Direct Observation of Polymer Chains in Solutions

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We have investigated polymerization and chemical reactions in thin solid films and many new findings on the reactions have been obtained. However, chemical spices are reacted usually in solutions, so that it is desirable to observe chemical reactions in solutions by molecularly resolved imaging. In order to observe directly the chemical reactions in solutions, this project was aimed to provide a new technique to observe organic molecules like polymer molecules in solutions. Since polymers are long in shape, it is expected to be easy and convenient to observe their images by electron microscopy.Though present transmission electron microscope has ability to resolve molecules or even atoms in materials, the specimen should be kept in vacuum. Then, molecules in solution could not be observed as they are in solution by conventional electron microscope. In this study, the specimen was frozen and observed with a cryo-electron microscope. The solution was quickly frozen by plunging it into liquid propane at 100K and observed with a cryo-transmission electron microscope with a specially designed cryotransfer system. The frozen specimen was observed at about 4K so as not to change the structure in solution during the microscopic observation.The chemical polymerization of pyrrole with a ionic polymer was investigated as an application of the technique. The polymerization process to form spherical polypyrrole particles was observed from micelle formation of ionic polymer to the final spherical product in water solution. The other example is the fine metal particles with some surfactants in water solution. As a result, the metal particles were found to be formed arbitrary places, but they are encapsulated with the surfactants. Accordingly they are dispersed as fine nano-particles in solution. The metal formation process was imaged step-by-step by freezing the solution.