Living polymerization of substituted acetylenes

For many years, considerable research efforts have been dedicated to π‐conjugated polymers because of their extraordinary electronic, optical, and structural properties. The employed transition‐metal‐based initiating systems comprise not only simple transition‐metal salts but also rather sophisticated mixtures of two, three, or four compounds and even highly defined single‐component systems such as transition‐metal alkylidene complexes. Extensive fine‐tuning of the electronic and steric properties of initiator–monomer systems eventually allowed the tailor‐made synthesis of conjugated materials via living polymerization techniques. This article focuses on recent developments in the field of the living polymerization of substituted acetylene derivatives. Ill‐defined group 5 and 6 transition metal halide‐based initiators, well‐defined transition‐metal alkylidene complexes, and rhodium(I)‐based systems that induce the living polymerization of numerous substituted acetylenes are reviewed. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 5723–5747, 2005 Various initiating systems, that is, ill‐de fined group 5 or 6 transition‐metal halide‐based complexes, well‐defined Schrock‐type or modified Grubbs–Hoveyda‐type transition‐metal alkylidenes, and rhodium(I)‐ based complexes induce the living polymerization of mono‐ or disubstit uted acetylenes or α,ω‐diynes. Nevertheless, monomer–initiator combinations appropriate for the tailor‐made synthesis of π‐conjugated polymers have to be selected carefully. Therefore, initiating systems mediating the living polymerization of substituted acetylenes are presented, some insight into mechanistic advancements is given, and advantages as well as limitations of the different groups of initiators are briefly discussed.