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-phenylene vinylene) and its derivative are studied. Dielectric constant and conductiv ity are measured in the frequency range from 10 Hz to 2 MHz and in the temp erature range from 78 to 300 K. Frequency dependence of ac dielectric const ant follows Debye or Cole-Cole dielectric relaxation equation, and temperat ure dependence of relaxation time tau follows Arrhenius equation tau = tau (0) exp(E-a/k(B)T). Frequency dependence of ac conductivity shows a constan t behavior in low-frequency regime (less than or equal to 10 kHz) and a pow er-law behavior (sigma similar to omega (s)) in high-frequency regime (grea ter 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, an d EMI shielding efficiency in high-frequency range (greater than or equal t o1 GHz) based on plane wave theory. (C) 2001 Elsevier Science B.V. All righ ts reserved.