Effect of emulsion polymerization conditions on the electromagnetic properties of magnetic and conductive polyaniline nanoparticles

Electrically conducting polyaniline(PANI)-magnetic oxide(Fe_3O_4)composites with electri- cal and ferromagnetic behaviors were synthesized by the way of emulsion polymerization in the presence of dodecyl benzene sulfonic acid(DBSA)as a suffactant and dopant and ammonium persulfate(APS)as the oxidant.The average diameter of the composites is about 120nm.The effects of the contents of Fe_3O_4,DBSA and APS in the polymerization on the electromagnetic parameters(e″,e′,μ′andμ″)were studied by the permittivity and permeability measurements in the range of 2-18GHz.The results show that Fe_3O_4 can improve the magnetic and dielectric loss of the composites in a wide frequency range,theμ″ande″have increased to 0.72 and 9.62 respectively.In order to design the multilayer gradient absorb- ing structure,the contents of Fe_3O_4,DBSA and APS can he adjusted to influence the permittivity and permeability of the composites.As a result,the FGM can be content with the impedance matching and absorb the microwave maximumly.