Polymerization reactions that allow the synthesis of polymers with predetermined molecular weights, with narrow molecular weight distributions and with functional end groups have propelled polymer science into the position of key contributor to advanced materials, nanosciences, and modern soft matter research. Such “living” or controlled polymerizations are used e.g. to synthesize amphiphilic blockcopolymers, which are needed as building blocks of self-assembled nanoobjects. Atom transfer radical polymerization (ATRP) is one of the most widely used controlled radical polymerizations. However, ATRP requires the use of transition metal complexes as catalysts, and these are difficult to remove from the polymer products and are often toxic as well as environmentally unfavorable. Recently, we discovery that some heme proteins and enzymes can catalyze the polymerization of an acrylamide under conditions of activators regenerated by electron transfer (ARGET) ATRP. The previously unknown enzymatic catalysis was termed ATRPase activity. As enzymes and proteins are non-toxic and environmental friendly, ATRPases could become green alternatives to transition metal complex catalysts used in ATRP.

Based on these initial findings, the proposed project will investigate the ATRPase activity of hemoglobin and of horseradish peroxidase in detail, in order to understand the mechanism of the reaction and the role of the biocatalyst, to quantify the rate constants of the reactions involved in ATRP, to identify and suppress possible side reactions, and to increase the degree of control over the polymerization. We expect that also other metalloenzymes and –proteins will show catalytic activity in ATRP reactions. Therefore, a diverse library of proteins and enzymes will be screened for this activity. Moreover, the potential of ATRPase activity will be investigated by using various monomers, synthesizing block copolymers and star-shaped polymers, and by investigating the operational stability and reusability of soluble and immobilized biocatalysts. In summary, the major aims of this project are to gain detailed knowledge of the molecular processes involved in ATRPase activity, to elucidate the scope of biocatalytic ATRP and to improve the catalytic performance of ATRPases to such levels that they become competitive, environmentally favorable alternatives to conventional ATRP catalysts.