Fabrication of anisotropic snowman-like magnetic particles and their magnetorheological response

Snowman-like anisotropic microparticles with a shell of Fe3O4 nanoparticles were synthesized using a two-step process, in which snowman-like poly(methyl methacrylate) particles were first synthesized by seeded polymerization, and then coated with Fe3O4 nanoparticles via an electrostatic interaction between the adsorbed ionic surfactant and Fe3+/Fe2+. The magnetic properties of the particles were examined by vibrating sample magnetometry. Their rheological characteristics when dispersed in silicone oil were observed using a rotational rheometer at a controlled shear rate mode under a range of magnetic field strengths, exhibiting typical magnetorheological characteristics.