Polymer composites filled with conductive fillers can demonstrate ultrahigh effective dielectric permittivity, which is generally attributed to an enhanced Maxwell-Wagner-Sillars interfacial polarization associated with the formation of microcapacitor networks. Here, we explore a composite of the ethylene-propylene-diene elastomer with carbon-black (CB) nanofillers and investigate its dielectric response over wide ranges of temperature and frequency. The dielectric relaxation exhibits atypical (counter-Arrhenius) temperature dependence, contradicting the widely assumed interfacial polarization mechanisms. It is shown that the relaxation/polarization is actually determined by electron displacement─primarily via e-conduction and tunneling within CB clusters─and that the composites' dielectric response can be quantitatively correlated with the CB cluster morphology via a set of scaling laws. Considering the selected composite as a paradigmatic system, the physical origins of the dielectric relaxation and the associated scaling relations seem to be generally applicable and expected to also pertain to other dielectric polymer/conductive-filler composites near percolation.
All Science Journal Classification (ASJC) codes
- Electronic, Optical and Magnetic Materials
- Physical and Theoretical Chemistry
- Surfaces, Coatings and Films