We have carried out a comparative experimental study of the dc electrical conductivity - and

magnetic susceptibility - of own-made polyaniline (PANI) pellets doped with dodecybenzenesulfonic

acid (DBSA), a long molecule with surfactant properties. For all the samples, we find [1] that - at low

temperatures (T) is governed by the variable-range hopping (VRH) in a homogeneously disordered

three-dimensional (3D) system of coupled 1D chains. Depending on the doping and the corresponding

disorder level, the VRH exponents are either 1/2, 2/5 or 1/4. At higher T, in all the samples we find the

exponent 1 that signifies nearest-neighbour hopping. All these exponents are predicted in a model by

Fogler, Teber and Shklovskii [2] for the charge transport in quasi-1D Mott-Anderson insulators, and

conditions for their appearance depend on disorder and T. We identified the presence of a soft

Coulomb gap in our samples, which signifies a long-range Coulomb interaction.

Changes from one exponent into another in -(T) appear at crossover temperatures T*, where

there are also noticeable features in -(T). This coupling of charge and spin is discussed in the spirit of

kBT* being the thermal energy which causes an enhancement of the density of delocalised (Pauli)

spins at the expense of localised (Curie) spins as T rises above T*.

Utilising a property that both PANI-DBSA and multi-wall carbon nanotubes (CNT) are

soluble in chloroform, we have produced bulk blends of these two materials, the achieved mass

fraction of CNT being up to 40%. This is as remarkable as the accompanying effective loss of the

temperature dependence of -: it decreases by only 3 times from room temperature to 10 K, whereas

this decrease for pure PANI-DBSA is by a factor of 106. Thus, our blends simultaneously solve the

problem of application of CNT in bulk form, as well as that of poor conductivity of PANI-DBSA at

low T. It is also possible to make thin films of the blends on a commercial plastic substrate.

[1] M. Bacani, M. Novak, I. Kokanovic, D. Babic, Synth. Met. 172, 28 (2013)

[2] M. M. Fogler, S. Teber, B. I. Shklovskii, Phys. Rev. B 69, 035413 (2004)