The synthesis of poly(tetrahydrofuran (THF)) having 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) moiety at the chain end and its application as a polymeric counter radical to the living radical polymerization of styrene were performed. The TEMPO moiety could be introduced in quantitative efficiency by the reaction of living poly(THF) initiated by methyl trifluoromethanesulfonate with sodium 4-oxy-TEMPO. The resulting polymer could serve as a polymeric counter radical in the radical polymerization of styrene with benzoyl peroxide to give the corresponding block copolymer quantitatively. Furthermore, it was found that this radical polymerization proceeded in accordance with a living mechanism because the molecular weight of the block copolymer linearly increased with increasing conversion of styrene and was inversely proportional to the initial concentration of poly(THF).

Synthesis of poly(styrene‐b‐tetrahydrofuran (THF)‐b‐styrene) triblock copolymers was performed by transformation from living cationic into living radical polymerization, using 4‐hydroxy‐2,2,6,6‐tetramethylpiperidine‐1‐oxyl (4‐hydroxy‐TEMPO) as a transforming agent. Sodium 4‐oxy‐TEMPO, derived from 4‐hydroxy‐TEMPO, reacted with the living poly(THF), which was prepared by cationic polymerization of THF using trifluoromethanesulfonic acid anhydride as an initiator, resulting in quantitative formation of the poly(THF) with TEMPO at both the chain ends. The resulting polymers were able to serve as a polymeric counter radical for the radical polymerization of styrene by benzoyl peroxide, to give the corresponding triblock copolymer in quantitative efficiency. The polymerization was found to proceed in accordance with a living mechanism, because the conversion of styrene linearly increased over time, and the molar ratio of styrene to THF units in the copolymer also increased as a result of increasing the conversion. The TEM pictures demonstrated that the resulting copolymers promoted microphase segregation. It was found that the films of these copolymers showed contact angles intermediate between those of poly(THF) and of polystyrene. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 2059–2068, 1998