Controlled free-radical miniemulsion polymerization of styrene using degenerative transfer

Controlled free-radical polymerization of styrene was performed in aqueous dispersed medium using a degenerative transfer process with iodine atom exchange: The transfer agent was the commercially available perfluorohexyl iodide. Its efficiency was shown to be low in conventional batch emulsion polymerization since polymer had molar mass higher than expected. This was explained by a slow rate of diffusion of the perfluorinated transfer agent through the water phase, from the monomer droplets to the active latex particles. This problem was overcome by using a batch miniemulsion process. In that case, 100% efficiency of the chain transfer agent was reached, and the experimental molar masses fit well with the theoretical ones. With that technique, the transfer agent could be directly located in the polymer particles without transportation. Moreover, when using a continuous addition of monomer, a linear increase of the number-average molar mass with conversion was observed.