Small-Angle X-Ray Scattering Study on PVA/Fe3O4 Magnetic Hydrogels

Abstract

A synchrotron small-angle X-ray scattering (SAXS) study on PVA/Fe3O4 magnetic hydrogels has been performed to investigate the effect of clustering on their magnetic properties. The hydrogels were prepared through freezing–thawing (F–T) processes. The structure, morphology and magnetic properties of magnetite (Fe3O4) nanoparticles (NPs) were investigated using X-ray diffractometry (XRD), transmission electron microscopy (TEM) and a superconducting quantum interference device (SQUID) magnetometer, respectively. In this study, SAXS data were used to reveal the structural dimensions of the magnetite and its distribution in the polymer-rich PVA and magnetic hydrogels. As calculated using the Beaucage and Teubner–Strey models, the average of the structural dimensions of the PVA hydrogels was 3.9[Formula: see text]nm (crystallites), while the average distance between crystallites was approximately 18[Formula: see text]nm. Further analysis by applying a two-lognormal distribution showed that the magnetite NPs comprised secondary particles with a diameter of 9.6[Formula: see text]nm that were structured by primary particles ([Formula: see text][Formula: see text]3.2[Formula: see text]nm). A two-lognormal distribution function has also been used in describing the size distributions of magnetite NPs in magnetic hydrogels. The clusters of magnetite NPs in the magnetic hydrogels are significantly reduced from 30.4[Formula: see text]nm to 12.8[Formula: see text]nm with decreasing concentration of the NPs magnetite from 15[Formula: see text]wt.% to 1[Formula: see text]wt.%. The saturation magnetization values of the magnetite NPs, the 15% and 1% magnetic hydrogels were 34.67[Formula: see text]emu/g, 6.52[Formula: see text]emu/g and 0.37[Formula: see text]emu/g, respectively.