Synthesis of Fe3O4/PAM superparamagnetic nano-hydrogels in water-in-oil emulsion

Abstract

In this study, the nano-sized water droplets (NWDs) in water-in-oil (W/O) emulsion were employed as mini-reactors, in which Fe₃O₄/PAM magnetic nano-hydrogels (MNHs) were obtained based on the coprecipitation and inverse emulsion polymerization. In addition, compound nonionic surfactant was used as the stabilizer of W/O emulsion. The test results showed that Fe₃O₄/PAM MNHs were quasi-sphere particles with a diameter of about 50–380?nm and had superparamagnetism. The percentage of PAM coating Fe₃O₄ was about 81%. The saturation magnetization of the Fe₃O₄/PAM MNHs was 21.6?emu/g (Fe₃O₄/AM (wt/wt)?=?16.63%). The W/O emulsion containing Fe₃O₄/PAM MNHs (E-2) changed from fluid to solidlike in an external magnetic field. As current intensified or shear rate increased, the shear stress of E-2 increased.