Synthesis of well-defined primary amine-based homopolymers and block copolymers and their Michael addition reactions with acrylates and acrylamides

A series of well-defined primary amine-based AB diblock copolymers were synthesised via atom transfer radical polymerisation (ATRP) using 2-aminoethyl methacrylate hydrochloride (AMA), with the other block comprising the following comonomers: 2-(diisopropylamino)ethyl methacrylate (DPA), 2-hydroxypropyl methacrylate (HPMA) and 2-(methacryloyloxy)ethyl phosphorylcholine (MPC). These copolymers were prepared with reasonably narrow polydispersities (Mw/Mn ≈ 1.1–1.4) in either 80 : 20 or 95 : 5 2-propanol–water mixtures at 50 °C using a 2-(N-morpholino)ethyl isobutyryl bromide initiator. The chain extension efficiency of PAMA was also investigated using a further charge of AMA. Unfortunately, such ‘self-blocking’ was problematic due to both catalyst deactivation and termination of the living chain ends. Nevertheless, low polydispersity all-methacrylic diblock copolymers were obtained in high yields via sequential monomer addition, provided that AMA was used as the second monomer in such syntheses. PAMA49 homopolymer and selected PAMA-based copolymers were reacted with various acrylates and acrylamides in aqueous solution at pH 9, with mean degrees of functionalisation being determined by 1H NMR spectroscopy. This facile Michael addition chemistry provides access to a library of novel functional water-soluble homopolymers and diblock copolymers.