Anisotropic nanoparticle-based magnetorheological elastomers: Effect of shape and orientation on the magnetorheological performance

Magnetorheological elastomers (MREs) respond to applied magnetic fields with a change in their mechanical properties. Within this work, iron oxide nanorods (IONRs) have been synthesized and the suitability of anisotropic nanoparticles to obtain highly responsive isotropic and anisotropic MREs has been demonstrated. Electron microscopy images show that the IONRs are well distributed inside the styrene-ethylene-butylene-styrene (SEBS) polymeric matrix and can be successfully oriented. The elastic modulus of the composites increases twofold with respect to the bare polymer. Room temperature magnetization loops of the composites show a difference in the orientations, with variations of the anisotropy field from 39.2 kA m-1 to 67.7 kA m-1. Magnetorheology measurements show that the relative magnetorheological effect experiences a twofold increase for the anisotropic MREs, from 8.3% to 17%. This, along with the improved mechanical properties of the anisotropic MREs, offers excellent possibilities for the design of high performance MREs that work optimally in the elastic region and possess improved applicability.