Ellipsoidal hybrid magnetic microgel particles with thermally tunable aspect ratios

We report on the synthesis and characterization of multiresponsive hybrid microgel particles. The particles consist of ellipsoidal silica-coated maghemite cores subsequently coated with thermoresponsive poly (N-isopropylacrylamide) (PNIPAM) shells. The PNIPAM shell enables the hybrid particle to alter its size and ratio of long to small axis with increasing temperature while the core morphology remains unchanged. The maghemite core can be magnetically oriented along the long axis as evidenced by small-angle X-ray scattering (SAXS) and confocal microscopy. Dynamic light scattering techniques and confocal microscopy have been applied to study the particles' morphological evolution with increasing temperature in terms of their aspect ratio. The aspect ratio of the particles was found to vary from 1.25 to 1.45 within a temperature range from 20 degrees C to 44 degrees C.