Abstract
The specimen preparation of film-forming or “soft” particle latexes is complicated by the tendency of these particles to deform and coalesce upon drying; these deformed particles appear indistinct in the electron microscope. Soft particles of butadiene-containing polymers can be hardened by bromination prior to deposition. The particular diameter increase of brominated styrene-butadiene copolymers is dependent upon their butadiene content and varies from about 0.2% for polystyrene to 24.8% for polybutadiene. Exposure of these particles to high-energy irradiation, e.g., from a van de Graaff accelerator, also hardens them owing to cross-linking reactions between adjacent polymer molecules. Particles hardened by this technique appear as well-defined spheres in the electron microscope. High-energy irradiation also hardens certain latex systems which do not respond to bromination, e.g., polyethyl acrylate and polyvinyl acetate.
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