Osmium tetroxide fixation of vinyl chloride emulsions

It is of interest to measure the monomer droplet size in emulsion polymerization. Unlike some monomers such as styrene and alkyl acrylates, vinyl chloride is in the gaseous state at the standard condition. Thus it is hard to measure the droplet size using any of the conventional methods. It is especially difficult when the droplet is smaller than 1 μm. Using a high-pressure-proof syringe, vinyl chloride emulsion droplets can be fixed and stained through rapid reactions with osmium tetroxide dilute solution. The resulting stained particles are ready for transmission electron microscope (TEM) measurement. Emulsion droplets as small as 0.1 μm can be identified. This technique can be utilized to study nucleation, particle growth mechanism, and the kinetics of emulsion polymerization.