Cellulose is the most abundant renewable material in nature, yet only a minute fraction of its annual natural production is utilized as raw material for fabrication of synthetic products, or as source for biofuel production. Its processing requires harsh solvents or procedures considered to be detrimental to the environment and are increasingly regulated. The use of ionic liquids (IL) as "green" solvents has attracted significant attention due to unique properties such as stability, low toxicity and non-volatility. Solvent systems based on semi-dilute aqueous alkali solutions at low temperature are also of recent interest. Cellulose hydrogel microparticle dispersions are fabricated from such solutions by regeneration with water under strong shear. We us a combination of scattering methods (light, x-rays and neutrons) to study the thermodynamic state and conformation of cellulose dissolved in an ionic liquid and its mixture with a polar organic solvent. The research reveals a true molecular solution of individual semi-flexible chains in an expanded coil conformation. A unique reaction occurs during cellulose dissolution in 1-ethyl-3-methyl-imidazolium-acetate with dichloromethane, yielding mono-acetylated cellulose which is water soluble. When a cellulose solution or a microgel dispersion is mixed vigorously with oil and water a stable oil-in-water emulsion is formed, stabilized by the regenerated amorphous cellulose coating on the oil droplets. Imaging by cryo-transmission electron microscopy, indicates a unique multilayered structure of the cellulose coating. This unique structure is quantitatively evaluated by small-angle neutron scattering measurements with contrast variation. The presented model describes a spherical oil core with two concentric shells: an inner shell is a water-imbibed cellulose hydrogel (~3% cellulose) and an outer coating of a dense (>85%) cellulose layer. These newly discovered characteristics lead to several potential applications by encapsulation of functional molecules. The hydrogel micro-particle suspension and cellulose-coated emulsions undergo enzymatic hydrolysis at a much faster rate compared to microcrystalline cellulose. Moreover, the use of cellulose-coated emulsions in a “one-pot” bio-fuel process is proposed, in which the emulsion particles can be utilized as micro-reactors for a cascade of enzymatic reactions: hydrolysis, fermentation and trans-esterification. 

Cellulose solutions, gels and emulsions: From polymer physics to biofuel

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.