Molecular Weight Studies on High Polymers with the Electron Microscope

Abstract

Some preliminary results are reported on measurements of molecular weight distributions for polychlorostyrene. The following technique of isolating single polymer molecules is used: A precipitating agent, such as propanol, is added to a very dilute (1 ppm) solution of the polymer in benzene, presumably causing the molecules to coil up. Drops of this mixture are evaporated on a silica screen and examined in the microscope. Circular particles ranging in diameter from 15A to 500A and believed to represent single polymer molecules have been obtained on various polymers. The relationship between measured particle diameter and molecular weight is reviewed in some detail. The data appear to favor the concept of a random coil to the extent that particle diameter varies as the square root of the molecular weight. The molecular weight distribution curves obtained are of the expected shape and extent, although the average molecular weights computed from the distribution curves are 4–5 times greater than values measured by an independent method. Finally, the role of electrical charges in stabilizing isolated polymer molecules is discussed.