SEM ultrastructure studies of N-acyl- and N-benzylidene-chitosan and chitosan membranes

Fine ultrastructures of the cross sections of membranes, which are derived from chitosan and utilizable as artificial kidney, are examined by scanning electron microscopy (SEM). Three types of unique ultrastructure of the membrane cross sections are present: N-acylchitosan membranes [N-acetyl (1), N-propionyl (2), N-butyryl (3), N-pentanoyl (4), N-hexanoyl (5), N-octanoyl (6), and N-benzoyl (7)], N-benzylidenechitosan membranes (8) and chitosan membranes (9). The vertical cross sections of membranes 1-7 consist of orderly arranged layers that are formed by an assembly of particle units of fibrils. Neither fibrils nor layers are present and a smooth surface is characteristic of the cross sections of (8). On the other hand, the particle units of fibrils are absent and a nappy rough surface is characteristic of the cross sections of (9). N-Acetylation of (9) affords the article units of fibrils that are disorderly oriented. Low- and middle-molecular compounds (MW less than 2000) pass through small pores among these fibrils present in orderly arranged layers of the membranes. Properties of these N-acyl-chitosan membranes well meet the requirements of artificial kidney membranes.