Living radical polymerization of styrene in the presence of 4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl, and radical transformation of the resulting polymer by other radicals

Radical polymerization of styrene was performed by benzoyl peroxide (BPO) as an initiator, in the presence of 4-hydroxy-2,2,6,6-tetramethylpiperidine-1-(HTEMPO) at 95 degrees C for 3.5 h, and then continued at 125 degrees C for another designated period. The polymerization was found to proceed in the accordance with a living mechanism, because the molecular weight of the polystyrene was in proportion to the conversion and was in inverse proportion to the initial concentration of HTEMPO. Further, it was found that all the resulting polystyrene had the HTEMPO moiety at their chain ends and that the initial concentration of HTEMPO determined the molecular weight of the polymer produced, from H-1 NMR analysis. The radical transformation of the HTEMPO-modified polystyrene by 4-methoxy-TEMPO (MTEMPO), was also performed. The transformation proceeded to give the polystyrene with MTEMPO moiety at the chain end, although the degree of the transformation decreased over time. It was found that decomposition of the MTEMPO-modified polystyrene obtained by the reaction occurred during the reaction.