IONIC LIQUID-MEDIATED SYNTHESIS OF CELLULOSE/MONTMORILLONITE NANOCOMPOSITE

Cellulose regeneration is a facile approach to produce biopolymer/clay composites with improved physical properties. In this study, a cellulose/montmorillonite nanocomposite was prepared using a novel ionic liquid, 1-butyl-3-ethylimidazolium bromide ([BEIm]Br). Montmorillonite clay was modified using cetyltrimethylammonium bromide (CTAB) and was characterized using X-ray diffraction (XRD) analysis, which revealed the substitution of cetyltrimethylammonium (CTA+) cations in the clay gallery. The exfoliation-adsorption method was used to prepare the cellulose/montmorillonite nanocomposites, and scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD) analyses confirmed the successful dispersion of cellulose into the clay matrix. Thermogravimetric analysis (TGA) further revealed the optimum thermal stability of the nanocomposite was achieved with 4 wt% montmorillonite, which provided a white cellulose/montmorillonite nanocomposite.

Effect of antisolvents on the structure of regenerated cellulose: development of an efficient regeneration process

In this study, the effect of antisolvents on the structure of regenerated microcrystalline cellulose (MCC) obtained from the extraction of 1-butyl-3-methylimidazolium chloride (BmimCl) was investigated; further, the usage of the aqueous N,N-dimethylmethanamide (DMF) solution was proposed as an effective antisolvent for cellulose regeneration. The results denoted that regeneration after dissolution resulted in a looser cellulose texture with a high specific surface area, low degree of polymerization (DP), low crystallinity index (CrI), and decreased thermostability, which are favorable for its downstream processing. Among the studied antisolvents, the DMF solution was superior in cellulose regeneration from BmimCl, as demonstrated by the kinetics of enzymatic hydrolysis. The improved ability of the DMF solution with respect to cellulose regeneration can be attributed to the effective dispersion of H-bonds and the inductive hydrophobic orientation of cellulose chains; correspondingly, a looser H-bond network was observed in the regenerated cellulose. The DMF solution as an antisolvent offers an effective cellulose regeneration method and an optimal structure for subsequent processing and applications.

Cellulose in Ionic Liquids and Alkaline Solutions: Advances in the Mechanisms of Biopolymer Dissolution and Regeneration

This review is focused on assessment of solvents for cellulose dissolution and the mechanism of regeneration of the dissolved biopolymer. The solvents of interest are imidazole-based ionic liquids, quaternary ammonium electrolytes, salts of super-bases, and their binary mixtures with molecular solvents. We briefly discuss the mechanism of cellulose dissolution and address the strategies for assessing solvent efficiency, as inferred from its physico-chemical properties. In addition to the favorable effect of lower cellulose solution rheology, microscopic solvent/solution properties, including empirical polarity, Lewis acidity, Lewis basicity, and dipolarity/polarizability are determinants of cellulose dissolution. We discuss how these microscopic properties are calculated from the UV-Vis spectra of solvatochromic probes, and their use to explain the observed solvent efficiency order. We dwell briefly on use of other techniques, in particular NMR and theoretical calculations for the same purpose. Once dissolved, cellulose is either regenerated in different physical shapes, or derivatized under homogeneous conditions. We discuss the mechanism of, and the steps involved in cellulose regeneration, via formation of mini-sheets, association into “mini-crystals”, and convergence into larger crystalline and amorphous regions. We discuss the use of different techniques, including FTIR, X-ray diffraction, and theoretical calculations to probe the forces involved in cellulose regeneration.

Cellulose regeneration and spinnability from ionic liquids

Ionic liquid solutions of cellulose can be spun into Lyocell-type textile fibers by dry-jet wet spinning.