Facilitating Polymer Conjugation via Combination of RAFT Polymerization and Activated Ester Chemistry

The synthesis of block copolymers via polymer conjugation of well-defined building blocks offers excellent control over the structures obtained, but often several coupling strategies need to be explored to find an efficient one depending on the building blocks. To facilitate the synthesis of polymers with adjustable functional end-groups for polymer conjugation, we report on the combination of activated ester chemistry with RAFT polymerization using a chain transfer agent (CTA) with a pentafluorophenyl ester (PFP-CTA), which allows for flexible functionalization of either the CTA prior to polymerization or the obtained polymer after polymerization. Different polymethacrylates, namely PMMA, P(t-BuMA) and PDEGMEMA, were synthesized with an alkyne-CTA obtained from the aminolysis of the PFP-CTA with propargylamine, and the successful incorporation of the alkyne moiety could be shown via H-1 and C-13 NMR spectroscopy and MALDI TOF MS. Further, the reactive alpha-end-groups of polymers synthesized using the unmodified PFP-CTA could be converted into azide and alkyne end-groups after polymerization, and the high functionalization efficiencies could be demonstrated via successful coupling of the resulting polymers via CuAAC. Thus, the PFP-CTA allows for high combinatory flexibility in polymer synthesis facilitating polymer conjugation as useful method for the synthesis of block copolymers. (C) 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 4758-4767, 2010