Structural study of anhydrous tendon chitosan obtained via chitosan/aceticacid complex

The molecular structure and packing arrangement of anhydrous tendon chitosa n was determined by the X-ray fibre diffraction method together with the li nked-atom least-squares refinement technique. The specimen was prepared fro m chitosan/acetic acid complex which was obtained by exposing tendon chitos an to acetic acid vapour at room temperature for several days. Then is high degree of orientation and crystallinity compared with the specimen obtaine d by the annealing method. Two chitosan chains are present in an orthorhomb ic unit cell of dimensions a = 8.26(2), b = 8.50(1), c (fibre axis)= 10.43( 2) Angstrom and space group P2(1)2(1)2(1). The 2-fold helical chain is stab ilised by O3 ... O5 hydrogen bond with the gt orientation of O6. There are direct hydrogen bonds (N2 ... O6) between adjacent chains along the a-axis, which makes a sheet structure parallel to the ac-plane. On the other hand, no hydrogen bond is found between the sheets. (C) 1999 Elsevier Science B. V. All rights reserved.