3-oxo-2,2,6,6-tetramethylpiperidine-N-oxyl (4-oxo-TEMPO)- and 4-acetamido-2,2,6,6-tetramethylpiperidine-N-oxyl (4-acetamido-TEMPO)-controlled free radical polymerization of styrene
Ch. Han et al., 3-oxo-2,2,6,6-tetramethylpiperidine-N-oxyl (4-oxo-TEMPO)- and 4-acetamido-2,2,6,6-tetramethylpiperidine-N-oxyl (4-acetamido-TEMPO)-controlled free radical polymerization of styrene, MACRO CH P, 200(7), 1999, pp. 1779-1783
The controlled free radical polymerization of styrene initiated with benzoy
l peroxide (BPO) in the presence of 4-oxo-2,2,6,6-tetramethylpiperidine-N-o
xyl (4-oxo-TEMPO) as well as 4-acetamido-2,2,6,6-tetramethylpiperidine-N-ox
yl (4-acetamido-TEMPO) at 135 degrees C was studied. The obtained results w
ere compared with those of the 2,2,6,6-tetramethylpiperidine-N-oxyl (TEMPO)
controlled free radical polymerization of styrene. Up to a nitroxide/BPO m
olar ratio of 1.5:1, the conversions in the 4-oxo-TEMPO/BPO-system are high
er than the conversions in the other systems. The conversion in the 4-aceta
mido-TEMPO/BPO-system is lower than that in the 4-oxo-TEMPO/BPO-system, but
higher than the conversion in the TEMPO/BPO-system under the same reaction
conditions. The shortest induction periods were observed in the 4-oxo-TEMP
O/BPO-system, while the longest induction periods were observed in the TEMP
O/BPO-system. Except in the lower region of nitroxide/BPO molar ratio (1:1)
, the number-average molecular weight ((M) over bar n) increases linearly w
ith conversion in all systems. Interestingly, the growth of the molecular w
eight (M,) is independent of the nitroxide/BPO molar ratio in the 4-oxo-TEM
PO-controlled free radical polymerization of styrene, while M, in the 4-ace
tamido-TEMPO/BPO- and the TEMPO/BPO-system decreases with increasing nitrox
ide/BPO molar ratio. The polydispersities ((M) over bar(w)/(M) over bar(n))
of the obtained polymers are below 1.4 except those of low nitroxide/BPO m
olar ratios, which indicates a controlled polymerization process.