Takayoshi Matsumoto

Effect of solvent exchange on the supramolecular structure, the molecular mobility and the dissolution behavior of cellulose in LiCl/DMAc

We investigated the effect of solvent exchange on the supramolecular structure and the molecular mobility of the cellulose molecule to clarify the mechanism of the dissolution of cellulose in lithium chloride/N,N-dimethylacetamide (LiCl/DMAc). Among the celluloses that were solvent exchanged in different ways, the DMAc-treated celluloses dissolved most rapidly. Dissolution of the acetone-treated celluloses was much slower than the DMAc-treated ones, but considerably faster than the untreated one. Such differences in the dissolution behavior were well explained by the differences in the surface fractal dimension calculated from the small-angle X-ray scattering profiles and in the (1)H spin-lattice and spin-spin relaxation times estimated from the solid-state NMR spectroscopic measurements. Furthermore, it was suggested from the IR spectra and the (13)C spin-lattice relaxation times of cellulose that DMAc is adsorbed on the surface of cellulose even after vacuum-drying and affects the molecular mobility and hydrogen-bonding state of cellulose.

Blended Solutions of Celluloses from Different Biological Origins

Solution properties of celluloses from different biological origins were investigated in terms of rheological properties in 8 wt% LiCl/amide solutions. The solution viscosities were proportional to the α‐th power of the polymer concentrations. The exponent, α, was 3, 4, and 7.5 for the solution from bacterial, wood and cotton, and tunicate cellulose in the semi‐dilute regions, respectively. These celluloses were blended to get solutions having various molecular weights and molecular distributions of the polymer. The high molecular weight component, tunicate cellulose: Mwu2009=u20094.13×106, had remarkable effect on the long‐time region of the viscoelastic functions of the blends. The weight fraction dependence of the zero‐shear viscosity of the blends can be expressed by a linear mixing relation based on Ninomiya theory. The zero‐shear viscosities of the blends are proportional to the 5/2‐th power of the weight‐average molecular weight calculated from a linear combination of that of each component. This indicates...