Ulf Olsson

Molecular self-diffusion coefficients were measured in solutions of microcrystalline cellulose (MCC) and dissolving pulp, in 40 wt% aqueous tetrabutylammonium hydroxide (TBAH), using pulsed field gradient stimulated echo NMR. From the cellulose diffusion coefficients, a weight averaged radius of hydration h>_w = 6.1 nm for MCC and h>_w = 15 nm for pulp were obtained. Water and TBA⁺ ions show a significantly different dependence on the cellulose concentration, revealing different molecular interactions with the polymer. Water-cellulose are essentially excluded volume. TBA⁺ ions, on the other hand, bind to cellulose with approximately 1.2 TBA⁺ ions per glucose unit.