Physical characterization of polyaniline-Na⁺-montmorillonite nanocomposite intercalated by emulsion polymerization

We report the results of temperature dependence of dc conductivity (σ_dc(T)), X-ray photoelectron spectroscopy (XPS), electron paramagnetic resonance (EPR), and X-ray diffraction (XRD) experiments for dodecylbenzenesulfonic acid (DBSA) doped polyaniline (PAN)-Na⁺-montmorillonite (MMT) nanocomposite. The PAN-Na⁺-MMT nanocomposite was synthesized by intercalating the emulsion of aniline monomer with zylene and DBSA in the layer of Na⁺-MMT with distilled water and then initiating the polymerization of aniline inside the layer of Na⁺-MMT. From the results of X-ray diffraction experiments, we observe the insertion of PAN-DBSA between the interlayer of the Na⁺-MMT, whose separation consequently becomes larger (1.52 nm) than in a polymer-free clay (0.96 nm). The σ_dc of the systems is approximately 10^-1 S/cm at room temperature, and its temperature dependence follows a quasi one-dimensional variable range hopping (VRH) model. The slope of σ_dc is approximately 7.0×10³ K. From the result of XPS experiment, we obtain the doping level of the system quantitatively. We measure temperature dependence of EPR linewidths. Base on those results, we discuss the effect of the layer of montmorillonite on PAN-DBSA samples.