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Wide-angle X-ray scattering has been used to study the crystalline structure and some structural properties of untreated and thermally treated samples of polycaproamide obtained by hydrolytic and anionic polymerisation of caprolactam. For untreated samples of polycaproamide two crystalline forms exist: a stable α-monoclinic form and an unstable γ * -pseudohexagonal modification. There are initial differences in the crystalline parameters of polycaproamide, i.e. content of α-and γ * -form, degree of crystallinity and size of lamellae. A more ordered structure has been observed for samples obtained by anionic polymerisation. Both temperature and duration of annealing have a considerable influence on the polymorph transition of the unstable γ * -pseudohexagonal crystalline form into the stable α-crystalline form, on the degree of crystallinity and on the lamellar thickness. It was found that the largest change in these parameters occurred at an annealing temperature at the lower end of the melting point range of polycaproamide.

The structural and thermal properties of chitin and chitosan isolated from different sources (Artemia sp.cysts (from the Aral Sea) and Silkworm pupae (Bombyx mori)) were studied by using FTIR, XRD, and DSC. It is shown, that the chitin and chitosan samples from different sources have a similar structure, however, depending on the sources differ in the ratio of the phase composition. Two types of crystalline modification of the structure (α-and β-modifications) are observed for chitin isolated from Artemia sp.cysts. The chitin isolated from Bombyx mori has three polymorphs (α-, β-and γ-modifications) with orthorhombic, monoclinic and triclinic syngonies. The thermal stability of chitin and chitosan samples was also depended on sources.