Synthesis of thermoresponsive oxazolone end-functional polymers for reactions with amines using thiol-Michael addition click chemistry

Well-defined poly(N-isopropylacrylamide) (PNIPAM) polymers with an oxazolone ring at the chain end have been synthesized by combining controlled radical polymerization and thiol-Michael addition click chemistry. First, PNIPAM was synthesized using reversible addition-fragmentation chain transfer (RAFT) polymerization to afford polymers of controlled molecular weight and molecular weight distribution (M-n (1H NMR) = 3200 g mol(-1); PDISEC = 1.05). The chain end was quantitatively converted to a thiol by aminolysis. Then, the functional monomer vinyl azlactone (VDM) was quantitatively clicked onto the chain end using a thiol-Michael addition reaction. The polymers were reacted with a model amine in order to demonstrate the potential of these polymers for bioconjugation.