Controlled Synthesis of Poly(N-ethyl-3-vinylcarbazole) and Block Copolymers via RAFT Polymerization

Poly(N-ethyl-3-vinylcarbazole), in which the carbazole unit is directly bound to the polymer main chain, has been synthesized by reversible addition−fragmentation chain transfer (RAFT) polymerization. The homopolymers with controlled molecular weights and low polydispersities (M w/M n = 1.15−1.29) were obtained by the polymerization of N-ethyl-3-vinylcarbazole (E3VC) with 2,2‘-azobis(isobutyronitrile) (AIBN) as an initiator in the presence of benzyl 1-pyrrolecarbodithioate as a chain transfer agent (CTA). Good control of the polymerization was confirmed by the linear first-order kinetic plot, linear increase in the molecular weight with the conversion, and the linear relationship between the molecular weight and the monomer/CTA molar ratio. Successful chain extension from dithiocarbamate-terminated poly(E3VC) was also observed. Well-defined block copolymers with poly(E3VC) segment have been synthesized using the dithiocarbamate-terminated polystyrene as a macro-CTA. The resulting polymers, poly(E3VC) and polystyrene-b-poly(E3VC), absorbed light in the range from 300 to 380 nm and exhibited excimer emission at 454 nm with blue fluorescence. These polymers showed thermal stability above 350 °C under nitrogen.