Dixanthate-terminated poly(butylene terephthalate). A novel RAFT/MADIX agent for the synthesis of well-defined triblock copolymers resulting from consecutive step- and chain-growthpolymerization processes

Well-defined triblock copolymers comprising a poly(butylene terephthalate) (PBT) mid-block and three different hydrophobic blocks (poly(tert-butyl acrylate) P(t-BA), poly(n-butyl acrylate) P(n-BA) and poly(tert-butyl acrylamide) P(t-BAm)) were successfully prepared by the combination of step-growth and RAFT/MADIX polymerizations. Two different synthetic strategies were investigated for the preparation of O-ethylxanthate-terminated PBT RAFT/MADIX agent. Firstly α,ω-dihydroxy-PBT synthesized by a step-growth polymerization was transformed into the corresponding dixanthate-functionalized PBT according to a two-step procedure. An alternative approach was performed by using a hydroxyl-functional xanthate as chain stopper in a single step-growth polymerization process. In both cases, the presence of xanthate terminal groups was confirmed by NMR spectroscopy and MALDI-TOF mass spectrometry. The resulting PBT with xanthate end-groups was used as a macro-chain transfer agent for the RAFT/MADIX polymerization of n-BA, t-BA and t-BAm. The synthesis of well-defined PBT-based triblock copolymers was confirmed by SEC analysis.