Copolymerization of Pentafluorophenylmethacrylate with Hydrophilic Methacrylamide Monomers Induces Premature Hydrolytic Cleavage

Abstract

Active ester polymers are commonly used for fast development of novel polymer libraries, but they require post-polymerization modification, which is not atom-efficient or economical. In order to more efficiently produce 2-hydroxypropyl methacrylamide (HPMAm) libraries, it would be advantageous to perform a direct copolymerization with active ester monomers. In this work, the synthesis of copolymer libraries of pentafluorophenyl methacrylate (PFPMA) and the hydrophilic monomer HPMAm is investigated. Surprisingly, HPMAm induces premature hydrolytic cleavage of PFPMA, which occurs during polymerization and depends on the HPMAm/PFPMA feed ratio. Copolymerization of PFPMA with N-isopropylmethacrylamide and the methacrylate monomers 2-hydroxypropylmethacrylate and N-isopropylmethacrylate reveals that the hydrolytic cleavage is promoted by copolymerization with methacrylamides only. By switching from a thermal- to a light-based initiator and lowering the reaction temperature, premature hydrolytic cleavage of PFPMA is avoided and allows direct copolymerization of HPMAm together with PFPMA to create polymer libraries for biomaterial screening.

Keywords: active ester monomers; hydrolytic cleavage; methacrylamide monomers; pentafluorophenylmethacrylate.