Cellulose Of Formic Acid And Glycine And Imidazole Salt Ionic Liquid Mechanism Theory Research

As the most abundant renewable organic polymer resources in nature, theutilization of cellulose is rather less due to its difficult to dissolve in common solvents.In recent years, ionic liquids have been paid more attentions due to their many goodadvantages, such as nontoxicity, low volatility, and high chemical and thermalstability. To develop novel and high-efficient ionic liquids to dissolve cellulose hasbecome a hot topic since the first report that ionic liquids can efficiently dissolvecellulose in2002.In this study, the intra-and intermolecular H-bonds in cellulose and the interactionmechanisms between cellulose and two types of ionic liquids have beensystematically investigated using density functional theory (DFT), atoms in molecules(AIM) theory, natural bond orbital (NBO) method, and energy decompositionanalyses (EDA).Three parts have been mainly discussed in this study as follows.First of all, the natures of the intra-and intermolecular H-bonds in different sizes ofcellulose models have been systematically investigated. It was found that the nature ofthe H-bonds has a less dependence on the numbers of the cellulose units, paving theway for the choice of the cellulose models and future studies on the dissolutionmechanisms of the cellulose in ionic liquids. Additionally, the relative acidities for thehydroxyl groups at three different sites and the strengths of the glycosidic bonds incellulose have been discussed detailedly.Second, the various possible coupling modes and interaction mechanisms between1,3-dimethyl-imidazolium formic acid salt ionic liquid and cellobiose dimer havebeen investigated systematically. The relative strengths between the anion and cationof the ionic liquid and cellulose have been analyzed. The thermodynamical behaviorsof the dissolution process for cellulose in ionic liquid have been clarified. Moreover,the possibility of the H-bonding interaction involving the proton at the C2site of theimidazolium ring has been confirmed.Finally, the interaction mechanisms between1,3-dimethyl-imidazolium glycineionic liquid and cellulose have been investigated systematically so as to clarify thepotential utilization of amino acid ionic liquids as novel solvents for cellulose infuture. These results can provide the scientific basis and theoretical guidance for theexperimental synthesis and screening of the novel, high-efficient, andenvironment-friendly cellulose solvents.