(467h) Suspensions of Magnetic Nanoparticles In Polymer Liquid Crystals. A New Type of Ferronematic

Complex fluids such as ferronematics show interesting changes in rheological behavior upon application of external magnetic fields. Ferronematics are known as magnetic suspensions of nanoparticles in a liquid crystalline matrix. Here Cobalt Ferrite (CoFe2O4) and Magnetite (Fe3O4) nanoparticles were suspended in the polymer liquid crystal HPC/m-cresol. Size was determined by Transmission Electron Microscopy (TEM) and Dynamic Light Scattering (DLS) revealing a size of approximately 10nm. Small angle X-Ray Scattering (SAXS) showed no structural effects on the liquid crystalline nature of the samples upon inclusion of the particles. Rheological measurements were performed using an Anton Paar rheometer with plate-plate geometry, with an attachment that generates uniform magnetic fields in the direction normal to the plates surface. Rheometry of the ferronematics showed increments of viscosity upon application of external magnetic fields. In addition Superconducting Quantum Interference Device (SQUID) measurements showed a ferronematic that possessed magnetic hysteresis. To our knowledge a fluid with magnetic hysteresis has not been previously reported.