Transmission Electron Microscopy

Transmission Electron Microscopy (TEM) provides high magnification imaging and electron diffraction capability for the ultrastructural analysis of polymer systems. Magnification typically ranges from x100 to x500,000. Specimen formats may be whole mounts, thin films, replicas or ultramicrotomed thin sections. Staining techniques enhance image contrast based on functional group constitution.

Examples

In blends of incompatible polymers or block copolymers, phase separation has a significant impact on the end use properties of the material. It is important to know the domain type and size in the processed material. In multicomponent systems, it is also desirable to know which polymers constitute the phases. Often, staining and beam interaction techniques will give identification to the phases.

In an attempt to improve the physical properties of a blend of incompatible polymers such as polyethylene, polystyrene, and poly(methyl methacrylate), a variety of compatibilizing agents and processing conditions are tried. After blending, the bulk polymer specimens are sectioned, stained and examined. The micrographs recorded give the researcher information about the efficacy of the compatibilizing agent based on domain type and size which may be measured from the micrograph.
In preparing a polymer latex, a variety of reaction conditions are tried to produce uniform particles. The various conditions result in different particle sizes and distributions. Dilute suspensions of the particles are sprayed on carbon coated specimen grids. The grids may then be shadowed at an angle with a heavy metal, or used directly. TEM images of the particles provide the researcher with measurements of particle sizes and information about the range and distribution of sizes in the specimen. The researcher is then able to correlate reaction conditions with product characteristics.

By using TEM, the researcher learned how to control the reaction conditions to make a reproducible product.

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