Effects of [SDS]/[H_2O] molar ratio on the electromagnetic properties of polyaniline/maghemite nanocomposites

摘要

Polyaniline (PANI)/maghemite (γ-Fe_2O_3) 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-Fe_2O_3 and surfactant, respectively. The effect of the molar ratio of [SDS]/[H_2O] on the electromagnetic properties of PANI/γ-Fe_2O_3 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-Fe_2O_3 nanocomposites was characterized by micrographs of transmission electron microscopy (TEM). Results showed that both the γ-Fe_2O_3 content and particle size in the nanocomposites decreased with molar ratio of [SDS]/[H_2O]. The γ-Fe_2O_3 phase is non-uniformly distributed in the PANI matrix, and exhibits a broader size distribution at higher [SDS]/[H_2O] molar ratio due to the reduced strength of PANI–γ-Fe_2O_3 interactions. In the presence of γ-Fe_2O_3, the growth rate of quinoid ring is markedly retarded. The retard effect is significantly reduced by increasing the [SDS]/[H_2O] 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]/[H_2O] molar ratio, resulting from the reduced γ-Fe_2O_3 content, smaller γ-Fe_2O_3 particle size, and the wider particle size distribution.