The central obstacle is thermodynamic. Cellulose chains are packed into dense crystalline domains held together by an extensive network of inter- and intramolecular hydrogen bonds. This bonding is so strong that cellulose decomposes before it melts, which rules out the extrusion and molding routes that the plastics industry relies upon. The only practical way to shape cellulose at the molecular level is therefore to dissolve it in a suitable solvent and then regenerate it, precipitating the polymer back into a solid form in a controlled geometry. Traditional industrial processes, such as the viscose route, achieve this by derivatizing cellulose, temporarily converting it into a chemical derivative such as xanthate. Non-derivatizing solvents, by contrast, dissolve native cellulose through physical interactions alone, offering zero derivatization, lower toxicity, and the possibility of closed-loop solvent recycling.

The review organizes the field around a unifying mechanistic concept: hydrogen-bond competition and reconfiguration. Every effective cellulose solvent works by disrupting the hydrogen-bond network that holds the crystal lattice together, outcompeting the cellulose-cellulose interactions with solvent-cellulose interactions. When solvent molecules penetrate the crystalline regions and bind to the hydroxyl groups on the glucose repeat units, the packing collapses in situ and individual chains disperse at the molecular level. Regeneration then reverses the process: a coagulant, typically water, an alcohol, or an acid bath, strips the solvent away from the hydroxyl groups, and the cellulose chains reassemble into a new solid whose crystallinity, porosity, and mechanical properties depend on how fast and how completely that reassembly occurs. Understanding and tuning this competition-reconfiguration mechanism is, according to the authors, the key to designing next-generation green cellulose materials.

Among the solvent families surveyed, aqueous alkali systems occupy a special place because of their low cost and low toxicity. Sodium hydroxide-based systems, often combined with urea or thiourea, dissolve cellulose at low temperatures, typically around minus five to eight degrees Celsius, where the hydration shells around the alkali and the hydrogen-bonding co-solvents most effectively pry apart the cellulose chains. Work on NaOH/urea and NaOH/thiourea solutions has shown that molecular weight and temperature strongly influence solubility, and that fibers spun from these systems can display competitive mechanical properties. Additives matter as well: zinc oxide in NaOH solutions improves cellulose reactivity, and ball-milling pretreatment of wood pulp facilitates dissolution in NaOH/urea. Coagulation conditions, including bath composition and temperature, directly determine the structure and properties of the regenerated films and fibers, giving processors multiple levers for tuning the final material.

A second classical system is N,N-dimethylacetamide/lithium chloride, or DMAc/LiCl, prized for its ability to dissolve even high-molecular-weight cellulose while preserving the degree of polymerization. Molecular interaction studies have revisited the dissolution mechanism, showing that lithium ions coordinate to the hydroxyl oxygens while chloride ions and the amide solvent disrupt the hydrogen-bond network. This system has enabled transparent, flexible regenerated films from sources as diverse as corn stalk pulp, wheat straw, and ginger pulp, including antibacterial packaging films. Its drawbacks are practical rather than chemical: DMAc raises toxicity and cost concerns, and residual salts must be removed from regenerated films, which motivates continued searches for greener alternatives.

Ionic liquids have transformed the field since the landmark 2002 demonstration that chloride-based imidazolium salts dissolve cellulose. These designer salts, which are liquid near room temperature, can be tuned at the molecular level: the cation and anion combinations determine hydrogen-bond basicity, viscosity, and thermal stability, parameters often quantified through Kamlet-Taft solvatochromic scales. Superbase-based protic ionic liquids, amino acid ionic liquids, and diacid-superbase combinations have pushed dissolution efficiency to new levels, enabling filament spinning, aerogel fibers with exceptional toughness for thermal insulation and impact protection, and the recycling of textile cotton waste into regenerated filaments. Transition metal ions can even reduce the viscosity of cellulose-ionic-liquid solutions, easing processing. Crucially, many ionic liquids can be recovered and reused, aligning the chemistry with closed-loop manufacturing.

Deep eutectic solvents and inorganic salt hydrates represent the newest and arguably most economical branch of the family. Deep eutectic solvents are mixtures of hydrogen-bond donors and acceptors, such as choline chloride with urea or organic acids, that form a liquid at a temperature far below the melting points of the individual components. Metal salt hydrates such as zinc chloride hydrate, lithium bromide hydrate, and calcium chloride-lithium chloride molten salts act on a similar principle, using their bound water and ionic species to compete for cellulose hydroxyl groups. Recent work has demonstrated room-temperature dissolution in ZnCl2 solutions, in AlCl3/ZnCl2 mixtures, and in low-viscosity TMAH hydrate/urea eutectics, producing strong, transparent films and lignin-containing composites from unbleached and underutilized biomass. NMR studies of molten salt hydrates have clarified how coordination interactions protect glycosidic bonds during dissolution, preserving the polymer backbone while the crystal structure is dismantled.

The industrial benchmark remains N-methylmorpholine-N-oxide, or NMMO, the solvent behind commercial Lyocell fiber production. NMMO monohydrate dissolves cellulose through its strongly polar N-O group, and the resulting dopes can be spun into fibers with a circular economy profile. The review highlights bidirectional concentration effects, in which NMMO concentration governs both dissolution and regeneration behavior, as well as ternary NMMO/water/DMSO mixtures that enhance dissolution capability. Applications emerging from NMMO and related systems include ultratough anisotropic nanofiber films, responsive patterned films, flexible sensors based on regenerated cellulose hydrogels, and personal cooling textiles incorporating boron nitride nanosheets. Across all solvent families, the review emphasizes that processing parameters, solvent choice, cellulose concentration, temperature, coagulation conditions, and pretreatment, collectively determine solubility, degree of polymerization retention, and the properties of the regenerated material.

What makes this review timely is its translation of fundamental mechanisms into a technical roadmap for high-value products. Membranes for oil-water separation, antibacterial food packaging, aerogels for thermal insulation, hydrogels for flexible electronics, sutures, and lightweight 3D-printed all-cellulose structures all flow from the same dissolution-regeneration logic, differing only in how the solvent, the coagulation, and the shaping step are orchestrated. The authors argue that precise control of hydrogen-bond competition allows molecular-level dispersion to be converted into deliberately designed architectures, whether by bottom-up assembly or top-down deconstruction of biomass. The remaining challenges are equally clear: scaling low-energy regeneration, achieving truly closed-loop solvent recycling, integrating functionality without sacrificing biodegradability, and ensuring that biobased microfibers do not simply replace one pollution problem with another. As the post-petroleum transition accelerates, the ability to dissolve and rebuild the world’s most abundant polymer with green, recyclable solvents may prove one of the decisive technologies of sustainable manufacturing.

Subject of Research: Non-derivatizing solvent systems for dissolving and regenerating cellulose into functional sustainable materials

Article Title: Non-derivatizing solvent systems for regenerated cellulose: from fundamentals to applications

Article References: Non-derivatizing solvent systems for regenerated cellulose: from fundamentals to applications. (n.d.). https://doi.org/10.1007/s00289-026-06698-7

Image Credits: AI Generated

DOI: 10.1007/s00289-026-06698-7

Keywords: cellulose, non-derivatizing solvents, ionic liquids, deep eutectic solvents, hydrogen bonds, regenerated cellulose, green chemistry, biodegradable polymers, Lyocell, sustainable materials, biomass, polymer processing