Magnetorheological Elastomer Films with Controlled Anisotropic Alignment of Polystyrene-Modified Fe₃O₄ Nanoplates

To develop high-performance magnetorheological (MR) elastomer (MRE) films, we design a facile method to prepare MRE composites under an external magnetic field, which enables magnetite (Fe 3 O 4 ) nanoplates to align in synthetic rubbers at room temperature. The introduction of polystyrene (PS) chains onto the surface of Fe 3 O 4 nanoplates ensures the dispersion stability and interfacial compatibility of Fe 3 O 4 nanoplates with synthetic rubbers. We find that several Fe 3 O 4 nanoplates can be surrounded by PS chains to form special spiral structures. The fluidity and chain-like structures of magnetic rubbers are confirmed upon application of an external magnetic field under high temperatures. In addition, special anisotropic alignment can be formed in synthetic rubbers, and the structures can still be maintained even after vulcanization treatment. Rheological measurements indicate that the anisotropic alignment reinforces the rheological properties based on a comparison of the MRE films with anisotropic alignment and isotropic alignment. Fe 3 O 4 nanospheres with isotropic shapes are introduced into the MRE films for a comparative experiment. The results reveal that PS-modified Fe 3 O 4 nanoplates with spiral structures exhibit a magnetic field-responsive behavior that leads not only to the formation of a uniaxial alignment nematic structure but also to enhancement of the rheological performance of MRE films.