The synthesis and characterization of isotropic magnetorheological elastomer (MRE) with significantly enhanced utility properties is presented. Common drawbacks of classical MREs, such as poor particle wettability, dispersibility, low thermooxidative stability, low chemical stability, and insufficient durability, were eliminated by grafting the carbonyl iron (CI) particles with poly(trimethylsilyloxyethyl methacrylate) (PHEMATMS) using surface-initiated atom transfer radical polymerization (ATRP). Two sets of the MREs were prepared containing bare CI and CI grafted with PHEMATMS chains (CI-g-PHEMATMS). The effects of the coating on magnetorheological behavior in oscillatory shear, as well as the sensing properties of the prepared MREs, were evaluated. The mechanical properties in tensile mode and the particle filler/polydimethylsiloxane (PDMS) matrix interactions were investigated using a dynamic mechanical analysis. The PHEMATMS grafts considerably improved the CI particles' mobility, probably by preventing a partial cross-linking with the PDMS matrix. Besides the plasticizing effect, the MRE containing CI-g-PHEMATMS exhibited moderate mechanical performance and a slightly improved relative magnetorheological effect, but significantly enhanced damping factor, improved magnetostriction, and provided good sensing capability, which make such material highly promising for intended practical applications.

This study is focused on the controllable coating of the carbonyl iron (CI) particles widely applied in magnetorheology. These particles were grafted with poly(glycidyl methacrylate) (PGMA) with narrow polydispersity via surface-initiated atom transfer radical polymerization. Two types of core-shell particles differing in molecular weights of grafted polymer chains were synthesized. The effect of shell thickness on the thermo-oxidation stability of particles as well as the sedimentation stability of their silicone oil suspensions was evaluated. The successful coating process was confirmed by Fourier transform infrared spectroscopy and energy-dispersive spectrometry. The differences in the magnetic properties of bare and coated CI particles were clarified through vibrating sample magnetometry. Due to the controllable length of the PGMA grafts, the magnetic properties remain almost the same as those for bare CI. The magnetorheological (MR) behavior of silicone oil suspensions containing 60 wt% of bare CI particles as well as PGMA-coated analogues was investigated in the absence and in the presence of various magnetic field strengths, demonstrating the negligible impact of surface modification on final MR performance. Thus, the grafting of the particles with PGMA negligibly affected magnetic properties but considerably enhanced thermo-oxidation and sedimentation stabilities. Finally, a novel tensiometric method for sedimentation stability measurements of MR suspensions was successfully implemented.

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The sedimentation caused by the high density of suspended particles used in magnetorheological fluids is a significant obstacle for their wider application. In the present paper, core-shell structured carbonyl ironpolyaniline particles in silicone oil were used as a magnetorheological suspension with enhanced dispersion stability. Bare carbonyl iron particles were suspended in silicone oil to create model magnetorheological suspensions of different loading. For a magnetorheological suspension of polyaniline-coated particles the results show a decrease in the base viscosity. Moreover, the polyaniline coating has a negligible influence on the MR properties under an external magnetic field B. The change in the viscoelastic properties of magnetorheological suspensions in the small-strain oscillatory shear flow as a function of the strain amplitude, the frequency and the magnetic flux density was also investigated.