Segmented polyurethane-magnetite nanocomposites with shape-memory behavior triggered by hyperthermia

G. SOTO; MARCOVICH, NORMA E.; P. MENDOZ ZÉLIS; D. G. ACTIS; C. MEIORIN; M. A. MOSIEWICKI

Rio de Janeiro

Conferencia; Fifth International Conference on Natural Polymers, Bio-Polymers, Bio-Materials, their Composites, Nanocomposites, Blends, IPNs, Polyelectrolytes and Gels: Macro to Nano Scales (ICNP 2017 Rio),; 2017

Shape-memory polymers (SMP) have emerged over the past years as a singular class of smart materials which offers several novel and useful applications in the biomedicine and aerospace fields, among others [1]. In particular, segmented polyurethanes (SP) are interesting materials because they exhibit this memory property, which is the result of their molecular structure formed by hard and soft segments that separate in phases leading to a complex morphology [2]. Moreover, thermoplastic SP are able to store and recover large strains through a thermo-mechanical cycle, which make them even more practical. On the other hand, the addition of magnetic particles such as magnetite to a polyurethane matrix would allow to modify not only the structural properties of the polymer but also to expand the ways to activate the shape-memory property, for example, by inducing the hyperthermia phenomena by the application of magnetic fields. In this work, the preparation and characterization of magnetic nanocomposites based on a commercial SP and different contents of magnetite (0 to 10%) is reported. Magnetite nanoparticles were dispersed in the SP solution (in DMF) by ultrasonication. Composite films were prepared by casting of the resulting suspensions followed by drying in a convective oven. Morphology analysis performed by FESEM indicated that magnetite crystals were homogeneously dispersed into the polyurethane network for all particle concentrations. Mechanical characterization carried out by tensile tests indicated that the addition of magnetite decreases slightly the tensile strength, although the elongation at break remained very high, reaching a maximum of nearly 550% for the film containing 5% magnetite. On the other hand, thermal analysis showed that the addition of magnetite to the SP did not modify the glassy transition temperature. Finally, preliminary results about shape fixation and recovery via hyperthermia indicated that as the magnetite concentration into the films increased, the increment in the temperature reached for the composite films was higher and the recovery of the original shape was faster. The results of the present study are promising since would allow enable shape recovery using remote activation (application of a magnetic field), which is more attractive for materials in medical uses and other applications that involve temperature constraints.