title: Ionization of Cellobiose in Aqueous Alkali and the Mechanism of Cellulose Dissolution.
abstract: Cellulose, one of the most abundant renewable resources, is insoluble in most common solvents but dissolves in aqueous alkali under a narrow range of conditions. To elucidate the solubilization mechanism, we performed electrophoretic NMR on cellobiose, a subunit of cellulose, showing that cellobiose acts as an acid with two dissociation steps at pH 12 and 13.5. Chemical shift differences between cellobiose in NaOH and NaCl were estimated using 2D NMR and compared to DFT shift differences upon deprotonation. The dissociation steps are the deprotonation of the hemiacetal OH group and the deprotonation of one of four OH groups on the nonreducing anhydroglucose unit. MD simulations reveal that aggregation is suppressed upon charging cellulose chains in solution. Our findings strongly suggest that cellulose is to a large extent charged in concentrated aqueous alkali, a seemingly crucial factor for solubilization. This insight, overlooked in the current literature, is important for understanding cellulose dissolution and for synthesis of new sustainable materials.
authors.affiliation: Division of Theoretical Chemistry, Lund University , 221 00 Lund, Sweden.
authors.forename: Erik
authors.initials: E
authors.lastname: Bialik
authors.affiliation: Division of Theoretical Chemistry, Lund University , 221 00 Lund, Sweden.
authors.forename: Björn
authors.initials: B
authors.lastname: Stenqvist
authors.affiliation: Division of Applied Physical Chemistry, Department of Chemistry, KTH Royal Institute of Technology , 114 00 Stockholm, Sweden.
authors.forename: Yuan
authors.initials: Y
authors.lastname: Fang
authors.affiliation: Sustainable Built Environment, SP Technical Research Institute of Sweden , 114 28 Stockholm, Sweden.
authors.forename: Åsa
authors.initials: Å
authors.lastname: Östlund
authors.affiliation: Division of Applied Physical Chemistry, Department of Chemistry, KTH Royal Institute of Technology , 114 00 Stockholm, Sweden.
authors.forename: István
authors.initials: I
authors.lastname: Furó
authors.affiliation: Division of Physical Chemistry, Lund University , 221 00 Lund, Sweden.
authors.forename: Björn
authors.initials: B
authors.lastname: Lindman
authors.affiliation: Division of Theoretical Chemistry, Lund University , 221 00 Lund, Sweden.
authors.forename: Mikael
authors.initials: M
authors.lastname: Lund
authors.affiliation: Swedish NMR Centre, University of Gothenburg , 405 30 Göteborg, Sweden.
authors.forename: Diana
authors.identifier: http://orcid.org/0000-0002-9611-2263
authors.initials: D
authors.lastname: Bernin