"One-Pot" Animolysis/Thiol-Maleimide End-Group Functionalization of RAFT Polymers: Identifying and Preventing Michael Addition Side Reactions
Document Type
Article
Publication Date
9-13-2016
Department
Polymers and High Performance Materials
Abstract
We show that many of the nucleophiles (catalysts, reducing agents, amines, thiols) present during “one-pot” aminolysis/thiol–maleimide end-group functionalization of RAFT polymers can promote side reactions that substantially reduce polymer end-group functionalization efficiencies. The nucleophilic catalyst 1,8-diazabicyclo[5.4.0]undec-7-ene and the reducing agent tributylphosphine were shown to initiate anionic polymerization of N-methylmaleimide (NMM) in both polar and nonpolar solvents whereas hexylamine-initiated polymerization of NMM occurred only in high-polarity solvents. Furthermore, triethylamine-catalyzed Michael reactions of the representative thiol ethyl 2-mercaptopropionate (E2MP) and NMM in polar solvents resulted in anionic maleimide polymerization when [NMM]0 > [E2MP]0. Base-catalyzed enolate formation on the α-carbon of thiol–maleimide adducts was also shown as an alternative initiation pathway for maleimide polymerization in polar solvents. Ultimately, optimal “one-pot” reaction conditions were identified allowing for up to 99% maleimide end-group functionalization of dithiobenzoate-terminated poly(N,N-dimethylacrylamide). Much of the work described herein can also be used to ensure near-quantitative conversion of small molecule thiol–maleimide reactions while preventing previously unforeseen side reactions.
Publication Title
Macromolecules
Volume
49
Issue
17
First Page
6193
Last Page
6202
Recommended Citation
Abel, B. A.,
McCormick, C. L.
(2016). "One-Pot" Animolysis/Thiol-Maleimide End-Group Functionalization of RAFT Polymers: Identifying and Preventing Michael Addition Side Reactions. Macromolecules, 49(17), 6193-6202.
Available at: https://aquila.usm.edu/fac_pubs/15188
COinS