Activation-Deactivation Equilibrium Associated With Iron-Mediated Atom-Transfer Radical Polymerization up to High Pressure

Abstract

The equilibrium constant, Kmodel, of iron-mediated atom-transfer radical polymerization (ATRP) is investigated for FeBr2/a-bromoester model systems in the absence of monomer. Quantitative analysis is carried out in solution of either N-methylpyrrolidin-2-one (NMP) or acetonitrile (MeCN) via high-pressure online VIS/NIR spectroscopy monitoring the formation of the FeIII species. The reaction volume is determined to be ?VR = 13 +/- 3 cm3 mol-1, which indicates that Kmodel decreases with pressure. This observation points to preferred formation of catalytically inactive or less active ironsolvent complexes toward higher pressure. Thus suitable solvent selection is important for the development of efficient iron-based ATRP catalysts.