Ch. Han et al., Controlled free radical polymerization of styrene initiated by a [BPO-polystyrene-(4-acetamido-TEMPO)] macroinitiator, ANGEW MAKRO, 265, 1999, pp. 69-74
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.