Competitive Equilibria in Atom Transfer Radical Polymerization

• Published in: Macromolecular symposia Vol. 248; no. 1; pp. 60 - 70
• Main Authors: Tsarevsky, Nicolay V., Braunecker, Wade A., Vacca, Alberto, Gans, Peter, Matyjaszewski, Krzysztof
• Format: Journal Article Conference Proceeding
• Language: English
• Published: Weinheim WILEY-VCH Verlag 01.02.2007; WILEY‐VCH Verlag; Wiley-VCH
• Subjects: Applied sciences; atom transfer radical polymerization; Catalysis; Catalysts; competitive complexation; complex stability; Complexation; electron transfer; Exact sciences and technology; Monomers; Organic polymers; Physicochemistry of polymers; Polymerization; Preparation, kinetics, thermodynamics, mechanism and catalysts; Radicals; Reduction; Solvents; Chemical equilibrium; State of the art; Disproportionation; Atom transfer polymerization; Living polymer; Reaction mechanism; Competitive reaction; Electron transfer; Copper complex; Chemical reaction kinetics
• ISSN: 1022-1360; 1521-3900
• DOI: 10.1002/masy.200750207

With the recent development of new initiation techniques in atom transfer radical polymerization (ATRP) that allow catalysts to be employed at unprecedented low concentrations (∼10 ppm), a thorough understanding of competitive equilibria that can affect catalyst performance is becoming increasingly important. Such mechanistic considerations are discussed herein, including i) factors affecting the position of the ATRP equilibrium; ii) dissociation of the ATRP catalyst at high dilution and loss of deactivator due to halide dissociation; iii) conditional stability constants as related to competitive monomer, solvent, and reducing agent complexation as well as ligand selection with respect to protonation in acidic media; and iv) competitive equilibria involving electron transfer reactions, including the radical oxidation to carbocations or reduction to carbanions, radical coordination to the metal catalyst, and disproportionation of the CuI‐based ATRP activator.