H. Baethge et al., Rate enhancement of the N-oxyl-controlled free radical copolymerization ofstyrene with N-vinylcarbazole, ANGEW MAKRO, 267, 1999, pp. 52-56
Poly(styrene-co-N-vinylcarbazole) copolymers with controlled molecular weig
hts and narrow polydispersities were synthesized by N-oxyl-controlled free
radical copolymerization using benzoyl peroxide as initiator and 2,2,6,6-te
tramethylpiperidine-N-oxyl as terminating agent. To improve the low polymer
ization rates, the radical initiator dicumyl peroxide (DCP) was introduced
and its effects on the polymerization rate, the molecular weight and the po
lydispersity were studied.
It was demonstrated that the introduction of DCP leads to a significant enh
ancement of the polymerization rate and that copolymers with high N-vinylca
rbazole contents as well as N-vinylcarbazole homopolymer can be obtained. T
he enhancement of the polymerization rate corresponds to a decrease in the
number of chain breaking reactions which leads to polymers with lower polyd
ispersities compared with those polymerized at the same monomer conversion
without DCP. This could be proved via comparative chain-extension experimen
ts with styrene leading to poly(styrene-co-N-vinylcarbazole)-block-poly( st
yrene) diblock copolymers.