volume Fractions of Silica-Supported Copper Nanoparticles

A new strategy for the synthesis of high permittivity polymer composites is demonstrated based on well-defined spatial distribution of ultralow amounts of conductive nanoparticles. The spatial distribution was realized by immobilizing Cu nanoparticles within the pore system of silica microspheres, preventing direct contact between individual Cu particles. Both Cu-loaded and unloaded silica microspheres were then used as fillers in polymer composites prepared with thermoplastic SEBS rubber as the matrix. With a metallic Cu content of about 0.26 vol % in the composite, a relative increase of 94% in real permittivity was obtained. No Cu-induced relaxations were observed in the dielectric spectrum within the studied frequency range of 0.1 Hz to 1 MHz. When related to the amount of conductive nanoparticles, the obtained composites achieve the highest broad-spectrum enhancement of permittivity ever reported for a polymer-based composite.