Electrical charge transport in polypyrrole/sulfated poly(β-hydroxyethers) blends

Electrical properties of polypyrrole/sulfated poly(β-hydroxyethers) (PPy/sulfated PHE), wherein the sulfated hydroxy groups in the latter component worked as dopants, were investigated, varying the doping level as well as the PHE molecular mass (Mn). The blends can be categorized into three groups: the slight-, moderate- and high-sulfation. In the moderate-sulfation, the charge transport above 80 K is characterized by the two-dimensional variable-range hopping (2D-VRH) through the PPy conducting channels formed on the surfaces of coiled PHE. In the high-sulfation, the dimensionality of the VRH changes from two to three. In addition, the carriers in the metallic states also participate in the charge transport. In the slight-sulfation, the hopping to the nearest neighbors operates in addition to the 2D-VRH. For all the samples, the dominant conduction below 80 K is the hopping governed by a Coulomb gap due to the electrostatic interaction between carriers. The change in the doping level causes the transition from one sulfation group to another when Mn is large, whereas most blends are categorized into the moderate sulfation group when Mn is small. This behavior is interpreted, considering the Mn dependence of the spatial distributions of the PPy in the PPy/PHE blends.