ABSTRACT
The availability of chitin in the form of a solid, highly polycrystalline material makes it the substrate of choice for X-ray diffraction and electron diffraction studies—first as a powder and then as oriented fibrillar forms, which helped identified the existence of three crystalline polymorphs: α-, β-, and γ-chitin. The most detailed elucidations of the crystalline structures of α-chitin, β-chitin, and chitosans are presented in this chapter. Detailed structural features, including the conformation of the chains and the networks of intra- and intermolecular interactions are discussed. Of particular interest is the relative orientation of polysaccharide chains in the solid-state. In α-chitin, chains are arranged in an antiparallel fashion, in contrast to β-chitin, where chains are parallel. The γ-chitin conformation is characterized by alternating parallel and antiparallel chitin chains.
