CONTROLLED FREE-RADICAL POLYMERIZATION

Precise control of macromolecular structure and architecture continues to be a dominant theme or contemporary polymer research. Amongst the armoury of polymerization techniques available to polymer chemists, fr ee radical polymerization is the oldest, most studied and extensively exploited in commercial practice. Nevertheless, free radical polymeriz ations have been most difficult to control and are generally character ized by broad molecular weight distribution, poor control of molecular weights and chain end functionality and inability to synthesize well- defined block copolymers. However, polymer chemists have, in recent ye ars, succeeded in effectively controlling the free radical polymerizat ion by invoking the concept of reversible termination involving an act ive species in rapid equilibrium with a dormant species. Using control led free radical polymerization it is feasible to produce poly(styrene )s with polydispersities as low as 1.05 with good control of molecular weight. Furthermore, a variety of novel end functionalized polymers a s well as random, block, graft, star and hyperbranched polymers have b een prepared using controlled free radical polymerization. The paper r eviews the explosive developments in this area since the appearance of the first publication in 1993. The scope of this new technique for po lymer synthesis is illustrated with representative examples.