PANI/Fe3O4 nanocomposites with different sized nanoparticles

An extensive effort has been spent to develop shielding materials able to reduce the electromagnetic interference (EMI). In order to tailor and achieve specific EM properties within a single material we studied the combination of poly(aniline) (PANI) with magnetic nanoparticles (MNPs) developing an innovative green method for the synthesis of PANI/Fe3O4 nanocomposites, which are obtained by oxidative polymerization of N4aminophenylaniline using magnetic Fe3O4 MNPs as both catalyst and filler. We prepared MNPs of different sizes using (i) a solvothermal protocol for MNP27 (dmedian=27 nm) and MNP10 (dmedian=10 nm) and (ii) Metal Vapour Synthesis (MVS) for the smaller MNP2 (dmedian=2.3nm). The PANI/Fe3O4 nanocomposites were characterized as to their structure (XRD, FTIR, UVVis), morphology (TEM, STEM), composition (AAS, EELS, EDX) and magnetic properties (SQUID). We evaluated the MNP size effect on the polymerization: the most catalytically active MNPs are the smallest ones (d = 2.3 nm). We proved that PANI/Fe3O4 nanocomposites possess a number of interesting features: the MNPs do not undergo chemical or crystallographic change under the used polymerization conditions? the MNPs are almost uniformly dispersed in the polymer matrix guaranteeing a good homogeneity of the nanocomposite? the PANI/Fe3O4 nanocomposites have tunable magnetic properties as a function of the MNPs size. Financial support by Fondazione Cariplo (Milano, Italy) under grant n. 20120872 is acknowledged