Dielectric characteristics of poly(N-vinylcarbazole) and its nanocomposites with ZnO and acetylene black

Dielectric constant and dielectric loss parameters of poly(N-vinylcarbazole) homopolymer and several nanocomposites of poly(N-vinylcarbazole) with ZnO were studied as a function of frequency. In the low frequency range (0-20 kHz) the dielectric constant values of the base polymer varied from similar to 30 to similar to 2, and the same for the composite varied from 8500 to 2000 (4.54), 5000 to 1000 (2.63) and 2000 to 500 (1.17), the figures in parenthesis denoting the ratio of ZnO:PNVC in the nanocomposites. Likewise, dielectric loss parameters were found to be (7-10 x 10(-3)) for the homopolymer and 4.0, 2.5 and 1.25 for the three PNVC-ZnO composites respectively. Notably, a mechanical mixture of ZnO and PNVC (1.17) exhibited much lower dielectric constant (400-25) and loss parameters (0.14-0.065). These features imply polarization was differently affected depending on factors such as grain size and grain-boundary interfaces being formed in these systems. Tan delta-temperature variation for the composites revealed the occurrence of a maximum between 60 and 70 degrees C. These features signified dipole group loss in the composite. Dielectric constant of a conducting nanocomposite of poly(N-vinylcarbazole) with acetylene black revealed very low negative value tending to zero at high frequency. (C) 2010 Published by Elsevier B.V.