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 de and ac conductivity measurements, magnetoresistance and electron-spin resonance (ESR)performed on composite films with PANI weight fraction p ranging from the percolation threshold-p(c)similar or equal to 0.1%-to a few percent. Three different PANT doping agents have been tested, namely, camphor sulfonic acid (CSA), di(i-octyl phosphate) (DiOP) and phenyl phosphonic acid (PPA). The percolative behavior of sigma(dc) resembles that of published results on PANI/PIMA blends. The onset frequency omega(xi) of the dispersion in sigma(ac) appears to follow the scaling law: omega(xi)proportional to sigma(dc)(z), with z similar or equal to 1. The temperature dependence is of the form of ln sigma(T)proportional to-(T-0/T)(gamma) 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. [S0163-1829(98)01235-1].