| Research Abstract |
Molecular properties of several celluloses from different sources, i.e., Plantae, Monera and Animal Kingdom, are studied. We used a soft wood dissolving pulp (dissolving pulp cellulose, DP), a hard wood kraft pulp and cotton linter (cotton cellulose, CC) as Plantae celluloses, a cellulose from Acetobacter xylinum (bacterial cellulose, BC) as a Monera cellulose and a cellulose from Ascidiacea Halocynthia (tunicin, TC) as Animal cellulose. When each cedllulose was dissolved in LiCl/N, N-dimethylacetamide, (LiCl/DMAc), the solutions of cellulose from Plantae is isotropic and homogeneous, however, the cellulose solution from Acetobacter shows an optical anisotropy, i.e. liquid crystalline behavior, and Halocynthia cellulose (tunicin) is insoluble. However we found that the TC is soluble in LiCl/1,3-dimethyl-2-imidazolidinone (DMI). This suggests that there is some difference in the molecular structure of cellulose from different biological sources.
The values of M_W of DP, CC, BC and TC are
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91.7x10^<4>, 170x10^<4>, 193x10^<4> and 413x10^<4>, respectively. The solution viscosity of DP is higher than that of BC solution in spite of the higher molecular weight of BC.
The solution viscosities were proportional to c^<α> (c; polymer concentration) in the dilute and semi-dilute regions, where the exponent α was 1 for all samples in the dilute region; and in the semi-dilute region, it was 4 for the DP and CC solutions, 3 for the BC solution and 8 for the TC solution. Molecular weight differences or density difference of the solvent were compensated by plotting the viscosity against cM_W or c[η]ρ (where [η] and ρ are the limiting viscosity number and the density of the solvent). The persistent difference in viscosity behavior at elevated solution concentration indicates that the cellulose molecules from DP and CC behave as flexible polymer chains and those of BC as rod-like ones.
These results suggest that differences in molecular structure and properties exist between celluloses from different sources, and that these differences relate to the mechanism or the type of the intermolecular interaction between the celluloses of plants (DP and CC), those of bacteria (BC) and Ascidiaces (TC). Less
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