Microscopic and Macroscopic Properties of Carbohydrate Solutions in the Ionic Liquid 1-Ethyl-3-methyl-imidazolium Acetate

Ries, Michael E.; Radhi, Asanah; Green, Stephen M.; Moffat, Jamie; Budtova, Tatiana

doi:10.1021/acs.jpcb.8b06939

Cited by 11 publications

(22 citation statements)

References 53 publications

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“…In order to dissolve cellulose, a solvent needs to break up the hydrogen bond network between the polymer strands [25] and replace it by hydrogen bonds to the solvent [8]. Most of the ILs proposed as cellulose solvents are based on imidazolium cations [10,[25][26][27][28], which is not surprising, as it has been known for long that many imidazolium-based ILs form very strong hydrogen bonds [29][30][31][32][33][34][35][36]. Some of these imidazolium-based ILs are able to dissolve more than 20 wt.-% of cellulose if the anions are strong hydrogen bond acceptors [3,37,38].…”

Section: Introductionmentioning

confidence: 99%

Dissolving Cellulose in 1,2,3-Triazolium- and Imidazolium-Based Ionic Liquids with Aromatic Anions

et al. 2020

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We present 1,2,3-triazolium- and imidazolium-based ionic liquids (ILs) with aromatic anions as a new class of cellulose solvents. The two anions in our study, benzoate and salicylate, possess a lower basicity when compared to acetate and therefore should lead to a lower amount of N-heterocyclic carbenes (NHCs) in the ILs. We characterize their physicochemical properties and find that all of them are liquids at room temperature. By applying force field molecular dynamics (MD) simulations, we investigate the structure and dynamics of the liquids and find strong and long-lived hydrogen bonds, as well as significant π–π stacking between the aromatic anion and cation. Our ILs dissolve up to 8.5 wt.-% cellulose. Via NMR spectroscopy of the solution, we rule out chain degradation or derivatization, even after several weeks at elevated temperature. Based on our MD simulations, we estimate the enthalpy of solvation and derive a simple model for semi-quantitative prediction of cellulose solubility in ILs. With the help of Sankey diagrams, we illustrate the hydrogen bond network topology of the solutions, which is characterized by competing hydrogen bond donors and acceptors. The hydrogen bonds between cellulose and the anions possess average lifetimes in the nanosecond range, which is longer than found in common pure ILs.

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Section: Introductionmentioning

confidence: 99%

Dissolving Cellulose in 1,2,3-Triazolium- and Imidazolium-Based Ionic Liquids with Aromatic Anions

et al. 2020

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“…The DP of V-cell was estimated from [η] using the simple relationship given below 45 η [ ] ≈ 0.42DP (5) giving a value of DP ≈ 833, and therefore, M ≈ 135,000 for Vcell. This DP is over 4.5 times larger than the DP of A-cell (DP = 180), 25 and therefore, the higher viscosities observed for Vcell/BmimAc solutions are clearly due to the significantly larger polymer chain size.…”

Section: ■ Results and Discussionmentioning

confidence: 80%

“…Vitacel powdered cellulose L 00 (JRS, supplied by Mondele ̅ z International) [degree of polymerization (DP) ≈ 730−830, as estimated below] and Avicel PH-101 microcrystalline cellulose (MCC) (Sigma-Aldrich, DP ≈ 180) 25 were both used to investigate the effect of DP on the viscosity of cellulose in IL solutions. The Vitacel cellulose and the Avicel cellulose are abbreviated to "V-cell" and "A-cell," respectively.…”

Section: Methodsmentioning

confidence: 99%

“…36−38 Low-field relaxometry experiments at single frequencies have also been used to compare the effects of cellulose, cellobiose, and glucose on the mobility of 1-ethyl-3-methylimidazolium acetate (EmimAc) ions, through measuring T 1 and T 2 relaxation times. 25 Interestingly, it was reported that cellulose solutions gave the longest T 1 times but the highest viscosities, indicating the highest level of mobility on a molecular scale and the lowest on a macroscopic scale. The authors highlight that the factors affecting the macroscopic and microscopic properties of cellulose/EmimAc solutions are different, and therefore, it is useful to investigate both when considering the dissolution of cellulose.…”

