title: Water in cellulose: evidence and identification of immobile and mobile adsorbed phases by2H MAS NMR.
abstract: The organization of water molecules adsorbed onto cellulose and the supramolecular hydrated structure of microfibril aggregates represents, still today, one of the open and complex questions in the physical chemistry of natural polymers. Here, we investigate by2H MAS NMR the mobility of water molecules in carefully2H-exchanged, and thereafter re-dried, microcrystalline cellulose. By subtracting the spectral contribution of deuteroxyls from the spectrum of hydrated cellulose, we demonstrate the existence of two distinct2H2O spectral populations associated with mobile and immobile water environments, between which the water molecules do not exchange at the NMR observation time scale. We conclude that those two water phases are located at differently-accessible adsorption sites, here assigned to the cellulose surfaces between and within the microfibril aggregates, respectively. The superior performance of2H MAS NMR encourages further applications of the same method to other complex systems that expose heterogeneous hygroscopic surfaces, like wood cell walls.
authors.affiliation: Division of Applied Physical Chemistry, Department of Chemistry, KTH Royal Institute of Technology, SE-10044 Stockholm, Sweden. ct499@cam.ac.uk and Wallenberg Wood Science Center, KTH Royal Institute of Technology, SE-10044 Stockholm, Sweden and Innventia AB, Box 5604, SE-114 86 Stockholm, Sweden.
authors.forename: E L
authors.initials: EL
authors.lastname: Lindh
authors.affiliation: Division of Applied Physical Chemistry, Department of Chemistry, KTH Royal Institute of Technology, SE-10044 Stockholm, Sweden. ct499@cam.ac.uk and Wallenberg Wood Science Center, KTH Royal Institute of Technology, SE-10044 Stockholm, Sweden.
authors.forename: C
authors.identifier: http://orcid.org/0000-0003-3278-026X
authors.initials: C
authors.lastname: Terenzi
authors.affiliation: Wallenberg Wood Science Center, KTH Royal Institute of Technology, SE-10044 Stockholm, Sweden and Innventia AB, Box 5604, SE-114 86 Stockholm, Sweden.
authors.forename: L
authors.initials: L
authors.lastname: Salmén
authors.affiliation: Division of Applied Physical Chemistry, Department of Chemistry, KTH Royal Institute of Technology, SE-10044 Stockholm, Sweden. ct499@cam.ac.uk.
authors.forename: I
authors.initials: I
authors.lastname: Furó