1 research outputs found
Synthesis of Electromagnetic Functionalized Fe<sub>3</sub>O<sub>4</sub> Microspheres/Polyaniline Composites by Two-Step Oxidative Polymerization
Composites consisting of Fe<sub>3</sub>O<sub>4</sub> microspheres
(FMS) and polyaniline (PANI), FMS/PANI, have been successfully prepared
through a two-step oxidative polymerization of aniline monomers in
the presence of Fe<sub>3</sub>O<sub>4</sub> microspheres. In our two-step
polymerization technique, Fe<sup>3+</sup> and ammonium persulfate
(APS) are used as the oxidants in each step. It is discovered that
the two-step oxidative process plays a dominant role in the morphology
of these composites: aniline oligomers oxidized by Fe<sup>3+</sup> are mainly produced in the first stage, and “egg-like”
PANI aggregates are obtained in the second stage. It can be found
that embedding Fe<sub>3</sub>O<sub>4</sub> microspheres in the polymer
matrixes will not only modulate the complex permittivity but also
produce magnetic resonance and loss in the composites. Therefore,
the characteristic impedance and reflection loss of these composites
are greatly improved. Especially, the composite with equal amount
of FMS and PANI, FMS/PANI<sub>50</sub>, displays very strong reflection
loss over a wide frequency range that can be manipulated by the absorber
thickness. More importantly, the composites prepared from the two-step
chemical oxidative polymerization using hierarchical magnetic materials
have better microwave absorption and environmental stability as compared
with those composites from Fe<sub>3</sub>O<sub>4</sub> nanoparticles,
one-step oxidative polymerization, and physical mixture. We believe
the two-step oxidative polymerization technique can be a novel route
for the design and preparation of lightweight and highly effective
microwave absorbers in the future