Enhancement of the Rate of Atom Transfer Radical Polymerization in Organic Solvents by Addition of Water: An Electrochemical Study.

Addition of water to organic solvents enhances the rate of atom transfer radical polymerization (ATRP). To understand the origin of this rate enhancement, the effects of H 2 O on the redox properties of [Cu II TPMA] 2+ and [BrCu II TPMA] + (TPMA=tris(2‐pyridylmethyl)amine), and on the ATRP equilibrium ( K ATRP ) and activation rate ( k act ) constants of methyl 2‐bromopropionate by [Cu I TPMA] + were investigated in CH 3 CN, DMF and DMSO and their mixtures with methyl acrylate (MA). E °s of the complexes allowed evaluation of the relative halidophilicities of [Cu II TPMA] 2+ and [Cu I TPMA] + , K II Br and K I Br , respectively. K II Br / K I Br dropped in pure solvents and solvent/MA mixtures when 11 % (v/v) H 2 O was added, suggesting that H 2 O hampers the stability of the deactivator [BrCu II TPMA] + . Conversely, both k act and K ATRP were enhanced by the presence of water. In solvent/MA mixtures (50/50, v/v), addition of 11 % (v/v) H 2 O increased K ATRP by a factor of 2–3, which could explain the accelerating effect of H 2 O on ATRP in organic solvents.