Enhancing the pre-polymerization coordination of 1-vinylimidazole

Abstract

Recent experimental investigations have found that the rate and conversion of the photopolymerization of 1-vinylimidazole (VIm) can be significantly accelerated with the addition of lithium bistriflimide (LiTf 2 N). However, the underlying molecular-level interactions responsible for this phenomenon are unclear. The two components, VIm and LiTf 2 N, are miscible over a wide range of concentrations and form liquid phases at ambient temperature, and if the fundamental behavior of this mixture can be clearly quantified, there are significant opportunities for tuning the polymerization dynamics, polymer structure, and properties. In this work, molecular dynamics (MD) simulations are used to model the underlying pre-polymerization structure of VIm + LiTf 2 N mixtures at several different concentrations. It is found that the Li + enhances the site-site interactions of key functional groups involved in the polymerization, and this is suggested to play a major role in the experimentally-observed enhancement of the polymerization behavior.

Photopolymerization of coordinated ionic liquid monomers: Realizing the benefits of structured media using only common reagents

“…Because of the relatively weak interactions between Li + and the monomer ligands in our study, compositions with monomer:salt ratios >1:1 likely exist as a mixture of complexes, as is suggested by the presence of small, high‐wavenumber shoulders in the CO peaks of the 2:1 monomer:salt spectra as well as the small peak corresponding to uncoordinated monomer present in the 2:1 AA:LiTf 2 N spectrum. This behavior is supported by a recent molecular dynamics (MD) study examining the coordination behavior of Vim in the presence of LiTf 2 N . Although the average degree of coordination was found to increase with Vim:LiTf 2 N ratio, the samples existed as a distribution of uncoordinated monomer and complexes of varying coordination number.…”

“…This behavior is supported by a recent molecular dynamics (MD) study examining the coordination behavior of Vim in the presence of LiTf 2 N. 71 Although the average degree of coordination was found to increase with Vim:LiTf 2 N ratio, the samples existed as a distribution of uncoordinated monomer and complexes of varying coordination number. However, the extension of this behavior to the systems examined in this study is limited to solutions with monomer:salt ratios >1:1, as the spectra of these ILs lack the small bands that are indicative of uncoordinated monomer.…”

Photorheology and Gelation during Polymerization of Coordinated Ionic Liquids

“…The photopolymerization kinetics of Vim/LiTf 2 N coordinated IL systems have previously been examined by using real-time Fourier transform infrared spectroscopy (RT-FTIR) where it was observed that addition of LiTf 2 N increases both the rate of polymerization and overall vinyl group conversion. Molecular dynamics simulations demonstrate that coordination of Li + to two or three Vim monomers induces the formation of prepolymerization structures that bring polymerizing vinyl CC groups into closer proximity, leading to the enhanced reaction rates. While the reaction kinetics of this and other photopolymerizing IL systems ,,− have been previously characterized, in situ rheological/mechanical property development has not yet been explored.…”