Amplifying Magneto-Mechanical Performance of Magnetorheological Elastomers through Surface Functionalization of Iron Nanoparticles

Challenges posed by the chemical incompatibility between nanoparticles and polymer matrices hinder the widespread use of polymer nanocomposites as the material platform for many innovations. In this study, we demonstrate the effectiveness of a versatile approach to the surface functionalization of commercial nanoparticles. To illustrate the importance of proper surface functionalization, the process was used to functionalize high-moment iron nanoparticles to enhance the magneto-mechanical performance of nanoparticle-based magnetorheological elastomers (MREs). We successfully grafted off-the-shelf iron nanoparticles with poly(dimethylsiloxane) (PDMS) ligands, and then used them to fabricate nanoparticle-based anisotropic MREs with reduced stiffness and improved magnetic properties compared with MREs fabricated with the original nonfunctionalized particles. Structural analysis revealed a regular arrangement of nanoparticles with reduced agglomeration within the elastomeric matrix when functionalized particles were used. Mechanical testing showed enhanced deflection and bending performance for these MREs. Furthermore, this improvement of magneto-mechanical performance was obtained at lower effective magnetic content compared with nonfunctionalized particle elastomers. Magnetic characterization, in turn, revealed amplified magnetic anisotropy and improved chain ordering inside the functionalized-particle MREs. Our findings highlight the potential of surface functionalization of magnetic nanoparticles to improve performance in nanocomposites, such as nanoparticle-based MREs with superior mechanical and magnetic properties.