Tetramethylpiperidine-1-oxyl-mediated polymerization of styrene using a macroazoinitiator of poly(ethylene oxide)

The radical polymerization of styrene was performed at 130 degreesC for 72 h using 4-methoxy-2,2,6,6-tetramethylpiperidine-1-oxyl (MTEMPO) and a macro azoinitiator of poly(ethylene oxide) (PEO-AZ). It was found that a block co polymer consisting of PEO and polystyrene (PSt) was quantitatively obtained when the ratio of MTEMPO to the azo moiety in PEG-AZ was 1.0. The polymeri zation proceeded in accordance with a living mechanism, because the molecul ar weight of the copolymer and unit ratio of styrene to EO linearly increas ed with increasing the conversion of styrene. DSC analysis demonstrated tha t the copolymers had two glass transition originating from the PEO and PSt segments, and a melting endotherm based on the PEG. Furthermore, the PEO-b- PSt copolymer initiated the polymerization of 4-methoxystyrene, giving a bl ock copolymer composed of PEG, PSt, and poly(4-methoxystyrene).