The Preparation And Properties Of PPy/Fe₃O₄Magnectic Nanocomposites In Ionic Liquid

Nano-sized Fe₃O₄is a kind of multifunctional magnetic materials which has smaller particle size,high specific surface area, and so on. Carbon nanotubes are widely used in the magnetic electricalmagnetic nanocomposites, due to its unique mechanical, electrical and magnetic properties.Polypyrrole （PPy） is one of the conjugated conducting polymers. It has high conductivity, goodstability, easily processing and so on. In addition, its size is in nanoscale. Therefor, to be comparedwith conventional materials, it has unique optical, electrical, acoustic and magnetic performance. Inthis paper, we prepared Fe₃O₄nanoparticles with magnetic ionic liquid1-butyl-3-methyllimidazoliumtetrachloroferrete （[bmim]FeCl₄）, which as the raw material and solvent for the first time.1-butyl-3-methyllimidazolium chloride （[bmim]Cl） was used as dispersant and solvent formultiwalled carbon nanotubes （MWCNTs） and then loaded Fe₃O₄nanoparticles on the surface of theMWCNTs. We prepared PPy/Fe₃O₄and PPy/Fe₃O₄/MWCNTs nanocomposites with [bmim]FeCl₄asthe solvent and the oxidant. This is a new method to prepare Fe₃O₄nanoparticles and conducingpolymer magnetic nanocomposites in magnetic ionic liquid without any additional dopant.Here the well ordered Fe₃O₄nanoparticles of5-8nm in diameter were synthesized by usingchemical codeposition method with [bmim]FeCl₄, FeCl2·4H2O and NH3·H2O as reactant. What’s moreNH3·H2O were fitted to control the pH. This was further supported by XRD results, characteristicpeaks of Fe₃O₄are observed in the nanoparticles, besides these peaks are relatively narrow and broad,showing an obvious crystal phase. Mossbauer spectra shows the Fe₃O₄nanoparticles has goodferromagnetism and superparamagnetism.The PPy/Fe₃O₄nanocomposites were synthesized by an in situ polymerization method in thepresence of [bmim]FeCl₄as the oxidation and solvent for polymerization of pyrrole monomer. Theexperimental results show that the content of pyrrole monomer has played a significant role on themorphology of polypyrrole coated Fe₃O₄composite. With incremental content of Pyrrole monomer,following a more efficient wrap and the composite is tent to grow, whereas the superfluous monomercould undoubtedly promote the comparticles growing along transverse direction from ball to nubble.According to morphology consequences, the conductivity of nanoparticles performs a simpleincrease-decrease trend with the maximum of3.1S/cm, which shows a relative modification of thepure PPy and a more stable in thermal analysis.The maximum reflection loss is-32dB, and thebandwidth below-10dB is more than5GHz. In a typical synthesis process, MWCNTs were dispressed in [bmim]Cl which contents magneticionic liquid（[bmim]FeCl₄） with continuous ultrasonic. Then, FeCl2·4H2O and NH3·H2O were added tothe homogeneous system in nitrogen atmosphere. The reaction was allowed to be kept for MWCNTsloading with Fe₃O₄nanoparticles. The morphology and molecular structure of composites wascharacterized by scanning electron microscope and transmission electron microscopes that substantivebonding was observed between the Fe₃O₄and MWCNTs, composites represent good crystalform（Fe₃O₄） through XRD tests, and no adverse effect introducing from MWCNTs. Mossbauerspectrum showed that the composite material has a certain ferromagnetism and superparamagnetism.The PPy/Fe₃O₄/MWCNTs composites were synthesized by an in situ polymerization methodusing [bmim]FeCl₄as the dispersant and solvent for Fe₃O₄/MWCNTs, and as oxidant for Pyrrolemonomer. As shown in SEM and TEM, a new core-shell structure was established, which involves acomplex mechanism which consists of a series of stages that lead to form total layers with differentstrata: an outer layer of PPy coating, an intermediate Fe₃O₄nanoparticles, and an innermost MWNCTslayer. With the content of Pyrrole monomer increasing, the outer thickness of PPy layer is increased,and tends to be a stereo crosslinking structure.The conductivity of composites represent a modestincrease-decrease trend in the content of pyrrole monomer, with a maximum of25S/cm. Existence ofPPy/Fe₃O₄/MWCNTs would be contributed to the magnetic properties, leading to thermal stabilitymagnetic functionalized composites. Mossbauer spectrum shows that the nanocomposites have acertain ferromagnetism and good superparamagnetic. The magnetic performance of thenanocomposites is gradually reduced with the increase of the mount of pyrrole monomer. Theelectromagnetic wave absorption properties were studied by N5244A type vector network analyzer.The results shows that the nanocomposites have certain microwave absorbing properties, but theimpedance matching of the nanocomposites was bad, because of its high dielectric loss, but lowmagnetic loss. So it need further optimization in the next work.