Controlled free radical polymerization of styrene initiated by a [BPO-polystyrene-(4-acetamido-TEMPO)] macroinitiator

The bulk polymerization of styrene at 125 degrees C was studied using a [BP O-polystyrene-(4-acetamido-TEMPO)] macroinitiator synthesized by a styrene polymerization in the presence of 4-acetamido2,2,6,6-tetramethylpiperidine- N-oxyl (4-acetamido-TEMPO) and benzoyl peroxide (BPO). The rates of polymer ization were independent of the initial macroinitiator concentration and th ey were very similar to that for the thermal autopolymerization of styrene, Additionally, different types of N-oxyls did not have any effect on the po lymerization rate. The number-average molecular weights (M-n) of the obtain ed polymers agreed very well with theoretical predictions, deviations were observed only at low macroinitiator concentrations. Increasing macroinitiat or concentrations resulted in lower magnitudes of the growing molecular wei ghts and reduced polydispersities (M-w/M-n) at the initial stage of the pol ymerization. The concentration of the polymer chains was calculated, and it was recognized that the concentration of polymer chains increased during t he polymerization as a result of an additional radical formation due to the thermal self-initiation of styrene. This thermal self-initiation could be proved qualitatively by the addition of N-oxyl to a macroinitiator polymeri zation system.