THE ELECTROMAGNETIC PROPERTIES OF POLY(P-PHENYLENE-VINYLENE) DERIVATIVES

We report the studies on the frequency dependence of the complex permi ttivity (epsilon = epsilon' - i.epsilon '') and of the electromagneti c interference shielding (EMI) of the conducting polymers such as poly (para-phenylene-vinylene) (PPV) and poly(2,5-dimethoxy,1,4-phenylene-v inylene) (DMeO-PPV) doped with different dopants. Permittivity measure ments from 10 kHz to 10 GHz point out that all conducting polymers dop ed with H2SO4 show a conductivity range of 10(-1)-10(+1) S cm(-1), but doped DMeO-PPV has conductivity slightly higher than that of PPV. Fro m these experimental data, the reflectivity coefficients of these mate rials are calculated in a frequency range 3-5 GHz, and have the values up to -30 dB depending on the frequency, on the thickness of the mate rials, on the dopant agents and specially on the doping levels of the materials. The potential applications of these materials in EMI shield ing are discussed. (C) 1998 Elsevier Science Ltd. All rights reserved.