The theoretical promise of ionic liquids (ILs) as ‘green’ designer solvents that can be tuned to facilitate key steps of lignocellulosic biomass processing has not been fully realized due to the sheer number of possible cation–anion combinations and concerns about toxicity of this class of chemicals. Although computational methods are being applied to identify ILs with specific functions, such as dissolution of cellulose, they are not used to iteratively design new ionic liquids with the goal of simultaneously optimizing multiple criteria, such as performance and environmental safety. Here we describe a tiered computational approach to develop new ILs based on mixed quantum and molecular mechanics simulations, which, combined with analysis of physicochemical properties of ILs can be used to guide structural modifications to design both better performing task-specific and safer IL analogs. The increase in computing requirements of the proposed approach over structure-based statistical models is relatively modest; yet, our approach is more robust than these models, and far less costly than highly-accurate but very demanding large-scale molecular simulations.
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Current Status of AMOEBA–IL: A Multipolar/Polarizable Force Field for Ionic Liquids
Computational simulations of ionic liquid solutions have become a useful tool to investigate various physical, chemical and catalytic properties of systems involving these solvents. Classical molecular dynamics and hybrid quantum mechanical/molecular mechanical (QM/MM) calculations of IL systems have provided significant insights at the atomic level. Here, we present a review of the development and application of the multipolar and polarizable force field AMOEBA for ionic liquid systems, termed AMOEBA–IL. The parametrization approach for AMOEBA–IL relies on the reproduction of total quantum mechanical (QM) intermolecular interaction energies and QM energy decomposition analysis. This approach has been used to develop parameters for imidazolium– and pyrrolidinium–based ILs coupled with various inorganic anions. AMOEBA–IL has been used to investigate and predict the properties of a variety of systems including neat ILs and IL mixtures, water exchange reactions on lanthanide ions in IL mixtures, IL–based liquid–liquid extraction, and effects of ILs on an aniline protection reaction.
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- Award ID(s):
- 1856162
- NSF-PAR ID:
- 10148506
- Date Published:
- Journal Name:
- International Journal of Molecular Sciences
- Volume:
- 21
- Issue:
- 3
- ISSN:
- 1422-0067
- Page Range / eLocation ID:
- 697
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Thermodynamic, structural, and transport properties of tetrabutylphosphonium hydroxide (TBPH) and tetrabutylphosphonium chloride (TBPCl)–water mixtures have been investigated using all-atom molecular dynamics simulations in response to recent experimental work showing the TBPH–water mixtures capability as a cellulose solvent. Multiple transitional states exist for the water—ionic liquid (IL) mixture between 70 and 100 mol% water, which corresponds to a significant increase in water hydrogen bonds. The key transitional region, from 85 to 92.5 mol% water, which coincides with the mixture’s maximum cellulose solubility, reveals small and distinct water veins with cage structures formed by the TBP+ ions, while the hydroxide and chloride ions have moved away from the P atom of TBP+ and are strongly hydrogen bonded to the water. The maximum cellulose solubility of the TBPH–water solution at approximately 91.1 mol% water, appears correlated with the destruction of the TBP’s interlocking structure in the simulations, allowing the formation of water veins and channeling structures throughout the system, as well as changing from a subdiffusive to a near-normal diffusive regime, increasing the probability of the IL’s interaction with the cellulose polymer. A comparison is made between the solution properties of TBPH and TBPCl with those of alkylimidazolium-based ILs, for which water appears to act as anti-solvent rather than a co-solvent.more » « less
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ABSTRACT The use of ionic liquids (ILs) as media in radical polymerizations has demonstrated the ability of these unique solvents to improve both reaction kinetics and polymer product properties. However, the bulk of these studies have examined the polymerization behavior of common organic monomers (e.g., methyl methacrylate, styrene) dissolved in conventional ILs. There is increasing interest in polymerized ILs (poly(ILs)), which are ionomers produced from the direct polymerization of styrene‐, vinyl‐, and acrylate‐functionalized ILs. Here, the photopolymerization kinetics of IL monomers are investigated for systems in which styrene or vinyl functionalities are pendant from the imidazolium cation. Styrene‐functionalized IL monomers typically polymerized rapidly (full conversion ≤1 min) in both neat compositions or when diluted with a nonpolymerizable IL, [C2mim][Tf2N]. However, monomer conversion in vinyl‐functionalized IL monomers is much more dependent on the nature of the nonpolymerizable group. ATR‐FTIR analysis and molecular simulations of these monomers and monomer mixtures identified the presence of multiple intermolecular interactions (e.g., π–π stacking, IL aggregation) that contribute to the polymerization behaviors of these systems. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem.
2018 ,56 , 2364–2375
- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.3390/ijms21030697
