Dissolution behavior of microcrystalline cellulose in DBU-based deep eutectic solvents: Insights from spectroscopic investigation and quantum chemical calculations

New solvents have been developed to dissolve microcrystalline cellulose by easily prepared DBU-based deep eutectic solvents (DESs), which have excellent solvent power for biopolymers. Cellulose/[DBU][MTU] as a typical example for detailed analysis, which was characterized (by means of FT-IR and NMR) and studied as potential cellulose dissolution media. Furthermore, selecting cellobiose as a model for density functional theory (DFT) calculation. The hydrogen bonds were explored to evaluate the strength of interaction between DESs and cellulose, which is by means of atoms in molecules (AIM), natural bond orbital (NBO) and reduced density gradient (RDG). Spectroscopic and theoretical analyses are conductive to in-depth understanding of the dissolution mechanism: both of hydrogen bond acceptor and donor in DESs interact with cellulose, contributed to the dissolution behavior. Intermolecular interactions in the complexes have been identified as non-covalent interactions, especially hydrogen bonds, which were considered to be the driving force of dissolution.