Influence of a polyester coating of magnetic nanoparticles on magnetic heating behavior of shape-memory polymer-based composites


Background: Magnetic composites of thermosensitive shape-memory polymers (SMPs) and magnetite nanoparticles (MNPs) allow noncontact actuation of the shape-memory effect in an alternating magnetic field. In this study, we investigated whether the magnetic heating capability of cross-linked poly(ε-caprolactone)/MNP composites (cPCLC) could be improved by covalent coating of MNPs with oligo(ε-caprolactone) (OCL). Methods: Two different types of cPCLC containing uncoated and OCL-coated MNP with identical magnetite weight content were prepared by thermally induced polymerization of poly(ε-caprolactone) diisocyanatoethyl methacrylate. Both cPCLCs exhibited a melting transition at Tm = 48°C, which could be used as switching transition. Results: The dispersion of the embedded nanoparticles within the polymer matrix could be substantially improved, when the OCL-coated MNPs were used, as visualized by scanning electron microscopy. We could further demonstrate that in this way the maximal achievable bulk temperature (Tbulk) obtained within the cPCLC test specimen in magnetic heating experiments at a magnetic field strength of H = 30 kA⋅m-1 could be increased from Tbulk = 48°C to Tbulk = 74°C.
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