title: Impact of selected solvent systems on the pore and solid structure of cellulose aerogels.
abstract: The impact of selected cellulose solvent systems based on the principal constituents tetrabutylammonium fluoride (TBAF), 1-ethyl-3-methyl-1H-imidazolium-acetate,N-methylmorpholine-N-oxide, or calcium thiocyanate octahydrate (CTO) on the properties of cellulose II aerogels prepared from these solvent systems has been investigated as a means towards tailoring cellulose aerogel properties with respect to specific applications. Cotton linters were used as representative plant cellulose. Cellulose was coagulated from solutions with comparable cellulose content, and dried with supercritical carbon dioxide after solvent exchange. The resulting bulk aerogels were comprehensively morphologically and mechanically tested to relate structure and mechanical properties. Different solvent systems caused considerable differences in the properties of the bulk samples, such as internal surface area (nitrogen sorption), morphology, porosity (He pycnometry, thermoporosimetry), and mechanical stability (compression testing). The results of SAXS, WAXS, and solid-state13C NMR spectroscopy suggest that this is due to different mechanisms of cellulose self-assembling on the supramolecular and nanostructural level, respectively, as reflected by the broad ranges of cellulose crystallinity, fibril diameter, fractal dimension and skeletal density. Both solid state NMR and WAXS experiments confirmed the sole existence of the cellulose II allomorph for all aerogels, with crystallinity reaching a maximum of 46-50 % for CTO-derived aerogels. Generally, higher fibril diameter, degree of crystallinity, hence increased skeletal density were associated with good preservation of shape and dimension throughout conversion of lyogels to aerogels, and enhanced mechanical stability, but somewhat reduced specific surface area. Amorphous, yet highly rigid aerogels derived from TBAF/DMSO mixtures deviated from this trend, most likely due to their particular homogeneous and nanostructured morphology.
authors.affiliation: Division of Chemistry of Renewable Resources, University of Natural Resources and Life Sciences Vienna, Konrad-Lorenz-Straße 24, 3430 Tulln, Austria.
authors.forename: Nicole
authors.initials: N
authors.lastname: Pircher
authors.affiliation: Institute of Chemistry of Clermont-Ferrand, Clermont Université, Ecole Nationale Supérieure de Chimie de Clermont-Ferrand, BP 10448, 63000 Clermont-Ferrand, France ; UMR 6296, Institute of Chemistry of Clermont-Ferrand, Centre National de la Recherche Scientifique, 24 Avenue des Landais, 63171 Aubière, France.
authors.forename: Leticia
authors.initials: L
authors.lastname: Carbajal
authors.affiliation: Division of Chemistry of Renewable Resources, University of Natural Resources and Life Sciences Vienna, Konrad-Lorenz-Straße 24, 3430 Tulln, Austria.
authors.forename: Christian
authors.initials: C
authors.lastname: Schimper
authors.affiliation: Division of Chemistry of Renewable Resources, University of Natural Resources and Life Sciences Vienna, Konrad-Lorenz-Straße 24, 3430 Tulln, Austria.
authors.forename: Markus
authors.initials: M
authors.lastname: Bacher
authors.affiliation: Institute of Physics and Material Sciences, University of Natural Resources and Life Sciences Vienna, Peter Jordan Straße 82, 1190 Vienna, Austria.
authors.forename: Harald
authors.initials: H
authors.lastname: Rennhofer
authors.affiliation: Institute of Chemistry of Clermont-Ferrand, Clermont Université, Ecole Nationale Supérieure de Chimie de Clermont-Ferrand, BP 10448, 63000 Clermont-Ferrand, France ; UMR 6296, Institute of Chemistry of Clermont-Ferrand, Centre National de la Recherche Scientifique, 24 Avenue des Landais, 63171 Aubière, France.
authors.forename: Jean-Marie
authors.initials: JM
authors.lastname: Nedelec
authors.affiliation: Institute of Physics and Material Sciences, University of Natural Resources and Life Sciences Vienna, Peter Jordan Straße 82, 1190 Vienna, Austria.
authors.forename: Helga C
authors.initials: HC
authors.lastname: Lichtenegger
authors.affiliation: Division of Chemistry of Renewable Resources, University of Natural Resources and Life Sciences Vienna, Konrad-Lorenz-Straße 24, 3430 Tulln, Austria.
authors.forename: Thomas
authors.initials: T
authors.lastname: Rosenau
authors.affiliation: Division of Chemistry of Renewable Resources, University of Natural Resources and Life Sciences Vienna, Konrad-Lorenz-Straße 24, 3430 Tulln, Austria.
authors.forename: Falk
authors.initials: F
authors.lastname: Liebner
keywords: Cellulose aerogels; Cellulose solvents; Porous solids; Thermoporosimetry