Influence of structural characteristics of conducting polymers on their microwave properties

Summary form only given. The complex dielectric constant /spl epsiv/* (/spl epsiv/* = /spl epsiv´-i /spl epsiv) of various conducting polymers (polyaniline and poly(3- alkyl thiophenes)) is studied over a firequency range spanning firom 130 MHz to 20 GHz. /spl epsiv/* is measured using an HP 8720 network analyser on pressed samples compatible with APC7 standard. The effects of structural parameters on the observed evolutions have been investigated. The effects of the counter-anion size, of the length of the alkyl chain on the substituted monomer, of polymer molar mass and of the defect rates along the chain are presented. In the case of polyaniline we have shown that an increasing size of the counter-anion leads to a decrease in /spl epsiv/* value (for a given doping level) and a decrease in /spl epsiv/´ value for a given /spl epsiv/ value at fixed frequency. In the case of poly(3- alkyl thiophenes) we find that the same effects are produced by increasing the length of the alkyl chain on the substituted monomer. We have also found out that by lowering the defects rate or increasing the molar mass of the polymer it was possible to increase /spl epsiv/* value (for a given doping level) and also to decrease the value of /spl epsiv/´ for a given /spl epsiv/ value (at fixed frequency). All of that results from the effects of inter-chain distance or localisation length along the chains.