Shape-memory polymer networks with fe ₃O ₄ nanoparticles for remote activation

Shape-memory polymers (SMPs) have recently shown the capacity to actuate by remote heating via the incorporation of magnetic nanoparticles into the polymer matrix and exposure to an alternating magnetic field. In this study, methacrylate-based thermoset SMP networks were synthesized through free-radical polymerization with varying amounts of Fe ₃O ₄ magnetite (0, 1, and 2.5 wt %). Furthermore, the chemistry of the networks was controlled to maintain a constant glass transition temperature (T _g while varying the degree of chemical crosslinking. Remote heating of the networks was shown to be a direct function of the nanoparticle concentration and independent of the chemistry. Magnetite reinforcement was shown to influence the thermomechanical properties of the networks; increasing Fe ₃O ₄ concentrations led to decreases in T _g and rubbery modulus. However, networks with a higher degree of crosslinking were more resistant to thermomechanical changes with respect to magnetite concentration. Strain to failure was shown to decrease with the addition of nanoparticles and the free-strain shape-memory cycle was investigated for all of the networks. Networks with lower degrees of crosslinking and high magnetite concentrations showed a significant amount of irrecoverable strain. Last, the use of remotely heated shape-memory materials is discussed in light of potential biomedical