Charge transport and structure of nanocomposites of polyaniline and inorganic clay

We report the charge transport and the structural properties of nanocomposites of polyaniline (PAN) with inorganic clay (Na⁺-montmorillonite), which were synthesized by using a emulsion polymerization method. Dodecylbenzenesulfonic acid (DBSA) and camphorsulfonic acid (CSA) were used to dope the PAN samples. In the X-ray diffraction patterns of the systems, we observed that the layer of conducting PAN-DBSA or PAN-CSA between the clay layers was in nanoscale layers (< 10 Å). The dc conductivity (σ_dc) of PAN-DBSA with the clay was ∼10^-1 S/cm and that of PAN-CSA with the clay was ∼1 S/cm, at room temperature. The temperature dependence of both systems followed a quasi-one-dimensional variable-range-hopping model. In electron paramagnetic resonance (EPR) experiments, we measured the temperature dependence of the EPR linewidth (ΔH_p-p) and of the signal intensity of the systems. The doping level of the systems was obtained from the ratio of the area of the nitrogen X-ray photoelectron spectroscopy (XPS) peak to that of the sulfur XPS peak. The charge transport, the spin dynamics, and the structure properties of PAN-DBSA without the clay, which was synthesized through the same emulsion polymerization method, were compared to the PAN-DBSA samples with clay samples.