The nanometric internal structure of polymeric fibres is fundamental for their mechanical properties. Two-dimensional small angle neutron scattering patterns were collected to obtain structural parameters of the elementary fibrils in regenerated cellulose fibres prepared by various fibre spinning technologies. Scattering features were fitted to model functions to derive parameters such as elementary fibril radius, long period of the repeating units of crystal and amorphous phase along the fibre axis, degree of orientation, and ellipticity. The correlation between structural parameters and the mechanical properties was studied for the fibres of different existing spinning processes and for the high-strength fibres. Former group showed high correlation with mechanical properties. The latter group showed generally lower correlation, but showed relatively high correlation with the long period. These structural parameters provide a basis for understanding the structure-property relationship of regenerated cellulose fibres as function of spinning types and conditions for further optimization.
The crystal and molecular structure and hydrogen bonding system in cellulose II have been revised using new neutron diffraction data extending to 1.2 Å resolution collected from two highly crystalline fiber samples of mercerized flax. Mercerization was achieved in NaOH/H2O for one sample and in NaOD/D2O for the other, corresponding to the labile hydroxymethyl moieties being hydrogenated and deuterated, respectively. Fourier difference maps were calculated in which neutron difference amplitudes were combined with phases calculated from two revised X-ray models of cellulose II, A and B'. The revised phasing models were determined by refinement against the X-ray data set of Kolpak and Blackwell,8 using the LALS methodology.37 Both models A and B' have two antiparallel chains organized in a P21 space group and unit cell parameters: a = 8.01 Å, b = 9.04 Å, c = 10.36 Å, and γ = 117.1°.15 Model A has equivalent backbone conformations for both chains but different conformations for the hydroxymethyl moieties: gt for the origin chain and tg for the center chain. Model B', based on the recent crystal structures of cellotetraose,21-23 has different conformations for the two chains but nearly equivalent conformations for the hydroxymethyl moieties. On the basis of the X-ray data alone, model A and model B' could not be differentiated. From the neutron Fourier difference maps, possible labile hydrogen atom positions were identified for each model and refined using LALS. We were able to eliminate model A in favor of model B'. The hydrogen-bonding scheme identified for model B' is significantly different from previous proposals based on the crystal structures of cellotetraose,21-23 MD simulations of cellulose II,25 and any potential hydrogen-bonding network in the structure of cellulose II determined in earlier X-ray fiber diffraction studies.7,8 The exact localization of the labile hydrogen atoms involved in this bonding, together with their donor and acceptor characteristics, is presented and discussed. This study provides, for the first time, the coordinates of all of the atoms in cellulose II.
Volume 2, no. 2, 45-50, 2016, DOI: 10.18869/acadpub.cmm.2.2.2 . The original version of this article contained incorrect dose of terbinafine. This erratum adds the correct dose as shown below. Terbinafine dosage should change from 250 mg/kg to 250 mg/day.
The dimensions of nanocelluloses are important factors in controlling their material properties. The present study reports a fast and robust method for estimating the widths of individual nanocellulose particles based on the turbidities of their water dispersions. Seven types of nanocellulose, including short and rigid cellulose nanocrystals and long and flexible cellulose nanofibers, are prepared via different processes. Their widths are calculated from the respective turbidity plots of their water dispersions, based on the theory of light scattering by thin and long particles. The turbidity-derived widths of the seven nanocelluloses range from 2 to 10 nm, and show good correlations with the thicknesses of nanocellulose particles spread on flat mica surfaces determined using atomic force microscopy.
A revised crystal structure for mercerized cellulose based on high-resolution synchrotron X-ray data collected from ramie fibers is reported (space group P21, a = 8.10(3) Å, b = 9.03(3) Å, c = 10.31(5) Å, γ = 117.10(5)°; 751 reflections in 304 composite spots; θ < 21.11°; λ = 0.7208 Å; LALS refinement with d > 1.5 Å, R' ' = 0.16; SHELX97 refinement with d > 1 Å, R = 0.21). As with regenerated cellulose the crystal structure consists of antiparallel chains with different conformations but with the hydroxymethyl groups of both chains near the gt position. However, the conformation of the hydroxymethyl group of the center chain in the structure reported here differs significantly from the conformation in regenerated cellulose. This may be related to a large observed difference in the amount of hydroxymethyl group disorder: ∼30% for regenerated cellulose and ∼10% for mercerized cellulose.
We prepared highly crystalline samples of a cellulose I−ethylenediamine (EDA) complex by immersing oriented films of algal (Cladophora) cellulose microcrystals in EDA at room temperature for a few days. The unit-cell parameters were determined to be a = 0.455, b = 1.133, and c = 1.037 nm (fiber repeat) and γ = 94.02°. The space group was P21. On the basis of unit cell, density, and thermogravimetry analyses, the asymmetric unit is composed of one anhydrous glucose residue and one EDA molecule. The chemical and thermal stabilities of the cellulose I−EDA complex were also investigated by the use of X-ray diffraction. When the cellulose I−EDA complex was immersed in methanol or water at room temperature, cellulose IIII or Iβ was obtained, respectively. However, immersion in a nonpolar solvent such as toluene did not affect the crystal structure of the complex. The cellulose I−EDA complex was stable up to a temperature of ∼130 °C, whereas the boiling point of EDA is 117 °C. This thermal stability of the complex is probably caused by intermolecular hydrogen bonds between EDA molecules and cellulose. When heated above 150 °C, the cellulose I−EDA complex decomposed into cellulose Iβ.