A STUDY OF MICROWAVE TRANSMISSION, REFLECTION, ABSORPTION, AND SHIELDING EFFECTIVENESS OF CONDUCTING POLYPYRROLE FILMS

Microwave transmission, reflection, and absorption behavior and the sh ielding effectiveness of electrochemically synthesized polypyrrole fil ms with dc conductivities ranging from 0.001 to 50 S/cm are presented. Results show that the electrical conductivity of the doped polypyrrol e films has a significant effect on transmission, reflection, and abso rption of microwaves. Heavily doped, conducting films were highly refl ective, whereas lightly doped, semiconducting films had very high tran smission. Intermediate conductivity polypyrrole samples were highly ab sorptive. The agreement between experimental data and theoretical mode ling provided confidence to extend the modeling to include the effect of sample thickness on the transmission, reflection, and absorption pr operties of films with a wide range of conductivity values, hence, pro viding valuable information for the design of microwave devices and fu ndamental understanding of the material properties. A method of measur ing the far-field shielding effectiveness of polypyrrole films is also presented. Results of shielding experiments indicated the potential f or such applications. (C) 1994 John Wiley & Sons, Inc.