Impact of the Combined Use of Magnetite Nanoparticles and Cellulose Nanocrystals on the Shape-Memory Behavior of Hybrid Polyurethane Bionanocomposites.

Hybrid bionanocomposites with shape-memory behavior are reported. The materials were accessed by combining a polyurethane matrix with a highly renewable carbon content, cellulose nanocrystals (CNCs), and magnetite nanoparticles (MNPs). The integration of the two nanoparticle types resulted in tough materials that display a higher stiffness and storage modulus in the glassy and rubbery state, thus contributing to the structural reinforcement, as well as magnetic properties, reflecting a synergistic effect of this combination. A quantitative characterization of the thermoactivated shape-memory effect made evident that the addition of CNCs increases the shape fixity, due to the higher glass transition temperature (Tg) and the higher stiffness below Tg than the neat PU, while the addition of MNPs made it possible to activate the shape recovery by applying an alternating magnetic field. Moreover, the new hybrid bionanocomposites showed good bio- and hemocompatibility.