Facile, Modular Transformations of RAFT Block Copolymers via Sequential Isocyanate and Thiol-ene Reactions

Joel D. Flores, University of Southern Mississippi
Nicholas J. Treat, University of Southern Mississippi
Adam W. York, University of Southern Mississippi
Charles L. McCormick, University of Southern Mississippi

Abstract

We describe a robust strategy utilizing reversible addition-fragmentation chain transfer (RAFT) polymerization and sequential transformations involving carbamate formation and thiol-ene click addition to synthesize well-defined functional block copolymers. The hydroxy-functional block copolymer scaffold, poly[(N,N-dimethylacrylamide)-b-(N-(2-hydroxyethyl)acrylamide)] (PDMA_n-b-PHEA_m) was first prepared via RAFT, requiring no protecting group chemistry. The hydroxyl groups of the HEA block were then reacted with 2-(acryloyloxy)ethylisocyanate (AOI) or allylisocyanate (AI) resulting in acrylate- and allyl-functionalized copolymer precursors, respectively. The efficiencies of both Michael and free radical-mediated thiol-ene addition reactions were investigated using model thiol compounds having alkyl, aryl, hydroxyl, carboxylic acid, amine and amino acid functionalities. The steps of RAFT polymerization, isocyanate-hydroxyl coupling and thiol-ene addition can be accomplished under mild conditions, thus offering a facile, modular route to the synthesis of functional copolymers from a single polymeric precursor.