Transmission Electron Microscope Studies of Polymers Stained with Ruthenium and Osmium Tetroxide

Abstract

We demonstrate the effectiveness of ruthenium tetroxide as a stain to enhance image contrast for transmission electron microscope studies of polymer morphology. The considerable microstruc-tural detail that can be brought out by the stain is exemplified by electron micrographs of thin films of incompatible blends of polystyrene with poly(methylmethacrylate). Crazes in strained solution-cast thin films of these polymer blends and in a strained solvent-cast thin film of high impact polystyrene can be seen readily, as ruthenium tetroxide stains the polystyrene component preferentially. Further, the stain darkens high-stress areas in these thin films. The use of osmium tetroxide and ruthenium tetroxide to stain a rubber-modified polymer of acrylonitrile and styrene reveals what appear to be three phases rather than the two conventionally accepted to occur. Morphological details of the spherulitic structure in Nylon 11 are made strikingly clear by the stain.