A widely used polymerizable monomer: 1-vinylimidazole

Imidazole and 1-vinylimidazole

Imidazole is of great interest to many researchers in the field of life science, as this heterocyclic aromatic ring plays significant roles in both natural molecules, including amino acids, nucleic acids, proteins, vitamins, etc., and synthetic products such as some antifungal drugs and antibiotics[1]. Polymers that contain imidazole rings are also an important class of materials, and they have been found to have a series of applications, including catalysis, fuel cells, polymeric ionic liquids, gene delivery, metal ion removal, functional actuators, quantum dots, hydrogels, and many others.

1-vinylimidazole (1VIM), a Vinyl imidazole, is the simplest version of a polymerizable monomer, which also includes 2-vinyl imidazole (2VIM) and 4-vinyl imidazole (4VIM). This compound contains the imidazole ring. It is a water-soluble monomer converted by free-radical polymerization into a high molecular weight water-soluble polymer—the polymer forms molecular complexes with numerous organic and inorganic substances[2].

Uses

1-Vinylimidazole is used because of its high reactivity for free-radical (UV) polymerization as a reactive diluent in UV lacquers, inks, and adhesives for coatings and lacquers. It is also used to functionalize polymer surfaces by UV-induced grafting to improve wettability and adhesiveness.

It could be used to synthesize Poly(vinyl imidazole) (poly(VIm)) via radical polymerization methods. Poly(VIm), an important substance, is hydrophilic. Features pendant imidazole groups that can act as bases, nucleophiles, and/or chelating agents and thus have been investigated for a broad range of applications, such as coating electrodes, fuel cell membranes, and separations applications, including CO2 adsorption and the adsorption of metal ions[3]. Research has found that the photopolymerization rate and conversion of 1-vinylimidazole (VIm) can be significantly accelerated with the addition of lithium bistriflimide (LiTf 2 N).

Like other vinyl monomers, vinyl imidazoles can be readily graft-copolymerized with various polymers. Several previous studies reported the graft copolymerization of vinyl imidazoles onto biomaterials and polymers, such as chitosan, carboxymethyl chitosan, polypropylene (PP), and nylon and demonstrated their potent antibacterial activities. The surface of polypropylene (PP) fiber was modified by UV-induced graft polymerization of 1-vinylimidazole (Vim), followed by quaternization with iodomethane, sulfonation with chlorosulfonic acid, or loading of silver (Ag) nanoparticles to endow the surface with antibacterial properties[4]. As shown in the above picture, SEM images of the substrate PP, PP-g-Vim, PP-g-Vim-CH3I, and PP-g-Vim-SO3H indicated that graft polymerization and subsequent surface modification reactions led to a thickening of the PP fibers by at least 2-fold.

References

[1] Fan, Bo et al. "Facile synthesis of well-controlled poly(1-vinyl imidazole) by the RAFT process†." Polymer Chemistry 35 (2020): 5649–5658.

[2] Chapiro, Adolphe . "Peculiar aspects of the free-radical polymerization of 1-vinylimidazole." International Journal of Radiation Applications & Instrumentation.part C.radiation Physics & Chemistry 40.2(1992):89-93.

[3] Hamilton, Jackie R. , et al. "Enhancing the pre-polymerization coordination of 1-vinylimidazole." Chemical Engineering Science 138(2015):646-654.

[4] Na, Choon Ki , G. Y. Park , and H. Park . "Polypropylene surface with antibacterial property by photografting 1-vinylimidazole and subsequent chemical modification." The Korean journal of chemical engineering 35.8(2018):1748-1755.