title: Rheological properties of cellulose/ionic liquid solutions: from dilute to concentrated states.
abstract: Steady state shear flow of different types of cellulose (microcrystalline, spruce sulfite and bacterial) dissolved in 1-ethyl-3-methylimidazolium acetate was studied in a large range of concentrations (0-15%) and temperatures (0-100 degrees C). Newtonian flow was recorded for all experimental conditions; these viscosity values were used for detailed viscosity-concentration and viscosity-temperature analysis. The exponent in the viscosity-concentration power law was found to be around 4 for temperatures from 0 to 40 degrees C, which is comparable with cellulose dissolved in other solvents, and around 2.5-3 for 60-100 degrees C. Intrinsic viscosities of all celluloses decreased with temperature, indicating a drop in solvent thermodynamic quality with heating. The data obtained can be reduced to a master plot of viscosity versus (concentration x intrinsic viscosity) for all celluloses studied in the whole temperature range. Mark-Houwink exponents were determined: they were lower than that for cellulose dissolved in LiCl/N,N-dimethylacetamide at 30 degrees C and close to theta-value. Viscosity-inverse temperature plots showed a concave shape that is dictated by solvent temperature dependence. The values of the activation energies calculated within Arrhenius approximation are in-line with those obtained for cellulose of comparable molecular weights in other solvents.
authors.affiliation: Mines ParisTech, Centre de Mise en Forme des Materiaux - CEMEF, UMR CNRS/Ecole des Mines de Paris 7635, BP 207, 06904 Sophia-Antipolis, France.
authors.forename: Martin
authors.initials: M
authors.lastname: Gericke
authors.forename: Kerstin
authors.initials: K
authors.lastname: Schlufter
authors.forename: Tim
authors.initials: T
authors.lastname: Liebert
authors.forename: Thomas
authors.initials: T
authors.lastname: Heinze
authors.forename: Tatiana
authors.initials: T
authors.lastname: Budtova