Selective single monomer addition in living cationic polymerization: Sequential double end‐functionalization in combination with capping agent

Amine‐functionalized and amine‐carboxylate double‐functionalized polymers ( I and II , respectively) have been synthesized by a selective single addition of a protected 2‐aminoethyl vinyl ether (BocVE) {CH₂ = CHOCH₂CH₂N(Boc)₂]; Boc = t‐butoxycarbonyl} onto a living cationic poly(n‐butyl vinyl ether) poly(NBVE)] initiated with the SnCl₄/n‐Bu₄NCl system: ( I ) ‐(NBVE)_n‐ CH₂CH(OCH₂CH₂NH₂)‐H; ( II ) ‐(NBVE)_n‐CH₂CH(OCH₂CH₂NH₂)‐CH₂CO₂H. The single addition was examined with a set of alkene monomers less reactive than NBVE, including BocVE, 2‐chloroethyl vinyl ether, 2‐vinyloxyethylphtalimide, and styrene (St). Upon addition of 10 molar excess of these alkenes onto the living ends, only BocVE led to the intended single adduct, and this was attributed to a chelating interaction of the two carboxylate groups in the terminal BocVE unit with the growing poly(NBVE) terminal, thus sterically hampering further propagation. A simple acid‐catalyzed Boc‐deprotection led to the amino‐functionalized version I . Alternatively, an additional quenching the BocVE‐capped living end (the precursor of I ) with sodium malonate, followed by double deprotection of the Boc and the malonate groups gave the double‐functionalized version II . The selective addition of a single monomer molecule is thus a new method for addressable or site‐specific introduction of functional groups along polymer chains. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 3375–3381, 2010