One-pot synthesis of magnetic nanoparticles assembled on polysiloxane rod and their response to magnetic field

Rod-like assembled magnetite (Fe₃O₄) nanoparticles (NPs) were successfully synthesized in a one-pot process using a polysiloxane template derived from a dialkoxysilane. The assembly was constructed using the thiol-ene click reaction between thiol groups on the polysiloxane chain and allyl groups on Fe₃O₄ NPs. The thiol-containing polysiloxane chain and the allyl-containing Fe₃O₄ NPs were synthesized by the hydrolysis–condensation of 3-mercaptopropyl(dimethoxy)methylsilane and iron (III) allylacetylacetonate, respectively. Fe₃O₄ NPs of around 5 nm were uniformly dispersed on the siloxane rods and exhibited neither remanent magnetization nor coercivity. A fluid containing a dispersion of rod-like assembled Fe₃O₄ NPs showed yield stress even without the application of an external magnetic field, whereas spherical Fe₃O₄ NPs exhibited no yield stress. The rod-like assembled Fe₃O₄ NPs on anisotropic siloxane clearly exhibited typical magnetorheological behavior.