Effects of [SDS]/[H2O] molar ratio on the electromagnetic properties of polyaniline/maghemite nanocomposites

Polyaniline (PANI)/maghemite (γ-Fe2O3) nanocomposites were prepared by using the reverse micelle polymerization, where aniline, ferrous and ferric salts and sodium dodecyl sulfate (SDS) act as monomer, precursor of γ-Fe2O3 and surfactant, respectively. The effect of the molar ratio of [SDS]/[H2O] on the electromagnetic properties of PANI/γ-Fe2O3 nanocomposites was investigated by Fourier transform spectroscopy (FTIR), UV–visible spectroscopy (UV–vis), X-ray photoelectron spectroscopy (XPS), wide angle X-ray diffraction diffractometer (WAXD), impedance analysis analyzer, micro-ohmetry and superconductor quantum interference device (SQUID). The nanostructure of the PANI/γ-Fe2O3 nanocomposites was characterized by micrographs of transmission electron microscopy (TEM). Results showed that both the γ-Fe2O3 content and particle size in the nanocomposites decreased with molar ratio of [SDS]/[H2O]. The γ-Fe2O3 phase is non-uniformly distributed in the PANI matrix, and exhibits a broader size distribution at higher [SDS]/[H2O] molar ratio due to the reduced strength of PANI–γ-Fe2O3 interactions. In the presence of γ-Fe2O3, the growth rate of quinoid ring is markedly retarded. The retard effect is significantly reduced by increasing the [SDS]/[H2O] molar ratio, leading to the improvement of crystallinity, conductivity and dielectric properties (i.e., permittivity and loss factor) of nanocomposites. Simultaneously, the ionic polarization relaxation time is shortened from 2.61 × 10−9 to 1.04 × 10−9 s. For SQUID analysis at room temperature, the typical superparamagnetic behavior is found with the saturation magnetization decreased with the [SDS]/[H2O] molar ratio, resulting from the reduced γ-Fe2O3 content, smaller γ-Fe2O3 particle size, and the wider particle size distribution.