Percolation scaling, inhomogeneity, and defects in polyaniline blends: A 1∕f noise diagnosis

The resistance fluctuation properties of a family of conducting polymer blends, poly(aniline)/poly(methyl methacrylate), are investigated as a function of conducting phase mass fraction. The blends exhibit 1∕f noise according to Hooge’s empirical formula. The noise amplitude scales with the conducting phase mass fraction and the resistance as expected by the percolation theory. The exponents of the scaling laws are within the bounds of the extended random void model, derived in the continuous percolation scheme. Noise characterization proves to be a much more sensitive tool to local current heterogeneities than resistance. As a consequence, sample preparation, sample holder design, and absence of defects are prominent criteria for convenient noise amplitude estimation. Surface effects, contact noise, and influence of geometrical defects are studied and analyzed.