Tri-block Terpolymers with Different Sequences Synthesized by Combination of Anionic and RAFT Polymerizations
Author(s): Li-feng Chen, Jun-po He, The State Key Laboratory of Molecular Engineering of Polymers, Department of Macromolecular Science, Fudan University
Pages: 973-981
Year: 2015 Issue: 8
Journal: Acta Polymerica Sinica
Keyword: Triblock terpolymers; Anionic polymerization; RAFT; Mechanism transformation;
Abstract: Triblock terpolymers with different block sequences( ABC,ACB,BAC) containing polyisoprene( PI),polystyrene( PS) and poly( N-isopropylacrylamide)( PNIPAM) segments were synthesized through a process that combines living anionic polymerization and radical polymerization based on reversible additionfragmentation chain transfer( RAFT) process. The synthesis involved a mechanistic switch step by in situ converting the living anionic propagating center into thiocarbonylthio moiety to afford macro chain transfer agent( macro-CTA),which was subsequently used to mediate RAFT polymerization. By changing the feed sequence of the monomers in anionic polymerization and RAFT polymerization,triblock terpolymers were synthesized with controlled block sequences and molecular weight. Specifically,PI-CTA,was prepared by anionic polymerization of isoprene and subsequent chain end transformation into thiocarbonylthio moiety through the reaction with CS2 and corresponding alkylbromide. The resulting PI-CTA was employed to successively mediate the RAFT polymerization of styrene and NIPAM in anhydrous 1,4-dioxane,forming the PI-b-PNIPAM-b-PS triblock copolymer. PI-b-PS-b-PNIPAM and PS-b-PI-b-PNIPAM were synthesized in a similar way but with different sequence of monomer addition. The successful chain extensions of the homopolymer or copolymer were demonstrated by gel permeation chromatography( GPC) results and the composition of triblock terpolymers was calculated by using1H-NMR results. The process may serve as a versatile approach to make ABC type block terpolymers with different block sequences from monomers that are incompatible in the polymerization method.
Pages: 973-981
Year: 2015 Issue: 8
Journal: Acta Polymerica Sinica
Keyword: Triblock terpolymers; Anionic polymerization; RAFT; Mechanism transformation;
Abstract: Triblock terpolymers with different block sequences( ABC,ACB,BAC) containing polyisoprene( PI),polystyrene( PS) and poly( N-isopropylacrylamide)( PNIPAM) segments were synthesized through a process that combines living anionic polymerization and radical polymerization based on reversible additionfragmentation chain transfer( RAFT) process. The synthesis involved a mechanistic switch step by in situ converting the living anionic propagating center into thiocarbonylthio moiety to afford macro chain transfer agent( macro-CTA),which was subsequently used to mediate RAFT polymerization. By changing the feed sequence of the monomers in anionic polymerization and RAFT polymerization,triblock terpolymers were synthesized with controlled block sequences and molecular weight. Specifically,PI-CTA,was prepared by anionic polymerization of isoprene and subsequent chain end transformation into thiocarbonylthio moiety through the reaction with CS2 and corresponding alkylbromide. The resulting PI-CTA was employed to successively mediate the RAFT polymerization of styrene and NIPAM in anhydrous 1,4-dioxane,forming the PI-b-PNIPAM-b-PS triblock copolymer. PI-b-PS-b-PNIPAM and PS-b-PI-b-PNIPAM were synthesized in a similar way but with different sequence of monomer addition. The successful chain extensions of the homopolymer or copolymer were demonstrated by gel permeation chromatography( GPC) results and the composition of triblock terpolymers was calculated by using1H-NMR results. The process may serve as a versatile approach to make ABC type block terpolymers with different block sequences from monomers that are incompatible in the polymerization method.
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