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

We report the studies on the frequency dependence of the complex permittivi ty, and on the electromagnetic interference (EMI) shielding of conductive b lends. The blends were obtained fi om conjugated oligomers of (p-phenylene- 1,3,5-hexatrienylene) end-capped by Schiff base units and dispersed in an i nsulating 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 e lectrical conductivity of experimental data 10(-5)-10(+1) S/cm. From these composites were in a ran on 250-500 mu m, the reflectivity coefficients [R( dB)] have been calculated for simulation of mm thick samples, they have val ues 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 modeliza tion of the radio-electric properties of conductive blends, using McLachlan 's General Effective Medium (GEM) Theory. The optimization of the GEM param eters suggests some informations about the shape of the particles as well a s the micro/macrostructure of the composite materials. Copyright (C) 2000 J ohn Wiley & Sons, Ltd.