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.
Abstract15N‐labeled tetrasulfur tetranitride (S415N4) was synthesized by reacting S2Cl2 with 15NH3. The reaction was finalized with 14NH3. The successful labeling was confirmed by solution 15N nuclear magnetic resonance (NMR) spectroscopy. S415N4 was used for the synthesis of poly(sulfur nitride) S15Nx via the intermediate species of S2N2. It was a topochemical polymerization in the solid state. The isotope ratio in the labeled polymer was obtained by laser deposition ionization time‐of‐flight mass spectroscopy. Solid‐state 15N NMR spectroscopy of S15Nx indicates that at least three different chemical environments for 15N atoms are present in the crystals. Finally, SNx was polymerized in the presence of two other superconductors, MgB2 and yttrium barium copper oxide (YBCO), which demonstrates the capability of SNx for grain boundary engineering.
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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