Superparamagnetic Nanocomposites Based on the Dispersion of Oleic Acid-Stabilized Magnetite Nanoparticles in a Diglycidylether of Bisphenol A-Based Epoxy Matrix: Magnetic Hyperthermia and Shape Memory

Abstract

Superparamagnetic nanocomposites were obtained by dispersion of oleic acid (OA)-coated magnetite NPs in an epoxy system based on diglycidylether of bisphenol A (DGEBA) modified with OA. Dispersion of conventional oleic acidstabilized magnetite NPs in a typical epoxy matrix is not possible due to the dissimilar chemical structures of the organic coating and the reactive solvent. However, by modification of a DGEBA-based epoxy with 20 wt % OA, we obtained a suitable reactive solvent to disperse up to at least 8 wt % of OA-stabilized magnetite NPs. A tertiary amine was used to catalyze the epoxy−acid reaction and initiate the homopolymerization of the epoxy excess. Both reactions occurred practically in series, first the epoxy−acid and then the epoxy homopolymerization. It was necessary to complete the first reaction to attain a very good dispersion of magnetite NPs in the reactive solvent previous to the occurrence of the final reaction. Magnetization curves and TEM images revealed a uniform dispersion of individual nanoparticles in the cross-linked epoxy. A sample containing 8 wt % OA-coated magnetite NPs exhibited a temperature increase of 25 °C at its surface when exposed to an alternating magnetic field. The temperature increase was enough to induce the shape memory effect of the nanocomposite.

Synthesis and characterization of polystyrene embolization particles doped with tantalum oxide nanoparticles for X-ray contrast

“…4b, c) show that TaOx has been successfully incorporated into the polystyrene matrix. The TGA results show that the mass of TaOx incorporated is lower than the theoretical maximum for the PS-TaOx microparticles with a maximum incorporation of TaOx into the PS-TaOx microparticles of 9.4 % for Sample E. This compares favourably with Puig et al [13] who achieved a maximum of 8 % incorporation of 9.5 nm oleic acid coated magnetite nanoparticles into a diglycidylether of bisphenol A (DGEBA) epoxy matrix.…”

“…Some of the methods used to increase the dispersion include chemical modification of the nanoparticles, in situ polymerization, high shear mixing or sonication [38]. The nanoparticles can be coated with a hydrophobic layer which encourages the nanoparticles into the oil phase during synthesis and therefore into the final polymer matrix [13]. The work presented here shows the successful coating of the TaOx nanoparticles with oleic acid which increased their stability across pH values of 2-9 (Fig.…”

“…In one iteration, TaOx nanoparticles were coated with oleic acid to increase the hydrophobicity of the particles and therefore increase their dispersion in the oil phase during polymer synthesis [13]. The coating method was modified from the method presented by Majewski and Krysinki [14] for the surface modification of ferrite nanoparticles with oleic acid.…”

Self-assembly of nanoparticles employing polymerization-induced phase separation

“…The bar was then 13 placed in an alternating magnetic field for 60 s producing a temperature increase above T g and allowing complete recovery of the initial shape (Fig. 14) [21].…”

Shape Memory Polymer–Inorganic Hybrid Nanocomposites

“…They achieved a transition temp of 51 C with a shape recovery time of 186 sec. In 2012, Williams et al showed that magnetic nanoparticles in epoxy matrices tended to aggregate as a result of incompatibilities between the matrix and the filler [128]. Modification of the epoxy matrix with oleic acid (up to 20 wt%) was shown to enhance dispersion of magnetite particles that had been surface-modified with oleic acid (up to 8 wt% dispersion), achieving a temperature increase of 25 C when activated by a magnetic field.…”