Iron-catalyzed atom transfer radical polymerization

In the last two decades, metal-catalyzed controlled radical polymerization (CRP), or atom transfer radical polymerization (ATRP) has become a ubiquitous tool for the facile synthesis of a wide range of materials with specific macromolecular architectures. The complex plays an important role in ATRP, and for this purpose researchers put a great deal of effort on studying the effect of various complexes on polymerization. However, one of the disadvantages of a copper complex, the most extensively studied catalyst system in ATRP, is the contamination of polymers resulting from a high concentration of stable catalyst. Efficiently and economically removing the catalyst from the resultant polymers will provide a wide variety of new functional polymers for specialty applications, especially for large-scale industrial manufacture. Iron-based catalysts have attracted particular attention because of their low toxicity, low cost, abundance, and environmental friendliness, and thus many iron catalysts have been designed for ATRP. This article reviews the preparation of polymers using iron-catalyzed atom transfer radical polymerization, and is organized according to: (a) mechanistic considerations; (b) iron complexes and ligand types.