Reflections on the Solubility of Cellulose

Wood cellulose can be used for producing biofuels and biopolymers, thus offering a solution to global concerns on the excessive use of fossil fuels. This requires a cellulose solvent that also allows the ecofriendly processing of selective wood components. Some ionic liquids (ILs) have shown promising results as cellulose solvents with many advantages over traditional approaches. It is agreed that their ionic nature is responsible for cleaving hydrogen bonds between cellulose chains, resulting in dissolution of the biopolymer. However, it is still necessary to establish a structural relationship between IL cations and anions, which explains why only certain ion combinations show the ability to dissolve cellulose. This work aims to analyze the structural similarities displayed by common cellulose solvents focusing on requirements for ionic liquids to qualify as such. A mutual relationship between IL anions and cations is postulated that offers an explanation for the ability or disability of certain ion combinations to dissolve the biopolymer.