Transport properties of polyaniline-cellulose-acetate blends

Transport properties of polyaniline (PANI)--cellulose acetate (CA) conducting blends have been investigated at various length scales and temperatures. We report on the results of dc and ac conductivity measurements, magnetoresistance and electron-spin resonance (ESR) performed on composite films with PANI weight fraction p ranging from the percolation threshold---pc0.1%---to a few percent. Three different PANI doping agents have been tested, namely, camphor sulfonic acid (CSA), di$(i$-octyl phosphate) (DiOP) and phenyl phosphonic acid (PPA). The percolative behavior of σdc resembles that of published results on PANI/PMMA blends. The onset frequency ω_ξ of the dispersion in σac appears to follow the scaling law: ω_ξ∝σdcᶻ with z1. The temperature dependence is of the form of lnσ(T)∝-(T₀/T)^γ the exponent decreasing from 0.75 to 0.5 with increasing $p.$ The microscopic metallic character of transport is found in ESR and microwave measurements. Spin-dependent conductivity is inferred from the (B/T)² universal behavior of magnetoresistance. Those results are discussed in conjunction with the ongoing debate on the nature of disorder in conducting polymers---homogeneous versus heterogeneous.