Deactivation Efficiency and Degree of Control over Polymerization in ATRP in Protic Solvents

Abstract

Copper-mediated ATRP in protic solvents is characterized by inefficient deactivation due to reversible dissociation of a halide ligand from the ATRP deactivator CuIILnX (L = bipyridine or another amine or imine, X = Br, Cl), which may be followed by competitive coordination of solvent to the CuII center. This process is strongly solvent-dependent and leads to fast and often poorly controlled polymerizations. The loss of a halide ligand from the deactivator in ATRP reactions in the presence of water or other coordinating compounds can be suppressed by the addition of halide salts allowing the regeneration of the dissociated CuII−X species and, therefore, increasing the deactivation rate. The deactivation step in ATRP, which is of primary importance for control over the polymerization, can also be accelerated by employing a catalyst system initially containing a sufficiently large amount of CuII−halide complex. These approaches are illustrated by conducting the controlled radical polymerization of 2-hydroxyethyl methacrylate, 2-(N,N-dimethylamino)ethyl methacrylate, 2-(trimethylammonio)ethyl methacrylate trifluoromethanesulfonate, and 2-(dimethylethylammonio)ethyl methacrylate bromide.