NEUTRON-DIFFRACTION STUDIES OF UNIT-CELL OF CELLULOSE 2

Unit cell dimensions of different polymorphic forms of cellulose have so far been controversial. Using a neutron diffraction technique, the authors recently confirmed the results of Honjo and Watanabe that a and c values of the unit cell of cellulose I (cotton) are about twice as large as those proposed by Meyer and Misch on the basis of x-ray diffraction. These results are in agreement with those reported later by Dobb et al based on electron diffraction studies of native cellulose. Since cellulose II is derived from cellulose I, it was decided to extend the neutron diffraction studies to cellulose II. Experimental study is described and results are presented an evaluated. Neutron diffraction studies of cellulose II have revealed that a and c values are twice as long as in the conventional cell. In the low-angle region, the authors have observed the peaks due to a single cell and additional peaks which can be explained on the basis of the double cell. As the angle of diffraction increases, there is greater overcrowding of the peaks and it is difficult to index the peaks unambiguously. The diffraction data indicates the existence of (010) peak, which means that cellulose does not belong to space group P2//1.