Photopolymerization of coordinated and non-coordinated ionic liquid monomers

Abstract

Photopolymerization is an industrially important polymerization technique that has numerous advantages in comparison to other radical based processes. Previous work has shown that ionic liquid media can improve the efficiency of these reactions; however, the applicability of these solvents is limited by the challenging separation processes required to isolate polymer products. In this work, we present a new method of radical polymerization in which coordinated ionic liquids were synthesized from salts containing bulky, non-coordinating anions and polar vinyl monomers that functioned as coordinating ligands. These polymerizable coordinated ionic liquids offer many of the benefits of conventional ionic liquid media in radical polymerizations with the additional advantage of allowing for relatively simple product separations. This reaction technique was shown to be useful in the photopolymerization of both common and niche vinyl monomers using multiple bistriflimide salts. In addition, composite materials containing ionic liquids and polymerized ionic liquids have found increasing applications and we were also interested in the reaction behavior of the systems used in their preparation. To this end, we examined the polymerization kinetics of polymerizable ionic liquids in a non-polymerizable imidazolium ionic liquid using infrared spectroscopy. The reaction kinetics of the monomers in these systems were found to be affected by a combination of intermolecular interactions that likely affect the behavior of a variety of reactive systems in which ionic liquids are present.