Kinetic Investigations of Cu‐Mediated ATRP in Aqueous Solution

Abstract

Cu‐mediated atom‐transfer radical polymerization (ATRP) is studied via on‐line vis/NIR spectroscopy in an aqueous solution of a monomer‐free model system, with CuBr/2,2′‐bipyridine acting as the catalyst, and 2‐hydroxyethyl 2‐bromoisobutyrate as the initiator, at a pressure of up to 2000 bar. Excess NaBr is added to avoid the water‐assisted dissociation of the Br–Cu(II)/L bond. The activation–deactivation equilibrium constant, Kmodel, is measured at different compositions of the water–poly(ethylene glycol) dimethylether (PEO) solvent mixture, in which PEO mimics a water‐soluble monomer. Kmodel increases by about three orders of magnitude in passing from a PEO to a water environment. The change in Kmodel is essentially due to the effect on the activation rate coefficient. Kinetic analysis of the model system upon variation of NaBr concentration in conjunction with predici simulations shows that the NaBr content has no significant impact on the activation and deactivation rate coefficients and thus on Kmodel, but on dispersity and on the degree of chain‐end functionality. image