A COMPOSITE OF POLYANILINE WITH BOTH CONDUCTING AND FERROMAGNETIC FUNCTIONS

A composite of polyaniline (PANI) with both conducting and ferromagnet ic functions was synthesized by a chemical method proposed by the auth ors. For the electrical properties, its room-temperature conductivity was measured to be about 10(-1) S/cm when doped with 1.0M HCl, and it is independent of the preparation conditions, such as reaction tempera ture and concentration of FeSO4 solution. Temperature dependence of th e conductivity of the composites at temperature between 77 and 450 K i s controlled by thermal activation and dedoping processes, which resul t in the decrease of conductivity with increase of temperature as T > 320 K. For their magnetic properties, unusual ferromagnetic properties with high saturated magnetization (M-s) and lower coercive force (H-c = 0) were observed. An effect of the preparation conditions on the fe rromagnetic properties of composites was observed. The higher the reac tion temperature and the concentration of FeSO4 solution, the higher t he saturated magnetization was observed. No hysteresis feature (i.e. H -c = 0) for any PANI composites synthesized in this paper was observed , and this is independent of the preparation conditions. This may be a ttributed to the nanometer size of the magnetic particles existing in composites. Thus, it suggests that the doping of PANI leads to electri cal properties of composites, whereas the nanocrystalline magnetic par ticles (Fe3O4) are responsible for the observed ferromagnetic properti es of PANI composites. (C) 1997 John Wiley & Sons, Inc.