Sustainable and green derivatization of cellulose under heterogeneous slurry and homogeneous solution conditions

Cellulose, a highly abundant polymeric material, is difficult to chemically modify due to its poor solubility. In industry, a common approach to derivatize cellulose is to use heterogeneous slurry conditions, consisting of an organic/water solvent system with caustic for cellulose swelling. Although homogeneous processes are not desirable on an industrial scale owing to their high viscosity, specially designed solvents like ionic liquids can be used for cellulose derivatization under homogeneous conditions, to obtain better control and reaction efficiency. In this presentation, we show the derivatization of cellulose with various renewable chemicals under both heterogeneous and homogeneous conditions. The goal of the cellulose derivatization was to obtain water-soluble cellulose derivatives and alkene-containing cellulose derivatives, useful for aqueous viscosity modification and further modification by thiol-ene click reaction with various thiols, respectively. The use of glycidol in heterogeneous slurry conditions produced high-quality water-soluble 2,3-dihydroxypropyl cellulose ethers which served as a fair viscosifying agent under aqueous conditions. Imidazolium-based ionic liquids and polarity switchable CO₂/DBU/DMSO solvent system were used as solvents for cellulose derivatization under homogeneous conditions to produce alkene-containing cellulose derivatives using several alkene-containing epoxides and halides. These cellulose derivatives were further functionalized via photo-initiated thiol-ene click chemistry. This presentation provides principles for rational reaction engineering of cellulose derivatizes based on reactants and targeted physicochemical properties.