End group transformations of RAFT‐generated polymers with bismaleimides: Functional telechelics and modular block copolymers.

Abstract

End group activation of polymers prepared by reversible addition-fragmentation chain transfer (RAFT) polymerization was accomplished by conversion of thiocarbonylthio end groups to thiols and subsequent reaction with excess of a bismaleimide. Poly(N-isopropylacrylamide) (PNIPAM) was prepared by RAFT, and subsequent aminolysis led to sulfhydryl-terminated polymers that reacted with an excess of 1,8-bismaleimidodiethyleneglycol to yield maleimido-terminated macromolecules. The maleimido end groups allowed near-quantitative coupling with model low molecular weight thiols or dienes by Michael addition or Diels-Alder reactions, respectively. Reaction of maleimide-activated PNIPAM with another thiol-terminated polymer proved an efficient means of preparing block copolymers by a modular coupling approach. Successful end group functionalization of the well-defined polymers was confirmed by combination of UV–vis, FTIR, and NMR spectroscopy and gel permeation chromatography. The general strategy proved to be versatile for the preparation of functional telechelics and modular block copolymers from RAFT-generated (co)polymers.