Molecular weight distributions of polystyrene samples by turbidimetric titration

Abstract

Abstract An analysis of the light scattered from suspended polymer aggregates formed during turbidimetric titration of the system polystyrene–benzene–methanol has been made. It has been shown that a knowledge of the precipitate composition and total number of aggregates is required before the precipitate mass can be calculated from turbidity measurements. Satisfactory results are obtained if the total number of aggregates is assumed to be proportional to the precipitate mass, provided the initial polymer concentration does not exceed 0.002% (w/v). On the basis of an empirical saturation law, two methods have been used to derive satisfactory molecular weight distributions for two polystyrene samples of known distribution. The better method is based on a Claesson grid. The other method is based on that given originally by Morey and Tamblyn. Turbidimetric titration tends to discriminate against the low‐molecular‐weight end of a distribution.