Controlled aqueous atom transfer radical polymerization under electrochemical activation of the active catalyst

Controlled Radical Polymerizations (CRPs) in aqueous medium are very attractive from an economic and environmental point of view; besides the production of water soluble polymers, aqueous media are largely employed in the polymerization of non polar monomers through emulsion or miniemulsion techniques. Moreover, the effectiveness of CRPs in aqueous saline buffers is a pre-requisite for the preparation of polymer-biomolecule conjugates under biological conditions. Atom Transfer Radical Polymerization (ATRP) is nowadays the most used method in the field of the CRPs; despite its importance, well controlled aqueous ATRP remains a challenge, achieving only a limited success in the literature. The main drawbacks stem from a relatively high equilibrium constant KATRP and the instability of X-CuIIL, resulting in a fast and uncontrolled polymerization. Recently, the first example of electrochemically mediated ATRP has been introduced as a technique allowing an unprecedented modulation of the rate of polymerization through the variation of the external applied potential, Eapp. In this communication, we report the successful controlled polymerization of poly(ethylene glycol) methyl ether methacrylate (PEOMA) in water under electrochemical reduction of the catalyst precursor CuIIL (L = TPMA, tris (2-pyridyl)methylamine). Herein, we demonstrate that the magnitude of Eapp not only acts as an electrochemical switch of the polymerization, but also as a tuner of the degree of control obtained in the final polymer.