X-RAY-DIFFRACTION AND SOLID-STATE C-13-NMR ANALYSES OF CELLULOSES TREATED WITH AMMONIA

Cellulose samples, which had cellulose I, II, and amorphous structures, were treated with liquid ammonia at -33-degrees-C under an atomospheric pressure or at 140-degrees-C (critical point of NH3 = 132-degrees-C) under a high pressure, and their crystallinities and crystal structures were studied by X-ray diffraction and solid-state C-13-NMR analyses. Crystallinity of cellulose III was low when the original samples were treated at -33-degrees-C, and some of the treated samples had disordered structures. On the other hand, highly crystalline cellulose III samples were obtained when the original samples were treated at 140-degrees-C. Cellulose samples with the higher crystallinities of cellulose I or II gave the higher crystallinity of cellulose III by the ammonia treatments. Solid-state C-13-NMR spectra showed that C4 and C6 resonances originating from cellulose I or II disappeared with the ammonia treatment at -33-degrees-C, and that the crystallinity of cellulose III was increased with shifting of the C4 resonance from 84 to 88 ppm by the ammonia treatment at 140-degrees-C. On the basis of these results, the mechanism of the formation of cellulose III by the ammonia treatment is discussed.