alpha-Chymotrypsin, a commonly used protease, was modified with well-defined oligomers synthesized by RAFT. The well defined polymers were synthesized based on the monomers N,N-dimethylacrylamide (DMAm) or oligo(ethylene oxide) methyl ether acrylate (OEOA). The polymers were conjugated to free amine groups on chymotrypsin through an in-situ 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide/N-hydroxysuccinimide (EDC/NHS) coupling approach. The protein-polymer conjugates retained enzymatic activity, and the higher molecular weight DMAm and OEOA polymer, created protein-polymer conjugates with significantly enhanced stability, presumably due to the high molecular weight polymer preventing autolysis of the alpha-chymotrypsin. (C) 2015 Elsevier Ltd. All rights reserved.