Kinetics of Amine–Bis(phenolate) Iron-Mediated ATRP Up to High Pressure

Atom-transfer radical polymerization (ATRP) of styrene catalyzed by chloro-substituted amine–bis(phenolate)iron complexes was investigated via online vis/NIR spectroscopy up to 6000 bar. Pressure significantly increases the rate of ATRP by enhancing both the equilibrium constant, KATRP, and the propagation rate coefficient, kp. The observed negative reaction volume, ΔrV(KATRP), is due to a stronger contraction of the ligand sphere for the Lewis-acidic FeIII complex compared to the FeII complex. Despite the enormous rate enhancement of ATRP, narrow molar mass distributions may be obtained even at very high pressure and thus very high rates.