Living/controlled radical polymerizations in dispersed phase systems

Living/controlled radical polymerization provides a route to synthesizing materials with designed microstructure and narrow molecular weight distributions. A variety of living radical systems have been developed in recent years, and are based on either reversible termination (SFRP, ATRP) or reversible transfer mechanisms (RAFT, degenerative transfer). Application of living radical polymerization to heterogeneous systems such as emulsion and miniemulsion polymerization may provide process and economic advantages over the traditional homogeneous bull: and solution polymerizations. However, adaptation of living radical chemistry to aqueous dispersions poses several challenges relating to maintaining effective control over the growth of living chains. These challenges originate from having two or even three phases in the reaction mixture, which can lead to issues related to phase partitioning of the controlling agent, transport of the controlling agent between phases, the role of aqueous phase kinetics, and the phenomena of particle nucleation and colloidal stability. This review examines recent progress in this area, with an emphasis on unresolved issues and future opportunities. (C) 2002 Elsevier Science Ltd. All rights reserved.