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

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. (C) 2008 Wiley Periodicals, Inc.