Modeling of the morphological change of cellulose microfibrils caused with aqueous NaOH solution: the longitudinal contraction and laterally swelling during decrystallization

Abstract

The conformation of cellulose microfibrils treated with aqueous NaOH was modeled as partially decrystallized cellulose chains before completing conversion to cellulose II, in order to elucidate the change in morphology of ramie fiber caused by NaOH treatment. Equations for the relative length and width of the microfibrils were derived on the basis of partially decrystallized microfibrils modeling. Each equation contains four parameters, n, β, w , and c , which correspond to the number of glucose residues between periodic defects along the untreated ramie cellulose microfibrils, the extension ratio of amorphous cellulose chain along length, the cross-section crystallinity, and the correction term of crystallinity, respectively. The validity of the derived equations was confirmed by two types of simulations. One is performed using experimental data L/L and W/W as a function of crystallinity, while the other is done using the relationship between the relative length and width obtained from the experimental data, which is independent of crystallinity, was performed. The best-fit simulation was obtained under n = 277, β = 2.813, and c w = 0.671 for the former and under n = 301 and β = 2.792 for the latter. These values of n and β correspond closely to the values reported in references for ramie microfibrils. Both simulation results show that macroscopic changes in the morphology of ramie fibers is attributable to the changes in cellulose chain conformation in the decrystallized regions created along the microfibrils upon NaOH treatment.

Robust Biobased Membrane: Self-Entangled Cellulose Nanofibrils–ZnO–Ag Composite with High Photocatalytic Performance for Efficient Dye-Contaminated Water Treatment

“…These conformational changes in cellulose chains during NaOH treatment contribute to the morphological changes in CNFs (Figure ). , These morphological changes of CNFs occur largely in the NaOH solution with a concentration over 15 wt %, which would lead to a strong entanglement of CNFs in the membrane . That is why we use the 20 wt % NaOH solution to make the CNF membrane.…”

Production and Characterization of Bacterial Cellulose Separators for Nickel-Zinc Batteries

“…The equally longitudinal and lateral shrinkage of the membranes is probably caused by the partial decrystallization of the microfibril structure due to the alkaline electrolyte. The initially crystalline and straight microfibrils rearrange into randomly oriented cellulose chains that contract and thus cause a shrinkage of the cellulosic membrane, which at the same time causes a small lateral expansion [69]. The latter is, however, expected to be less pronounced and thus compensated in case of BC-5 and BC-10 by the shrinkage.…”