Fe3O4-PVAc nanocomposites: surface modification of sonochemically prepared magnetite nanoparticles via chemical grafting of poly(vinyl acetate)

In the present study, magnetite nanoparticles (MNPs) were synthesized at room temperature under ultrasonic irradiation. The synthesized MNPs were then silylated with triethoxyvinylsilane to give a core-shell structure containing vinyl moieties on the surface. Encapsulation of the MNPs in a polysiloxane shell was clearly shown by transmission electron microscopy (TEM). The radical polymerization of the silylated product with vinyl acetate (VAc) leads to the formation of polymer nanocomposites (PN) in which some of the polymer chains are chemically grafted onto the MNPs. The homopolymer (PVAc) formed during polymerization was separated from the grafted MNPs using Soxhlet extraction. Chemical grafting of the polymer onto the MNPs was confirmed by Fourier transform infrared spectroscopy (FTIR). The amount of grafted polymer was calculated using thermogravimetric analysis (TGA). The thermal properties of the prepared MNPs, silylated MNPs, PVAc-grafted MNPs and PNs were studied using TGA. The MNPs and the nanocomposite containing 15 wt% of the PVAc-grafted MNPS (PN 15 wt%) were further investigated by scanning electron microscopy (SEM), TEM, XRD and energy dispersive X-ray analysis (EDAX). Vibrating sample magnetometry (VSM) showed the unique phenomenon of superparamagnetism for the prepared MNPs, silylated MNPs and PVAc-grafted MNPs.