Nitroxide-mediated radical polymerization of N-ethyl-2-vinylcarbazole

The hole-transporting ability of carbazole-containing polymers makes them attractive for applications in organic electronics. Nitroxide-mediated radical polymerization (NMRP) offers the potential to create complex macromolecular architectures, including block copolymers, but N-vinylcarbazole, the simplest and most widely studied carbazole monomer, is known to polymerize poorly by NMRP. Here, we investigate the NMRP of N-ethyl-2-vinylcarbazole (2VK), a monomer structurally more similar to the styrenes which are known to polymerize well by NMRP, and whose polymer offers a hole mobility an order of magnitude higher than poly(N-vinylcarbazole). Polymerization of 2 VK from a unimolecular alkoxyamine shows a molecular weight which increases steadily with time, though termination or decomposition of the "living" radical ends is clearly evident from the progressive formation of a low-molecular-weight tail as conversion increases. However, a sufficient fraction of the chains remain living that P2VK-PS diblock copolymer can be formed by chain extension of the P2VK macroinitiator with styrene.