Polymorphism of cellulose I family: Reinvestigation of cellulose IV

Polymorphs of cellulose I, IIII, and IVI have been investigated by X-ray diffraction, FT-IR, and solid-state C-13 NMR spectroscopy. Highly crystalline cellulose IIII samples were prepared by treating cellulose samples in supercritical ammonia at 140 degreesC for 1 h, and conventional cellulose IIII samples were prepared by liquid ammonia treatment. The cellulose IVI sample of highest crystallinity was that prepared from Cladophora cellulose IIII in supercritical ammonia, followed by the sample treated in glycerol at 260 degreesC for 0.5 h, whereas the lowest crystallinity was observed in ramie cellulose prepared by conventional liquid ammonia treatment followed by glycerol annealing. In general, the perfection of cellulose IVI depends on the crystallinity of the original material: either of the starting cellulose I or of the cellulose IIII after ammonia treatment. The product thus obtained was analogous to cellulose I-beta, which is what it should be called rather than cellulose IVI. If the existence of the polymorph cellulose IVI is not accepted, the observations on which it has been based may be explained by the fact that the structure termed cellulose IVI is cellulose I-beta which contains lateral disorder.