Living Radical Polymerization in Miniemulsion Using Reversible Addition−Fragmentation Chain Transfer

Living radical polymerizations using reversible addition−fragmentation chain transfer (RAFT) have been conducted successfully in miniemulsions stabilized by nonionic surfactants. The miniemulsion stability was found to be a key issue. Both anionic and cationic surfactants were not able to maintain the original droplet morphology during the reaction. The application of nonionic surfactants allowed the controlled polymerization of methacrylate and styrene 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 typically below 1.20, never exceededing 1.40. The “living” character of the latex material was further exemplified by its transformation into block copolymers. The increased polymerization rate of the compartmentalized system allowed for improved block copolymer purity compared to that of homogeneous systems. Furthermore, it was shown that latex blends containing particles with very different characteristics could be prepared in a single polymerization by a careful choice of reaction conditions allowing the design of sophisticated materials.