AC electrical properties of conjugated polymers and theoretical high-frequency behavior of multilayer films

AC electrical properties of various conjugated polymers such as emeraldine base form of polyaniline, polyacetylene derivatives, and poly(1.4-phenylenevinylene) and its derivative are studied. Dielectric constant and conductivity are measured in the frequency range from 10 Hz to 2 MHz and in the temperature range from 78 to 300 K. Frequency dependence of ac dielectric constant follows Debye or Cole-Cole dielectric relaxation equation, and temperature dependence of relaxation time tau follows Arrhenius equation tau = tau (0) exp(E-a/k(B)T). Frequency dependence of ac conductivity shows a constant behavior in low-frequency regime (less than or equal to 10 kHz) and a power-law behavior (sigma similar to omega (s)) in high-frequency regime (greater than or equal to 100 kHz). For the applications of multilayer films of conducting polymers such as electromagnetic interference (EMI) shielding or optical filter, we theoretically calculate the reflectance, absorbance, and EMI shielding efficiency in high-frequency range (greater than or equal to1 GHz) based on plane wave theory. (C) 2001 Elsevier Science B.V. All rights reserved.