Structural changes of polyaniline/montmorillonite nanocomposites and their effects on physical properties

Abstract

Polyaniline/montmorillonite (MMT) nanocomposites containing different PANI contents were prepared by the intercalation of aniline monomer into pristine MMT followed by the subsequent oxidative polymerization of the aniline in the interlayer spacings. The polyaniline/MMT nanocomposite structure intercalated with polyaniline (PANI) was examined by X-ray diffraction (XRD) and transmission electron microscopy (TEM). From the full-width at half-maximum (FWHM) of the (001) reflection peaks in the XRD patterns, the PANI/MMT nanocomposite containing 12.3 wt% PANI (PMN12) was found to be in the most disordered state. The physical interaction between the intercalated PANI and the basal surfaces of MMT was monitored by FT-IR. The room-temperature conductivity (σ_RT) varied from 9.1 × 10⁻⁹ to 1.5 × 10⁰ S cm⁻¹ depending on the PANI content in the nanocomposites. The temperature dependence of dc conductivity (σ_dc(T)) of all the samples follows the quasi-1D variable range hopping (quasi-1D VRH) model (i.e., σ_dc(T) ∝ exp [−(T₀/T)^1/2]). The charge transport behavior of this system was interpreted from the slopes (T₀) of the σ_dc curves and the highest T₀ value was found for the PANI/MMT nanocomposite with 12.3 wt% PANI (PMN12). The FT-IR, σ_dc(T) and σ_RT results for the nanocomposites with varying content of PANI are consistently related to the structure of the PANI/MMT nanocomposites discussed in the XRD analysis. The structural argument was further supported by scanning electron microscopy (SEM) of all the samples. Thermogravimetric analysis (TGA) showed improved thermal stability for the intercalated nanocomposites in comparison with the pure PANI and a simple PANI/MMT mixture.