Abstract: The N-methyl chitosan or N-ethyl chitosan was cast into films at high vacuum.Then the cast film crystallized at 25 ℃ and 65% relative humidity and the feather-like crystals appeared.The feather-like crystals were different with spherulites,which grew in the films cast at low vacuum.In addition to morphology,the birefrigence nature of feather-like crystals and spherulites was completely different.The former was negative,but the latter was positive.The feather-like crystals were believed to belong to one kind of dendritic crystals.

Key words: chitosan, N-alkyl chitosan, crystalline morphology lamella, dendritic crystals