Determination of nanocellulose fibril length by shear viscosity measurement
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- Tanaka, R., Saito, T., Ishii, D. et al. Cellulose (2014) 21: 1581. doi:10.1007/s10570-014-0196-4
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The lengths of ten types of cellulose nanofibrils were evaluated by shear viscosity measurement of their dilute dispersions. Aqueous dispersions of surface-carboxylated cellulose nanofibrils with a uniform width of ~3 nm were prepared from wood cellulose by 2,2,6,6-tetramethylpiperidine-1-oxyl-mediated oxidation and successive mechanical treatment. Cellulose nanofibril samples with different average lengths were prepared by controlling the conditions of the oxidation or mechanical treatment. The viscosity-average lengths, Lvisc, of the nanofibrils were calculated by applying the shear viscosities of the dilute dispersions to an equation for the dilute region flow behavior of rod-like polymer molecules. The obtained Lvisc values ranged from 1,100 to 2,500 nm and showed a linear relationship to the length-weighted average length, Lw, measured by microscopic observation; the relation was described as Lvisc = 1.764 × Lw + 764. The influences of the electric double-layer of the nanofibrils and surface-carboxylate content on the value of Lvisc were also investigated.