Transparent Large-Strain Thermoplastic Polyurethane Magnetoactive Nanocomposites

Organically modified superparamagnetic MnFe2O4/thermoplastic polyurethane elastomer (TPU) nanocomposites (0.1-8 wt %) were prepared by solvent mixing followed by solution casting. Linear aliphatic alkyl chain modification of spherical MnFe2O4 provided compatibility with the TPU containing a butanediol extended polyester polyol-MDI. All MnFe2O4/TPU nanocomposite films were superparamagnetic and their saturation magnetization, a increased with increasing MnFe2O4 content. All nanocomposite films exhibited large deformations (>10 mm) under a magneto-static field. This is the first report of large actuation of magnetic nanoparticle nanocomposites at low-loading levels of 0.1 wt % (0.025 vol %). The maximum actuation deformation of the MnPe(2)O(4)/TPU nanocomposite films increased exponentially with increasing nanoparticle concentration. An empirical correlation between the maximum displacement, saturation magnetization, and magnetic nanoparticle loading is proposed. The cyclic deformation actuation of a 6 wt % surface modified MnFe2O4/TPU, in a low magnetic field 151 < B(y) <303 Oe, exhibited excellent reproducibility and controllability. MnFe2O4/TPU nanocomposite films (0.1-2 wt %) were transparent and semitransparent over the wavelengths from 350 to 700 nm.