Utilization of Cellulose to Its Full Potential: A Review on Cellulose Dissolution, Regeneration, and Applications

As the most abundant natural polymer, cellulose is a prime candidate for the preparation of both sustainable and economically viable polymeric products hitherto predominantly produced from oil-based synthetic polymers. However, the utilization of cellulose to its full potential is constrained by its recalcitrance to chemical processing. Both fundamental and applied aspects of cellulose dissolution remain active areas of research and include mechanistic studies on solvent–cellulose interactions, the development of novel solvents and/or solvent systems, the optimization of dissolution conditions, and the preparation of various cellulose-based materials. In this review, we build on existing knowledge on cellulose dissolution, including the structural characteristics of the polymer that are important for dissolution (molecular weight, crystallinity, and effect of hydrophobic interactions), and evaluate widely used non-derivatizing solvents (sodium hydroxide (NaOH)-based systems, N,N-dimethylacetamide (DMAc)/lithium chloride (LiCl), N-methylmorpholine-N-oxide (NMMO), and ionic liquids). We also cover the subsequent regeneration of cellulose solutions from these solvents into various architectures (fibers, films, membranes, beads, aerogels, and hydrogels) and review uses of these materials in specific applications, such as biomedical, sorption, and energy uses.

Alkali Can Accelerate The Cellulose Dissolution In Aqueous 1-Ethyl-3-Methylimidazole Acetate (EmimAc/10% Water)

Ionic liquids are potential and successful cellulose solvent but still suffer technical and economic issues in the cellulose commercialization. In this work, a relative low-viscosity aqueous 1-ethyl-3-methylimidazole acetate (EmimAc with 10% water) was used instead of EmimAc to dissolve cellulose; the results showed that adding NaOH to water can significantly accelerate cellulose dissolution and the cellulose solubility increased with the NaOH concentration in the EmimAc/10% water solution. NaOH can weaken the strong interaction between water and EmimAc because it can bond preferentially with water by hydrogen bonding and therefore release Ac - from Ac - -water cluster; which can enhance the reaction between Emim + and Ac - and therefore improve the cellulose dissolution. Unfortunately, the NaOH introduction inevitably cause a cellulose degradation via peeling reaction.