LAUSR

This Letter studies the dielectric responses of nanocomposites of poly(ether methyl ether urea) (PEMEU) with alumina nanofillers at less than 0.7% volume loading (0.7 vol. %). The results show that the dielectric constant K of PEMEU nanocomposites is enhanced by the nanofillers. The enhancement peaks at 0.33 vol. % nanofiller loading, from K = 3.9 of neat polymer to K = 5.5 of nanocomposites from room temperature to 200 °C, above the glass transition (∼150 °C) of the polymer. Except for an enhanced dielectric constant, the nanocomposite maintains a low dielectric loss and a high breakdown strength of 500 MV/m at room temperature and 300 MV/m at 150 °C, respectively. Thus, the nanocomposite with 0.33 vol. % nanofillers delivers discharged energy densities of 6.5 J/cm3 at room temperature and 2 J/cm3 at 150 °C with better than 90% charge/discharge efficiency, 40% higher than the neat polymer.