Shape-memory composites based on a commercial segmented polyurethane and magnetite (Fe 3 O 4) nanoparticles (NPs) were prepared by a simple suspension casting method. The properties of the resulting nanocomposites, containing 1 to 10 nominal wt.% magnetic particles, were evaluated by thermogravimetric tests, contact angle measurements, differential scanning calorimetry, infrared and X-ray spectroscopy, static and thermal cyclic tensile tests, dynamic mechanical analysis and experiments of alternating-magnetic-field heating. It was found that most of the suspended NPs could be successfully incorporated into the polyurethane matrix, and thus composite samples with up to 7 wt.% actual concentration were obtained. On the other hand, the incorporation of magnetite nanoparticles to the shape memory polyurethane did not significantly affect most of the matrix properties, including its shape memory behavior, while added magnetic response to the nanocomposites. Thus, nanocomposites were able to increase in temperature when exposed to an alternating magnetic field, which allowed them to recover their original shape quickly by an indirect triggering method.

Shape-memory composites based on a commercial segmented polyurethane and magnetite (Fe 3 O 4) nanoparticles (MNPs) were prepared by a simple suspension casting method. The average sizes of individual magnetic particles/clusters were determined by TEM microscopy and corroborated from SAXS patterns. The magnetization properties of selected samples were evaluated using zero field cooling/field cooling (ZFC/FC) measurements and magnetization loops obtained at different temperatures. The results showed that magnetization at high field (20 kOe) and coercitivity measured at 5 K increase with magnetite content and that all the composite films exhibit superparamagnetic behavior at 300 K. The specific absorption rate (SAR) of the nanocomposites was calculated by experimentally determining both the specific heat capacity and the heating rate of the films exposed to an alternant magnetic field. All nanocomposites were able to increase their temperature when exposed to an alternant magnetic field, although the final temperature reached resulted dependent of the MNPs concentration. What is more, a fast and almost complete recovery of the original shape of the nanocomposites containing more than 3 nominal wt.% MNP was obtained by this remote activation applied to the previously deformed samples.