A series of cyclobutene-based macromonomers
derived from monomethyl ether poly(ethylene oxide) (PEO),
poly(ethyl acrylate) (PEA), poly(N-isopropylacrylamide)
(PNIPAM), and PEO-b-PNIPAM were synthesized by
“click” copper-catalyzed azide−alkyne cycloaddition
(CuAAC) and reversible addition−fragmentation chain transfer
(RAFT) polymerization. First, original di- and trifunctional
cyclobutene precursors with azido, alkyne and/or chain
transfer agent were successfully obtained and fully characterized.
Azido- and alkyne-functionalized cyclobutenes were then conjugated with modified PEO bearing azido or alkyne groups,
resulting in cyclobutene-based PEOs in quantitative conversions as ascertained by NMR spectroscopy and MALDI−TOF mass
spectrometry. The new chain transfer agent-terminated cyclobutene was used to mediate the RAFT polymerization of ethyl
acrylate and N-isopropylacrylamide. Well-defined polymers with controlled molecular weights (Mn = 3700−11 500 g·mol−1) and
narrow molecular weight distributions (PDI = 1.06−1.14) were thus obtained that retain the cyclobutene functionality,
demonstrating the orthogonality of the RAFT process toward the cyclobutenyl insaturation. Combination of CuACC and RAFT
polymerization was used to afford PEO-b-PNIPAM block copolymer functionalized by a cyclobutene end-group
