Phase differentiation of a tri-phase polymer composite using energy-filtering transmission electron microscopy

Energy-filtering transmission electron microscope (EFTEM) in the image-spec trum mode was used to differentiate the phases in a triphase polymeric comp osite (PS/PB/PMA), by imaging characteristic chemical bondings. Although th e sample suffered irradiation damage, image acquisition was performed on it at ambient temperature for convenience. The mapping of polystyrene (PS) wa s easily obtained from the pi --> pi* transition at 7 eV, a characteristic of the undamaged aromatic ring. Poly(methyl acrylate) (PMA) was imaged usin g the C 1s --> pi* (C=C) transition at 284.8 eV from damaged residues, with the elemental mapping revealing oxygen artifacts due to irradiation damage . Finally, the polybutadiene (PB) phase could be directly imaged, only afte r staining with osmium tetroxide, through the elemental mapping of osmium. This work shows that it is possible to differentiate the phases of an unsta ined polymeric composite at a sub-micron scale. A reasonable interpretation of the filtered images must, however, be based on a perfect understanding of the polymer degradation processes. This technique will be particularly u seful to map the distribution of organic additives inside the polymer, such as peroxides. (C) 2000 Elsevier Science Ltd. All rights reserved.