Abstract
Polyvinyl-pyrrolidone loaded with different fractions of dispersed nano-graphene platelets (NGPs) were studied by Broadband Dielectric Spectroscopy in the frequency range of 1 mHz to 1 MHz. Complex permittivity and dynamic ac conductivity as a function of frequency, temperature, and composition were explored. The concentration-dependent insulator-to-conductor transition was traced through the dependence of the dc conductivity and the onset of the dispersive ac conductivity. The temperature evolution of the dielectric spectra below and above the fractional threshold exhibits different dynamics and signs the critical percolation threshold. Percolation is dictated by quantum penetration of the effective potential barrier set by the polymer matrix operating in parallel with conduction along physical contact of NGPs, in accordance with predictions for systems consisting of a semi-conducting matrix and dispersed conducting inclusions.
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