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

Energy-filtering transmission electron microscope (EFTEM) in the image-spectrum mode was used to differentiate the phases in a triphase polymeric composite (PS/PB/PMA), by imaging characteristic chemical bondings. Although the sample suffered irradiation damage, image acquisition was performed on it at ambient temperature for convenience. The mapping of polystyrene (PS) was easily obtained from the pi --> pi* transition at 7 eV, a characteristic of the undamaged aromatic ring. Poly(methyl acrylate) (PMA) was imaged using 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 after staining with osmium tetroxide, through the elemental mapping of osmium. This work shows that it is possible to differentiate the phases of an unstained 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 useful to map the distribution of organic additives inside the polymer, such as peroxides. (C) 2000 Elsevier Science Ltd. All rights reserved.