An efficient O-phthalaldehyde-amine coupling reaction for the synthesis of a bottlebrush polymer under physiological conditions

A new method to prepare the bottlebrush polymer poly(2-aminoethyl methacrylate hydrochloride)-graft-poly(N,N-dimethylacrylamide) (PAMA-g-PDMA) by the combination of “grafting onto” strategy and catalyst-free o-phthalaldehyde (OPA)-amine coupling reaction was proposed. The PAMA backbone with primary amine side groups and OPA-terminated PDMA side chains were prepared separately. The coupling of the PDMA side chains onto the backbone via the OPA-amine reaction under physiological conditions yielded worm-like bottlebrush polymers. The grafting density achieved 97.4% for PAMA147-g-PDMA26 in 15 min and 90.6% for PAMA147-g-PDMA47 in 60 min, demonstrating the high reaction efficiency. This is the first study to employ the OPA-amine reaction for the preparation of bottlebrush polymer.