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 addition-fragmentation 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 using 1H-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.