Preparation of Methacrylate End-Functionalized Poly(2-ethyl-2-oxazoline) Macromonomers

Three methods for the functionalization of 2-ethyl-2-oxazoline (EtOx) oligomers with a methacrylate or methacrylamide unit are compared to identify the best suitable route to obtain such macromolecules. In the first method, a functional initiator, namely methacryloyl chloride, was used for the cationic ring-opening polymerization of EtOx, which proceeded in a living manner. However, the formation of a large amount of hydrogen initiated chains resulted in a low degree of functionalization (21%). The second method was based on the termination of active oligo(EtOx) chains with an aqueous sodium carbonate solution yielding hydroxyl-terminated oligomers. These end-groups were subsequently modified by an esterification reaction with methacryloyl chloride yielding oligomers with a large variety of different end-groups, as demonstrated by MALDI-TOF-MS. In the last method, the living chain ends were reacted with in situ formed triethyl ammonium methacrylate yielding macromonomers with a high degree of functionalization (>80%). Besides, MALDI-TOF-MS analysis revealed only a single oligomer distribution with the desired end-groups. Furthermore, these directly end-capped oligomers revealed narrow molar mass distributions with PDI values below 1.2 making this the best method for macromomonomer synthesis.