Living Radical Polymerization of Styrene by a Stable Nitroxyl Radical and Macroazoinitiator

The radical polymerization of styrene was performed at 130 °C for 72 h using 4-methoxy-2,2,6,6-tetramethylpiperidine-1-oxyl (MTEMPO) and poly(dimethylsiloxane) (PDMS) containing azo moiety (PDMS-AZ) as a macroinitiator. It was found that the block copolymer of DMS with styrene was quantitatively obtained when the ratio of MTEMPO to the azo moiety in PDMS-AZ was 0.6. The structure was expected to be of the A−B type, rather than A−B−A, when the low initiator efficiency and the molecular weight of the PSt segments isolated were taken into account. The polymerization proceeded in accordance with a living mechanism, because the conversion of styrene linearly increased over time, and the molecular weight of the copolymer produced was directly proportional to the conversion. Furthermore, the polymerization of p -methoxystyrene was also found to proceed where the PDMS- block -polystyrene was used as an initiator, to give the triblock copolymer quantitatively.