AbstractPolyalkane imides based on 3,3′,4,4′‐diphenyloxidetetracarboxylic, pyromellitic and 1,4,5,8‐naphthalenetetracaboxylic acids, and aliphatic diamines containing 4, 6, 8, 10, or 12 methylene groups have been studied. Relations governing the effect of structure on solubility, heat resistance, density, and crystallizability have been established. Conformation analysis has been carried out and models of the macromolecules have been constructed. The morphology of the crystalline polymers has been studied. For the polymers of the given class, crystallization capability is shown to be associated with the conformational flexibility of the macromolecular unit determining a given acid moiety by the number of methylene groups in the diami