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Non-covalent interactions in bmimCl/co-solvent mixtures: a FTIR spectroscopy and computational study
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SYSNO ASEP 0504639 Document Type J - Journal Article R&D Document Type Journal Article Subsidiary J Článek ve WOS Title Non-covalent interactions in bmimCl/co-solvent mixtures: a FTIR spectroscopy and computational study Author(s) Kotov, Nikolay (UMCH-V) RID, ORCID
Raus, Vladimír (UMCH-V) RID, ORCID
Dybal, Jiří (UMCH-V) RID, ORCIDSource Title Journal of Molecular Liquids. - : Elsevier - ISSN 0167-7322
Roč. 285, 1 July (2019), s. 688-696Number of pages 9 s. Language eng - English Country NL - Netherlands Keywords ionic liquids ; organic electrolyte solutions ; non-covalent interactions Subject RIV CD - Macromolecular Chemistry OECD category Polymer science R&D Projects GA17-03810S GA ČR - Czech Science Foundation (CSF) Method of publishing Limited access Institutional support UMCH-V - RVO:61389013 UT WOS 000472698800074 EID SCOPUS 85064908096 DOI 10.1016/j.molliq.2019.04.092 Annotation Ionic liquids such as 1-butyl-3-methylimidazolium chloride (bmimCl) are efficient solvents for cellulose, but high viscosity of the resulting solutions hampers further cellulose shaping and derivatization. To solve this problem, mixtures of ILs with various organic co-solvents are often employed in place of neat ILs. So far, the intermolecular interactions in such mixtures are poorly understood, which hinders further development of this class of cellulose solvents. In this work, we utilized infrared spectroscopy (IR) and quantum chemical model calculations to study the intermolecular interactions in differently concentrated mixtures of bmimCl with two typical co-solvents, dimethyl sulfoxide (DMSO) and N,N-dimethylacetamide (DMAc). First, we refined the assignment of the relevant characteristic bands in the IR spectra of the individual mixture components. This then helped us to reveal that bmim+-DMSO and bmim+-DMAc associates, stabilized by hydrogen bonds between the imidazolium ring CH groups and oxygens of DMSO or DMAc, are formed in the studied mixtures. Importantly, only a relatively small fraction of co-solvent molecules (up to ca. 20 mol% for DMSO and ca. 45 mol% for DMAc) are involved in the associate formation, leaving a large proportion of bmimCl molecules non-solvated. While the maximum co-solvent concentration at which direct cellulose dissolution can be achieved is considerably different for DMSO and DMAc, the corresponding molar ratio of bmimCl to interacting co-solvent molecules was the same for both the studied systems (about 2.5:1). We propose that this ratio might be related to the critical size of bmimCl clusters necessary for achieving cellulose dissolution. Furthermore, increasing the temperature from 25 to 80 °C resulted in a significantly decreased fraction of interacting solvent molecules for bmimCl/DMSO but not for bmimCl/DMAc. This indicates that the comparatively lower tendency of DMSO to form associates with bmimCl is due to the lower strength of the underlying hydrogen bond. The results of this study illustrate how intermolecular interactions influence the macroscopic performance of different IL-based solvent systems. Workplace Institute of Macromolecular Chemistry Contact Eva Čechová, cechova@imc.cas.cz ; Tel.: 296 809 358 Year of Publishing 2020 Electronic address https://www.sciencedirect.com/science/article/pii/S0167732219301898?via%3Dihub
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