title: Solubility of cellulose in supercritical water studied by molecular dynamics simulations.
abstract: The insolubility of cellulose in ambient water and most aqueous systems presents a major scientific and practical challenge. Intriguingly though, the dissolution of cellulose has been reported to occur in supercritical water. In this study, cellulose solubility in ambient and supercritical water of varying density (0.2, 0.7, and 1.0 g cm(-3)) was studied by atomistic molecular dynamics simulations using the CHARMM36 force field and TIP3P water. The Gibbs energy of dissolution was determined between a nanocrystal (4 × 4 × 20 anhydroglucose residues) and a fully dissociated state using the two-phase thermodynamics model. The analysis of Gibbs energy suggested that cellulose is soluble in supercritical water at each of the studied densities and that cellulose dissolution is typically driven by the entropy gain upon the chain dissociation while simultaneously hindered by the loss of solvent entropy. Chain dissociation caused density augmentation around the cellulose chains, which improved water-water bonding in low density supercritical water whereas the opposite occurred in ambient and high density supercritical water.
authors.affiliation: †Department of Forest Products Technology, Aalto University, P.O. Box 16300, FI-00076 Espoo, Finland.
authors.forename: Lasse K
authors.initials: LK
authors.lastname: Tolonen
authors.affiliation: ‡Wallenberg Wood Science Center, KTH Royal Institute of Technology, Teknikringen 56-58, SE-10040 Stockholm, Sweden.
authors.forename: Malin
authors.initials: M
authors.lastname: Bergenstråhle-Wohlert
authors.affiliation: †Department of Forest Products Technology, Aalto University, P.O. Box 16300, FI-00076 Espoo, Finland.
authors.forename: Herbert
authors.initials: H
authors.lastname: Sixta
authors.affiliation: ‡Wallenberg Wood Science Center, KTH Royal Institute of Technology, Teknikringen 56-58, SE-10040 Stockholm, Sweden.
authors.forename: Jakob
authors.initials: J
authors.lastname: Wohlert
mesh_terms: D002482:Cellulose / Q000737:chemistry*; D019277:Entropy; D006860:Hydrogen Bonding; D056004:Molecular Dynamics Simulation; D053758:Nanoparticles / Q000737:chemistry; D011312:Pressure; D012995:Solubility; D012997:Solvents / Q000737:chemistry; D013696:Temperature; D014867:Water / Q000737:chemistry*
chemical_list: D012997:Solvents; D014867:Water; D002482:Cellulose