Controlled Polymerization of N-Vinyl Imidazole, N-Vinyl Pyrrolidone, and N-Vinyl Carbazole with Dithiocarbamates toward High Molar Mass Polymers

Achieving control over the polymerization of less activated monomers like N-vinyl carbazole (NVC), N-vinyl pyrrolidone (NVP), and N-vinyl imidazole (NVIm) to produce high molar mass polymers poses a significant challenge. To accomplish this, eight different dithiocarbamate-based reversible addition-fragmentation chain transfer (RAFT) agents are synthesized and employed to polymerize NVIm, NVC, and NVP in order to understand and establish a suitable agent for their controlled polymerization to achieve high molar mass polymers. Chain end presence of these RAFT-derived polymers is established through H-1 NMR studies. Further, these active chain ends are used for chain extension reactions to prepare block copolymers. Synthesized RAFT agents 04, 05, 06, and 08 that are bearing primary leaving groups (methyl 2-acetate, ethyl 2-acetate, tert-butyl 2-acetate, and cyanomethane) display moderate to good control over the polymerization of NVIm and NVC. Among these, RAFT agent-08 with cyanomethane leaving group produces poly(NVIm) and poly(NVC) with the highest molar masses of 44 670 Da (1.52) and 53 620 Da (1.4), respectively. Interestingly, RAFT agents bearing both secondary and primary leaving groups show good control over the NVP polymerization. Notably, RAFT agent-02 with ethyl-2-propionate leaving group yields poly(NVP) with the highest molar mass of 89 450 Da and dispersity of 1.43.