Influence of the morphology of polyaniline on the microwave absorption properties of epoxy polyaniline composites

This study reports on the electrical conductivity and dielectric properties of conductive epoxy composites containing polyaniline (PANI) with various morphologies. Globular, fibrillar, and flake-like PANIs, with more or less high aspect ratios (ratio of length to diameter or thickness), were synthesized and dispersed into an epoxy resin. It was found that increasing the aspect ratio of PANI reduces the electrical percolation threshold of the composites (from 3.9 to 1.3 vol.%), and enhances their electrical conductivity up to sigma > 10(-3) S/cm. Moreover, it was found that flake-like PANI, with increased aspect ratio, improves the microwave absorption properties of the composites in a microwave range: 2.4-8.8 GHz. The imaginary permittivity (epsilon '') was doubled for composites containing flake-like PANI, compared to globular and fibrillar PANI. These higher values of dielectric losses have been attributed to the highly polarizable structure of flake-like PANI, which contributes to more important polarization mechanisms. (c) 2012 Elsevier Ltd. All rights reserved.