The electromagnetic properties of blends of poly(p‐phenylene‐vinylene) derivatives

We report the studies on the frequency dependence of the complex permittivity, and on the electromagnetic interference (EMI) shielding of conductive blends. The blends were obtained from conjugated oligomers of (p‐phenylene‐1,3,5‐hexatrienylene) end‐capped by Schiff base units and dispersed in an insulating matrix of poly(vinyl chloride) (PVC) and doped with sulfuric acid, H₂SO₄. Permittivity measurements from 10 kHz to 10 GHz have pointed out that the electrical conductivity of composites were in a range 10⁻⁵–10⁺¹ S/cm. From these experimental data performed on 250–500 µm, the reflectivity coefficients R(dB)] have been calculated for simulation of mm thick samples, they have values of −9 to −20 dB depending on the frequency and on the thickness of the composites. These permitivity data have also allowed us to develop modelization of the radioelectric properties of conductive blends, using McLachlan's General Effective Medium (GEM) Theory. The optimization of the GEM parameters suggests some informations about the shape of the particles as well as the micro/macrostructure of the composite materials. Copyright © 2000 John Wiley & Sons, Ltd.