Solvated Structure of Cellulose in a Phosphonate-Based Ionic Liquid

Abstract

We investigated the solvated structure of cellulose in a phosphonate-based ionic liquid (IL) solution utilizing scattering experiments and all-atom molecular dynamics (MD) simulations. Based on the high-energy Xray total scattering experiment and MD simulations, a predominant interaction between cellulose and the IL was established, i.e., hydrogen bonding between the IL anion species and hydroxyl groups of cellulose. In addition, it was found that intramolecular hydrogen bonds existed within cellulose molecules, even when dissolved in the IL. Furthermore, the conformation of cellulose chains in the IL was investigated by a small-angle X-ray scattering experiment. As a result, it was found that cellulose molecules were dispersed at the molecular level and existed as rigid-rod-like polymers because of the intramolecular hydrogen bonds within the cellulose molecules. In dynamic light scattering experiments, a speckle pattern was observed for concentrated cellulose solutions. This indicated the existence of a physical-gel-like frozen inhomogeneity.

Macro- and Microstructural Evolution during Drying of Regenerated Cellulose Beads

“…It is well established that the I(q) ∼ q −1 behavior of the scattering profile for dilute solution corresponds to a characteristic scattering pattern of rodlike structures. 64,65 This behavior is observed for the cellulose solution over a relatively broad region q > 0.1 nm −1 (red curve in Figure S5). This suggests that cellulose chains exist as rodlike rigid polymers in DMAc/LiCl on large length scales, likely due to the intramolecular interactions between the adjacent glucose segments within cellulose molecules.…”

“…Similar behavior was observed by Hirosawa et al . by dissolving cellulose in a phosphonate-based ionic liquid . Surprisingly, the I ( q ) ∼ q –1 behavior is also found at a much higher q -region, q > 0.4 nm –1 , for water swollen beads after 1 h of drying (black dot curve in Figure S5).…”

“…Similar behavior was observed by Hirosawa et al by dissolving cellulose in a phosphonate-based ionic liquid. 64 Surprisingly, the I(q) ∼ q −1 behavior is also found at a much higher q-region, q > 0.4 nm −1 , for water swollen beads after 1 h of drying (black dot curve in Figure S5). This suggests that the cellulose chains in the beads drying from water have a similar rodlike conformation, on the smaller length scale, as in cellulose solution.…”

Functionalized Imidazalium Carboxylates for Enhancing Practical Applicability in Cellulose Processing

“…Cellulose, the most abundant biosynthesized polymer on earth, has been regarded as a potential alternative to oil resource for fuels, chemicals and materials due to its low-cost, reproducibility and biodegradability . However, the conversion of cellulose into valuable products still remains challenging in that cellulose is recalcitrant toward dissolution due to its highly ordered structure. − For this reason, efforts to develop efficient solvents for cellulose dissolution has been going on in scientific community. Conventional cellulose dissolution includes the viscose and cuprammonium process which have environmental problems. , The other developed solvents include aqueous N -methylmorpholine- N -oxide solvent, LiCl/ N , N -dimethylacetamide solvent, tetrabutyl ammonium fluoride/dimethyl sulfoxide solvent, N 2 O 4 / N , N -dimethylformamide, and LiClO 4 ·3H 2 O. − However, these solvent systems suffer from such drawbacks as environmental toxicity, inferior dissolution capacity, difficulty in solvent recovery, harsh processing conditions or high cost.…”

Flame Retardant-Functionalized Cotton Cellulose Using Phosphonate-Based Ionic Liquids

“…Note that the dissolution was performed at low temperatures in this work (50 • C versus 100 • C in our work and 120 • C in the work of Vo et al). Furthermore, Hirosawa et al [24] analyzed cellulose/ILs interactions in the dissolved state and not in the solid and crystallized state, as was the case in our study.…”