RAFT in Emulsion Polymerization: What Makes it Different?

Abstract

Reversible addition-fragmentation chain transfer (RAFT) polymerization techniques have been the focus of a great deal of recent work, particularly in their application to emulsion polymerization, which is the method of choice for implementing most free-radical polymerizations on an industrial scale. RAFT/emulsion polymerizations have considerable technical potential: to 'tailor-make' material properties, to eliminate added surfactant from surface coatings, and so on. However, considerable difficulties have been experienced in using RAFT in emulsion polymerization systems. Here, progress in the application of RAFT techniques to emulsion polymerization is reviewed, summarizing the difficulties that have been experienced and mechanisms that have been postulated to explain the observed behaviour. Possible origins of the difficulties in implementing RAFT in emulsion polymerizations include polymerization in droplets, water sensitivity of some RAFT agents, slow transport of highly hydrophobic RAFT agents across the water phase, and surface activity of some RAFT agents.