Facile synthesis of well-controlled poly(1-vinyl imidazole) by the RAFT process

Abstract

Poly(vinyl imidazole)s, which contain heterocyclic aromatic rings on the polymer side chains, are of increasing interest for a wide variety of applications ranging from catalysis, polymeric ionic liquids to membrane material. However, the controlled radical polymerization of vinyl imidazoles, including 1-vinyl imidazole (1VIM), 2-vinyl imidazole (2VIM) and 4-vinyl imidazole (4VIM), proved to be extremely challenging in the past decades. Here, we demonstrate, for the first time, that well-controlled and low dispersity (Đ as low as 1.05) poly(1VIM) could be synthesized via RAFT polymerization by using acetic acid as a special solvent. Acetic acid not only works as a solvent that allows homogeneous polymerization, it also protonates 1VIM, thereby, allowing the stabilization of propagating radicals during polymerization. To verify the efficacy of the RAFT polymerization of 1VIM in acetic acid, various polymerization parameters including different RAFT agents, initiator and monomer concentrations, temperatures, etc. had been examined. Moreover, detailed kinetic studies revealed a linear, pseudo-first-order polymerization behavior of 1VIM in acetic acid, and the apparent rate constants were calculated. Furthermore, the living characteristic of this RAFT process was demonstrated by chain extension with n-butyl acrylate (nBA) and N,N-dimethyl acrylamide (DMA) to form respective block copolymers with low dispersities. Overall, the synthesis of well-controlled poly(1VIM) is expected to greatly expand the design and utility of vinyl imidazole-based materials and their applications in catalysis, membrane material, heavy metal removal, fuel cells and many other fields.