Broadband microwave absorption and shielding properties of a poly(aniline)

Conducting polymers (CPs) have evinced much interest recently in applications involving microwave absorption and electromagnetic interference (EMI) shielding. In this respect, prior microwave measurements on CPs have been limited to single frequencies or narrow bands, to thin films, and to permittivity measurements. In the present communication, we report comprehensive, cumulative broadband measurements and computations of all microwave parameters of a CP relevant for practical application, viz.: conductivity, absorption, complex permittivity, shielding and reflection. The specific CP selected is poly(aniline) (P(ANi)) doubly doped with two unique sulfonate dopants, which impart to it a DC conductivity of 11 S/cm at room temperature and high environmental stability. Measurements have been carried out over a 4 to 18 GHz band, encompassing the X and Ku bands of military radar interest, on the bulk CP, using coaxial line techniques. In comparison with prior work, a much more robust algorithm has been used to extract the material parameters from the measured data. Comparison with prior results on CPs also shows high microwave attenuation for this polymer. (C) 1999 Elsevier Science S.A. All rights reserved.