Atom transfer radical polymerization (ATRP) is a versatile reversible-deactivation radical polymerization (RDRP) method. ATRP employs transition metal catalysts, often Cu, to create precisely controlled polymers with various architectures including block, star and branched architectures. However, aqueous media have traditionally presented a significant challenge to ATRP, especially using low catalyst concentrations, due to the high activity of CuI in aqueous media leading to a high termination rate; potential disproportionation of CuI; the loss of the deactivator complex due to the dissociation of the CuII-halide deactivator complex in water, and also loss of chain ends by hydrolysis/elimination. A strategy for overcoming these challenges will be discussed, by using highly active Cu complexes, slowly regenerating the activating species and adding an excess of halide salt to minimize the dissociation of the deactivator complex. Various techniques that allow polymerizations with parts per million catalyst loadings will be presented, by using an excess of halide salts, regenerating the activator complexes using either conventional radical initiators, reducing agents such as ascorbic acid, or Cu0 that acts as a supplemental activator and reducing agent. These techniques allow the direct synthesis of bioconjugates.

Aqueous atom transfer radical polymerization: From challenges to solutions and bioconjugates

248th National Meeting (2014)

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