Monomer in the Reaction Locus

Concentration of Monomer in the Reaction Locus.—Blackley and Haynes have published data for the emulsion pol3rmerization of styrene in the presence of organic diluents which are open to the interpretation that the concentration of monomer in the reaction locus in the absence of diluent is not the same as it would have been were no monomer being consumed by polymerization. Whatever is the correct interpretation of these results, they are interesting in themselves as showing just how sensitive the rate of an emulsion polymerization reaction can be to the presence of an apparently inert diluent. Thus the rate of emulsion polymerization of styrene in the presence of, say, ethylbenzene (a good solvent for polystyrene) is approximately third order with respect to the concentration of styrene in the oil phase of the reaction system as a whole. 

Ryabova et al. have presented evidence for believing that the rate of diffusion of styrene into reaction loci is considerably higher than the rate of polymerization, and that, in consequence, the concentration of monomer in the reaction locus is little affected by the occurrence of polymerization. On the other hand, Gritskova et al. believe that the concentration of monomer in the polymer-monomer particles is variable, depending upon the reaction conditions. 

Liegeois has recently proposed a model for the emulsion polymerization of 

Sakota and Okaya have described the preparation of cationic surfactant-free 

Continuous Emulsion Polymerization.—A useful discussion of theories of continuous emulsion polymerization and review of experimental data has been published recently by Poehlein and Dougherty. Thompson and Stevens have developed a population-balance approach to the modelling of continuous emulsion polymerization reactions. They base their approach upon the Smith-Ewart recursion formula, and allow for both radical desorption from, and finite rate of termination within, reaction loci. Cauley et aU have also attempted to model a continuous emulsion polymerization by means of a population balance, the assumed reaction system being such that bimolecular termination of radicals occurs instantaneously within reaction loci. The effect of flow regime on the continuous emulsion polymerization of styrene in a tubular reactor is the subject of a paper by Rollin et 

---