Living radical polymerization in miniemulsion using reversible addition-fragmentation chain transfer

Living radical polymerizations using reversible addition-fagmentation chain transfer (RAFT) have been conducted successfully in miniemulsions stabiliz ed by nonionic surfactants. The miniemulsion stability was found to be a ke y issue. Both anionic and cationic surfactants were not able to maintain th e original droplet morphology during the reaction. The application of nonio nic surfactants allowed the controlled polymerization of methacrylate and s tyrene monomers, resulting in stable dispersions free of coagulate. Typical particle sizes for these latices were around 200-300 nm. The molar mass of the polymer was close to the predicted value, and polydispersity was typic ally below 1.20, never exceededing 1.40. The "living'' character of the lat ex material was further exemplified by its transformation into block copoly mers. The increased polymerization rate of the compartmentalized system all owed for improved block copolymer purity compared to that of homogeneous sy stems. Furthermore, it was shown that latex blends containing particles wit h very different characteristics could be prepared in a single polymerizati on by a careful choice of reaction conditions allowing the design of sophis ticated materials.