Investigation of Surface Properties of Magnetorheological Elastomers by Atomic Force Microscopy

Magnetorheological elastomers generally consist of a natural or synthetic rubber matrix interspersed with micron-sized ferromagnetic particles. The magneto-elastic properties of such a composite are not merely a sum of the elasticity of the polymer and the stiffness and magnetic properties of the filler, but also the result of a complex synergy of several effects, relevant at different length scales and detectable by different techniques. In our present work we investigate the microstructures, the surface magnetic properties, and the elastic properties of new isotropic and anisotropic magnetorheological elastomers prepared using silicone rubber and soft magnetic carbonyl iron microspheres. Similar samples were previously investigated by means of small-angle neutron scattering, which proved to be a useful method in the investigation of their microscopic properties. We combined the data from the atomic force microscopy measurements with those from small-angle neutron scattering to better understand the complicated behaviour of the studied materials. The measurements were performed by atomic force microscopy in the following modes: standard imaging non-contact atomic force microscopy, magnetic force microscopy, and nanoindentation. A comparative study of samples with different particle concentrations and strength of magnetic field applied during the polymerization process is developed.