Poly(N-methylaniline)/magnetite microsphere and its electrical and magnetic dual responses

Abstract

Dual electric/magnetic field-responsive magnetite coated poly(N-methylaniline)/magnetite (PNMA/Fe3O4) microspheres were synthesized via a straightforward synthetic route of chemical oxidative polymerization for monodispersed PNMA microspheres and chemical co-precipitation of Fe3O4 onto the PNMA surface. Along with their chemical and physical characterizations such as morphology, size, and crystalline structure, the electrical conductivity, magnetic properties, and dielectric properties were investigated using a low resistivity meter, vibrating sample magnetometry, and an LCR meter, respectively. All tests and analyses on the particles have proved that they have been successfully synthesized and have good magnetic saturation and dielectric properties. Studies have shown that PNMA had an appropriate conductivity so that these particles do not need for de-doping for electrorheological (ER) test. On the other hand, as a superior soft magnetic material, Fe3O4 has a good magnetic susceptibility for magnetorheological (MR) performance. The synthesized PNMA/Fe3O4 microspheres were adopted in both ER and MR fluids. The suspension made of the PNMA/Fe3O4 particles with a volume fraction of 10 vol% showed a good dual ER and MR response via a rotational rheometer. It is also found that the yield stress of ER and MR fluids followed a power-law behavior under electric/magnetic field strength with their slopes of 1.5 and 1.0, respectively. Thus, the synergistic effects of Fe3O4 and PNMA with both electrical and magnetic behaviors demonstrate their suspension possessing both ER/MR characteristics, widening their potential engineering applications.