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).

Radical polymerization of p‐bromostyrene was investigated with benzoyl peroxide (BPO) as an initiator in the presence of 4‐methoxy‐2,2,6,6‐tetramethylpiperidine‐1‐oxyl (MTEMPO). The polymerization was performed in bulk for 3.5 h at 95°C and then continued for another 48 h at 125°C to afford the corresponding polybromostyrene with a narrow molecular weight distribution in high yield. 1H NMR study revealed that the polymer obtained had BPO and MTEMPO moieties at its head and tail, respectively. It was confirmed that the polymerization proceeded in accordance with living mechanism, because the molecular weight linearly increased with an increase of the conversion, and it was directly proportional to the reciprocal of the initial concentration of BPO. Furthermore, the polystyrene obtained in the present study could quantitatively act as the initiator for the polymerization of p‐bromostyrene in the living radical manner to afford the corresponding block copolymer, and vice versa. © 1996 John Wiley & Sons, Inc.

In order to introduce the C-O-N linkage at the polymer chain end, the reactions of poly-(styryllithium) with l-oxo-4-methoxy-2,2,6,6-tetramethylpiperidinium salt (OAS) and with the corresponding nitroxyl radical (MTEMPO) were investigated in THE at -78 °C. The aminoxy terminal was found to be introduced in quantitative efficiency by the reactions of the living polymer with OAS in the presence of MTEMPO. It is considered that the reactions proceed via one-electron transfer from the polystyryl anion to OAS, resulting in the polymer radical, which is coupled with MTEMPO to yield the polystyrene with an aminoxy terminal. Similarly, the electron-transfer reaction proceeded between the poly(styryllithium) and MTEMPO to yield the aminoxy-terminated polystyrene quantitatively. The resulting polystyrene could initiate the radical polymerizations of methyl, ethyl, and butyl acrylates to afford the corresponding block copolymers.

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The quantitative synthesis of poly(ε-caprolactone) (PCL) with 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) at one chain end was attained through the anionic polymerization of CL by an aluminum tri(4-oxy-TEMPO), which was prepared by the reaction of triethylaluminum and 4-hydroxy-TEMPO. The TEMPO-supported PCL behaved as a polymeric counter radical for the radical polymerization of styrene, giving poly(CL-block-styrene) in quantitative efficiency. The radical polymerization was found to proceed in accordance with a living mechanism, because the conversion of styrene linearly increased over time, and the molecular weight was directly proportional to the reciprocal of the initial concentration of the PCL. The resulting copolymers had two glass transition temperatures due to the PCL block and polystyrene and one melting endotherm based on the crystalline phases of PCL. The TEM picture of the film obtained from the block copolymer demonstrated microphase segregation.