Rate enhancement of the N-oxyl-controlled free radical copolymerization ofstyrene with N-vinylcarbazole

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.