Abstract
A polystyrene sample, which had been distributed by “The committee on molecular weight and molecular weight distribution in Japan” for co-operative measurements of the molecular weight distribution, was fractionated by the successive precipitation method using toluene as solvent and polyethylene glycol as non-solvent. It was characteristic of the phase separations in this ternary system that the separated two phases were liquid and the concentration of the polymer in the more concentrated phase was lower than that obtained with other systems of solvent and non-solvent usually used. These features in this system allows a sample of polystyrene to separate into many small fractions and thus this system may be used for precise fractionation of this polymer.
Thirty five fractions were separated from 5 g. of the sample, and the first two fractions of them were refractionated. The molecular weight distributions of the sample calculated from the data obtained before and after the refractionation showed an appreciable difference. This result indicates that a sigle successive precipitation is not sufficient for the precise determination of the molecular weight distribution, even if the number of fractions was large.
The results were compared to those obtained on the same sample by other methods.
