Ogawa K, Yui T, Miya M
a Research Institute for Advanced Science and Technology, University of Osaka Prefecture , 1-2 Gakuen-cho, Sakai, Osaka 593 , Japan.
b Department of Industrial Chemistry , Miyazaki University , Miyazaki 889-21 , Japan.
Biosci Biotechnol Biochem. 1992 Jan;56(6):858-62. doi: 10.1271/bbb.56.858.
Differences in the polymorphism and crystallinity of chitosan were found in membranes prepared by different procedures when examined by X-ray diffraction measurements for four samples of chitosan differing in the degree of polymerization. When an acetic acid solution of chitosan was dried in air and then soaked in an alkaline solution (method A), both hydrated and anhydrous polymorphs of chitosan were present in the resulting membranes; the latter polymorph made chitosan insoluble in common solvents of chitosan, and its crystallinity increased with decreasing chitosan molecular weight. When a highly concentrated chitosan solution in aqueous acetic acid was neutralized with an alkaline solution (method B), no anhydrous polymorphs were detected in the membrane because of incomplete drying. When aqueous formic acid was used as the solvent, behavior basically similar to that in aqueous acetic acid was observed. In contrast, even with method A, aqueous hydrochloric acid gave a chitosan membrane having very little anhydrous crystallinity. The crystalline polymorph called "1-2", which has been proposed to be one of four chitosan polymorphs, is considered to be a mixture of hydrated and anhydrous crystals.
通过对四种聚合度不同的壳聚糖样品进行X射线衍射测量发现，采用不同制备方法得到的壳聚糖膜在多晶型和结晶度方面存在差异。当壳聚糖的醋酸溶液在空气中干燥，然后浸泡在碱性溶液中（方法A）时，所得膜中同时存在壳聚糖的水合和无水多晶型物；后一种多晶型物使壳聚糖不溶于壳聚糖的常用溶剂，并且其结晶度随着壳聚糖分子量的降低而增加。当用碱性溶液中和高浓度的壳聚糖醋酸水溶液时（方法B），由于干燥不完全，膜中未检测到无水多晶型物。当使用甲酸水溶液作为溶剂时，观察到的行为与在醋酸水溶液中基本相似。相反，即使采用方法A，盐酸水溶液得到的壳聚糖膜几乎没有无水结晶度。被认为是壳聚糖四种多晶型物之一的“1-2”晶型多晶型物，被认为是水合晶体和无水晶体的混合物。
