Manufacture of colloidal polymer ellipsoids for anisotropic conducting nano-composites

This project aimed to make anisotropic conducting nano-composites based on a segregated system of 20 nm gold particles and deformed polyethylene spher es of colloidal size. Two methods for achieving the deformation of the coll oidal polyethylene spheres were attempted, namely to exploit the elongation al flow field at the entrance to a capillary and alternatively to make cast films of a water soluble polymer containing the colloidal particles and dr aw them in the solid state. In the latter method, sections of film were elo ngated at an elevated temperature using a tensile testing machine. The draw n films were dissolved in water and the deformed particles were extracted a nd concentrated by ultracentrifugation. This method was successful in produ cing ellipsoids of a prescribed aspect ratio. Further successful deformatio n was carried out using PMMA particles and monodisperse polystyrene particl es. Polystyrene spheres containing 20 nm diameter magnetite particles could not be deformed using this process. A range of experimental techniques wer e exploited to characterise the ellipsoidal particles, including transmissi on electron microscopy and photocorrelation spectroscopy. Subsequent additi on of metal oxide particles to the polymer ellipsoids resulted in some succ ess in that a small number of 20 nm diameter magnetite particles was observ ed to be attached to the surfaces of the much larger (1 mum) polystyrene el lipsoids. The mechanism of attachment has not yet been elucidated but this has significant potential for future composite device production. (C) 2001 Kluwer Academic Publishers.