β Scribed by Nishiyama, Yoshiharu ;Langan, Paul ;Wada, Masahisa ;Forsyth, V. Trevor
No coin nor oath required. For personal study only.
A series of cellulose crystal allomorphs has been studied using high-resolution X-ray and neutron fibre diffraction to locate the positions of H atoms involved in hydrogen bonding. One type of position was always clearly observed in the Fourier difference map (F(d)-F(h)), while the positions of other H atoms appeared to be less well established. Despite the high crystallinity of the chosen samples, neutron diffraction data favoured some hydrogen-bonding disorder in native cellulose. The presence of disorder and a comparison of hydrogen-bond geometries in different allomorphs suggests that although hydrogen bonding may not be the most important factor in the stabilization of cellulose I, it is essential for stabilizing cellulose III, which is the activated form, and preventing it from collapsing back to the more stable cellulose I.
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## Abstract Review: 50 refs.
## Abstract It was puzzling that cellulose could be dissolved rapidly in 4.6 wtβ% LiOHβ/β15 wtβ% urea aqueous solution precooled to β12βΒ°C, whereas it could not be dissolved in the same solvent without prior cooling. To clarify this important phenomenon, the structure and physical properties of LiO