Spherulitic crystallization of chitosan oligomers

Chitosan crystallization, performed by simple drying of an oligomer or poly mer solution on a glass or mica surface, was studied at room temperature. P olarizing microscopy revealed the formation of two-dimensional spherulites that were shown to have a negative birefringence. After metal shadowing, el ectron microscopy investigations allowed the molecular arrangements of thes e structures to be described more precisely. X-ray and selected area electr on diffraction experiments led to the identification of the crystalline str ucture which corresponds to the monoclinic chitosan hydrochloride. The pres ence of water in the crystalline lattice was also revealed.