Living Radical Polymerization

Abstract

Abstract Living Radical Polymerization (LRP) is the general name for a family of polymerization techniques. The techniques have in common that the propagating species is a free radical, and that an equilibrium exists between active (free radical) species and dormant species. Because of this equilibrium (nearly) all chains grow throughout the polymerization reaction. This leads to polymers with predetermined degree of polymerization and (usually) narrow molar mass distribution. A historical overview of the development of LRP is provided, and the three most important techniques are discussed in more detail. These three techniques are ( 1 ) nitroxide‐mediated polymerization (NMP), ( 2 ) atom transfer radical polymerization (ATRP), ( 3 ) reversible addition–fragmentation chain‐transfer–mediated polymerization (RAFT) The general kinetics and some boundary conditions for obtaining low polydispersity index (PDI) polymers are discussed. Further, the scope and limitations of the three major polymerization techniques are outlined. Apart from the predetermined molar mass and the PDI, LRP is of particular interest in the synthesis of advanced architectures. These architectures include block copolymers, star‐branched polymers, telcchelic polymers, gradient or tapered copolymers, etc. Among the major advantages of LRP is the fact that most of the benefits of free‐radical polymerization (FRP) are retained. Thus, the possibility to (co)polymerize functional monomers (hydroxyl, epoxy, amide, anhydride, etc) and the possibility to polymerize under nondemanding conditions are typical for FRP as well as for LRP.