Morphology and magnetic properties of sulfonated poly[styrene-(ethylene/butylene)-styrene]/iron oxide composites

Abstract α-Fe₂O₃ structures were initiated in the sulfonated polystyrene block domains of poly[styrene-(ethylene/butylene)-styrene] (SEBS) block copolymers via a domain-targeted in-situ chemical precipitation method. The crystal structure of these particles was determined using wide-angle X-ray diffraction and selected area electron diffraction using a transmission electron microscope (TEM). TEM revealed that for less sulfonated SEBS (10 mole%), nanoparticles were aggregated with aggregate size range of 100-150 nm whereas for high sulfonation (16 and 20 mole% sSEBS) there were needle-like structures with length and width of 200-250 nm and 50 nm, respectively. Dynamic mechanical analyses suggest that initial iron oxide nanoparticle growth takes place in the sulfonated polystyrene block domains. The magnetic properties of these nanocomposites were probed with a superconducting quantum interference device magnetometer at 5 and 150 K as well as with an alternating gradient magnetometer at 300 K. The materials exhibited superparamagnetism at 150 K and 300 K and ferrimagnetism at 5 K.