Multifunctional oleophilicity coatings fabricated from hyperbranched polymers to achieve high anti-settling of magnetorheological fluids with less magnetism loss

Magnetorheological fluids (MRFs) are magnetically responsive smart materials widely employed in damping systems. However, their broader application is hindered by significant sedimentation-related issues. In this study, magnetic particles undergo surface modification using a hyperbranched surfactant, with the modification process guided by finite element simulations. Magnetization characterization demonstrates that, compared to unmodified magnetic particles, the polymer-modified particles exhibit increased oleophilicity while maintaining a minimal 1.1 % reduction in saturation magnetization. Correspondingly, the magneto-induced dynamic yield stress at 400 mT decreases by 5.59 % in MRFs containing modified particles relative to those with unmodified particles. Furthermore, the polymer modification enhances the interfacial bonding between particles and the carrier liquid, leading to an increase in the storage modulus. Notably, the anti-settling improves significantly, with the suspension stability increasing from 45.96 % to 88.68 % after 15 days. Molecular dynamics simulations further confirm that the polymer acts as an obstacle, preventing direct particle contact and thereby mitigating inter-particle interaction. These findings provide valuable insights into enhancing the long-term performance and reliability of MRF applications, thereby contributing to their continued development in engineering applications.