Kinetics of Catalysed Polymerization of Styrene

Abstract

INVESTIGATIONS of polymerization kinetics have often required rather cumbersome experimental methods, but Hammick and Langrish¹ have recently applied a convenient bromination method for estimating cyclopentadiene and indene to a study of the polymerization rates of these compounds in carbon tetrachloride. We have been using, for some time, a very similar method to follow the kinetics of the polymerization of styrene, catalysed by anhydrous stannic chloride, in carbon tetrachloride and chloroform solutions at 25° C. The amount of residual monomeric styrene in the reaction mixture is determined, at known intervals of time, by quantitative bromine addition to the double bond, using an excess of bromine which is estimated by titration in the usual way. The accuracy of the analysis (better than 0.5 per cent) is not impaired by the presence of polystyrene ; but with polystyrene in the presence of stannic chloride, the excess bromine must be destroyed without delay, in order to avoid a slow attack of bromine on the polymer. The styrene disappearing during polymerization has been proved to be equivalent to the polymer formed by weighing the amount of polystyrene precipitated in methyl alcohol². The polymers produced have molecular weights of the order 5,000 as determined by viscosity measurements.