Interfacial step growth polymerization in miniemulsion for the incorporation of magnetic nanoparticles into polyurethane particles
May 10-15, 2015
Polyurethane (PU) is a versatile polymer with excellent physical properties1-2 ranging from very soft elastomers to very rigid plastics3-4. PU nanoparticles have been synthesized using several techniques such as suspension, miniemulsion and interfacial polymerization 5-6-7. Magnetite nanoparticles have remarkable electromagnetic properties and below a critic diameter (up to 20 nm)8 they present a superparamagnetic behavior. Polymer particles containing magnetic nanoparticles are very interesting for different application areas including biomedical, pharmaceutical, as well as for enzyme immobilization. In this work interfacial step growth polymerizations in miniemulsion were performed to prepare PU particles containing magnetite nanoparticles and the results were evaluated in terms of morphology and magnetic behavior. Magnetite nanoparticles with diameters around 10 nm were prepared by the co-precipitation method and these particles were coated with oleic acid to provide colloidal stability and protect against aggregation9. Interfacial step growth polymerizations in miniemulsion were performed according to an adaptation from literature10. The aqueous phase was prepared with water, sodium dodecyl sulfate as surfactant and 1,6-hexanediol as water soluble monomer. The organic phase was prepared using isophorone diisocyanate (IPDI) in a 2.5 molar ratio (NCO:OH), Crodamol GTCC as co-stabilizer and the amount of magnetite was varied among the reactions with up to 30 wt% in relation to the organic phase. TEM images in Figure 1a show spherical PU particles with around 250 nm decorated with a high amount of magnetite nanoparticles. Figure 1b shows the magnetization curves of the magnetite nanoparticles coated with oleic and incorporated into PU particles. Both samples indicated a superparamagnetic behavior, i.e. zero coercivity and remanescence. The decrease in the magnetization from 50 emu/g for the oleic acid-coated magnetite nanoparticles to 39 emu/g PU particles with magnetite nanoparticles is due to the incorporation into a non-magnetic material (PU particles).
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