Microwave characterisation of smart materials based on conducting polymer composite material

Conducting polymers have created some interest as replacements for metals in electromagnetic shielding technology because of their distinctive properties, not least their relationship to plastics. Conjugated polymers, such as polypyrrole and polyaniline, may be applied to paper or textile substrates and readily formulated to give prescribed impedance characteristics at microwave frequencies. However, the electronic communications industry also recognises a requirement for `smart´ surfaces whose microwave reflectivity can be controlled by the application of an external stimulus, such as an electric field. We report on studies into a new concept in microwave active materials and attempts to understand the observed electrical behaviour at d.c. and microwave frequencies