Section: ■ Introductionmentioning

confidence: 99%

“…Rheological experiments generally characterize the bulk or macroscopic properties of a polymer solution, which are determined by how much volume the solute occupies in the dilute regime. 25 On the other hand, it is useful to analyze cellulose−IL solutions on a molecular or microscopic level in order to gain further insights into specific solvent−solute interactions. Nuclear magnetic resonance (NMR) spectroscopy has been successfully applied to the study of cellulose−IL interactions during dissolution, 26−29 through determination of self-diffusion coefficients (D).…”

Section: ■ Introductionmentioning

confidence: 99%

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Rheological and NMR Studies of Cellulose Dissolution in the Ionic Liquid BmimAc

2021

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Solutions of two types of cellulose in the ionic liquid 1-butyl-3-methyl-imidazolium acetate (BmimAc) have been analyzed using rheology and fast-field cycling nuclear magnetic resonance (NMR) spectroscopy, in order to analyze the macroscopic (bulk) and microscopic environments, respectively. The degree of polymerization (DP) was observed to have a significant effect on both the overlap (c*) and entanglement (c e) concentrations and the intrinsic viscosity ([η]). For microcrystalline cellulose (MCC)/BmimAc solutions, [η] = 116 mL g–1, which is comparable to that of MCC/1-ethyl-3-methyl-imidazolium acetate (EmimAc) solutions, while [η] = 350 mL g–1 for the commercial cellulose (higher DP). Self-diffusion coefficients (D) obtained via the model-independent approach were found to decrease with cellulose concentration and increase with temperature, which can in part be explained by the changes in viscosity; however, ion interactions on a local level are also important. Both Stokes–Einstein and Stokes–Einstein–Debye analyses were carried out to directly compare rheological and relaxometry analyses. It was found that polymer entanglements affect the microscopic environment to a much lesser extent than for the macroscopic environment. Finally, the temperature dependencies of η, D, and relaxation time (T 1) could be well described by Arrhenius relationships, and thus, activation energies (E a) for flow, diffusion, and relaxation were determined. We demonstrate that temperature and cellulose concentration have different effects on short- and long-range interactions.

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Lactate‐based ionic liquids as chiral solvents for cellulose

Radicke

Roos

Sebastiani

et al. 2022

Journal of Polymer Science

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We report the first example of a chiral polymer-cellulose-being dissolved in both enantiomers of a chiral solvent. We synthesized six room temperature ionic liquids (ILs) based on imidazolium and 1,2,3-triazolium cations and lactate as chiral anion. Some of them have not been described before. We characterize the dissolution of cellulose in the ILs, which are found to be relatively good cellulose solvents with a solubility of up to 18.5 wt.-%. At the same time, we find solubility differences of up to a factor of 3 between the enantiomers of the solvent, which is a very pronounced chiral recognition effect. Interestingly, the racemate of the solvent dissolves significantly less cellulose than either enantiopure form, which is a significant deviation from ideal mixing behavior. We also report the physicochemical properties of the six ILs (density, viscosity, decomposition temperature, NMR and circular dichroism spectra). Based on molecular dynamics simulations of the solutions and a model which we have published before, we attempt a semi-quantitative prediction of the cellulose solubility, which yields solid results for the enantiopure solvents. From the simulation results, we obtain microscopic insight into the hydrogen bond network of the complex mixtures in which many different hydrogen bond donors and acceptors compete.

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Microscopic and Macroscopic Properties of Carbohydrate Solutions in the Ionic Liquid 1-Ethyl-3-methyl-imidazolium Acetate

Cited by 11 publications

References 53 publications

Dissolving Cellulose in 1,2,3-Triazolium- and Imidazolium-Based Ionic Liquids with Aromatic Anions

Dissolving Cellulose in 1,2,3-Triazolium- and Imidazolium-Based Ionic Liquids with Aromatic Anions

Rheological and NMR Studies of Cellulose Dissolution in the Ionic Liquid BmimAc

Lactate‐based ionic liquids as chiral solvents for cellulose

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