Determination of the number of particles/unit volume of latex during the emulsion polymerization of styrene

The variation of the number of particles/unit volume of latex (N) with conversion was determined during the emulsion polymerization of styrene. The results showed that, contrary to what is required by the Smith‐Ewart theory, N increased during the constant rate period. This conclusion was supported by the variation of the particle size distribution with conversion. Further evidence that latex particles could form in the absence of micelles was given by using systems in which the soaps were below the CMC. The chain length of the soaps used had a marked effect on the rate of polymerization. This effect was shown not to be due to the variation of the CMC with chain length, but possibly to the stronger adsorption of the longer chain length soaps at the polymer–water interface.